In-SITU hydrogen generation and production from petroleum reservoirs

Abstract

A system and method of producing hydrogen from a petroleum reservoir includes providing a porous configuration of catalyst particles within one or more wellbores in the petroleum reservoir, heating the catalyst particles using one or more electromagnetic wave generators such that hydrocarbons passing through or near the porous configuration of catalyst particles react with the heated catalyst particles and generate syngas. The porous configuration of catalyst particles is disposed only within the one or more wellbores proximate to the one or more electromagnetic wave generators. The hydrogen is separated and extracted from the syngas at the surface or within the one or more wellbores.

Description

IN-SITU HYDROGEN GENERATION AND PRODUCTION FROM PETROLEUM RESERVOIRSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] None.TECHNICAL FIELD OF THE INVENTION

[0002] The present invention relates in general to the field of petroleum production, and more particularly, to generating and producing hydrogen (H2) gas directly from petroleum reservoirs.STATEMENT OF FEDERALLY FUNDED RESEARCH

[0003] None.BACKGROUND OF THE INVENTION

[0004] Without limiting the scope of the invention, its background is described in connection with developing petroleum reservoirs for clean hydrogen energy.

[0005] Petroleum has been continuously produced from reservoirs in the form of gases, liquids, or solids for many years. Vertical and horizontal wells are typically drilled to allow oil and gas to flow from formations to the surface.

[0006] Different technologies have been developed for conventional reservoirs, heavy oil reservoirs, and unconventional reservoirs in the stage of primary, secondary, and tertiary recovery. For example, microwave heating is used for improving the recovery of heavy oil and oil shale. For unconventional shale reservoirs, hydraulic fracturing is usually performed to create highly permeable fractures for shale oil and / or shale gas flow into wellbores. The ultimate objective of these technologies is to produce hydrocarbons as much as possible.

[0007] However, the burning of petroleum emits huge amount of carbon dioxide (CO2) to the atmosphere, which is blamed for the main reason of global warming. To achieve net-zero by 2050 as outlined in the Paris Agreement, the petroleum industry is facing increasing pressure to reduce the carbon footprint of their business, as well as to decarbonize fossil fuels. This necessitates a significant energy transition through the decarbonization of petroleum consumption.

[0008] Transforming oil and gas into a clean hydrogen (H2) supplier emerges as a promising solution in this decarbonization process. In fact, around 95% of industrial hydrogen in U.S. has been produced annually by steam methane reforming (SMR) technology using natural gas as the feedstock (Chen et al., 2020). However, this technology suffers from high carbon dioxide (CO2) emissions (e.g., -9-10 times CO2 emissions than generated H2 (Sun et al., 2019)), leading to substantial cost to dispose the generated CO2 via the implementation of carbon capture, utilization, and storage (CCUS).

[0009] Accordingly, there is a need for a hydrogen generation process that can be conducted within petroleum reservoirs using the abundant hydrocarbons and water in reservoirs such that hydrogen is produced to the surface from the production well and emissions are significantly reduced.SUMMARY OF THE INVENTION

[0010] Various embodiments of the present invention generate and produce high-purity hydrogen directly from petroleum reservoirs using electromagnetic wave (e.g., microwaves, etc.) heating in the presence of catalysts, which are delivered deeply into the reservoirs through adapting hydraulic fracturing processes. The whole process can happen in underground reservoirs, instead of at the surface facilities. It is for hydrogen generation and production, rather than for enhanced oil or gas recovery in traditional petroleum industry.

[0011] In one embodiment, a method of producing hydrogen from a petroleum reservoir includes providing a porous configuration of catalyst particles within one or more wellbores in the petroleum reservoir, heating the catalyst particles using one or more electromagnetic wave generators such that hydrocarbons passing through or near the porous configuration of catalyst particles react with the heated catalyst particles and generate a syngas. The porous configuration of catalyst particles is disposed only within the one or more wellbores proximate to the one or more electromagnetic wave generators. The hydrogen is from the syngas at the surface or within the one or more wellbores.

[0012] In one aspect, the porous configuration of catalyst particles includes metal-based catalytic particles integrated into silicon carbide particles. In another aspect, the silicon carbide particles include beta-phase (P-phase) silicon carbide particles. In another aspect, the metal-based catalytic particles contain Fe, Ti, K, Mn, Ni, Co, or a combination thereof. In another aspect, a weight percentage of metal-based catalytic particles is between 0.1% and 50% of a total weight of the porous configuration of catalyst particles. In another aspect, a size of the metal-based catalytic particles is less than or equal to 500 nanometers, or a shape of metal-based catalytic particles includes tri-lobe,spherical, or agglomerated. In another aspect, the method further includes manufacturing the porous configuration of catalyst particles by: integrating the metal -based catalytic particles into the silicon carbide particles, customizing a permeability of the porous configuration of catalyst particles to be 0.01 to 100 Darcys, and configuring the catalyst particles into a substantially annular cylinder having an inner diameter larger than an outer diameter of the one or more electromagnetic wave generators and an outer diameter smaller than a diameter of the one or more wellbores. In another aspect, one or more support materials are also integrated into the silicon carbide particles. In another aspect, the one or more support materials include AI2O3, SiC>2, activated carbon, or Zeolites. In another aspect, the method further includes varying a ratio of the one or more support materials to the silicon carbide particles to: increase a material strength of the porous configuration of catalyst particles, adjust a permeability of the porous configuration of catalyst particles, or reduce a cost of the porous configuration of catalyst particles. In another aspect, a size of the one or more support materials and the silicon carbide particles is less than or equal to 100 micrometers. In another aspect, the method further includes coating or doping the metal-based catalytic particles on the one or more support materials and the silicon carbide particles.

[0013] In another aspect, the one or more wellbores include one or more vertical wellbores, one or more horizontal wellbores, one or more multilateral wellbores, or a combination thereof, the petroleum reservoir includes a conventional, an unconventional, a new, a depleted or an abandoned oil and gas reservoir, or the syngas includes the hydrogen, methane, carbon monoxide, carbon dioxide, and other light hydrocarbons. In another aspect, wherein providing the porous configuration of catalyst particles includes embedding the porous configuration of catalyst particles to an outside of the one or more electromagnetic wave generators. In another aspect, the porous configuration of catalyst particles comprises an annular cylinder having an inner diameter larger than an outer diameter of the one or more electromagnetic wave generators and an outer diameter smaller than an inner diameter of the one or more wellbores. In another aspect, the porous configuration of catalyst particles has a substantially similar length as the one or more electromagnetic wave generators. In another aspect, a thickness of the porous configuration of catalyst particles varies according to a size of the one or more electromagnetic wave generators and the one or more wellbores. In another aspect, the catalyst particles are heated to a temperature range of 250 to 1000°C, and the catalyst particles are heated for a time period of hours, days, seasons or years. In another aspect, the electromagnetic waves generated by the one or more electromagnetic wave generators are continuous, pulsed, intermittent, time dependent or time independent. In another aspect, the method further includes adjusting afrequency of the one or more electromagnetic wave generators to optimize a heating efficiency of the catalyst particles or the generation of the hydrogen. In another aspect, the method further includes using off-peak electricity from one or more renewable energy sources to power the one or more electromagnetic wave generators. In another aspect, the method further includes positioning one or more electromagnetic wave generators within the one or more wellbores, connecting the one or more electromagnetic wave generators to a power source, and generating electromagnetic waves using one or more electromagnetic wave generators. In another aspect, the method further includes removing carbon deposited on the catalyst particles and regenerating the catalyst particles in-situ using water or steam. In another aspect, the water is pre-existing within the petroleum reservoir or injected into the one or more wellbores, or the steam is injected into the one or more wellbores. In another aspect, the method further includes sequestrating carbon oxides from the one or more wellbores into a sequestration formation using a production packer. In another aspect, the method further includes improving an injection of the carbon oxides into the sequestration formation using surface compressors or downhole pumps.

[0014] In another aspect, the method includes injecting water into the one or more wellbores to increase a production and a purity of the hydrogen. In another aspect, the water is injected into the one or more wellbores to have an approximate ratio of one to one with the hydrocarbons within the one or more wellbores or proximate to the porous configuration of catalyst particles. In another aspect, the injected water approximately doubles the production of the hydrogen and increases the purity of the hydrogen to approximately 50% or more. In another aspect, the porous configuration of catalyst particles further comprises biochar, or the biochar is in injected into the one or more wellbores. In another aspect, the biochar comprises approximately 5 to 10 wt% of the catalyst particles. In another aspect, a particle size of the biochar comprises approximately 38-100 f rn. In another aspect, the method is carbon negative.

[0015] In another embodiment, a system for generating hydrogen within a petroleum reservoir includes one or more wellbores into the petroleum reservoir, a power source at a surface above the petroleum reservoir, a porous configuration of catalyst particles within the one or more wellbores, and one or more electromagnetic wave generators within the one or more wellbores and connected to the power source. The one or more electromagnetic wave generators heat the catalyst particles such that hydrocarbons passing through or near the porous configuration of catalyst particles react with the heated catalyst particles and generate a syngas. The porous configuration of catalyst particles is disposed only within the one or more wellbores proximate to the one or more electromagnetic wavegenerators. One or more hydrogen separators located within the one or more wellbores or at the surface that separate and extract the hydrogen from the syngas.

[0016] In one aspect, the porous configuration of catalyst particles includes metal -based catalytic particles integrated into silicon carbide particles. In another aspect, the silicon carbide particles include beta-phase (P-phase) silicon carbide particles. In another aspect, wherein the metal-based catalytic particles contain Fe, Ti, K, Mn, Ni, Co, or a combination thereof. In another aspect, a weight percentage of metal-based catalytic particles is between 0.1% and 50% of a total weight of the porous configuration of catalyst particles. In another aspect, a size of the metal-based catalytic particles is less than or equal to 500 nanometers, or a shape of metal-based catalytic particles includes tri-lobe, spherical, or agglomerated. In another aspect, the porous configuration of catalyst particles has a permeability of 0.01 to 100 Darcys. In another aspect, the porous configuration of catalyst particles is a substantially annular cylinder having an inner diameter larger than an outer diameter of the one or more electromagnetic wave generators and an outer diameter smaller than a diameter of the one or more wellbores. In another aspect, one or more support materials are also integrated into the silicon carbide particles. In another aspect, the one or more support materials include AI2O3, SiC>2, activated carbon, or Zeolites. In another aspect, a ratio of the one or more support materials to the silicon carbide particles is varied to: increase a material strength of the porous configuration of catalyst particles, adjust a permeability of the porous configuration of catalyst particles, or reduce a cost of the porous configuration of catalyst particles. In another aspect, a size of the one or more support materials and the silicon carbide particles is less than or equal to 100 micrometers. In another aspect, the metalbased catalytic particles are coated or doped on the one or more support materials and the silicon carbide particles.

[0017] In another aspect, the one or more wellbores include one or more vertical wellbores, one or more horizontal wellbores, one or more multilateral wellbores, or a combination thereof, the petroleum reservoir includes a conventional, an unconventional, a new, a depleted or an abandoned oil and gas reservoir, or the syngas includes the hydrogen, methane, carbon monoxide, carbon dioxide, and other light hydrocarbons. In another aspect, the one or more wellbores, or the porous configuration of catalyst particles is embedded to an outside of the one or more electromagnetic wave generators. In another aspect, the porous configuration of catalyst particles has a substantially similar length as the one or more electromagnetic wave generators. In another aspect, a thickness of the porous configuration of catalyst particles varies according to a size of the one or more electromagnetic wave generators and the one or more wellbores. In another aspect, the catalyst particles are heated toa temperature range of 250 to 1000°C, and the catalyst particles are heated for a time period of hours, days, seasons or years. In another aspect, electromagnetic waves generated by the one or more electromagnetic wave generators are continuous, pulsed, intermittent, time dependent or time independent. In another aspect, a frequency of the one or more electromagnetic wave generators is adjusted to optimize a heating efficiency of the catalyst particles or the generation of the hydrogen. In another aspect, the power source includes off-peak electricity from one or more renewable energy sources. In another aspect, carbon deposited on the catalyst particles is removed and the catalyst particles are regenerated in-situ using water or steam. In another aspect, the water is pre-existing within the petroleum reservoir or injected into the one or more wellbores, or the steam is injected into the one or more wellbores. In another aspect, carbon oxides from the one or more wellbores are injected into a sequestration formation using a production packer. In another aspect, the injection of the carbon oxides into the sequestration formation is improved using surface compressors or downhole pumps.

[0018] In another aspect, water is injected into the one or more wellbores to increase a production and a purity of the hydrogen. In another aspect, the water is injected into the one or more wellbores to have an approximate ratio of one to one with the hydrocarbons within the one or more wellbores or proximate to the porous configuration of catalyst particles. In another aspect, the injected water approximately doubles the production of the hydrogen and increases the purity of the hydrogen to approximately 50% or more. In another aspect, the porous configuration of catalyst particles further comprises biochar, or the biochar is in injected into the one or more wellbores. In another aspect, the biochar comprises approximately 5 to 10 wt% of the catalyst particles. In another aspect, a particle size of the biochar comprises approximately 38-100 [im. In another aspect, the system provides a carbon negative process.

[0019] Note that the invention is not limited to the embodiments, instead it has the applicability beyond the embodiments herein. The brief and detailed descriptions of this invention are given in the following.BRIEF DESCRIPTION OF THE DRAWINGS

[0020] For a more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description of the invention along with the accompanying figures and in which:

[0021] Figure 1 is a flow chart of a method in accordance with one embodiment of the present invention;

[0022] Figure 2 is a diagram of a system in accordance with one embodiment of the present invention;

[0023] Figure 3 is a diagram of a hydraulic fracturing process;

[0024] Figure 4 is a diagram showing the placement of catalysts where the mixtures of propping agents and catalyst particles are pumped into the fractures through wells in accordance with one embodiment of the present invention;

[0025] Figure 5 is a diagram showing the pumping back of fracturing fluids in accordance with one embodiment of the present invention;

[0026] Figure 6 is a diagram showing syngas (e.g., hydrogen, CO, and other gases) generated in a shale reservoir by radiofrequency / microwave heating in the presences of hydrocarbons, water, and catalysts, and the generated hydrogen is produced from a horizontal well in accordance with one embodiment of the present invention;

[0027] Figure 7 is a diagram showing syngas is generated and flows upward under buoyancy in a conventional reservoir in which hydrogen is produced from both an upper side well and lower side well in accordance with one embodiment of the present invention;

[0028] Figure 8 is a diagram showing hydrogen or the mixture of hydrogen and methane is produced to surface with the help of a downhole hydrogen membrane separator in a shale reservoir in accordance with one embodiment of the present invention;

[0029] Figure 9 is a diagram showing hydrogen or the mixture of hydrogen and methane is produced to surface with the help of downhole hydrogen membrane separators installed on both the upper side well and the lower side well in a conventional reservoir in accordance with one embodiment of the present invention;

[0030] Figure 10 is a diagram showing a process to mitigate coke deposition and to re-activate catalysts by injecting water or steam in accordance with one embodiment of the present invention;

[0031] Figure 11 is a diagram showing the ultimate hydrogen purity in generated gases and the ultimate hydrogen generation selectivity, mb I g crude oil in accordance with one embodiment of the present invention;

[0032] Figure 12 is a diagram showing the percentage of generated gases in lab experiments in accordance with one embodiment of the present invention;

[0033] Table 1 shows the combinations of the materials used for hydrogen generation using microwave heating in lab experiments in accordance with one embodiment of the present invention;

[0034] Table 2 shows the mass change and gas production during lab experiments in accordance with one embodiment of the present invention;

[0035] Table 3 shows the compositions of generated gases in lab experiments in accordance with one embodiment of the present invention;

[0036] Figures 13A, 13B and 13C are diagrams of creating an artificial catalytic generator for in-situ hydrogen production from petroleum reservoirs via EM / RF -assisted heating for vertical wells, horizontal wells, and multilateral wells, respectively, in accordance with various embodiments of the present invention;

[0037] Figure 14 is a flowchart of a method of producing hydrogen from a petroleum reservoir in accordance with one embodiment of the present invention;

[0038] Figure 15 is a diagram showing the temperature profiles for different materials under EM heating, demonstrating SiC is an excellent heating material under EM irradiation in accordance with one embodiment of the present invention;

[0039] Figure 16 is a diagram showing the evident catalytic effect of iron-based artificial catalyst for methane cracking in accordance with one embodiment of the present invention;

[0040] Table 4 shows the combinations of the experimental results from lab-scale catalytic methane cracking, showing the highest methane conversion can reach 100% around 650-750°C in accordance with one embodiment of the present invention;

[0041] Figure 17 demonstrates the real-time gas concentration in the experimental process of methane cracking in the sample of 80% Sandstone, 15% SiC, and 5% Fe. It shows the composition of the syngas is mainly H2, minor CH4 and CO in accordance with one embodiment of the present invention;

[0042] Figure 18 illustrates the gas production generated from the carbon-containing samples in the presence of H2O, showing the hydrogen can be enhanced by coke-gasification in accordance with one embodiment of the present invention;

[0043] Figures 19A-19D illustrates the real-time gas production of carbon-containing samples saturated with two types of water (H2O and D2O) in accordance with one embodiment of the present invention: (19A) Generated gas flow rate vs. temperature using H2O, (19B) Cumulative gas production using H2O, (19C) Generated gas flow rate vs. temperature using D2O, and (19D) Cumulative gas production using D2O;

[0044] Figures 20A-20B illustrate different results between H2O and D2O in accordance with one embodiment of the present invention: (20A) Total volume of produced gases, and (20B) Total gas concentration;

[0045] Figures 21 A-21F illustrate sample characterizations at different stages during the experiments in accordance with one embodiment of the present invention: (21A) Raman spectrum, (21B) EDX results, (21C) SEM image of generated carbon, (21D-21E) TEM image of generated carbon, and (2 IF) XRD results;

[0046] Figures 22A-22C illustrate experimental results from CH4 conversion using the non-carbon sample saturated with 0.25 g of D2O in accordance with one embodiment of the present invention: (22A) Real-time flow rate of produced gases, (22B) Total gas production, and (22C) Real-time cumulative gas production;

[0047] Figures 23A-23D illustrate experimental results of CH4 conversion using the carbon-containing sample saturated with 0.25 g of D2O in accordance with one embodiment of the present invention: (23 A) Real-time flow rate of produced gases, (23B) Total gas production, (23C) Real-time cumulative gas production, and (23D) Contributions of different reactions to hydrogen production;

[0048] Figures 24A-24B illustrate hydrogen production from methane cracking under two scenarios in accordance with one embodiment of the present invention: (24 A) Sample without water treatment, and (24B) Sample after water treatment;

[0049] Figures 25A-25D illustrate simulation results of produced gases in the methane-water system at various temperatures in accordance with one embodiment of the present invention: (25A) 0% H2O + 100% CH4, (25B) 10% H2O + 90% CH4, (25C) 20% H2O + 80% CH4, and (25D) 50% H2O + 50% CH4;

[0050] Figures 26A-26B illustrate gas production under various water content in accordance with one embodiment of the present invention: (26A) T=950°C, and (26B) T=1000°C;

[0051] Figures 27A-27B illustrate reaction flux analysis based on H-atom at 1 atm and 950°C in accordance with one embodiment of the present invention: (27A) No water, and (27B) 10% water;

[0052] Figure 28 illustrates reaction sensitivity analysis towards H2 at 1 atm and 950°C in accordance with one embodiment of the present invention;

[0053] Figure 29 is a schematic depicting the process of in-situ hydrogen production from natural gas reservoirs in accordance with one embodiment of the present invention;

[0054] Table 5 shows the energy input data for the techno-economic analysis;

[0055] Figures 30A-30B illustrate real-time concentration of gases generated from CH4 in different catalytic conditions in accordance with one embodiment of the present invention: (30A) 80 wt.% Sandstone + 20 wt.% SiC, and (30B) 80 wt.% Sandstone + 15 wt.% SiC + 5 wt.% catalyst;

[0056] Figures 31A-31B illustrate the composition of gases produced from methane at different flow rates in accordance with one embodiment of the present invention: (31 A) Sandstone; (3 IB) Sandstone with catalyst;

[0057] Figure 32 illustrates cumulative hydrogen production under various conditions (e.g., different catalytic condition and different flow rate of methane) in accordance with one embodiment of the present invention;

[0058] Table 6 is a summary of the experimental results regarding energy analysis;

[0059] Figure 33 illustrates results of energy efficiency under various experimental conditions in accordance with one embodiment of the present invention:

[0060] Table 7 is the economic assumptions for the techno-economic analysis;

[0061] Table 8 is the design for four cases for the techno-economic analysis;

[0062] Table 9 is the hydrogen tax credit under Section 45 V of Inflation Reduction Act;

[0063] Figures 34A-34D illustrate the breakdown of levelized cost of hydrogen for different cases in accordance with one embodiment of the present invention: (34A) Case #1, (34B) Case #2, (34C) Case #3, and (34D) Case #4;

[0064] Figures 35A-35D illustrate the breakdown of capital expenditure (CapEx) for hydrogen costs across different cases in accordance with one embodiment of the present invention: (35A) Case #1, (35B) Case #2, (35C) Case #3, and (35D) Case #4;

[0065] Figure 36 illustrates GHG emissions comparison among different hydrogen production processes in accordance with one embodiment of the present invention;

[0066] Figure 37 illustrates GHG emissions under renewable energy mix to Texas grid electricity in accordance with one embodiment of the present invention;

[0067] Figure 38 illustrates GHG emissions at different EM -heating energy (100% Texas grid electricity) in accordance with one embodiment of the present invention;

[0068] Figures 39A-39B illustrate gas production from the decomposition of a 2.0-gram shale sample in accordance with one embodiment of the present invention: (39A) real-time flow rate of generated gases; and (39B) cumulative gas production;

[0069] Figures 40A-40B illustrated real-time gas production from the oil-only sample and the oilplus-water sample in accordance with one embodiment of the present invention: (40A) 0.2 grams of shale oil; and (40B) 0.2 grams of shale oil mixed with 0.2 grams of H2O;

[0070] Figure 41 illustrates total gas production from the oil-only sample and the oil-plus-water sample in accordance with one embodiment of the present invention;

[0071] Figures 42A-42B illustrate total gas concentrations from the oil-only sample and the oil-plus-water sample in accordance with one embodiment of the present invention: (42A) 0.2 grams of shale oil; and (42B) 0.2 grams of shale oil mixed with 0.2 grams of H2O;

[0072] Figures 43A-43B illustrate gas production from the OilHZhO sample in accordance with one embodiment of the present invention: (43 A) Key gases; and (43B) other carbonaceous gases;

[0073] Figure 44 illustrates total gas concentrations from the OH+D2O sample in accordance with one embodiment of the present invention

[0074] Figures 45A-45D illustrate TEM images of solid carbon generated from shale oil pyrolysis in accordance with one embodiment of the present invention;

[0075] Figures 46A-46D illustrate gas production from carbon-containing shale samples with water in accordance with one embodiment of the present invention: (46A) real-time gas flow rate from the sample saturated with 0.2 grams of H2O; (46B) real-time gas flow rate from the sample saturated with 0.3 grams of D2O; (46C) total gas concentrations for the H2O-saturated sample; and (46D) total gas concentrations for the D2O-saturated sample;

[0076] Figures 47A-47C illustrate characterization of the carbon-containing sample before and after reaction with water in accordance with one embodiment of the present invention: (47 A) SEM image of the carbon-containing sample; (47B) SEM image of the sample after reacting with water; and (47C) Raman spectra of the carbon-containing sample before (oil cracking sample) and after reaction with water (water spent sample);

[0077] Figures 48A-48D are SEM images of biochar particles at different magnifications;

[0078] Table 10 illustrates an experimental design in accordance with one embodiment of the present disclosure;

[0079] Figures 49A-49D illustrate temperature profiles and EM powers for various scenarios in accordance with one embodiment of the present disclosure: (49A) Pure sandstone; (49B) 90% Sandstone + 10% SiC; (49C) Pure biochar; and (49D) 90% Sandstone + 10% biochar;

[0080] Figures 50A-50B illustrate gas release during sample decomposition in accordance with one embodiment of the present disclosure: (50A) pure biochar; and (50B) 80% sandstone + 20% SiC;

[0081] Figures 51A-51B illustrate gas production and power consumption for four samples in accordance with one embodiment of the present disclosure: (51 A) cumulative gas production; and (5 IB) power usage in the experiments;

[0082] Figures 52A-52D illustrate experimental results of CFU-to-FE using different biochar dosage in accordance with one embodiment of the present disclosure: (52A) pure biochar; (52B) 85% sandstone + 15% biochar; (52C) 90% sandstone + 10% biochar; and (52D) 95% sandstone + 5% biochar;

[0083] Figures 53A-53D illustrate hydrogen production and input power for biochar samples with different particle sizes in accordance with one embodiment of the present disclosure: (53A-53C) realtime hydrogen concentration and cumulative hydrogen production; and (53D) input power for the samples;

[0084] Figures 54A-54D illustrate gas production in Scenario I and Scenario II in accordance with one embodiment of the present disclosure: (54A) cumulative gas yield from PB FLO; (54B cumulative gas yield from CCSB FLO; (54C) gas composition from PB FLO; and (54D) gas composition from CCSB FLO;

[0085] Figures 55A-55F illustrate a characterization of carbon in Scenario I and Scenario II in accordance with one embodiment of the present disclosure: (55A)-(55B) SEM images of pure biocharafter EM heating; (55C)-(55D) SEM images of carbon generated from methane cracking; (55E) Ramam spectrum of pure biochar (PB Fresh), pure biochar after EM heating (PB Spent), sandstonebiochar sample (SB Fresh), and sandstone-biochar sample after methane cracking (SB Spent or CCSB); (55F) Ramam spectrum of the samples after Scenario I (PB FLO) and Scenario II (CCSB H2O);

[0086] Figures 56A-56B illustrate gas production in Scenario III in accordance with one embodiment of the present disclosure: (56A) cumulative gas from CCSB D2O; and (56B) gas composition from CCSB D2O;

[0087] Figure 57 illustrate evolution of hydrogen production and temperature in biochar samples before and after reacting with water in accordance with one embodiment of the present disclosure; and

[0088] Figures 58A-58B are SEM images of biochar after reacting with water in accordance with one embodiment of the present disclosure.DETAILED DESCRIPTION OF THE INVENTION

[0089] While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention.

[0090] To facilitate the understanding of this invention, a number of terms are defined below. Terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention. Terms such as “a”, “an” and “the” are not intended to refer to only a singular entity but include the general class of which a specific example may be used for illustration. The terminology herein is used to describe specific embodiments of the invention, but their usage does not limit the invention, except as outlined in the claims.

[0091] Various methods are described below to provide an example of each claimed embodiment. They do not limit any claimed embodiment. Any claimed embodiment may cover methods that are different from those described above and below. The drawings and descriptions are for illustrative, rather than restrictive, purposes.

[0092] In this invention, the terms, expressions, and statements are used according to their ordinary meanings. The additional terms are defined in the following.

[0093] The term “petroleum reservoirs”, as used herein, is intended to be the petroleum formation composed of porous rock, water, oil, and / or gas at the certain depths below the surface. The reservoirs refer to, but are not limited to, conventional sandstone and carbonate reservoirs, heavy oil and bitumen reservoirs, shale oil and shale gas reservoirs, and oil shale reservoirs.

[0094] The terms “hydrocarbons”, “petroleum”, and “oil and gas”, as used herein, are used interchangeably. They refer to organic compounds composed of hydrogen, carbon, and other elements.

[0095] The terms “electromagnetic”, “electromagnetic / radio frequency”, “radio frequency / microwave”, and “radio frequency” are used interchangeably.

[0096] The term “catalyst particles” and “artificial catalyst particles”, as used herein, are intended to be, but are not limited to, metal -based catalytic particles containing iron (Fe), nickel (Ni), titanium (Ti), titanium oxide (TO), potassium (K), manganese (Mn). The metal-based catalytic particles are integrated into activated carbon (AC) or silicon carbide (SiC). In some embodiments, one or more support materials, such as AI2O3, SiO2, activated carbon, or Zeolites, are also integrated into the catalysts. In some embodiments, the catalysts with better electromagnetic / radio frequency absorbing capability are preferred, or the catalysts with lower economic cost are preferred, or a combination of both are preferred. The size of catalyst particles ranges from several nanometers to millimeters. The shape of catalysts includes, but is not limited to, tri-lobe, spherical, and agglomerated.

[0097] The term “syngas”, as used herein, refers to a fuel gas mixture generated at high temperature during and after electromagnetic / radio frequency heating in reservoirs. The syngas consists primarily of hydrogen, carbon monoxide, and a little carbon dioxide and hydrocarbon gas.

[0098] In-Situ Hydrogen Production

[0099] Various embodiments of the present invention generate and produce high-purity hydrogen directly from petroleum reservoirs using electromagnetic wave heating (e g., microwaves, etc.) in the presence of catalysts, which are delivered deeply into the reservoirs through adapting hydraulic fracturing processes. The whole process can happen in underground reservoirs, instead of at the surface facilities. It is for hydrogen generation and production, rather than for enhanced oil or gas recovery in traditional petroleum industry.

[0100] In one embodiment as shown in Figure 1, a method 100 generates hydrogen within a petroleum reservoir and produces the hydrogen. One or more wellbores into the petroleum reservoir from a surface are provided in 102, wherein the petroleum reservoir contains fractures by hydraulic fracturing. Catalyst particles are heated within the fractures of the petroleum reservoir using electromagnetic waves in block 104, wherein the heated catalyst particles generate a syngas from hydrocarbons within the petroleum reservoir. The hydrogen is separated from the syngas at the surface or within the one or more wellbores in block 106, and the hydrogen is produced at the surface or to the surface in block 108.

[0101] In one aspect, the one or more wellbores further include one or more horizontal wellbores. In another aspect, the one or more horizontal wellbores include one or more upper side wells and one or more lower side wells. In another aspect, the heating is performed using the one or more lower side wells, and the syngas is produced using the one or more upper side wells. In another aspect, one or more antennas are positioned within the petroleum reservoir, wherein the one or more antennas are connected to a power source at the surface, and the electromagnetic waves are generated using one or more antennas. In another aspect, the catalyst particles proximate to the one or more antennas are heated to a temperature of up to 1000°C, and a rock or hydrocarbons within the petroleum reservoir are heated to a temperature of about 100°C to up to 800°C. In another aspect, the electromagnetic waves are continuous, pulsed, intermittent, time dependent or time independent. In another aspect, the catalyst particles are heated for a time period of hours, days, seasons or years. In another aspect, the electromagnetic waves have a frequency from about 100 Hz to about 100 GHz. In another aspect, the frequency is adjusted according to saturations of water, oil and gas in the hydrocarbon reservoir. In another aspect, the syngas includes the hydrogen, methane, carbon monoxide, carbon dioxide, and other light hydrocarbons (e.g., C2 to C4). In another aspect, the method further includes separating the mixture of the hydrogen and the methane from the syngas using membrane separators and co-transporting the mixture of the hydrogen and the methane using natural gas pipeline. In another aspect, carbon byproducts (e.g., CO2 and CO) are injected or sequestered in the petroleum reservoir. In another aspect, the catalyst particles include iron catalysts, nickel catalysts, or titanium oxide (TO), a size of the catalyst particles ranges from nanometers to millimeters, or a shape of catalysts includes tri-lobe, spherical, or agglomerated. In another aspect, the catalyst particles are injected into the fractures within the petroleum reservoir in a continuous, pulsed, or slug manner. In another aspect, the catalyst particles are contained within a polymer fluid. In another aspect, the catalyst particles are injected at a pressure greater than a fracturing pressure of the petroleumreservoir. In another aspect, a buffer fluid is injected into the petroleum reservoir. In another aspect, support materials or propping agents are also injected into the fractures. In another aspect, the support materials include activated carbon (AC) or silicon carbide (SiC). In another aspect, a ratio of the proppant agents to the catalyst particles includes a range of about 0 to 100%. In another aspect, steam or water is injected into the hydrocarbon reservoir to re-generate the catalyst particles in-situ by removing coke deposited on a surface of the catalysts or in the fractures. In another aspect, the fractures within the petroleum reservoir are created using hydraulic fracturing. In another aspect, the petroleum reservoir is re-fractured, and the catalyst particles are replaced in the petroleum reservoir.

[0102] In another embodiment as shown in Figure 2, a system 200 for generating hydrogen within a petroleum reservoir 202 and producing the hydrogen includes one or more wellbores 204 into the petroleum reservoir 202 from a surface 206, wherein the petroleum reservoir 202 contains fractures 208 by hydraulic fracturing, a power source at the surface 206, one or more antennas 210 within the petroleum reservoir 202 and connected to the power source, catalyst particles 212 within the fractures of the petroleum reservoir 202, and one or more hydrogen separators located within the one or more wellbores 204 or at the surface 206. The one or more antennas 210 generate electromagnetic waves (radiation) 214 creating a heating zone 215 that heats the catalyst particles 212, which generate a syngas 216 from hydrocarbons within the petroleum reservoir 202. The one or more hydrogen separators separate the hydrogen from the syngas 216.

[0103] In one aspect, the one or more wellbores further include one or more horizontal wellbores. In another aspect, the one or more horizontal wellbores include one or more upper side wells and one or more lower side wells. In another aspect, the heating is performed using the one or more lower side wells, and the syngas is produced using the one or more upper side wells. In another aspect, the catalyst particles proximate to the one or more antennas are heated to a temperature of up to 1000°C, and a rock or hydrocarbons within the petroleum reservoir are heated to a temperature of about 100°C to up to 800°C. In another aspect, the electromagnetic waves are continuous, pulsed, intermittent, time dependent or time independent. In another aspect, the catalyst particles are heated for a time period of hours, days, seasons or years. In another aspect, the electromagnetic waves have a frequency from about 100 Hz to about 100 GHz. In another aspect, the frequency is adjusted according to saturations of water, oil and gas in the hydrocarbon reservoir. In another aspect, the syngas includes the hydrogen, methane, carbon monoxide, carbon dioxide, and other light hydrocarbons (e.g., C2 to C4). In another aspect, the one or more hydrogen separators include one or more membrane separators, and a natural gas pipeline is coupled to the one or more wellbores or theone or more membrane separators at the surface that co-transport the mixture of the hydrogen and the methane. In another aspect, CO2 is injected or sequestered in the petroleum reservoir. In another aspect, the catalyst particles include iron catalysts, nickel catalysts, or titanium oxide (TO). A size of the catalyst particles ranges from nanometers to millimeters, or a shape of catalysts includes tri-lobe, spherical, or agglomerated. In another aspect, the catalyst particles are injected into the fractures within the petroleum reservoir in a continuous, pulsed, or slug manner. In another aspect, the catalyst particles are contained within a polymer fluid. In another aspect, the catalyst particles are injected at a pressure greater than a fracturing pressure of the petroleum reservoir. In another aspect, a buffer fluid is injected into the petroleum reservoir. In another aspect, support materials or propping agents are also injected into the fractures. In another aspect, the support materials include activated carbon (AC) or silicon carbide (SiC). In another aspect, a ratio of the proppant agents to the catalyst particles includes a range of about 0 to 100%. In another aspect, steam or water is injected into the hydrocarbon reservoir to regenerate the catalyst particles in-situ by removing coke deposited on a surface of the catalysts or in the fractures. In another aspect, the fractures within the petroleum reservoir are created using hydraulic fracturing. In another aspect, the petroleum reservoir is refractured and the catalyst particles in the petroleum reservoir are replaced.

[0104] As described above and further explained below, the method relates to generation and production of hydrogen from subsurface petroleum reservoirs using radiofrequency / microwave heating. The integration of hydraulic fracturing in this method allows the creation of fractures and fracture networks in petroleum reservoirs so that the catalyst particles and support materials in different sizes can be placed in both large and small fractures. The radiofrequency / microwave then directly deliver energy to these materials and locally heat them to very high temperatures (i.e., up to 1000°C on catalyst particle surface). These materials, as well as water, preferentially absorb microwaves such that the reservoir rock and hydrocarbon can be heated to a high temperature ranging from about 100°C to up to 800°C, depending on the distance from microwave antenna along the well and the distance from catalyst particles. Several reactions happen on the catalyst surface and rock pores in reservoirs at different temperatures including:Hydrocarbon thermal cracking: CxHy-> x C + y / 2 H2Coke- water reaction: C + H2O - CO + H2Water-gas-shift reaction: CO + H2O CO2 + H2

[0105] The hydrogen and syngas are therefore generated. To produce high-value hydrogen, the gas mixtures are pumped to surface, separated, and then the by-produced carbon oxides are injected into the reservoirs. Another way is to use a downhole hydrogen membrane separator that only allows hydrogen to pass through and then produce out, while all other gases, including CO2, will be simultaneously sequestrated in reservoirs.

[0106] Referring to Figure 3, a schematic diagram of the stage one which is a traditional hydraulic fracturing process where a single horizonal well 302 is used in a target reservoir 202 in accordance with one embodiment of the present invention is shown. Hydraulic fluids 304 are pumped into the lower well 306, which is open. When the pressure is above the fracturing pressure, the fractures 208 are created with both large and small fractures in an oil and gas formation 202. The oil and gas saturate the fractures 208 and matrix. In some embodiments, acid fluids are injected to create larger fractures for pumping more catalysts for in-situ hydrogen generation.

[0107] Turning to Figure 4, a schematic of stage two for pumping mixtures of catalyst particles, support materials, and proppant in accordance with one embodiment of the present invention is shown. The downhole pressure is higher than the pressure of the target oil and gas formation so that the mixtures and fluids 402 will flow into the target formation under pressure gradient. Different sizes of proppants and / or catalyst particles 404 are used ranging from nanometers to millimeters. Larger catalysts particles act as both microwave absorbers and propping agents. Smaller catalyst particles (e g., diameters below 100 micrometers or even several nanometers) can be transported into smaller fractures in deeper formation.

[0108] In some embodiments, the mixtures of catalyst particles, support materials, and propping agents are pumped at a constant rate so that the mixtures continuously flow to the deeper oil and gas formation under pressure gradient.

[0109] In some embodiments, the mixtures of catalyst particles, support materials, and propping agents are pumped in a pulsed manner with an alternating high and low injection pressure and / or injection rate. This is favorable for pushing catalyst particles into deeper target formation.

[0110] In some embodiments, the pumping pressure is above the fracturing pressure so that new fractures are created, and more catalyst particles are placed into these fractures.

[0111] In some embodiments, a slug of mixtures of catalyst particles, support materials, and propping agents is injected, followed by cheap buffer fluids. This allows to push the mixtures into adeeper target formation and reduce the amount of usage of catalysts, support materials, and propping agents.

[0112] In some embodiments, polymers are used as fluids to more efficiently carry the mixtures of catalyst particles, support materials, and propping agents into deeper target formation.

[0113] In other embodiments, the ratio of proppant / catalyst ratio is varied to achieve better heating effects and save the usage of catalyst.

[0114] In stage two shown in Figure 4, using different pumping schemes is helpful for more catalyst particles placed into the fractures in deeper formation and the reduction of the costs.

[0115] Referring now to Figure 5, a schematic of stage 3 for pumping back the hydraulic fluids 502 in accordance with one embodiment of the present invention is shown. When downhole pressure is less than the pressure of target formation, the hydraulic fluids 502 flow back to wellbore under pressure gradient. The catalyst particles, support materials, and propping agents stay in the fractures in the fluid pumping back stage.

[0116] Figures 6 to 9 depict different scenarios for stage four.

[0117] Turning to Figure 6, a schematic for scenario one for low permeability reservoirs 602, including but not limited to shale oil reservoir, shale gas reservoirs, and tight sandstone reservoirs in accordance with one embodiment of the present invention is shown. The permeability of such reservoir matrix is typically lower than 0.1 mD. The radiofrequency / microwave heating is started through the antenna 210, which is connected to surface electrical cables (not shown). The strong radiofrequency / microwave absorbing materials are preferentially heated such as the iron catalyst particles 212 and water. Note the iron catalyst particles 212 can be heated to superhot spot with temperatures up to 1000°C within a certain distance from the wellbore. Hydrogen and syngas are generated under such high pressure within reservoirs 602 through the hydrocarbon thermal cracking, coke-water reaction, and water-gas-shift reaction. Because of the very low permeability of the matrix and the very high permeability of fracture network, most gases flow to the wellbore under pressure gradient. The amount of gases flowing upward due to buoyancy is negligible. Hydrogen and syngas 216 are then produced to surface. The CO2 in the syngas can be separated and then re-injected to reservoirs for CO2 sequestration.

[0118] In some embodiments, the radiofrequency / microwave heating is continuous and will last for months to years until the oil and / or gas flowing to wellbore is too slow and not economic.

[0119] In some embodiments, the radiofrequency / microwave heating is in a pulsed manner with many heating / no-heating periods or in an intermittent way. The length of a period can be one day, several days, or a season. The electricity for such radiofrequency / microwave heating is from peak-time electricity from renewable energy such as wind and solar energy which is out of the delivery capability of the grid.

[0120] In some embodiments, the electromagnetic waves create microfractures in matrix which can increase the permeability of matrix near the well, thus favorable for hydrogen and syngas flowing to wells.

[0121] In some embodiments, the electromagnetic frequency is adjusted by changing the settings at the surface according to the saturations of water, oil, and gas in a target formation. This allows the electromagnetic waves to penetrate and heat larger volume of formation for hydrogen generation.

[0122] In some embodiments, the downhole gas / liquid separator is used in the wellbore so that only hydrogen and / or syngas is produced, while the liquids such as water and oil remain in the target formation.

[0123] In some cases, there is solid coke deposition in matrix, fractures, and catalyst surface. They can deactivate catalysts. But the in-situ coke-water reaction can regenerate the catalysts. Another approach is to inject water or steam through the well to regenerate catalyst.

[0124] In some embodiments, under the high temperature by radiofrequency / microwave heating, the natural catalysts in rocks can enhance the hydrocarbon thermal cracking, coke-water reaction, and water-gas-shift reaction and generate more hydrogen.

[0125] In some cases, more of the water in reactions are from reservoir brine. Some hydrogen is also generated from water because of the water-gas-shift reaction.

[0126] Referring now to Figure 7, a schematic for stage four scenario two for hydrogen generation from high-permeable reservoirs 702, including but not limited to, conventional oil and gas reservoirs, and sandstone and carbonate reservoirs in accordance with one embodiment of the present invention is shown. One upper side well 704 and one lower side well 706 are drilled with the same wellhead, but the hydraulic fracturing and radiofrequency / microwave heating are with the lower side well 706. Technically, the upper side well 704 and the lower side well 706 are still one well as they are using the same wellhead at surface. Because of both buoyancy and the higher vertical permeabilityeffects, the generated hydrogen and other gases 216 flow upward and are produced from both upper side well 704 and lower side well 706. The heavier oil and water in target formation will flow downward because of gravity and pressure gradient. Once produced, the hydrogen is separated from syngas at surface. The carbon oxides in separated gas are then reinjected into reservoir for carbon sequestration.

[0127] In some embodiments, the vertical distance between the upper side well and lower side wells varies from 5 meters to the formation thickness.

[0128] In some embodiments, the radiofrequency / microwave heating is either continuous, or pulsed, or intermittent, depending on the electricity from grid.

[0129] In some embodiments, the gas production rate and / or wellhead pressure is controlled so that the fluid flow rate from the formation to wellbore is consistent with the generation rate of hydrogen within the formation.

[0130] In some embodiments, the downhole controlling device is used in both the upper side well and lower side well to separately control fluid flow rate from the target formation to wellbore, according to the amount of hydrogen generated by the lower side well and the hydrogen accumulation near the upper side well.

[0131] In other embodiments, the upper side well may be closed to allow oil and water at the upper location of the target formation to flow downward to near lower side well under gravity. This provides more feedstock, i.e., oil and water, for hydrogen generation.

[0132] Figure 8 is a schematic of scenario three for the hydrogen generation and production with the assistance of downhole hydrogen membrane separator 802 in unconventional or low-permeable oil and gas reservoirs 804 in accordance with one embodiment of the present invention. Different with Figure 4, the downhole hydrogen membrane separator 802 only allows small-molecular hydrogen to pass through so that only hydrogen is produced to surface while all other gases remain in reservoirs. In some embodiments, the downhole hydrogen membrane separator 802 allows a mixture of hydrogen and methane to pass through. Thus, pure hydrogen or a mixture of hydrogen and methane can be produces 806.

[0133] Turning to Figure 9, a schematic of scenario four for the hydrogen generation and production with the assistance of downhole hydrogen membrane separators 802 in conventional or high-permeable oil and gas reservoirs 902 in accordance with one embodiment of the presentinvention is shown. The separators 802 are installed in both upper side well 704 and lower side well 706 so that high-purity hydrogen is produced simultaneously. In some embodiments, the downhole hydrogen membrane separator 802 allows a mixture of hydrogen and methane to pass through. Thus, pure hydrogen or a mixture of hydrogen and methane can be produces 806.

[0134] In some cases, a large number of solid coke 1002 is generated from hydrocarbon thermal cracking but cannot be removed by the coke-water reaction. The solid coke 1002 may deposit in surfaces of both fractures and catalysts, as shown in Figure 10. The solid coke 1002 deposition can reduce the permeability of the target formation, thus reducing hydrogen transport from deeper formation to wellbore. Coke deposition on catalyst surface can also de-activate catalysts. Eventually, the hydrogen generation may stop. So, stage five is to re-generate catalysts in-situ and remove solid coke in formation, either steam or water 1004 is injected through the well. With the high temperature in reservoirs and radiofrequency / microwave heating 1006, the coke can react with water in liquid and gas forms. Then, the permeability of target formation and the catalyst activation are recovered. One advantage is that the injected water or steam can react with coke and generate more hydrogen and syngas. Although oxygen was used to re-generate activation of catalyst at surface, it is not recommended because of the high possibility of explosion when oxygen contacts with the remaining hydrogen in the wellbore or target formation.

[0135] Stages four and five can be repeated for many cycles until the catalysts cannot be regenerated or the re-generated catalysts have low activation in formation. Stage six is for a repeated process from stages one to five (Figures 3 to 10). In this stage, the target formation is re-fractured and new catalyst particles, support materials, and propping agents are placed in the fracture network. The radiofrequency / microwave heating is again used for in-situ hydrogen generation in target formation for different scenarios. This process can also be repeated until the hydrogen generation is too low or not economic.

[0136] Examples

[0137] The field pilot test using this invention is costly and impossible at the current stage in actual reservoir formation. However, the inventors validate this invention through lab experiments. Seven experiments were conducted in a 1.13 cm3reactor with different combinations of catalysts, rock powders, crude oil, and water, as shown in Table 1.

[0138] The 5% Fe means there is 5% weight percentage of Fe catalysts in the mixture of Fe catalysts and support materials such as activated carbon (AC) and silicon carbide (SiC). The catalystused herein is iron particles with diameters about 100 nm. The AC is a very good MW adsorber which favors quick heating in experiments. The SiC has excellent dielectric and mechanical thermal properties.

[0139] The 2.45 GHz frequency and 750 W power were used for microwave heating.

[0140] An infrared (IR) pyrometer was used to measure the temperature and accurately control the power of microwave generator.

[0141] The microwave heating process usually lasted for 10 to 40 minutes depending on the amount of feedstock in the reactor.

[0142] Table 2 lists the relevant metrics to evaluate hydrogen generation selectivity and hydrogen purity.

[0143] Figure 11 shows the comparison of two metrics (ultimate H2 generation selectivity and H2 purity) for all seven experiments in accordance with one embodiment of the present invention. The hydrogen generation efficiencies show a wide range (157.63-441.43 mb H2 / g crude oil). The high purities of hydrogen generated are noteworthy, and they are around 45.81-63.49%. In contrast, the highest CO2 content is negligible (i.e., less than 1%).

[0144] Table 3 shows the evolution of the compositions of gas streams, including H2, CH4, CO, CO2, C2H4, and other intermediate components C2-C5 (i.e., the sum of C2H6, C3H6, C3H8, C4H8, C4H10, and C5). Some gas samples were measured twice.

[0145] Figure 12 shows the comparison of the compositions for selected gas components at the (a) early and (b) late period in accordance with one embodiment of the present invention. Generally, the fraction of produced gas follows the ranking: H2 > CO > CH4 > C2H4 > C2-C5 > CO2. H2 constitutes the largest volume fraction, and the ranges for all the tests are around 45.8-66.5% (Table 3), whereas CO2 constitutes the smallest volume fraction (less than 1%). This is favorable to the mitigation of carbon emissions as one advantage of this microwave-initiated hydrogenation process. Overall, the H2 fraction is the highest in all experiments at both the early and late periods of the tests.

[0146] Other embodiments

[0147] According to some embodiments, a method of generating and producing hydrogen from petroleum reservoirs is provided. The method includes conducting hydraulic fracturing through a horizontal well in an oil and gas formation; pumping the mixture of proppant and catalyst particlesinto fractures; pumping back the hydraulic fluids while leaving catalysts in reservoirs; heating the reservoirs using radiofrequency / microwave to generate syngas (e.g., hydrogen and other gases) within reservoirs; producing syngas through a single horizontal well from low-permeable unconventional reservoir or through both upper side well and lower side well from high-permeable conventional reservoirs; and / or installing downhole hydrogen membrane separator and only produce hydrogen through either the single well from shale reservoirs or two horizontal wells (e.g., lower side well and upper side well) from conventional reservoirs; injecting water or steam to re-generate the catalysts in-situ and resume formation permeability; restarting radiofrequency / microwave heating to generate and produce hydrogen; and re-fracturing formation and placing new catalysts for hydrogen generation.

[0148] According to some embodiments, the method includes integrating radiofrequency / microwave heating with hydraulic fracturing within petroleum reservoirs to create high permeable fractures to create a suitable environment for generating and producing hydrogen.

[0149] According to some embodiments, the method includes placing catalysts in different size (i.e., diameter from nanometer to millimeter) in large and microfractures to promote heating effects by the radiofrequency / microwave absorbers, i.e., the catalysts and / or reservoir fluids such as water, and to create high enough temperature near the wells in reservoirs.

[0150] According to some embodiments, the method includes heating the catalyst surface to a temperature up to 1000°C in a certain distance near the microwave antenna.

[0151] According to some embodiments, the method includes heating the reservoir formation to a temperature from 100°C to up to 800°C in a certain distance near the microwave antenna.

[0152] According to some embodiments, the method includes enhancing hydrogen generation and yield through the superhot catalyst particles and catalytic effects in hydrocarbon thermal cracking, coke-water reaction, and water-gas-shift reaction within reservoirs.

[0153] According to some embodiments, the method includes creating highly permeable fractures for generated hydrogen flowing from reservoirs to wellbores.

[0154] According to some embodiments, the method includes providing flexible ways to produce syngas with surface separation and only hydrogen by hydrogen membrane separators.

[0155] According to some embodiments, the method includes providing flexible ways to produce hydrogen and / or syngas from either a single horizonal well or a well design with an upper side well and a lower side well according to reservoir permeabilities and fluid flow performance.

[0156] According to some embodiments, the method includes injecting steam or water to regenerate catalysts in situ by removing deposited coke on catalyst surface.

[0157] According to some embodiments, the method includes injecting steam or water to remove deposited coke in fractures and resume permeability of fractures.

[0158] According to some embodiments, the method includes re-fracturing and re-placing catalysts in reservoirs to enhance hydrogen generation.

[0159] According to some embodiments, the method includes using a wide range of electromagnetic frequency ranging from less than 100 Hz to above 100 GHz for heating and hydrogen generation.

[0160] According to some embodiments, the method includes adjusting the electromagnetic frequency according to the time-varying water and oil and gas saturation in reservoirs in order to penetrate deeper reservoirs and heat larger area / volume.

[0161] According to some embodiments, the method includes using electricity generated by fossil fuels.

[0162] According to some embodiments, the method includes using peak electricity from renewable energy such as wind and solar energy for radiofrequency / microwave heating during the hydrogen generation process.

[0163] According to some embodiments, the method includes applying this method in various petroleum reservoirs including conventional reservoirs, heavy oil and bitumen reservoirs, shale oil and shale gas reservoirs, oil shale reservoirs and so on.

[0164] According to some embodiments, the method includes applying this method in both new, in-production, and depleted / abandoned petroleum reservoirs.

[0165] In-Situ Artificial Catalytic Generator

[0166] An in-situ artificial catalytic generator produces hydrogen from petroleum reservoirs via electromagnetic (EM) or radio frequency (RF) assisted heating. The method includes manufacturing an artificial porous catalytic generator by integrating specific metal-based artificial catalysts into silicon carbide (SiC) particles within a hydrogen generation zone under EM / RF irradiation. In some embodiments, support materials are also integrated into the SiC particles. When the artificial catalytic generator is installed between the reservoir formation and the EM / RF antenna,high concentrations of hydrogen can be generated from hydrocarbon’s pyrolysis and cracking and hydrocarbon-water reactions when the petroleum flows towards wellbore. With the assistance of downhole hydrogen membrane separators and production packers, pure hydrogen can be extracted to the surface and the other undesired by-product gases can be stored in the targeted sequestration formations. The low-cost, clean hydrogen via in-situ EM / RF-assisted catalytic heating leverages the abundant petroleum resources in reservoirs, existing oilfield infrastructure, and inexpensive off-peak electricity from renewable energy (i.e., wind and solar).

[0167] Specifically, an electromagnetic wave generator, such as a dipole antenna comprised of standard oil-field tubulars, is installed in situ to deliver EM / RF energy into the surrounding formation. Once the surrounding zone is heated to a required temperature, hydrogen will be produced by hydrocarbon cracking and hydrocarbon-water reactions under the catalysis of natural rocks or artificial catalysts, during the process of oil and gas flowing through the heated zone. Then with the assistance of production packers and downhole hydrogen membrane separators, pure hydrogen will be extracted to surface while all other byproducts, such as CO, CO2, carbonaceous gases, etc., remain in the reservoir. This distinct approach is therefore carbon-zero.

[0168] However, the efficiency of the above mentioned approach depends on the capabilities of reservoir rocks for absorbing EM / RF energy. Therefore, the following embodiments provide a new method of building a robust artificial catalytic zone via the utilization of materials that can easily absorb EM / RF energy and be heated, such as silicon carbide particles and artificial catalysts nanopowder. The targeted artificial catalytic generator is therefore directly heated instead of heating the rock formation. The materials inside this artificial catalytic generator collectively contribute to a low-cost and high-efficient artificial catalytic media. This artificial media is installed in a downhole wellbore to act as a generation zone or generator in the process described below. Employing this method can significantly improve both the EM / RF heating efficiency and catalytic effect, substantially reducing the cost of in-situ hydrogen production from oil and gas reservoirs.

[0169] As previously described, the following methods relate to a highly efficient technology of hydrogen production from subsurface petroleum reservoirs using an artificial catalytic generator by EM / RF-assisted heating. The integration of artificial catalysts, support materials and silicon carbide enable the establishment of a robust purpose-built hydrogen generation zone. Therefore, the targeted artificial catalytic generator can be directly heated instead of heating the rock formation. The EM / RF wave then directly deliver energy to these materials and locally heat them to requiredtemperatures (i.e., 250-1000°C) of hydrocarbon cracking for hydrogen production. The materials inside this artificial catalytic generator collectively contribute to a low-cost, low-carbon and high-efficient approach for in-situ hydrogen production. The main hydrogen generation is contributed by the hydrocarbon pyrolysis and cracking:1) long-chain hydrocarbon short-chain hydrocarbon + H2; and2) short-chain hydrocarbon - solid carbon + H2.Another significant contribution of hydrogen may be provided by the coke gasification reaction (C + H2O CO + H2) initiated by the deposited solid coke or carbon and the presence of the formation water. By this reaction, more hydrogen is produced, and solid carbon can be removed from the surface of the artificial catalytic generator. Then, the permeability of the artificial catalytic generator and the catalyst activation are resumed. In addition, water-gas-shift reaction (CO + H2OCO2 + H2) may also involve in the process.

[0170] Now turning to Figures 13A-13C, schematic diagrams of applying an artificial catalytic generator in either vertical well 1300, horizontal well 1340 or multilateral well 1380 in petroleum reservoirs for in-situ hydrogen production in accordance with various embodiments of the present invention are shown. The system for generating hydrogen within a petroleum reservoir 1302 (e.g., conventional or unconventional oil and gas formation) includes one or more wellbores 1304 into the petroleum reservoir 1302, a power source 1306 (e.g., renewable energy, etc.) at a surface above the petroleum reservoir 1302, and a porous configuration of catalyst particles 1308 (e.g., artificial catalytic generator) within the one or more wellbores 1304, one or more electromagnetic wave generators 1310 (e.g., EM / RF antenna) within the one or more wellbores 1304 and connected to the power source 1306. The porous configuration of catalyst particles 1308 may include support materials, which may include adhesive substances (e.g., AI2O3, SiCh, clay material, etc.), or energy enhancers (e.g., silicon carbide, biochar, activated carbon, Zeolites, etc.), or both. The one or more electromagnetic wave generators 1310 heat the catalyst particles 1308 such that hydrocarbons passing through or near the porous configuration of catalyst particles 1308 react with the heated catalyst particles 1308 and generate syngas. The porous configuration of catalyst particles 1308 is disposed only within the one or more wellbores 1304 proximate to the one or more electromagnetic wave generators 1310. Note that the hydrogen can be a mixture of hydrogen and methane. The syngas may include hydrogen along with carbon monoxide, carbon dioxide, and other light hydrocarbons. One or more hydrogen separators 1312 (e.g., downhole H2 membrane separators) located within the one ormore wellbores 1304 separate and extract the hydrogen from the syngas. Alternatively, the hydrogen separators are located on the surface in the H2 recovery facilities 1314. Carbon oxides from the one or more wellbores 1304 can be injected into a sequestration formation 1316 using one or more production packers 1318 and perforations 1320 in the well. In some embodiments, the injection of the carbon oxides into the sequestration formation 1316 is improved using surface compressors or downhole pumps. The syngas can also be injected into the sequestration formation after the hydrogen is removed.

[0171] In one aspect, the porous configuration of catalyst particles 1308 include metal -based catalytic particles integrated into silicon carbide particles. In another aspect, the silicon carbide particles include beta-phase (P-phase) silicon carbide particles. In another aspect, the metal-based catalytic particles contain Fe, Ti, K, Mn, Ni, Co, or a combination thereof. Note that any efficient metals with strong catalytic abilities can be used. In another aspect, a weight percentage of metalbased catalytic particles is between 0.1% and 50% of a total weight of the porous configuration of catalyst particles 1308. In another aspect, a size of the metal-based catalytic particles is less than or equal to 500 nanometers, or a shape of metal-based catalytic particles includes tri-lobe, spherical, or agglomerated. In another aspect, the porous configuration of catalyst particles 1308 has a permeability of 0.01 to 100 Darcys. In another aspect, the porous configuration of catalyst particles 1308 is a substantially annular cylinder having an inner diameter larger than the outer diameter of the one or more electromagnetic wave generators 1310 and an outer diameter smaller than the diameter of the one or more wellbores 1304. In another aspect, one or more support materials are also integrated into the silicon carbide particles. In another aspect, the one or more support materials include AI2O3, SiC>2, activated carbon, or Zeolites. In another aspect, a ratio of the one or more support materials to the silicon carbide particles is varied to: increase a material strength of the porous configuration of catalyst particles 1308, adjust a permeability of the porous configuration of catalyst particles 1308, or reduce a cost of the porous configuration of catalyst particles 1308. In another aspect, a size of the one or more support materials and the silicon carbide particles is less than or equal to 100 micrometers. In another aspect, the metal-based catalytic particles are coated or doped on the one or more support materials and the silicon carbide particles.

[0172] In another aspect, the porous configuration of catalyst particles 1308 is embedded to an outside of the one or more electromagnetic wave generators 1310. In another aspect, the porous configuration of catalyst particles 1308 has a substantially similar length as the one or more electromagnetic wave generators 1310. In another aspect, a thickness of the porous configuration ofcatalyst particles 1308 varies according to a size of the one or more electromagnetic wave generators 1310 and the one or more wellbores 1304. In another aspect, the catalyst particles are heated to a temperature range of 250 to 1000°C, and the catalyst particles are heated for a time period of hours, days, seasons or years. In another aspect, electromagnetic waves generated by the one or more electromagnetic wave generators 1310 are continuous, pulsed, intermittent, time dependent or time independent. In another aspect, a frequency of the one or more electromagnetic wave generators 1310 is adjusted to optimize a heating efficiency of the catalyst particles or the generation of the hydrogen. In another aspect, the power source 1306 includes off-peak electricity from one or more renewable energy sources. In another aspect, carbon deposited on the catalyst particles is removed and the catalyst particles are regenerated in-situ using water or steam. In another aspect, the water is preexisting within the petroleum reservoir 1302 or injected into the one or more wellbores 1304, or the steam is injected into the one or more wellbores 1304.

[0173] In another aspect, water is injected into the one or more wellbores 1304 to increase a production and a purity of the hydrogen. In another aspect, the water is injected into the one or more wellbores 1304 to have an approximate ratio of one to one with the hydrocarbons within the one or more wellbores 1304 or proximate to the porous configuration of catalyst particles 1308 or proximate to the one or more electromagnetic wave generators 1310. In another aspect, the injected water approximately doubles the production of the hydrogen and increases the purity of the hydrogen to approximately 50% or more. In another aspect, the porous configuration of catalyst particles further comprises biochar, or the biochar is in injected into the one or more wellbores. In another aspect, the biochar comprises approximately 5 to 10 wt% of the catalyst particles. In another aspect, a particle size of the biochar comprises approximately 38-100 [im. In another aspect, the system provides a carbon negative process.

[0174] Turning now to Figure 14, a method 1400 of producing hydrogen from a petroleum reservoir in accordance with one embodiment of the present invention is shown. The method 1400 of producing hydrogen from a petroleum reservoir includes providing a porous configuration of catalyst particles disposed between one or more electromagnetic wave generators and the one or more wellbores in the petroleum reservoir in block 1402. The catalyst particles are heated using one or more electromagnetic wave generators in block 1404 such that hydrocarbons passing through or near the porous configuration of catalyst particles react with the heated catalyst particles and generate a syngas. The porous configuration of catalyst particles is disposed only within the one or morewellbores proximate to the one or more electromagnetic wave generators. The hydrogen is separated and extracted from the syngas at the surface or within the one or more wellbores in block 1406.

[0175] In one aspect, the porous configuration of catalyst particles includes metal-based catalytic particles integrated into silicon carbide particles. In another aspect, the silicon carbide particles include beta-phase (P-phase) silicon carbide particles. In another aspect, the metal-based catalytic particles contain Fe, Ti, K, Mn, Ni, Co, or a combination thereof. Note that any efficient metals with strong catalytic abilities can be used. In another aspect, a weight percentage of metalbased catalytic particles is between 0.1% and 50% of a total weight of the porous configuration of catalyst particles. In another aspect, a size of the metal-based catalytic particles is less than or equal to 500 nanometers, or a shape of metal-based catalytic particles includes tri-lobe, spherical, or agglomerated. In another aspect, the method further includes manufacturing the porous configuration of catalyst particles by: integrating the metal-based catalytic particles into the silicon carbide particles, customizing a permeability of the porous configuration of catalyst particles to be 0.01 to 100 Darcy s, and configuring the catalyst particles into a substantially annular cylinder having an inner diameter larger than the outer diameter of the one or more electromagnetic wave generators and an outer diameter smaller than the diameter of the one or more wellbores. In another aspect, one or more support materials are also integrated into the silicon carbide particles. In another aspect, the one or more support materials include AI2O3, SiCh, activated carbon or Zeolites. In another aspect, the method further includes varying a ratio of the one or more support materials to the silicon carbide particles to: increase a material strength of the porous configuration of catalyst particles, adjust a permeability of the porous configuration of catalyst particles, or reduce a cost of the porous configuration of catalyst particles. In another aspect, a size of the one or more support materials and the silicon carbide particles is less than or equal to 100 micrometers. In another aspect, the method further includes coating or doping the metal-based catalytic particles on the one or more support materials and the silicon carbide particles.

[0176] In another aspect, the one or more wellbores include one or more vertical wellbores, one or more horizontal wellbores, one or more multilateral wellbores, or a combination thereof, the petroleum reservoir includes a conventional, an unconventional, a new, a depleted or an abandoned oil and gas reservoir, or the syngas includes the hydrogen, methane, carbon monoxide, carbon dioxide, and other light hydrocarbons. In another aspect, wherein providing the porous configuration of catalyst particles includes embedding the porous configuration of catalyst particles to an outside of the one or more electromagnetic wave generators. In another aspect, the porous configuration ofcatalyst particles comprises an annular cylinder having an inner diameter larger than an outer diameter of the one or more electromagnetic wave generators and an outer diameter smaller than an inner diameter of the one or more wellbores. In another aspect, the porous configuration of catalyst particles has a substantially similar length as the one or more electromagnetic wave generators. In another aspect, a thickness of the porous configuration of catalyst particles varies according to a size of the one or more electromagnetic wave generators and the one or more wellbores. In another aspect, the catalyst particles are heated to a temperature range of 250 to 1000°C, and the catalyst particles are heated for a time period of hours, days, seasons or years. In another aspect, the electromagnetic waves generated by the one or more electromagnetic wave generators are continuous, pulsed, intermittent, time dependent or time independent. In another aspect, the method further includes adjusting a frequency of the one or more electromagnetic wave generators to optimize a heating efficiency of the catalyst particles or the generation of the hydrogen. In another aspect, the method further includes using off-peak electricity from one or more renewable energy sources to power the one or more electromagnetic wave generators. In another aspect, the method further includes positioning one or more electromagnetic wave generators within the one or more wellbores, connecting the one or more electromagnetic wave generators to a power source, and generating electromagnetic waves using one or more electromagnetic wave generators. In another aspect, the method further includes removing carbon deposited on the catalyst particles and regenerating the catalyst particles in-situ using water or steam. In another aspect, the water is pre-existing within the petroleum reservoir or injected into the one or more wellbores, or the steam is injected into the one or more wellbores. In another aspect, the method further includes sequestrating carbon oxides from the one or more wellbores into a sequestration formation using a production packer. In another aspect, the method further includes improving an injection of the produced carbon oxides into the sequestration formation using surface compressors or downhole pumps.

[0177] In another aspect, the method includes injecting water into the one or more wellbores to increase a production and a purity of the hydrogen. In another aspect, the water is injected into the one or more wellbores to have an approximate ratio of one to one with the hydrocarbons within the one or more wellbores or proximate to the porous configuration of catalyst particles. In another aspect, the injected water approximately doubles the production of the hydrogen and increases the purity of the hydrogen to approximately 50% or more. In another aspect, the porous configuration of catalyst particles further comprises biochar or the biochar is in injected into the one or more wellbores. In another aspect, the biochar comprises approximately 5 to 10 wt% of the catalyst particles. In anotheraspect, a particle size of the biochar comprises approximately 38-100 ^m. In another aspect, the method is carbon negative.

[0178] According to some embodiments, a method of creating a downhole artificial catalytic generator to produce H2 from petroleum reservoirs via EM / RF heating includes manufacturing a porous catalytic generator by integrating specific artificial catalysts (i.e., Iron oxides) as well as other support materials such as AI2O3 and SiCh into silicon carbide particles, installing the artificial catalytic generator to a downhole location between the production formation and the EM / RF antenna, installing production pipes including downhole H2 membrane separators and production packers, combining renewable energy (i.e., solar and wind) to deliver EM / RF energy to heat the artificial catalytic generator to the required temperatures, generating syngas (i.e., H2 and other gases) as oil and gas flowing through the heated artificial catalytic generator from reservoir to wellbore, via hydrocarbon cracking and hydrocarbon-water reactions under the artificial catalysts, extracting pure H through downhole H2 membrane separators in vertical, horizontal, and multilateral wells from oil and gas reservoirs, and sequestrating undesired gases such as carbon oxides into the targeted sequestration formation with the help of production packers. Water can be injected, if needed, to remove the carbon deposited on the surface of the generator during the reactions, enhance hydrogen production, and regenerate the catalysts in situ. Another step may include perforating the well in the sequestration formation for sequestrating undesired gases. Note that the oil and gas flows through the artificial catalytic generator due to the pressure gradient between reservoir and the wellbores. Other steps and features can be used as described herein.

[0179] In some embodiments, the surface H2 facilities include compressor, gas-liquid separator, hydrogen storage tank, connecting pipe fittings, safety facilities, etc. The H2 production pipes include anti -corrosion tubing, downhole H membrane separator, production packer, EM / RF antenna, artificial catalytic generator and so on.

[0180] According to some embodiments, the method includes creating a downhole artificial catalytic generator within petroleum reservoirs to create a highly catalytic, highly permeable, and high temperature porous zone for producing hydrogen in situ by EM / RF-assisted heating.

[0181] According to some embodiments, the method includes integrating specific artificial catalysts and other support materials into silicon carbide particles, to fabricate a robust artificial catalytic generator with high mechanical strength, excellent thermal stability, and high oxidation resistance abilities.

[0182] According to some embodiments, the method includes customizing the permeability of the artificial catalytic generator to be at a range of 0.01 to 100 Darcy s.

[0183] According to some embodiments, the method includes employing metal -based artificial catalysts, of which the elements are not limited to Fe, Ti, K, Mn, Ni, Co, and so on. The weight percentage of the metal elements should be between 0.1% and 50% in total mass of the artificial catalytic generator.

[0184] According to some embodiments, the method includes employing other support materials, which are not limited to AI2O3, SiCh, activated carbon, Zeolites, and so on, to meet certain requirements in the fabrication process such as increase the material strength, adjust the permeability, act as an adhesive, and reduce cost, etc.

[0185] According to some embodiments, the method includes employing beta-phase (|3-phase) silicon carbide as the basic material for improving the heating efficiency of the downhole artificial catalytic generator.

[0186] According to some embodiments, the method includes employing artificial metal catalysts and support materials with a particle size varying from several nanometers to below one millimeter.

[0187] According to some embodiments, the method includes either coating or doping artificial catalysts into the support material and silicon carbide particles.

[0188] According to some embodiments, the method includes installing the artificial generator along the wellbore in vertical, horizontal, and multilateral wells.

[0189] According to some embodiments, the method includes customizing the artificial catalytic generator to be an annular cylinder, with its inner diameter larger than the outer diameter of the EM / RF antenna, while the outer diameter is slightly smaller than the wellbore size.

[0190] According to some embodiments, the method includes varying the dimensions of the artificial catalytic generator to fit the size of antennas and wellbores.

[0191] According to some embodiments, the method includes customizing the length of the artificial catalytic generator same as the EM / RF antenna, generally from 10 to 1000 meters. With multilateral well type, the length can be even longer.

[0192] According to some embodiments, the method includes installing the artificial catalytic generator to the targeted formation, either by embedding it to the outer wall of the EM / RF antenna or installing it separately in the center of the wellbore.

[0193] According to some embodiments, the method includes heating the artificial catalytic generator by EM / RF energy to a temperature range from 250 to up to 1000 °C for hydrogen generation.

[0194] According to some embodiments, the method includes enhancing hydrogen generation via hydrocarbon cracking, coke gasification reaction, and water-gas-shift reaction.

[0195] According to some embodiments, the method includes extracting pure hydrogen or controlled hydrogen concentration from generated syngas with the help of downhole hydrogen membrane separators and production packers. A surface gas-liquid separator can be used to separate hydrogen gas and potential unreacted liquid hydrocarbons.

[0196] According to some embodiments, the method includes selecting a suitable sequestration formation to store carbon oxides (i.e., medium-high permeable and good caprock for seal, etc.). Surface compressors or downhole pumps can be used to increase pressure to inject undesired gases into the formation if needed.

[0197] According to some embodiments, the method includes involving water to regenerate catalysts in situ by removing cokes deposited on the surface of catalysts.

[0198] According to some embodiments, the method includes injecting water to a certain proportion of the artificial generator if there is no formation water produced in the reservoir, while heating the rest proportion of the artificial generator in the meantime for hydrogen production.

[0199] According to some embodiments, the method includes using an adjustable EM / RF frequency matched with the downhole artificial catalytic generator to optimize heating efficiency and hydrogen generation.

[0200] According to some embodiments, the method includes using electricity to power the EM / RF antenna, especially preferring the off-peak electricity from renewable energy (i.e., wind and solar) to further reduce the energy cost.

[0201] According to some embodiments, the method includes applying it to various petroleum reservoirs including conventional, unconventional, new, depleted or abandoned oil and gas reservoirs.

[0202] In some embodiments, the gas production rate and / or wellhead pressure is controlled so that the fluid flow rate from formation to wellbore is matchable with the generation rate of hydrogen within target formation.

[0203] Turning to Figure 15, the EM heating performance comparisons between SiC and rocks are illustrated. The solid blue line 1502 is 100% SiO2. The solid black line 1504 is 100% shale. The solid orange line 1506 is SiC. The dashed blue line 1508 is 40% SiO2+ 60% SiC. The dotted black line 1510 is 40% Shale + 60% SiC Fresh. The dashed black line 1512 is 40% Shale + 60% SiC Spent. The solid green line 1514 is 40% Shale + 55% SiC + 5% Fe3O4. The solid red line 1516 is 40% Shale + 55% SiC + 5% Fe. The results clearly show that SiC is much easier to be heated to high temperatures compared to rock samples under the same input power (100 W), meaning SiC only needs significantly lower energy than rocks to achieve the same required temperatures under EM irradiation. That is why heating the proposed artificial catalytic generator can drastically reduce energy cost compared to heating the rock formation directly.

[0204] Turning now to Figure 16, the diagram shows the experimental results of catalytic methane conversion by iron-based catalyst in two types of material. The solid red line 1602 is 60% Shale + 35% SiC + 5% Fe3O4. The solid black line 1604 is 60% SiO2+ 35%SiC + 5% Fe3O4. It demonstrates that the complete methane cracking can happen under the catalysis of the iron-based catalyst at the temperature range of 600-780°C, which is much lower than that temperature (over 1300°C) without any catalysts according to previous research. This provides another piece of evidence that the iron-based catalyst is indeed an efficient catalyst for hydrocarbons conversion to hydrogen.

[0205] Examples

[0206] While EM / RF-assisted catalytic heating for in-situ H2production from petroleum reservoirs is still in its early stages, no field pilot tests have been conducted yet. Nevertheless, the inventors validated this invention through lab-scale methane cracking experiments using iron-based catalysts. Here EM / RF-assisted catalytic heating experiments were performed in a microwave reactor system with different combinations of rock powders, catalysts, methane flowing, and water in the samples.

[0207] The microwave heating system consists of a solid-state microwave generator (up to 450 W, frequency 2450 ± 50 MHz). An infrared (IR) pyrometer was used to measure the temperature and accurately control the power of microwave generator. The gas composition was measured by areal-time, online gas analyzer. The experimental process generally lasted for 15 to 90 minutes depending on various situations.

[0208] The 5% Fe or FesCh means there is 5% weight percentage of iron-based nano particles with diameters of 50- 100 nm, which are the catalysts in the samples. SiCh and shale represent different types of support materials. Silicon carbide (SiC) is the basic heating promoter under microwave irradiation.

[0209] Table 4 shows the design and results of the methane cracking experiments. It lists the relevant metrics to evaluate the starting temperature for Fb production, hydrogen generation, and methane conversion. It shows that the methane is converted to hydrogen at as low as 420 °C from the samples under microwave heating. The highest methane conversion rate can be 100 % during the process, which demonstrates the excellent catalytic effect of iron-based catalysts and validates the feasibility of the proposed approach.

[0210] Figure 17 shows the real-time gas concentration in the experimental process of methane cracking in the iron-mixed sample. The solid green line 1702 is H2. The dashed red line 1704 is CO. The dotted black line 1706 is CO2. The solid blue line 1708 is CH4. The solid red line 1710 is Temperature. It can be seen that hydrogen gas dominates in the syngas resulting from the methane cracking. The hydrogen is continuously produced from 400-700°C, with a value of H2 concentration peak at 91 % at 668 °C. Strikingly, the concentration of CO is very low, and the generation of CO2 is negligible during the experiment. The results demonstrate that hydrocarbon can be effectively converted to clean hydrogen under the iron-based catalysts, which can potentially make this approach a low-carbon technology.

[0211] Figure 18 illustrates the fact that hydrogen production can be enhanced by the presence of water. The solid green line 1802 is H2. The dashed red line 1804 is CO. The dotted black line 1806 is CO2. The solid blue line 1808 is CH4. The solid red line 1810 is Temperature. In this test, 0.45 g of water (H2O) was added into the spent sample of 80% Sandstone, 15% SiC, and 5% Fe, in which solid carbon has deposited in the previous methane cracking. No methane was involved in this test. It is evident that H2 and CO are the main products during the test, which is in accordance with the products of the coke gasification reaction (C + H2O — > CO +H2). With H2O and pre-deposited carbon in the sample, H2 starts to be generated at about 335°C and then reaches the highest flow rate of 12.5 seem at 581°C. Notably, the production of CO almost has the same trend as the H2 production but is always lower than the flow rate of H2 through the process. Meanwhile, a small amount of CO2 is generatedalong with the CO production. This can be attributed to the water-gas shift reaction (CO+IEO^CCh+tE). These findings indicate that H2 enhancement in the presence of carbon and water is mainly contributed by coke gasification and followed by the water-gas shift reaction. The coke gasification therefore benefits the re-activation of the catalytic effect through removal of previously deposited carbon.

[0212] Water’s Role in Enhancing In-Situ Hydrogen Production

[0213] In-situ conversion of subsurface hydrocarbons via electromagnetic (EM) heating has emerged as a promising technology for producing carbon-zero, affordable hydrogen (H2) production directly from natural gas reservoirs. However, the reaction pathways and role of water as an additional hydrogen donor in EM-assisted methane-to-hydrogen (CH4-to-H2) conversion are poorly understood. Herein, a combination of lab-scale EM-heating experiments and reaction modeling analyses were employed to unravel the reaction pathways and elucidate water’s role in enhancing hydrogen production. The labelled hydrogen isotope of deuterium oxide (D2O) is used to trace the sources of hydrogen. The results show that water significantly boosts hydrogen yield via coke gasification at around 400°C and steam methane reforming (SMR) reaction at over 600°C in the presence of sandstone. Water-gas shift reaction exhibits a minor impact on this enhancement. Reaction mechanism analyses reveal that the involvement of water can initiate auto-catalytic loop reactions with methane, which not only generates additional hydrogen but also produces OH radicals that enhance the reactants’ reactivity. This work provides crucial insights into the reaction mechanisms involved in water-carbon -methane interactions and underscores water’s potential as a hydrogen donor for in-situ hydrogen production from natural gas reservoirs. It also addresses the challenges related to carbon deposition and in-situ catalyst regeneration during EM heating, thus derisking this technology and laying a foundation for future pilots.

[0214] Decarbonization has become a paramount issue in the petroleum industry to mitigate the negative impacts of carbon emissions. Generating and extracting hydrogen (H2) directly from petroleum reservoirs via electromagnetic (EM)-assisted catalytic heating offers an alternative pathway to carbon-zero hydrogen source [1], This technology has been recently validated and investigated through a series of studies [2-4], with H2 concentration reaching 91 mol.% and 77 mol.% generated from methane (CH4) and shale oil, respectively, in the presence of reservoir rocks [5, 6], Techno-economic assessments show that the hydrogen cost of this technology can be potentially as low as $0.86 / kg H2 [7, 8], Despite the promising results and significant potential of in-situhydrocarbon conversion to hydrogen via this new technology, the involvement of water has been scarcely considered in the research yet. Importantly, petroleum reservoirs always contain formation water, either as free water or connate water. Therefore, the participation of water in the process cannot be ignored during in-situ H2 production. Yet, the role of water and reaction pathways during EM-assisted H2 production remain largely unknown in the presence of reservoir rocks.

[0215] On one hand, water can play a positive role in enabling more H2 production during CH4-to-H2conversion. For instance, H2 production can be enhanced via the steam methane reforming (SMR) reaction when natural gas and water coexist [9, 10], even at relatively low temperatures below 600 °C [11, 12], Additionally, since the primary H2 production from gas reservoirs results from the pyrolysis of subsurface hydrocarbons via EM heating, solid carbon or coke may be generated during this process. This carbon may further react with water to produce syngas, including H2, through the coke-gasification and the water-gas shift reaction [13-16], further increasing H2 production.

[0216] On the other hand, water may lower H2 production due to its detrimental impact on catalytic effect. First, water is often identified as a negative substance causing catalyst poisoning, associated with the oxidation of the active metal and acceleration of sintering of the active metals

[0017] , Second, water vapor may also react with the catalyst’s surface to produce inactive surface phases

[0018] , leading to deactivation. According to the concept of in-situ H2 production via EM heating, the catalytic effect for natural gas conversion to H2 is provided by either the pre-placed synthetic catalysts or the natural mineral catalysts existing in reservoir rocks [19, 20], Therefore, the presence of water in reservoir rocks may potentially cause a noticeable deactivation of these catalysts, resulting in lower H2 production converted from natural gas.

[0217] To date, EM-heating experiments on crude oil pyrolysis with rocks [1] and without rocks

[0021] have both shown that additional H2 could be generated from water, indicating the potential for water to enhance H2 production. However, the fundamentals and reaction mechanisms are still unknown, and several critical knowledge gaps need to be addressed. First, the role of water for H2 production from gas reservoirs is poorly understood. It is unclear how much H2 will be generated from methane and water when they both serve as hydrogen donors. Second, the specific reaction pathways involving water in methane are yet to be discovered. Third, the impact of water on natural catalysts of reservoir rocks needs to be investigated under EM irradiation. Additionally, due to the solid carbon or coke generated during the pyrolysis of natural gas, the real in-situ circumstancesinvolve the coexistence of reservoir rocks, water, natural gas, and deposited carbon. An in-depth understanding of H2 production in such complex circumstances is urgently needed.

[0218] The fundamentals of water-enhanced H2 production from natural gas are examined below through a combination of experimental and simulation methods. To learn the in-situ H2 enhancement contributed by water, EM-heating experiments were performed involving the presence of sandstone, water, carbon, and methane to mimic practical in-situ conditions of gas reservoirs. The utilizations of deposited carbon and deuterium oxide (D2O) clearly elaborate the water-carbon reactions and water’s role as a hydrogen donor. Furthermore, water’s influence on natural catalytic effects within sandstone is also investigated by purpose-designed experiments. Importantly, simulation analyses was conducted to understand the chemical reaction pathways when water participates in CFU-to-FE conversion.

[0219] The solid samples used were 80 wt. % San Saba sandstone and 20 wt. % silicon carbide (SiC, Sicat Catalyst). Sandstone is used as a type of reservoir rock. Note that while pure sandstone can be heated to the high temperatures necessary for hydrogen generation, thermal runaway may occur

[0022] , leading to uncontrolled temperature increases. Therefore, SiC is used to easily control the temperatures during EM irradiation due to its excellent EM-absorbing ability. For simplicity, both the sandstone and SiC are crushed into particles ranging from 38 to 100 pm in diameter and thoroughly mixed using a pestle and mortar for 15 minutes prior to experiments.

[0220] To trace the source of the hydrogen produced in the presence of water, two types of water are employed: hydrogen oxide (H2O) and deuterium oxide (D2O, Sigma-Aldrich Inc.). By comparing the gas composition converted from methane in the presence of H2O or D2O, deeper insights into the reaction pathways will be obtained. Before experiments, water is saturated into the solid samples for 30 minutes.

[0221] To explore the role of carbon when it coexists with water and methane, a specialized sandstone sample is prepared. This involves performing a 20-minute methane cracking on the rock sample without water, resulting in carbon deposition in the sample. By subsequently saturating water and injecting methane into the sample, scenario is created involving water, methane, and carbon. This sample is referred to as the “carbon-containing sample” or “sample with carbon” in the following sections.

[0222] In this lab-scale study, microwave irradiation is chosen as a representative form of EM heating. Microwave is a type of EM wave with relatively higher frequency which can enable rapidachievement of high temperatures compared to lower-frequency EM waves. The microwave setup used is identical to that described in previous research [4, 6], After preparation, the samples are carefully loaded into the reactor tube (ID 10 mm, length 360 mm) supported by quartz wool plugs. Once the reactor tube is placed into the microwave cavity, the entire system is checked for hermetic sealing to ensure no gas leakage during experiments. Argon (Ar) gas is then purged at a flow rate of 60 standard cubic centimeters per minute (seem) until no oxygen is detected by the gas analyzer, creating an inert environment.

[0223] For experiments without methane, only Ar gas is inj ected into the reactor at a flow rate of 60 seem as a carrier gas. For experiments involving methane, both CFU and Ar are introduced into the system at a flow rate of 30 seem each. As an inert gas, Ar does not react with other reactants, even at high temperatures. Thus, the constant rate of Ar gas and its monitored concentration at the outlet serve to calculate the flow rates of the generated gases during the experiments. Once gas flow stabilizes, the experiments start under microwave irradiation. The composition of generated gases is monitored by an online gas analyzer (Extrel MAX300™-IG mass spectrometer, detailed information is listed in the supplementary document), which can detect the gas sample within 5 seconds. This realtime data, along with instantaneous measurement of reaction temperatures, enables the identification of the detailed pathways behind the reactions.

[0224] Various characterization techniques are utilized to examine the properties of the reactants before and after different reactions. These techniques include X-ray Diffraction (XRD), X-ray Fluorescence (XRF), Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Transmission Electron Microscope (TEM), and Dispersive Raman microscopy (Raman).

[0225] Simulations are conducted using the LOGEresearch software package

[0023] , which performs reactive simulations based on detailed kinetic models. In this study, a 0D constant pressure reactor model was employed. The reactor is treated as a closed system with no inflow or outflow, assuming perfect and instantaneous mixing of the reactants. The software solves the mass, energy, and momentum equations.

[0226] Simulation conditions are set at 1 atm pressure, with a temperature range of 700-1000°C and a residence time of 5 minutes. The fuels used are CFU and CH4 / H2O for different cases. The detailed chemical kinetic model used is adopted from Shrestha et al.

[0024] ,

[0227] Previous studies have demonstrated that solid carbon tends to deposit in the sample during CH4-to-H2 conversion under EM irradiation [2, 25, 26], Hence, carbon-water reactions cannot be disregarded when water is involved in the process at high temperatures. Several studies also indicate that coke gasification (C + H2O — CO + H2) may play a pivotal role in promoting hydrogen production [4, 27], However, the fundamentals of carbon- water reactions under EM irradiation, including the temperatures and the involved reaction pathways, remain unclear. To further investigate the details, two experiments are designed and conducted using different quantities (0.35 g and 0.25 g) and types (H2O and D2O) of water. The varied quantities of water aim to elucidate gas production under different water content, while the use of D2O with deuterium (D) as a tracer can unveil detailed reaction pathways by distinguishing the hydrogen source.

[0228] The samples used in this section are spent samples from methane cracking under EM heating, meaning they already contain deposited carbon (carbon-containing samples). To prevent interference from other gases, an inert environment is maintained by introducing a pure gas flow of Ar at an injection rate of 60 seem. Note that there is no CH4 involved in this section. Therefore, the reactants during the experiments are theoretically limited to the deposited carbon and the saturated water in the rock sample.

[0229] Figures 19A-19D show the real-time data of both transient flow rate and cumulative volume of the produced gases from carbon-containing samples saturated with two types of water: H2O and D2O. Regardless of water type, it is evident that hydrogen (H2 and D2) and carbon monoxide (CO) are the primary products in the experiment, which is in accordance with the products of the coke gasification reaction. The solid green line 1902 is H2, the solid orange line 1904 is CO, the dotted black line 1906 is CO2, the red line 1908 is Temperature, the dashed green line 1910 is D2, and the dashed magenta line 1912 is HD (hydrogen deuteride).

[0230] In the presence of 0.35 grams of H2O as depicted in Figure 19A, H2 starts to be generated at about 440°C corresponding to 1 mol. % H2 in the generated gas mixture and then reaches the highest flow rate of 11.0 seem at 580°C. As to CO production, it follows a similar trend with H2 and peaks at around 580°C with a flow rate of 8.7 seem. Notably, the flow rate of CO is slightly lower than that of H2 throughout the process. Additionally, a small amount of CO2 is generated along with CO. This trend is also reflected in the cumulative gas volumes illustrated in Figure 19B where the cumulative volume of H2 was the highest at 14.1 cc, followed by CO at 10.6 cc, and CO2 at the lowest at 1.3 cc. These results suggest that H2 and CO production is primarily contributed by cokegasification. In addition to that, the water-gas shift reaction (CO + H2O — CO2 + H2) also occurs at a low level, contributing minor amounts of CO2 and additional H2. Consequently, the total production of H2 increases while the production of CO decreases due to its consumption in the water-gas shift reaction.

[0231] Regarding the sample saturated with 0.25 grams of D2O, the real-time gas production of D2, CO, and CO2 generally exhibits a similar pattern to that of the sample with H2O, as shown in Figure 19C. D2 starts to be generated at 390°C and then peaks at around 550°C with a flow rate of 7.6 seem. As shown in Figure 19D, the cumulative production of D2, CO, and CO2 throughout the experiment reaches 7.7, 7.1, and 0.5 cc, respectively. Interestingly, minor amounts of H2 and HD are also detected, which differs from the sample saturated with H2O. This may be attributed to the minor H atoms adsorbed in the deposited carbon during CH4 cracking [28-30], Therefore, H2 and HD may be generated by the following reaction: C-Hx (carbon with H-atoms) + D2O — > CO + D2 + HD + H2.

[0232] When examining the results of total gas produced throughout the experiments, contrasting facts are observed for the two scenarios (0.35 g H2O and 0.25 g D2O). As shown in Figure 20 A, there is no doubt that more water results in more produced gases, as the volume of each gas produced from the sample with 0.35 grams of H2O water is higher than that of the sample with 0.25 grams of D2O water (H2 and D2: 14.2% vs. 9.1%; CO: 10.7% vs. 7.1%; CO2: 1.3% vs.0.5%). However, upon comparing the total concentration of each gas, their values are found to be quite similar in the two experiments (H2 and D2: 54.2% vs. 54.5%; CO: 40.8% vs. 42.5%; CO2: 5% vs.3%), as illustrated in Figure 20B. This unique observation suggests that the pathways of water-carbon reactions between the two types of water are identical, thereby resulting in a similar total concentration regardless of their differing gas volumes. Note that the hydrogen produced from the sample using D2O includes D2, HD, and H2, and total gas means cumulative gas (at standard conditions) produced during the period when the detected gas concentration exceeds 1 mol.%.

[0233] Based on the above discussions, some conclusions can be summarized regarding water-carbon reactions as follows: 1) water-carbon reactions under EM heating occur within a relatively low temperature range of 390-550°C; 2) the carbon deposited in CH4 cracking may contain not only carbon element, but also minor H-atoms due to absorption; 3) coke gasification is the dominating reaction for H2 production; and 4) water-gas shift reaction is a minor occurrence under the experimental conditions.

[0234] To better understand the characteristics of the reactants during reactions, various characterization techniques are employed to comprehensively illustrate the process. Figures 21A-21F show some features of the samples at different stages during the experiments. To distinguish samples, the following were defined: 1) the sample does not experience methane cracking as the “Fresh sample” (black line), 2) the sample undergoes methane cracking under EM heating as the “CFE spent sample” (orange line), and 3) the CFU spent sample reacts with water as the “Water spent sample” (blue lines 1 and 2).

[0235] The Raman spectrum shown in Figure 21A indicates that well-ordered carbon is produced following methane conversion under EM heating, as evidenced by the carbon peaks at wavelengths of 1330 cm'1(D band), 1590 cm'1(G band), and 2700 cnTl (G' band). Some carbon is removed after reacting with water, as indicated by the “water spent 1” blue line, while a portion may still remain, as indicated by the “water spent 2” blue line. The generation of carbon is further monitored by the increased carbon peak in EDX after methane cracking (red solid line 2102), compared to the fresh sample (black dotted line 2104) in Figure 2 IB. Figures 21C-21E show detailed morphology under SEM and TEM of the generated carbon, which is primarily deposited in spherical and tubular forms, with size ranging from nanometers to micrometers. The well-ordered crystalline carbon sheets were also confirmed by the layered structure of carbon observed in the TEM analysis. The XRD results in Figure 21F indicate that the components of the sandstone samples do not undergo significant changes during the process. However, the increased intensity of quartz in the spent samples suggests that a higher degree of crystallinity or larger crystal size after the reactions, which may be caused by the TR phenomenon during EM heating

[0022] ,

[0236] The discoveries in this section confirm that water can enhance hydrogen production in the presence of deposited carbon primarily through coke gasification, followed by the water-gas shift reaction. Furthermore, these reactions effectively facilitate the removal of solid carbon generated from hydrocarbon cracking. By consuming carbon in these processes, water may help prevent coke blockages in field applications.

[0237] The fundamentals of water-carbon reactions without involving any CH4 in the process were discussed above. To understand the reactions of the in-situ hydrogen production from natural gas in the presence of water, this section will focus on conducting CH4 conversion experiments under EM irradiation with two samples both saturated with 0.25 grams of D2O. To investigate the impact ofcarbon, two sandstone samples are used: one without carbon (non-carbon sample) and one with carbon (carbon-containing sample).

[0238] In Figures 22A and 22C, the solid green line 2202 is H2, the dashed green line 2204 is D2, the dashed magenta line 2206 is HD, the solid orange line 2208 is CO, the dotted black line 2210 is CO2, and the red line 2212 is Temperature. Figure 22A shows the real-time flow rate of gases produced from the non-carbon sample. When temperature reaches 630°C, H2, CO, and HD gases start to be produced simultaneously. The production of these three gases then all peak at around 695°C. The total gas production shown in Figure 22B encompasses all the gases produced during the period from the 2nd to the 7th minute in the experiment. It reveals that H2 is the dominant gas, accounting for 75.6% of the syngas, followed by CO and HD with concentrations of 13.3% and 9.9%, respectively. This high production of H2 can be attributed to CH4 cracking at high temperatures, facilitated by natural catalysis within sandstone [5], The values of cumulative gas volume are calculated at standard conditions.

[0239] Notably, HD is identified with a cumulative volume of 12.1 cc in the gas production, indicating that D2O also participates in the reactions. This likely results from the steam methane reforming (SMR) reaction: CH4 + D2O — > CO + H2 + 2HD. According to the mass balance of this reaction, the concentration of HD should be twice that of CO. However, the actual HD production is even lower than that of CO in terms of both flow rate and concentration as shown in Figures 23 A-23B. The solid green line 2302 is H2, the dashed green line 2304 is D2, the dashed magenta line 2306 is HD, the solid orange line 2308 is CO, the dotted black line 2310 is CO2, and the red line 2312 is Temperature. This discrepancy is due to the CO generation during the process of thermal runaway (TR) phenomenon of sandstone [22, 31, 32], The occurrence of TR results in a rapid increase in temperature, as indicated in Figure 23A, causing the actual temperature in the sample to be much higher than the measured temperature. Consequently, methane conversion is high during TR, leading to the first hydrogen peak observed alongside TR. As TR ends, the actual temperature decreases, leading to a reduction in hydrogen. However, as the temperature continues to rise under EM heating, another hydrogen peak appears at around the 5th minute. The total gas refers to the cumulative gases produced in the first 4 minutes. The cumulative gas volume is calculated at standard conditions.

[0240] Interestingly, the generation of D2 throughout the experiment is quite low. The small proportion of D2 indicated in Figure 23B may be generated via coke gasification, initiated by the presence of D2O and the generated carbon from methane cracking. The negligible CO2 productionsuggests that the water-gas shift reaction is still rarely involved in this scenario. This might be attributed to the limited availability of water as only 0.25 grams of D2O is used. Another reason could be the influence of reaction kinetics during the process, but it cannot be concluded in this work due to the limited data, necessitating further investigations in the future.

[0241] Figure 23 C provides real-time cumulative gas production when using the non-carbon sample saturated with D2O. It clearly demonstrates that H2, HD, and CO gases start to be produced at the 3.5th minute. After the 5th minute, almost no CO and HD are produced, indicating the depletion of D2O in the experiment. Consequently, the production of CO and HD mainly occurs in the time range of the 3.5th to the 5th minute, as marked by red zone I. On the other hand, H2 production lasts throughout the entire experiment, resulting from the methane cracking reaction at high temperatures in the catalysis of sandstone. This period of H2 production is marked as black zone II.

[0242] Based on these observations, the reactions in the two time zones can be concluded as below:Zone 1 SMR: CH4+ D2O CO + H2+ 2HDZone II Methane cracking: CH4— C + 2H2

[0243] From the discussions of the non-carbon sample, it is evident that water can enhance hydrogen production via the SMR reaction at temperatures over 600°C under EM heating when water is involved in natural gas. Nevertheless, it is worth noting that while this process can increase hydrogen production, it also results in additional CO generation. This may pose a burden on the downhole gas separation during the in-situ H2 extraction process.

[0244] Previous results have demonstrated that additional H2 can be produced via coke gasification when water and carbon are present in sandstone samples. Nevertheless, natural gas is the main hydrogen donor for in-situ hydrogen production under reservoir conditions. To mimic the actual situation of the coexistence of natural gas, water, and carbon, an experiment is carried out within sandstone under EM irradiation in the presence of methane, carbon, and water. The sample used is a carbon-containing sandstone sample which is saturated with 0.25 grams of D2O before the experiment.

[0245] Figure 23 A demonstrates that D2 and CO are produced starting at 410°C, reaching their peaks shortly after the 1st minute. This can be attributed to coke gasification occurring when water and carbon coexist, as discussed earlier. Although HD and H2 are produced simultaneously,they are generated later than D2, indicating that the temperature required for generating HD and H2 is higher than that of D2 when methane, carbon, and D2O are present in the sample. This confirms that the coke gasification reaction happens at a lower temperature compared to the SMR reaction. The peak flow rate of HD occurs at 655°C with an approximate value of 20 seem. After this peak, the production of HD, CO, and D2 rapidly drops due to the depletion of D2O. However, H2 production increases due to methane cracking at elevated temperatures under EM heating.

[0246] When comparing the results between the samples with and without carbon, several similarities in gas production can be observed: 1) H2, HD, and CO are the top three gases produced in both cases, as shown in Figure 22B and Figure 23B, respectively; 2) The levels of CO production are similar in both samples, both in terms of cumulative gas and concentration during the process; 3) The CO2 production is negligible for both samples; 4) The peak flow rate of HD production occurs after 650°C in both samples, as seen in Figure 22A and Figure 23 A.

[0247] However, the differences between the two samples are also evident. For the noncarbon sample (Figures 22A-22C), the production of D2 is very minor throughout the experiment. In contrast, for the carbon-containing sample (Figures 23A-23D), D2 is produced at a relatively low temperature range starting from 410°C.

[0248] Consequently, the production of D2 is significantly higher in the carbon-containing sample, reaching a cumulative volume of 13.9 cc, which accounts for 11.3 mol.% of the total syngas.

[0249] Based on these findings, some consensus can be summarized here. First, in the presence of water and carbon, hydrogen production can be significantly enhanced via the cokegasification and SMR reaction. Second, coke gasification occurs at a lower temperature compared to SMR and methane cracking under EM heating. Last, the water-gas shift reaction has minimal participation during the process, as indicated by the low concentration of produced CO2.

[0250] Similar conclusions can be obtained by the real-time cumulative gas data of the carbon-containing sample shown in Figure 23C. It is evident that D2 is the first type of hydrogen produced in the experiment due to coke gasification. The main production of D2 is marked by the blue square, Zone I, representing the period from the 0.8th to the 2nd minute and the temperature range from 410 to 650°C. Following this, the production of HD and H2 occurs. HD production is primarily from the 1.5th to the 3.7th minute, corresponding to temperatures from 605 to 695°C, marked by the red square, Zone II. Notably, after the 2.4th minute, H2 production exceeds HD production, indicating that the H2 produced from methane cracking has surpassed the HD generated from SMR due to thedepletion of D2O and the elevated temperatures. This zone of H2 production is marked by the black square, Zone III.

[0251] Therefore, the main reactions in the marked zones can be summarized as below:Zone I Coke-gasification reaction: C + D2O — > CO + D2Zone II SMR reaction: CH4 + D2O CO + H2 + 2HDWater-gas shift reaction: CO + D2O CO2 + D2Zone III Methane cracking: CH4 — C + 2H2

[0252] Additionally, Figure 23D shows that the methane cracking reaction contributes to the highest H2 production (51%) during the EM-heating experiment in the presence of methane, water, and carbon. This indicates that natural gas remains the primary hydrogen donor in the system. SMR and coke-gasification reactions account for 35% and 14% of the hydrogen production, respectively. Their contributions could be improved if more water and carbon were involved.

[0253] Several conclusions can be drawn here about the involvement of water in methane conversion under EM heating. First, once carbon has been deposited from methane cracking, more hydrogen will be produced through coke gasification at relatively low temperatures. Second, water enhances hydrogen production via the SMR reaction at the required temperatures, even in the absence of carbon. Notably, the water-gas shift reaction is also involved in the process, but it appears to play a limited role. These findings indicate that water acts as a hydrogen doner to produce additional hydrogen through water-carbon and water-methane reactions. It suggests the potential of water for enhancing in-situ hydrogen production from natural gas reservoirs via EM heating.

[0254] Studies indicate that carbon deposited during methane cracking can cause deactivation or activity loss of catalysts by occupying and blocking the active sites [33, 34], Other research suggests that water can be used to minimize the catalyst fouling caused by coke or carbon

[0035] , The Raman results in previous sections have demonstrated that part of the generated carbon can be removed through water-carbon reactions. After reacting with water (water treatment), the carbon-containing sample exhibits a significant reduction in carbon content compared to the sample without water treatment. Consequently, one might wonder whether the natural catalytic effect of the carbon-containing sample can be regenerated after the carbon has been removed by water.

[0255] For further investigation, two experiments are conducted using sandstone samples with and without water treatment. Initially, both samples undergo a round of methane cracking tointentionally induce catalyst deactivation through carbon deposition during the process. Subsequently, the sample without water treatment undergoes a second round of methane cracking, with the gas production results shown in Figure 24A. The solid green line 2402 is H2, the solid orange line 2404 is CO, the dotted black line 2406 is CO2, and the red line 2408 is Temperature. For the sample with water treatment, 0.25 grams of H2O are saturated into the sample to facilitate water-carbon reactions under EM heating. Once water is completely consumed, it is assumed that part of the carbon in the sample has been removed. This sample then undergoes another round of methane cracking under the same conditions, with the results presented in Figure 24B. By comparing the differences of hydrogen production between Figure 24A and Figure 24B, the impact of water on the natural catalytic effect of methane cracking in sandstone can be assessed.

[0256] For both samples, various peaks of hydrogen production can be observed at different temperatures, as methane conversion is proportional to temperatures [2, 26], At a temperature of 700°C, the flow rate of H2 produced in the sample without water treatment peaks at 6.9 seem, whereas the flow rate of H2 produced in the sample with water treatment peaks at 7.8 seem. When it comes to a temperature range of 740-750°C, the peak H2 production of the sample without water treatment reaches 13.0 seem, while the peak H2 production of the sample with water treatment stands at 13.5 seem. These results show that the hydrogen production of the sample with water treatment appears slightly better than that of the sample without water treatment.

[0257] There is no doubt that the involvement of water in the process does not detrimentally impair the natural catalytic effect of sandstone in methane conversion. Moreover, the carbon generated during methane conversion can be clearly removed by water. This is beneficial for mitigating potential pore-throat clogging due to carbon deposition in reservoirs. Additionally, a slight improvement of the natural catalytic effect is observed after water treatment. However, efficiently regenerating catalysis or reviving deactivation through water-carbon reactions needs further investigation.

[0258] As previously discussed, water enhances hydrogen production through reactions (I), (II), and (III). Additionally, certain minerals in sandstone act as a catalyst, facilitating the occurrence of heterogeneous reactions, which further complicates the process. The reactions validated by experiments in this work are well-known in the literature; however, they are global reactions. While global reactions may be useful for obtaining the equilibrium composition, they do not provide a complete picture of the underlying chemical mechanisms in this complex process. Multi-step reactionmechanisms can offer detailed insights, but developing such analyses for a heterogeneous system is highly challenging. Therefore, to gain some degree of chemical insights, a non-catalytic investigation was performed on the influence of water on hydrogen production in the gas phase using the simulation method.

[0259] Figures 25A-25D show the simulation results of different gas species for various water-methane ratios: (a) no water, (b) 10% water, (c) 20% water, and (d) 50% water. The solid green line 2502 is H2, the solid red line 2504 is CO, the dotted black line 2506 is CO2, and the solid blue line 2508 is CH4. The aim of this section is to investigate the role of water in methane conversion. Therefore, the focus is on the gas species of interest — H2, CO and CO2 — in the results. In Figure 25 A, it can be observed that the onset temperature for H2 generation from CH4 is ~850°C when water is not involved. This temperature is higher than the onset temperature for H2 generation from the experiments within sandstone in previous sections. This further confirms that sandstone indeed provides a catalytic effect on methane conversion. The consumption of CH4 and formation of H2 exhibit an almost linear trend. Specifically, 3% CH4 is consumed while 2% H2 is formed at 900°C, whereas -10% CH4 is consumed while 8% H2 is generated at 1000°C. It is noticed that the generation of H2 is smaller than the consumption of CH4, this is because some CF are consumed to form other hydrocarbon species such as C2H4, C2H2, and even C2H6 in the process. It is worth noting that the concentration of these hydrocarbon species is quite low, with all values below 5%.

[0260] Figures 25A-25D demonstrate the results when different water contents are involved. It can be observed that the onset temperatures of H2 production for the cases with water are almost the same as the case without water (Figure 25A). However, there are several notable differences when water is involved: 1) the consumption of CH4 is significantly increased, reaching approximately 40%, 36%, and 25% at 1000°C for 10%, 20%, and 50% water content, respectively; 2) the generation of H2 is at least four times higher than that of the case without water, reaching 34%, 37%, and 38% at 1000°C for 10%, 20%, and 50% water content, respectively; 3) carbon oxides (CO and CO2) are produced in higher quantities with increased water content. These findings suggest that water significantly enhances hydrogen production during methane conversion and enables a limited production of CO and CO2 as well. This is consistent with our previous experimental results.

[0261] Although H2 production is greatly improved by water, the water content itself does not significantly affect hydrogen production. This is clearly demonstrated by the results with various water contents at two temperatures, as demonstrated in Figures 26A-26B. The solid green line 2602is H2, the solid orange line 2604 is CO, and the solid black line 2606 is CO2. It is evident that higher temperatures result in higher concentrations of H2, CO, and CO2. The hydrogen produced in cases with water is several times higher than in the case without water. However, the hydrogen concentrations remain at a same level when the water content increases from 10% to 50% for both temperatures. This may be attributed to the decreased availability of H-atoms when increasing water content in methane because CH4 has four H atoms, while H2O has only two. Conversely, the production of both CO and CO2 seems to increase with increased water content. It is understandable that the O atoms is contributed by H2O. However, the availability of C atoms in the system decreases because the increasing water content leads to lower CH4 content, resulting in fewer C atoms. This suggests that water not only enhances hydrogen production but also plays a crucial role in increasing the chemical reactivity of the system.

[0262] To get insights into underlying mechanisms of water’s influence, reaction pathway analyses are conducted. Figures 27A-27B show the integrated mass flux analysis based on H-atom at 1 atm and 950°C. The term “therm” means unimolecular decomposition. For the condition without water (Figure 27 A), the model suggests that CH4 can react with H-atom to yield CH3 and H2 via Reaction (1) and can also undergo unimolecular decomposition via Reaction (2) as below (M) in Reaction 2 represents the third body which can promote reaction.Reaction ( 1 ) CH4+ H CH3 + H2Reaction (2) CH4(+M) _CH3+H(+M)

[0263] Reaction (1) is the primary pathway for CH4 consumption (59% goes to CH3 and 32 % goes to H2) while Reaction (2) is the secondary pathway that consumes the remaining 9% of CH4. The formed CH3 primarily undergoes self-recombination reaction to yield C2H6 (CH3 + CH3 _C2Hg). Further, C2H6 then exclusively reacts with CH3 radical to form C2H5 (56%) and CH4 (44%) (C2He + CH3 C2H5 + CH4). As can be seen this reaction routes back CH4 in the system. The formed C2H5 undergoes unimolecular decomposition to yield C2H4 (80%) and H-atom (20%). Likewise, C2H4 reacts with CH3 radical to form C2H3 (34%) and CH4 (44%) (C2H4 + CH3C2H3 + CH4). The formed C2H3 then exclusively undergoes unimolecular decomposition to yield C2H2 (67%) and H-atom (33%). The C2H2 undergoes self-recombination reaction, yielding higher hydrocarbons (C4H2) and producing H2 as well (C2H2 + C2H2 C4H2 + H2). The H-atom is crucial here as it is the main source of CH4 consumption, and all the formed H-atom is also consumed via Reaction (1) to the generated H2. The H-atom in the system is primarily formed via the unimoleculardecomposition of CH4, C2H5, and C2H3 The initiation reaction here is the unimolecular decomposition of CH4 via Reaction (2), which initiates the reaction process by producing H-atoms.

[0264] In the system with 10% water (Figure 27B), the primary reaction pathways for CH4 consumptions basically remain the same but with some changes in the flux involving water. Here also, CH4 mainly reacts with H-atoms, however it can also react with C2H5 and C2H3 radicals (unlike unimolecular decomposition in the case where no water is present). The pathways for the consumption and formation of CH3, C2H5, and C2H5 remain the same as those shown in Figure 27A. The main difference is observed in C2H4 consumption. Here, C2H4 reacts with CH3 and OH radicals to yield C2H3 + CH4 and C2H3 + H2O. The formed C2H3 degrades via the same reaction pathway as in the case of no water (Figure 27A). The formed H2O is crucial here; it reacts with CH3 and H-atoms to yield OH radicals via reversible Reactions (3) and (4):Reaction (3) CH4+ OH CH3+ H2OReaction (4) OH + H2_H + H2O

[0265] The formed OH radicals then react with C2H4 to yield C2H3 + H2O. This auto-catalytic loop (red arrows in Figure 27B) continuously generates OH in the system by consuming H2O and enhances the radical pool. The OH radical is a highly reactive species that enhances the system’s reactivity. It is also noteworthy to mention that Reaction (4) (reverse) does not only generate OH radicals but also produces H2 which is the additional pathway for H2 production beside Reaction (1). Further, Reaction (3) (reverse) is an additional reaction to circulate back CH4 into the system which eventually leads to H2 formation. This clearly explains the role of water in promoting H2 production. To be specific, Reactions (3) and (4) are the major contributors for more H2 production in the system with water.

[0266] The reaction sensitivity analysis was further conducted towards H2 for the case with water as shown in Figure 28. The positive and negative sensitivity implies reaction promotes and inhibits H2 formation respectively. It can be observed that most of the reactions that appeared in the flux analysis (Figure 27B) are also among the most sensitive reactions. In Figure 28, the reaction of C2H4 + CH3 C2H3 + CH4 and C2H5 + CH3 CH4 + C2H5 exhibits the highest positive and negative sensitivity. This may be explained by the fact that the C2H5 and C2H4 competes for the C2H5 formation and consumption (Figure 27B) together with the reaction of C2H5 + CH3 C2H4 + CH4 and CH3 + CH3 C2H5 + H. As expected, the direct H2 formation reaction CH4 + H CH3 + H2 (Reaction 1) and C2H4 + H C2H3 + H2 shows positive sensitivity, however they belong to the least sensitivereactions. Furthermore, Figure 27B indicates that the reaction of C2H4 + OHC2H3 + H2O opens a new path, and this reaction is also found to be among the sensitive reactions (Fig. 10). Additionally, other reactions are also found to be sensitive such as C2H2 + 0H(+M) C2H2OH(+M) for H2 generation (Figure 28) and CH2CHOH + CH3 CH2CHO + CH4 towards CH4 formation.

[0267] The C- and O-atom flux analysis reveals that C2H2OH is formed by the recombination of C2H2 with OH radicals while CH2CHOH is formed by OH reacting with C2H4 via the reaction of C2H4 + OH CH2CHOH + H. It should be noted here that these reactions paths are the route to CO and CO2 formation. CO is mainly formed by the unimolecular decomposition of HCO and CH2CO through the reaction of HC0(+M) CO + H(+M) and CH2CO(+M)CH2 (singlet) + CO, respectively. The formed CO exclusively reacts with OH radicals to yield CO2 via CO + OH CO2 + H. From the above analysis, it is evident that H-atoms and CH3 radicals are crucial for systems both with and without water. However, the OH radical plays a critical role in the system involving water.

[0268] The reaction mechanisms and influence of water on both enhancement and natural catalytic effect for hydrogen production have been explored by purpose-designed methane conversion experiments using two types of water (H2O and D2O). Chemical mechanism analyses are conducted to elucidate the fundamentals underlying water-methane reactions.

[0269] During EM-assisted CH4-to-H2 experiments in the presence of sandstone, even a small amount of water (i .e., 0.2 g) can significantly enhance hydrogen production. The enhanced hydrogen is mainly produced through coke gasification at around 400°C and the SMR reaction at over 600°C. It also demonstrates that the water-gas shift reaction plays a limited role in enhancing hydrogen production during the process. Importantly, the reaction-simulation analyses show the hydrogen production is 3-4 times higher in systems involving water (10% - 50 %) compared to those without water. It indicates that water can initiate auto-catalytic loop reactions with methane, resulting in not only more hydrogen production but also OH radicals that significantly enhance the system reactivity for reactions. Furthermore, water plays a positive role in removing the solid carbon generated during methane cracking. Meanwhile, water does not negatively impact the natural catalytic effect of minerals in sandstone.

[0270] This work reveals the reaction mechanisms when water is involved in natural gas at high temperatures. It shows that water can act as a hydrogen donor and promote hydrogen production from natural gas within reservoir rocks. Moreover, water may also aid in the removal of the generated solid carbon to prevent clogging of the formation in field applications.

[0271] Energy Efficiency, Techno-Economic Viability and Life Cycle Assessment of In-Situ Hydrogen Production

[0272] Recently, a subsurface technology of in-situ hydrogen production using electromagnetic (EM) heating shows great potential for extracting clean hydrogen directly from natural gas reservoirs. However, critical knowledge gaps persist, particularly in technical assessments. This study addresses these gaps by evaluating energy efficiency, techno-economic viability, and greenhouse gas (GHG) emissions throughout the process. The system energy efficiency was analyzed under various experimental conditions using sandstone and synthetic catalysts. The results highlight the potential for field improvements through the optimization of catalysts and methane flow rates. Techno-economic analysis (TEA), based on a developed reservoir-scale model, indicates hydrogen production cost can be potentially as low as $0.86 / kg with the integration of renewable energy. Key cost drivers include membrane expenses and EM-heating electricity for hydrogen production. Life cycle assessment (LCA) indicates that methane pyrolysis in gas reservoirs does not generate GHG emissions throughout its life cycle. However, GHG emissions associated with electricity use (i.e., EM heating) in the process should be considered. Moreover, the technology's eligibility for Section 45 Vof Inflation Reduction Act (IRA 45 V) clean hydrogen credits is contingent upon the source of electricity used. And the qualification for the credits depends on the proportion of renewable energy in the electricity consumption mix. This study provides insights into efficiency optimization, cost competitiveness, and environmental considerations for in-situ hydrogen production from gas reservoirs using EM heating.

[0273] Transforming the natural gas sector into a clean hydrogen (H2) supplier emerges as a pivotal solution to reduce greenhouse gas (GHG) emissions in the decarbonization of the petroleum industry. Recently, a subsurface technology of in-situ hydrogen production from natural gas reservoirs has been proposed and validated [52, 50], The primary mechanism involves initiating the conversion of natural gas (mainly methane) in subsurface reservoirs to hydrogen using external electromagnetic (EM) energy delivered by customized downhole tools. With the assistance of hydrogen-permeable membranes installed downhole, high concentration of hydrogen can be extracted to the surface while carbon-based byproducts such as CO, CO2, and unreacted gaseous hydrocarbons can be retained in reservoirs, enabling a carbon-zero process [2],

[0274] Although not for in-situ hydrogen production, extensive research and industrial pilots in the oil industry have demonstrated the feasibility of using EM heating in reservoirs [42, 41, 37],Pilot tests conducted in shale rocks during the 1980s show that EM heating could raise the temperature of oil shale to 400°C

[0036] , The temperature could be much higher with an optimized EM frequency and higher power. Studies also indicate that EM waves can penetrate rocks into depths of 1-5 meters and even deeper depending on the frequency [43, 48], Therefore, designing a downhole EM antenna distributed along horizontal wellbores could effectively heat a large volume of formation using EM heating. This heated formation can serve as a reactor or generation zone, facilitating the conversion of subsurface hydrocarbons into hydrogen production.

[0275] A series of lab-scale studies have highlighted the promising results of the in-situ hydrogen production from petroleum reservoirs using EM heating. One study demonstrates that up to 66 mol.% of H2can be obtained from crude oil in the presence of synthetic catalysts

[0053] , Other experimental results show the EE concentration produced from methane cracking achieves 91.0 mol.% and 99.8 mol.% under catalytic conditions with and without sandstone rocks respectively [5, 25], Two studies indicated that hydrocarbon conversion in bulk shale exceeds that in quartz samples and shale oil pyrolysis in shale yields a H2 concentration of 77.2 mol.% even without any catalyst, highlighting the catalytic role of minerals in shale for hydrogen production under EM heating [2, 4], This underscores the potential of utilizing reservoir rocks as natural catalysts to enhance hydrogen efficiency. Moreover, by employing artificial catalysts pre-placed in targeted zones

[0051] , the efficiency of converting hydrocarbons to H2 can be further optimized. In addition, numerical simulations at a reservoir scale indicate that the H2generation can occur across the target reservoir with minimal deformation of the formation [3],

[0276] Furthermore, this approach holds potential for cost-effectiveness by eliminating the need for petroleum extraction, transportation, and carbon capture and storage (CCS). Repurposing existing assets in the petroleum industry, such as depleted wells, datasets, and field infrastructure, further drives down the hydrogen production cost. Additionally, renewable energy sources like wind and solar power, as well as locally low (even negative in some cases) electricity prices

[0047] , can be leveraged for on-site EM heating to make the technology more cost-effective. Notably, a recent preliminary Techno-economic analysis shows that the hydrogen cost of this technology could be reduced to below $ 1 / kg H2

[0044] ,

[0277] However, as an early-stage technology, no field pilot test has been conducted for the proposed technology. Many critical knowledge gaps persist in the process, particularly in technical assessments. For instance, energy efficiency assessments have not yet been conducted, even at lab-scales, leaving a significant gap in understanding the dynamics of energy input and output in the system. Additionally, the techno-economic viability at reservoir scales remains largely unknown, introducing substantial uncertainties for the field application of the technology. Moreover, since the proposal involves an interdisciplinary approach with multiple stages, the GHG emissions across the life cycle are still unclear. Addressing these technical components is crucial to fill these knowledge gaps and advance the technology readiness level (TRL).

[0278] In this work, the system's energy efficiency is evaluated through EM-heating experiments under various scenarios involving sample variations, catalyst utilization, and methane flow rates. Techno-economic analysis (TEA) and life cycle assessment (LCA) were conducted by developing a methane pyrolysis process under reservoir conditions, considering methane conversion rates, EM-heating energy consumption, and energy requirements for hydrogen cooling and compressing systems. TEA utilizes the H2A-Lite model to analyze in-situ hydrogen production costs (H2A-Lite, NREL). GHG emissions from in-situ hydrogen technology are evaluated using LCA methodology with GREET model

[0039] , This study aims to provide detailed insights into the technical aspects and environmental implications of in-situ H2 production from natural gas reservoirs using catalytic EM heating, with the goal of enhancing the feasibility, scalability, and overall efficiency of this technology.

[0279] The solid materials utilized include San Saba sandstone, silicon carbide (SiC, Sicat Catalyst), and synthetic KM^Ch-AhCh / SiCh catalyst (refer as ‘catalyst’ in the following text). The sandstone is used to mimic the subsurface conditions of gas reservoirs, which is crushed into particles ranging from 38 to 100pm in diameter for experimental convenience. The same sized particles of SiC are added into the samples to easily control temperatures under microwave irradiation due to its excellent EM-absorbing ability. Before experiments, all solid samples with different components are physically mixed using a pestle and mortar for 15 minutes. Methane (CH4) is used as the feedstock for H2 through CH4 cracking under EM heating, while Ar is employed as a carrier and calibration gas. As an inert gas, Ar cannot react with other reactant seven at high temperatures, therefore its constant flow rate can help to determine the real-time flow rates of the generated gases during the experiments.

[0280] Synthetic catalyst powder is employed to evaluate hydrogen production efficiency under catalytic conditions, providing insights into the strategy of catalysts utilization for in-situ hydrogen production. The catalyst in this study is synthesized using a wet chemistry method, as detailed in the following steps: 1) Dissolve 3.95g of Al(NOs)3 9H2O, 0.89g of Fe(NO3)3 9H2O, andA; 2) At 80°C, add NH4OH to solution A till the PH reaches 8.9; 3) Centrifugally wash the resulting precipitate with distilled water; 4) Dry the precipitate at 98°C for 12 hours; 5) Obtain the 3 wt.% Fe- based catalyst after calcination at 980°C for 6 hours.

[0281] The experimental setup used in this study is identical with the setup described in previous works [2, 6], The total mass of one sample is typically 2.0 grams. After preparation, the sample is carefully loaded into the reactor tube supported by a quartz wool plug. The reactor tube is then inserted into the microwave cavity followed by the examination of hermetic sealing to the system. To remove residual air from the samples, argon gas (Ar) is purged first at a flow rate of 60 standard cubic centimeters per minute (seem) for 15 minutes to establish an inert environment. Subsequently, a mixture of CH4 and Ar is introduced into the reactor at specified flow rates. The flow rate of Ar is consistently set at 30 seem for all experiments, while the flow rate of CH4 varies at 50 seem, 100 seem, and 150 seem across different cases. Once the gas flow stabilizes, the experiments start with the activation of microwave irradiation. The temperature of the sample is monitored by an 1R pyrometer. And the composition of generated gases is detected by an online real-time mass spectrometer (Extrel IS 300).

[0282] In this work, the energy efficiency analyses are conducted based on the low heating value (LHV) of the hydrogen produced in the system. The heating value of other produced gases in the system is not considered. The energy efficiency (77 ) is obtained from the following equation:LHVH271 = - X 100%ETwhere LHVH2is the toral low heating value of generated hydrogen and Er is the total electricity energy used for EM-heating.

[0283] In this work, the implementation of TEA and LCA is based on a simplified process scheme as illustrated in Figure 29. The assumed reservoir conditions are l,000°C and 150 bars. Under these conditions, the methane conversion rate is 50%, which is lower than the lab-scale experimental results due to the high pressure used to model the reservoir condition. The process extracts 99.9% high-purity hydrogen to the surface through a palladium-based (Pd) membrane with a 90% recovery rate. Surface operations involve cooling the hydrogen to 40°C and compressing it to 20 bars. Electricity for these operations can be sourced from the Local / Texas electricity grid or renewablesources like wind or solar power. A model was developed based on this process scheme, and the energy requirements for heating, cooling, and compressing are summarized in Table 5.

[0284] At a certain temperature and pressure, the hydrogen production rate is proportional to the amount of natural gas in the reservoir. Therefore, identifying a gas reservoir with a high natural gas production rate is crucial for efficient hydrogen production. Although natural gas production declines with time, the annual production rate could be managed by fracking frequency, fracking pressure, or other enhanced conditions. Hence, a steady hydrogen production rate is assumed to avoid the excessive capital investment for the Pd membrane which can become the main cost driver when sized based on the max production rate.

[0285] Two gas fields are selected to compare low and high hydrogen production rates: Bone Spring Avalon (NM) and Haynesville (LA). The natural gas production data from two fields are obtained from data provided by collaborators and the EIA database (U.S. EIA), respectively. Based on the model, the estimated hydrogen production rates are 2,282 kg / day for Bone Spring Avalon and 35,124 kg / day for Haynesville.

[0286] To conduct energy efficiency analysis, it is essential to quantify the hydrogen production within the system. Figures 30A-30B illustrate the real-time gas composition of the gases produced during experiments where the CH4 flow rate is set at 50 seem. The solid green line 3002 is H2, the solid orange line 3004 is CO, the dotted black line 3006 is CO2, and the red line 3008 is Temperature. It is evident that hydrogen is the predominant gas converted from CH4, whether with only sandstone samples or with added catalyst. This underscores the catalytic effect of sandstone on CH4 cracking, which is consistent with findings from previous studies [5], Additionally, a minor amount of carbon monoxide (CO) is also observed, likely due to the thermal runaway (TR) phenomenon of sandstone during EM heating

[0022] ,

[0287] While the maximum hydrogen concentration reaches 82 mol.% in the sandstone sample under non-catalytic conditions (Figure 30A), the sample containing 5% catalyst shows superior performance across several aspects, as shown in Figure 30B: 1) achieving a peak hydrogen concentration of 87 mol.%; 2) sustaining hydrogen concentrations above 80 mol.% for a longer duration compared to the non-catalytic sample; and 3) exhibiting a slower decline in hydrogen concentration over time, indicating that sandstone is more prone to deactivate than the synthetic catalyst. This suggests that artificial catalysts are more effective in converting methane to hydrogen compared to sandstone.

[0288] This observation is further supported by the total gas concentrations depicted in Figures 31 A-3 IB over a 5-minute period. The solid green line 3102 is H2, the solid orange line 3104 is CO, the dotted black line 3106 is CO2, and the red line 3108 is Temperature. In Figure 31 A, the green bars 3102, 3104 and 3106 show the hydrogen concentration at flow rates of 50, 100 and 150 seem, respectively, in sandstone. The orange bars 3112, 3114 and 3116 show the carbon monoxide concentration at flow rates of 50, 100 and 150 seem, respectively, in sandstone. In Figure 3 IB, the green bars 3152, 3154 and 3156 show the hydrogen concentration at flow rates of 50, 100 and 150 seem, respectively, in sandstone plus a catalyst. The orange bars 3162, 3164 and 3166 show the carbon monoxide concentration at flow rates of 50, 100 and 150 seem, respectively, in sandstone plus a catalyst. Across CH4 flow rates of 50 seem, 100 seem, and 150 seem, the total hydrogen concentration in the samples with catalyst is consistently about 10% higher than in the samples without catalyst. Interestingly, both catalytic and non-catalytic scenarios show a noticeable decrease in hydrogen concentration when increasing CH4 flow rate from 50 seem to 100 seem. This means the conversion of CH4-to-H2is decreased by the increasing amount of CH4. Consequently, optimizing natural gas flow rates in practical applications is crucial for achieving high-efficient in-situ hydrogen production.

[0289] Figure 32 demonstrates the real-time cumulative hydrogen production under various scenarios. For sandstone samples (blue lines), cumulative hydrogen volumes are 264 cc, 343 cc, and 559 cc at methane flow rates of 50 seem 3202, 100 seem 3204, and 150 seem 3206, respectively. In contrast, sandstone samples with catalyst (green lines) produce more hydrogen with cumulative volumes of 374 cc, 450 cc, and 749 cc at methane flow rates of 50 seem 3208, 100 seem 3210, and 150 seem 3212, respectively. This further verifies that the synthetic catalyst produces more hydrogen compared to sandstone. Moreover, higher methane flow rates are shown to increase hydrogen production, despite potentially slightly lower methane conversion rates as discussed previously.

[0290] Based on the summarized results in Table 6, the energy efficiency of the system is calculated and depicted in Figure 33. Generally, the energy efficiency values across different scenarios range from 6.1% to 14.6%. The highest energy efficiency is observed in the sandstone sample with catalyst at a methane flow rate of 150 seem, while the lowest is noted in the sandstone sample without catalyst at a methane flow rate of 50 seem. This indicates that catalyst utilization and higher methane flow rates tend to favor higher energy efficiency. Therefore, enhancing hydrogen production efficiency through effective catalysts and optimizing methane flow rates is crucial for improving the overall system energy efficiency.

[0291] Techno-economic analysis (TEA)

[0292] The cost analysis is developed using the H2A-Lite model. The tool provides the levelized cost of hydrogen (i.e. the minimum selling price to have a net present value of zero) and the investor cash flow of the project. Costs for the above ground equipment are obtained from Aspen Plus Economic Analyzer, while the costs associated with the well (construction, completion, abandon) are obtained from the FECM / NETL Unconventional Well Economic Model. The assumptions used in the TEA are listed in Table 7.

[0293] To investigate the main cost drivers and their relationship with the production rate, four case studies are designed as summarized in Table 8. The membrane cost of $7,500 / m2is based on previous research

[0046] , while costs of $3,500 / m2and $2,000 / m2are used to conduct the sensitivity analysis. In the analyses, the levelized cost includes several components: capital expenditures (CapEx), fixed operational expenditures (Fixed OpEx), variable operational expenditures (Variable OpEx), annual maintenance, property insurance, and taxes. The CapEx mainly comprises the costs associated with membrane, compressor, cooling, EM-heating, and well construction. The levelized cost and the capital expenditures (CapEx) of hydrogen for different cases are discussed in the following sections.

[0294] Figures 34A-34D illustrate the breakdown of the levelized cost of hydrogen across different scenarios. CapEx is orange 3402, Variable OpEx is yellow 3404, Fixed OpEx is light green 3406, Annual maintenance is red 3408, Property insurance is brown 3410 and Taxes are dark green 3412. In Case #1, where hydrogen production is low, the levelized cost is approximately $5 / kg, primarily driven by CapEx which accounts for 62% of the total cost. This can be attributed to the high proportion of EM-system building and well construction costs when the hydrogen production rate is low. In contrast, increasing hydrogen production from 2,282 to 35,124 kg / day in Case #2 reduces the levelized cost to $1.47 / kg, as shown in Figure 34B. This underscores that higher production rates result in a lower levelized cost of hydrogen. Moreover, by decreasing specific membrane costs to $3,500 / m2 and $2,000 / m2, the levelized cost of hydrogen can be further reduced to $1.07 / kg and $0.86 / kg for Case #3 and Case #4, respectively.

[0295] These findings emphasize the crucial role of capital expenditures in determining the levelized cost of hydrogen. Increasing hydrogen production rates and lowering membrane costs are key factors that help to reduce the levelized cost of hydrogen.

[0296] The breakdown of capital expenditures for hydrogen costs, as illustrated in Figures 35A-35D, provides more detailed insights into the primary cost driver for in-situ hydrogen production. Membrane is orange 3502, Compressor is yellow 3504, Cooling is green 3506, EM system is red 3508 and Well costs are brown 3510. In Case #1, the total CapEx amounts to $20.2million, with EM system and well construction emerging as the main contributors. In contrast, when the hydrogen production rate increases, Case #2 saw a threefold rise in CapEx, reaching $83 million, despite a significant decrease in the levelized cost of hydrogen to $1.47 / kg (see previous discussion). In this case, the membrane requires the highest capital investment, representing about 80% of the total CapEx (see Figure 35B). When the membrane costs are decreased to $3,500 / m2and $2,000 / m2for Case #3 and Case #4 respectively, a significant proportion reduction of membrane cost is found in both cases. However, membrane costs still dominate CapEx, even with specific membrane costs as low as $2,000 / m2. Combining these results with the previous analyses of the levelized cost of hydrogen, it becomes evident that membrane is the primary cost driver for in-situ hydrogen production.

[0297] Life cycle assessment (LCA)

[0298] No direct GHG emissions exist in the process as hydrogen production and separation occurs in-situ (assuming no leakage from underground). However, indirect emissions by electricity consumption should be counted in the LCA. The major electricity consumptions are for EM-heating, cooling, and compressing (Table 5). The GHG emissions by grid electricity are calculated based on the GREET 2022 with two electricity sources: Texas grid mix and renewables. Texas grid 2021 GHG emissions data is applied for the U.S grid mix case (EP A). If the electricity source is renewable (i.e., wind / solar), there will be zero GHG emissions. Note that the embodied carbon emissions of renewable electricity are not considered in this study.

[0299] The GHG emissions of the in-situ hydrogen production technology are shown in Figure 36. If the process electricity is supplied by Texas grid mix, the GHG emissions is 4.6 kg / kg. Compared to other hydrogen production, the in-situ hydrogen production with Texas grid mix emitted less GHG than the conventional SMR process (11.6 kg / kg), and similar GHG to the conventional SMR process with CCS (3.4 kg / kg). Notably, in-situ hydrogen production using renewable electricity achieves zero emissions, which is comparable to hydrogen production via electrolysis using low-carbon electricity sources, such as PEM (polymer electrolyte membrane) electrolysis with renewables and SOEC (solid oxide electrolyzer cell) with nuclear power.

[0300] According to Section 45 V under Inflation Reduction Act of 2022 (IRA 45 V), there will be a 10-year tax credit for zero (or low) carbon intensity hydrogen (Office of Energy Efficiency & Renewable Energy). The clean hydrogen credit can be eligible for up to $3 per kg of hydrogen with less than 0.45 kg / kg of GHG emissions, or a minimum of $0.6 per kg of hydrogen with less than 4 kg / kg of GHG emissions (see Table 9). The GHG emissions of in-situ hydrogen production (4.6 kg / kg) with the Texas grid mix exceed the 1RA45 V criteria, as shown in Figure 36. EM Heating is orange 3602, Compressor is green 3604, Cooling is blue 3606, Process and Combustion is light blue 3608, Emission for Electricity is purple 3610 and Emission for NG Feed is gray 3612. Therefore, to qualify for IRA 45 V, either renewable electricity sources should be utilized, or the electricity consumption of the process should be reduced.

[0301] Renewable electricity is intermittent by nature. When renewables are not available, the Texas grid is utilized for in-situ hydrogen production, necessitating a mixed usage of renewable and Texas grid electricity. The effect of the renewable mix to the Texas grid on the GHG emissions is illustrated in Figure 37. It indicates that for maximum qualification under IRA 45V ($3 / kg H2), renewable electricity must exceed 90%. A renewable mix of 50% qualifies for a $0.75 / kg credit, while less than 14% renewable mix results in no credit eligibility.

[0302] Another approach to reduce GHG emissions is improving the heating efficiency of in-situ hydrogen technology. Figure 38 illustrates varying GHG emissions based on different heating energy inputs from the Texas grid. Currently, EM -heating energy stands at 10.3 kWh / kg. With 100% reliance on the Texas grid, the in-situ hydrogen production does not qualify for the IRA 45 V credit. To become eligible, the heating efficiency must be improved to 8.7 kWh / kg for $0.6 / kg credit, 4.9 kWh / kg for $0.75 / kg credit, and 2.3 kWh / kg for $l / kg credit. However, since cooling and compressing already exceed the 0.45 kg / kg GHG emissions threshold, the process cannot be qualified for the max credit by only improving the heating efficiency. Therefore, optimizing the cost of in-situ hydrogen requires a combination of both renewable energy integration and enhanced heating efficiency.

[0303] In this section, the technical aspects of in-situ hydrogen production from gas reservoirs using EM heating were comprehensively evaluated. This includes preliminary energy efficiency analysis, Techno-economic analysis (TEA), and greenhouse gas (GHG) emissions throughout the life cycle. Several conclusions are summarized as follows:

[0304] At a lab-scale methane flow rate of 150 seem, the system energy efficiency achieves 14.6% in the sandstone sample with catalyst. It is anticipated that energy efficiency could be much improved in field applications with higher methane flow rates. This underscores the importance of enhancing hydrogen production efficiency through strategies such as employing effective catalysts and optimizing methane low rates.

[0305] Based on TEA results, the production cost of hydrogen ranges from $l / kg to $5 / kg, potentially reaching as low as $0.86 / kg. The hydrogen production cost can be competitive with the conventional SMR hydrogen process. Two pivotal factors in cost reduction are 1) low membrane cost (e.g., $2,000 / m2), and 2) large gas reserves for high hydrogen production rate. Also, it is important to keep a steady hydrogen production rate to avoid excess capital cost expense on the membrane.

[0306] LCA shows that the proposed technology can be qualified for the IRA 45V clean hydrogen credit under certain conditions. While methane pyrolysis in gas reservoirs results in no GHG emissions, the emissions from electricity consumption must be considered. The EM-heating is the major electricity demand (87%) for in-situ hydrogen technology followed by compressing and cooling. If the entire process relies on the local electricity grid, it may not meet IRA 45V credit qualifications. To qualify for the maximum credit ($3 / kg hydrogen), the local electricity grid must incorporate renewables exceeding 90%.

[0307] Additional Investigation of the Role of Water in Enhancing In-Situ Hydrogen Production from Shale Oil

[0308] The effect of water on in-situ hydrogen production from shale oil will now be described. Real-time temperature profile and gas compositions are monitored using an IR pyrometer and an online gas analyzer, respectively. These measurements provide valuable insights into reaction mechanisms, temperature dependencies, gas concentrations, and production rates. Both ordinary water (H2O) and heavy water (D2O) are employed to identify and quantify water's contribution to hydrogen production by tracing the sources of different hydrogen (H2, HD, and D2). In addition, carbon-containing rock samples are employed to further investigate the impact of water on the solid carbon produced during the process. This discussion elucidates the fundamentals of shale decomposition, the role of water in hydrogen production, and its influence on both gaseous and solid products formed during EM-assisted in-situ shale oil conversion to hydrogen.

[0309] Methodology

[0310] The experimental materials employed herein include shale rock (Kocurek Industries, Inc.), silicon carbide (SiC, Sicat Catalyst), shale oil, water or hydrogen oxide (H2O), and heavy water or deuterium oxide (D2O, Sigma-Aldrich Inc.). Mancos shale, a fine-grained sedimentary rock that is widely distributed across the western United States, is used to mimic the subsurface formation conditions for in-situ hydrogen production. The rock contains 0.83% total organic content (TOC) and 22.73% carbonate. The SiC used is cubic 3C-SiC (also known as 0-SiC), which possesses exceptional EM wave absorption properties that help to improve heating efficiency and facilitate a smoother experimental process. Both the shale rock and SiC were crushed into powders before experiments with particle sizes ranging from 38 to 100 pm. The oil used is a type of shale oil sourced from the Permian Basin in the United States. During the experiments, it acts as a hydrogen feedstock when saturated with shale rock samples. The oil contains no asphaltenes, and impurity elements such as nitrogen (N), sulfur (S), and oxygen (O) are present in very low concentrations, as detailed in Table SI. Two types of water — H2O and D2O — were used and mixed with various samples at different oil / rock ratios to identify the origin of the produced hydrogen and to quantitively investigate the role of water in the conversion of shale oil to hydrogen under EM heating.

[0311] The experimental apparatus is largely the same as previously described apart from the quartz reactor. Instead of the previously used open-ended quartz tube (open at both ends), a closed-end quartz reactor — with a sealed plug in the middle — was employed throughout the experiments. In this reactor, the samples are placed directly on top of the plug in the closed-end quartz tube, rather than on quartz wool as in the open-ended tube. Therefore, it ensures complete reactions of the reactants (e.g., oil and water) in the reactor, as it eliminates potential liquid loss through the quartz wool during the process. As a result, the upgraded design allows for more accurate and reliable experimental results for liquid samples.

[0312] As natural catalysis has been demonstrated previously (An, et al., 2024a; An, et al., 2024b), all experiments in this work are conducted using rock samples without external catalysts. The samples include shale rock and / or SiC (typically 2.0-3.0 grams) are thoroughly mixed using a pestle and mortar for 15 minutes before loading into the quartz reactor. Subsequently, approximately 0.2-0.3 grams of oil and / or water are saturated into the rock samples to simulate reservoir conditions. The reactor is then placed into the cavity of the EM-setup, and the hermetic sealing of the system is carefully checked. To remove residual air from the reactor, argon (Ar) is purged at a flow rate of 60 standard cubic centimeters per minute (seem) for 15 minutes to establish an inert atmosphere. Once no oxygen is detected at the system outlet — confirmed by a real-time gas analyzer (Extrel Core MassSpectrometer MAX300-IG) — the Ar flow rate is adjusted to 40 seem to carry the produced gases to the analyzer for detection. The experiment is then initiated by activating EM irradiation.

[0313] To gain a comprehensive understanding of reactants’ characteristics during reactions, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and dispersive Raman microscopy are employed to provide detailed structural and compositional insights. SEM analysis, performed using a Hitachi S-4700 Field Emission Scanning Electron Microscope (FE-SEM), reveals the morphological features of the samples before and after the reactions, helping to confirm water-carbon reactions. Images are acquired at an accelerating voltage of 2 kV and a working distance of 3 mm. TEM analysis, conducted with a Hitachi H-9500 instrument, offers further information on carbon products, including crystallinity, amorphous content, and grain size. Due to its high sensitivity to symmetric covalent bonds, Raman spectroscopy is employed to analyze the structural characteristics of the produced carbon throughout the experiments, validating the role of water in the process. These measurements are carried out using a Senterra Dispersive Raman Microscope Spectrometer, with a laser wavelength of 532 nm and an energy setting of 2 pW.

[0314] Results and Discussions

[0315] As previously discussed, higher hydrogen production in the presence of reservoir rocks typically requires temperatures over 600°C under microwave irradiation. However, shale rock may undergo decomposition at such elevated temperatures due to its content of carbonates and organic matter, both of which have been shown to decompose at temperatures above 300 °C (Olszak-Humienik & Jablonski, 2015; Gersten et al., 2000). This decomposition can result in gas generation that may affect the concentration of in-situ hydrogen. To investigate this effect, pure shale rock samples — containing no oil or SiC — were used to study gas emissions resulting from shale decomposition under EM heating. Specifically, shale samples were heated from ambient temperature to approximately 800 °C in an inert environment. Once the temperature reached 800 °C, the EM irradiation was terminated to end the experiments. All gases released during the heating process were monitored.

[0316] Figures 39A-39B present the results of gas production from the decomposition of a 2.0-gram shale sample in accordance with one embodiment of the present disclosure. As previously discussed, shale rocks exhibit a thermal runaway (TR) phenomenon under EM heating at temperatures around 250-280 °C. In this study, TR occurs at 310 °C, and the temperature rapidly rises to 800 °C within just 30 seconds (from the 8th to the 8.5th minute), as shown by the temperature profile (redline) in Figure 39A. During this period, four gases — CO2, CO, H2, and CH4 — are clearly observed in the released gas stream. Figure 39B summarizes the cumulative gas production over time, indicating the gas volumes from shale decomposition: 45.6 cc of CO2 (51.4%), 30.9 cc of CO (34.7%), 10.1 cc of H2(11.3%), and 2.4 cc of CH4(2.6%).

[0317] The high CO2 production is likely due to the pyrolysis of carbonates at temperatures exceeding 500 °C (Bartels et al., 2024), as the shale used in this study contains 22.73% carbonate. The moderate amounts of CO and H2 are primarily attributed to the gas release during TR process (An et al., 2024b). It is worth noting that organic matter pyrolysis also contributes to the generation of minor CH4 and negligible CO2 and H2 (Li et al., 2017; Li et al., 2018) due to the low TOC content (0.8%) in the shale.

[0318] To ensure repeatability, a similar experiment was conducted using a 3.0-gram shale sample. In this experiment, CFLproduction is barely detectable, further confirming the minimal contribution of organic matter pyrolysis to overall gas production in this type of shale. Nevertheless, the production of CO2, CO, and H2 remains consistent with that observed in the 2.0-gram sample, particularly in terms of the ratio of cumulative gases. Based on these findings, the gas generation from the decomposition of the shale under EM heating can be summarized as below:<

[0319] To investigate the role of water in the conversion of oil to hydrogen, two comparative experiments were conducted — one in the absence of water and the other in its presence. In the first experiment, a rock sample was saturated with 0.2 grams of oil (oil-only sample), while in the second, an identical sample was saturated with 0.2 grams of oil and 0.2 grams of water (H2O) (oil-plus-water sample). Note that both samples consist of 80 wt.% shale and 20 wt.% SiC, with an oil-to-water weight ratio of 1:1. Since shale decomposition releases gases, as discussed in Section 3.1, all rock samples were preheated to 800 °C prior to the experiments to eliminate any interference from shale decomposition in the analysis of produced gases.

[0320] Figures 30A-40B present the real-time flow rates of gases generated from shale oil in the two samples in accordance with one embodiment of the present disclosure. Several similarities are observed between the oil-only sample and the oil-plus-water sample: 1) both exhibit comparable temperature profdes, peaking at approximately 650 °C; 2) eight gas components are detected in both samples, including H2, CO, CO2, CH4, C2H4, C2H6, C3H8, and C4H10; and 3) hydrogen is the mostabundantly produced gas in both cases. Despite these similarities, notable differences emerge between the two conditions: 1) production of H2, CO, and CO2 is significantly higher in the oil-plus-water sample compared to the oil-only sample; and 2) yields of CH4, C2H4, and C2-C4 seem to decrease when water is added. Note: (1) The concentrations of C2H6, C3H8, and C4H10 are very low; therefore, they are collectively represented as C2-C4. (2) A certain amount of CO and CO2 is generated even in the oil-only sample, the oxygen element in these carbon oxides may originate from the oil components, adsorbed oxygen on the solid samples (Jie et al., 2019), lattice oxygen in the materials (An et al., 2024a), and even from shale decomposition.

[0321] The quantitative summary of the total gas production from both samples, as shown in Figure 41 in accordance with one embodiment of the present disclosure, further clarifies water's impact on individual gas components. While the oil-only sample yields 22.6 cc of H2 from 0.2 grams of oil, the addition of 0.2 grams of H2O increases hydrogen production to 51.0 cc. One explanation for this enhancement is that water may act as a hydrogen donor, contributing additional hydrogen. Furthermore, the observed reduction in CH4, C2H4, and C2-C4 hydrocarbon gases in the Oil+FEO sample suggests that water further promotes their conversion into hydrogen. In addition, the O1I+H2O sample exhibits a fivefold increase in CO and a threefold increase in CO2 production compared to the oil-only sample. These increases indicate that the oxygen in these carbon oxides likely originates from water, implying that H2O actively participates in the oil-to-FE reactions.

[0322] The total gas concentrations shown in Figures 42A-42B provide additional evidence that water enhances the conversion of oil to hydrogen in accordance with one embodiment of the present disclosure. When 0.2 grams of water is added into 0.2 grams of oil, the hydrogen concentration in the produced gases increases from 41.3% to 47.5%. Simultaneously, the total concentration of carbonaceous gases such as CH4, C2H4, and C2-C4 decreases by approximately 67% (from 45.3% to 14.9% as indicated by the yellow parts in Figures 42A-42B). This reduction is likely due to the formation of reactive radicals during hydrocarbon-water interactions, facilitating more hydrocarbons converted to hydrogen (Yan et al., 2025a). However, it is important to note that water's participation in these reactions also introduces oxygen element, which leads to the formation of carbon oxides. As a result, the concentrations of CO and CO2 increase significantly — an undesirable outcome for in-situ hydrogen.

[0323] Based on the foregoing discussion, the following points can be drawn regarding the basic role of water in enhancing oil conversion to hydrogen: 1) water not only doubles the volume ofthe produced hydrogen by acting as a hydrogen donor, but also increases the hydrogen purity by enhancing reaction activity; 2) water significantly promotes the conversion of short-chain hydrocarbons into hydrogen; and 3) water contributes to higher concentrations of CO and CO2 in the produced gas stream due to its oxygen content.

[0324] Although water enhances hydrogen production during shale oil conversion under EM heating, the specific contribution of water to the total hydrogen yield remains unclear. It is therefore essential to distinguish the hydrogen production contributed by water and shale oil, respectively. To enable this distinction, the labeled hydrogen isotope in heavy water (deuterium oxide, D2O) is employed to identify the source of different types of hydrogen. In this section, a similar experiment was conducted using an oil-plus-water sample, with the only difference being that D2O was used as the water source instead of H2O.

[0325] Figures 43 A-43B display the real-time flow rates of gases generated from the Oil-plus- D2O sample in accordance with one embodiment of the present disclosure. In addition to the eight gas components identified in the Oil-plus-FEO sample (Section 3.2), two additional gases — HD and D2 — are detected in the Oil-plusJZhO sample. To facilitate a clearer presentation of the results, the gases H2, D2, HD, CO, and CO2 are categorized as key gases in Figure 43 A, as they are directly associated with the involvement of D2O in the reactions, which is a central focus of this section. Other gases such as CH4, C2H4, and C2-C4 are grouped as carbonaceous gases in Figure 43B due to their low production and clear origin (from oil pyrolysis), which is not the primary focus of this analysis. Based on the data presented in Figures 43A-43B, the discussion will focus on two aspects: hydrogen production and reaction dynamics.

[0326] In terms of hydrogen production, it is evident from Figure 43 A that H2 is the first type of hydrogen generated from the sample, instead of D2 or HD. It begins to appear at the 3.5th minute, corresponding to a temperature of around 480 °C, and reaches a peak flow rate of 9.7 seem at 660 °C. This strongly suggests that H2 originates from shale oil pyrolysis, as D2O cannot supply hydrogen atoms to form H2. Following the appearance of H2, HD emerges as the second hydrogen species. It becomes detectable at the 4th minute, when the temperature reaches about 590 °C, and gradually increases to a peak flow rate of 2.1 seem around 700 °C. Finally, D2 appears as the third type of hydrogen from the 6th minute and remains at a relatively low production level. The formation of both HD and D2 can be clearly attributed to the involvement of D2O.

[0327] From the reaction dynamics perspective, oil pyrolysis represents the initial stage of the process, occurring between the 3.5th and the 6th minute. This is evidenced by the production of H2 in Figure 43 A and the concurrent production of carbonaceous gases in Figure 43B. It is also noteworthy that carbon oxides (i.e., CO and CO2) are produced during this stage. In addition to the factors discussed in the note for Figures 40A-40B, the effect of water on the reactions is further evidenced by a noticeable time shift in gas production: the peak generation of carbon oxides occurs approximately 40 seconds later (at the 5th minute as the blue dashed line shown in Figure 43A) compared to the peak of other carbonaceous gases, which appears at the 4.3rd minutes as shown by the blue dashed line in Figure 43B. The time shift suggests that D2O alters the reaction equilibrium, either by contributing deuterium and oxygen atoms or enhancing overall reaction activity (Yan et ak, 2025a).

[0328] As the reaction progresses into its second stage, the global reaction CxHy+ D2O — > CO + CO2 + HD + H2 is proposed to be active. This leads to the production of HD starting from the 4th minute, alongside the increased generation of carbon oxides. Subsequently, D2 is produced as the third hydrogen species beginning at the 6th minute, when oil pyrolysis is nearly complete. The formation of D2 is primarily attributed to the coke gasification reaction (Csoiid + D2O —> CO + D2), which occurs when D2O reacts with solid carbon produced from oil at temperatures above 450 °C (Ifticene et al., 2024; Yan et al., 2025a). This solid carbon is a product of oil pyrolysis that takes place between 3.5 and 6 minutes.

[0329] Figure 44 summaries the concentration of gases accumulated during the experiment using the Oil-plus-D2O sample in accordance with one embodiment of the present disclosure. When comparing the results of the D2O sample (Figure 44) with those of the H2O sample (Figure 42B), a high degree of consistency in gas composition is observed between the samples: hydrogen (50.2% vs.47.5%), carbon oxides (32.5% vs. 37.5%), and carbonaceous gases (17.3% vs. 14.9%). This consistency not only confirms the repeatability of the experiments but also suggests that the underlying reaction mechanisms are fundamentally similar for both types of water. The data clearly show that approximately 50% hydrogen can be produced from an oil-water mixture with a 1 : 1 weight ratio under EM heating. Most importantly, the use of D2O allows us to determine that 61.5% (in the form of H2) of the total hydrogen generation originates from oil, while the remaining 38.5% (i.e., HD and D2) is associated with water.

[0330] The following discussion focuses on the effect of water on the solid products formed in the process. As established by numerous studies, solid carbon is a primary solid product resulting from oil pyrolysis (Poutsma, 1990; Devi et al., 2021). The solid carbon produced from shale oil conversion is further characterized using TEM, as shown in Figures 45A-45D. The TEM image in Figure 45A clearly shows that the solid carbon exhibits a long-range crystalline structure, with well-ordered carbon layers stacked together. In terms of morphology, most of the carbon appears as amorphous, as illustrated in Figures 45B and 45C. Additionally, carbon tubes with diameters in the hundreds of nanometers were observed (Figure 45D); however, they are much less prevalent than the amorphous carbon.

[0331] The presence of such solid carbon may inhibit reactions by occupying the active sites of rocks or catalysts during oil conversion. More importantly, as carbon accumulates, it may deposit within the channels and pore structures of shale oil reservoirs, leading to significant permeability reduction and consequently decreasing in-situ hydrogen production. Therefore, investigating the impact of water on the formation and behavior of solid carbon is essential.

[0332] To investigate this, two identical carbon-containing shale samples were prepared via oil pyrolysis under EM heating, using shale samples saturated with 0.4 grams of oil. Following the pyrolysis, the resulting carbon-containing rock samples were saturated with two types of water (H2O and D2O) and then heated by EM irradiation to enable reactions between the water and solid carbon. All gases produced during the process were analyzed using the same methodology described in earlier sections. To gain further insights into the effect of thermal and water content, the two experiments were conducted using varying maximum temperatures (650 °C and 750 °C) and different water quantities (0.2 grams and 0.3 grams) for the H2O and D2O cases, respectively.

[0333] The gas production results from the two experiments are presented on Figures 46A-46D in accordance with one embodiment of the present disclosure. Based on the real-time gas flow rates shown in Figures 46A and 46B, hydrogen (H2 or D2), CO, and CO2 are the primary gaseous products in both cases, regardless of the type of water used. Generally, hydrogen and CO are produced simultaneously, beginning at 460-530 °C — within the temperature range for coke gasification under EM heating (Yan et al., 2025a). Their production trends are similar in both cases, suggesting that hydrogen and CO primarily originate from coke gasification (Csoiid + H2O — CO + H2; Csoiid + D2O CO + D2). Interestingly, CO2 production begins later than hydrogen and CO and is significantly lower in quantity. This means that the water-gas shift reaction (CO + H2O — CO2 + H2 or CO + D2OCO2 + D2) might occur at a low level in the process, contributing small amounts of CO2 and additional hydrogen. In other words, a proportion of CO in the system is consumed by water to form more hydrogen, leading to a slightly higher hydrogen flow rate than CO throughout the process, as shown in Figures 46A and 46B.

[0334] Despite these similarities, notable differences exist between the H2O- and D2O-saturated samples. First, higher water content leads to more gas production. For instance, the peak flow rates of hydrogen, CO, and CO2 in the sample saturated with 0.3 g of D2O are substantially higher than those in the sample with 0.2 g of H2O (D2 / H : 18.9 vs. 7.1 seem; CO: 10.1 vs. 5.4 seem; CO2: 2.8 vs. 0.9 seem). Second, unlike the FbO-saturated sample, minor amounts of H2 and HD are detected in the D2O-saturated sample (Fig. S4), possibly due to hydrogen atoms adsorbed in the carbon formed during oil cracking (Narayanan et al., 2012; Rajasekaran et al., 2013; Strobel et al., 1999). Furthermore, temperature differences cause noticeable fluctuations in gas production. Note that the maximum temperatures reached are approximately 650 °C and 750 °C for the H2O- and D2O-saturated samples, respectively. Correspondingly, the gas production rates are lower in the H2O case, suggesting that higher temperatures enhance gas yield. Examining the total gas composition further supports this: the H2O-saturated sample produced 50% H2, 42% CO, and 8% CO2, whereas the D2O-saturated sample yielded 58% D2, 32% CO, and 10% CO2, as shown in Figures 46C and 46D. These differences likely reflect equilibrium shifts in the reaction dynamics due to temperature variation (Galwey & Brown, 1999).

[0335] Supporting evidence from SEM and Raman analyses confirms that the solid carbon reacts with water during the reaction. SEM images show visibly less carbon in the carbon-containing sample after reaction with water (Figure 47B) compared to the pre-reaction sample (Figure 47 A). Raman spectra of the oil cracking sample in Figure 47C show that the intensity ratio of the D to G band (ID / IG) is close to 1.0, suggesting the presence of amorphous carbon in the sample (Palmer et al.2020). However, there is no carbon signal in the sample after reaction with water (water spent sample), indicating that the carbon was consumed in water-carbon reactions. These findings confirm that the carbon produced from oil conversion can be effectively removed by water under EM heating.

[0336] Several conclusions can be drawn from this section: 1) the majority of solid carbon formed during shale oil conversion to hydrogen is amorphous carbon with a long-range crystalline structure; 2) water reacts with this carbon — primarily via coke gasification, followed by a minor contribution from the water-gas shift reaction — significantly enhancing hydrogen production.Temperature plays a critical role in driving these reactions; and 3) these carbon-water reactions can effectively reduce solid carbon accumulation from shale oil cracking, potentially improving reservoir permeability and thereby increasing the production efficiency of in-situ hydrogen.

[0337] Conclusions

[0338] This study quantitatively investigates the role of water in shale oil conversion to in-situ hydrogen using electromagnetic (EM) heating. It provides new insights into the contributions of water as both a hydrogen donor and a reaction enhancer. The key findings are summarized as follows:

[0339] When shale rock is heated to 800 °C under EM heating, the gaseous products are CO2 (—55%), CO («30%), H2 (—10%), and minor CH4. CO2 primarily originates from the decomposition of carbonates within the shale. CO and H2 come from gas release during thermal runaway (TR) process while minor CH4 is generated from decomposition of organic matters in shale. The decomposition of shale also results in a more porous structure, thereby improving flow conditions within shale reservoirs.

[0340] In oil-water mixtures with a 1:1 weight ratio, water not only doubles the volume of hydrogen produced but also enhances hydrogen purity up to 50% by promoting reactions such as the conversion of short-chain hydrocarbons into hydrogen. Our findings show 61.5% of the total hydrogen originates from oil, while the remaining 38.5% is attributed to the involvement of water.

[0341] Most carbon formed during shale oil conversion is amorphous carbon with a long-range crystalline structure. Water reacts with this carbon primarily through coke gasification and to a lesser extent via the water-gas shift reaction, significantly enhancing hydrogen production. These carbon-water reactions help reduce solid carbon accumulation from shale oil conversion, potentially improving reservoir permeability and supporting sustained in-situ hydrogen production.

[0342] It is worth noting that water also contributes to increased concentrations of CO and CO2 in the produced gas stream due to its inherent oxygen content. This may pose additional challenges for in-situ gas separation processes.

[0343] Biochar for carbon-negative hydrogen production from fossil fuel reservoirs

[0344] Biochar serves as an ideal promoter and catalyst for enhancing energy efficiency and hydrogen production efficiency in the proposed technology. First, being a cost-effective and highly efficient EM-absorbing material (Wen et al., 2024), biochar can lower the required energy to reach the reaction temperatures for methane conversion, thereby enhancing energy efficiency. Second,biochar’s superior catalytic effect will enable more hydrogen production converted from natural gas due to its high specific surface area, rich functional groups, and complex network structure (Zou et al., 2022). Most importantly, biochar is a carbon-rich substance originally formed through the absorption of CO2 by plants. One study has characterized that various types of biochar contain 44-72 % carbon (Novak et al., 2009). Assuming that 10 % of the biochar is applied to the pore volume of a medium-scale gas reservoir (Radius 5,000 m and depth 8 m), approximately 3.7-5.6 million tons of biomass waste could be captured underground, leading to the sequestration of 1.6-4.0 million tons of carbon in the reservoir. Therefore, applying biochar to subsurface reservoirs can facilitate long-term carbon sequestration, highlighting its substantial carbon-negative potential.

[0345] Natural gas, also known as fossil gas, methane gas, or simply gas, is a natural mixture of gaseous hydrocarbons consisting primarily of methane95 %). Natural gas accounts for approximately 30 % of the energy consumed in the United States. Due to its high atom ratio of hydrogen to carbon (H:C « 4), natural gas holds great potential for conversion to hydrogen. Therefore, in this work, we propose biochar-assisted in-situ hydrogen production from gas reservoirs rather than oil reservoirs. The application of biochar in the conversion of natural gas to hydrogen will be mainly discussed.

[0346] Several uncertain aspects may pose risks to the implementation of the proposed approach. For one thing, the parameters and feedstocks used for biochar synthesis affect biochar’s properties, potentially resulting in unstable performance of biochar for methane conversion. Secondly, successful implementations of technologies necessitate collaboration across various industries and societal endeavors; any uncertainty during its life cycle may impair the viability. Furthermore, current technologies face multiple challenges in EM-heating efficiency, natural gas conversion, well integrity, and membrane separation. Addressing these potential risks is crucial, particularly when integrating interdisciplinary disciplines as a new approach. In the following sections, we will evaluate the feasibility and outline the pathway by critically reviewing current technological advancements and identifying key bottlenecks and limitations.

[0347] Biochar preparation and application

[0348] The synthesis of biochar is primarily influenced by 1) feedstock materials, 2) temperature, and 3) heating parameters including heating method, heating rate, and residence time. These factors collectively affect the yield and the physicochemical properties of biochar, which in turn impacts its enhancing role in natural gas conversion to hydrogen under EM heating.

[0349] Cellulose, hemicellulose, and lignin are the three primary components of lignocellulosic biomass crucial for biochar formation during pyrolysis (Jin et al., 2021). Both cellulose and hemicellulose consist of simple monomers that can decompose below 450 °C (Lee et al., 2019), undergoing a depolymerization pyrolysis (Wan et al., 2020). In contrast, lignin is a complex, three-dimensional benzene-propane polymer with a high molecular weight and significant functional groups (Stefanidis et al., 2014), requiring temperatures exceeding 500 C for complete decomposition. Cellulose plays an irreplaceable role in forming the biochar skeleton and carbon fixation (Zou et al., 2022), whereas higher lignin content in the feedstock leads to higher biochar production (Cagnon et al., 2009; Shariffet al. 2016).

[0350] Moisture is another component in feedstock that impacts the yield of biochar. Higher moisture content not only impedes biochar formation (Kloss et al, 2012), but also substantially increases the required energy for heating compared to the material with lower content of water (Tripathi et al., 2016). Therefore, low moisture levels in feedstock are preferred for biochar production. Furthermore, the ash content in biomass can also influence biochar’s formation. Metal compounds found in ash, such as K, Fe, and Mg, can have notable catalytic effects on biomass pyrolysis, potentially reducing the biochar production (Yaman, 2004).

[0351] The type of feedstock also affects the specific surface area (SSA or BET surface area) of the synthetic biochar. Several studies indicate that woody biomass with higher lignin content produces biochar with a greater SSA compared to those with lower lignin content (Li et al., 2023). This phenomenon is primarily attributed to the degradation of lignin during pyrolysis, which promotes the development of pores and porosity through the release of hydrocarbon liquids and gases (Chen et al., 2012). Additionally, the ash content in feedstock also has a detrimental effect on SSA (Wang et al., 2015). According to the research data (Ronsse et al., 2013), the feedstock derived from wood with the lowest ash content yields the biochar with the highest SSA. This is likely due to molten ash filling or blocking pores within the biochar structure, thereby reducing its surface area.

[0352] Based on the above discussion, woody biomass with high lignin, low moisture, and low ash content appears more suitable for higher biochar yield compared to non-woody biomass, which typically has low lignin, high moisture, and high ash content. This choice benefits both the production of biochar and its specific surface area. Nevertheless, pursuing low ash content may negatively impact the catalytic effect of biochar. Research shows that certain inorganic elements can enhance natural gas conversion to hydrogen under EM heating (An et al., 2024b; Yan et al., 2024b).Therefore, the role of ash content for biochar yield and hydrogen production under EM heating requires further investigations.

[0353] Temperature is the most critical factor in determining biochar yield and its properties during biomass pyrolysis (Tomczyk et al., 2020; Cheah et al., 2016). Typically, abiochar yield of 30-40 % can be achieved at around 500 °C, with higher temperatures generally resulting in lower biochar production, as evidenced by many studies. (Zama et al., 2017; Rafiq et al., 2016; Zhao et al., 2017). Biochar is mainly formed during the primary pyrolysis of biomass below 450 °C. If the temperature continues to increase, the input energy will surpass the bond dissociation energy of some other volatile components in the biomass and even the generated char. As a result, these substances will decompose through secondary reactions, i.e., reforming, tar cracking, and dehydrogenation, thereby reducing biochar yield (Tripathi et al., 2016; Kan et al., 2016). Therefore, a relatively lower temperature is often preferred for higher biochar yield. However, biochar produced at low temperatures may exhibit low thermal stability, which can affect its catalytic effectiveness at high temperatures.

[0354] The temperature of biomass pyrolysis highly influences SSA of produced biochar. Biochar generated at higher temperatures can exhibit 3-5 times greater SSA compared to that produced at lower temperatures (Zama et al., 2017; Rafiq et al., 2016; Zhao et al., 2017). This enhancement is likely attributable to the decomposition of organic components like cellulose and lignin, leading to the formation of vascular bundles, micropores, and channel structures (Zhao et al„ 2017; Katyal et al., 2003). Consequently, these porous structures lead to larger SSA of biochar (Rafiq et al., 2016). Typically, biochar produced at temperatures below 400 °C has a relatively low SSA (Kloss et al., 2012; Uchimiya et al., 2010). With such low SSA, the biochar may not be of significant industrial importance. Therefore, to achieve an effective SSA in biochar for enhancing methane conversion to hydrogen, a temperature of 500 °C for biomass pyrolysis is necessary (He et al., 2018).

[0355] Furthermore, pyrolysis temperature also affects the ash content in biochar. Increasing pyrolysis temperature results in higher ash content of biochar, because of the gradual concentration of inorganic constituents during biomass pyrolysis (Chen et al., 2008; Chen et al., 2014). A high ash content in biochar may improve its catalytic performance for natural gas conversion to hydrogen, as ash contains significant amounts of trace metal elements (Yargicoglu et al., 2015). Furthermore, high pyrolysis temperatures can break and rearrange chemical bonds in biomass, shaping and forming more surface functional groups in biochar (Parvez et al., 2019), thereby enhancing the catalytic effect ofbiochar. However, in-depth fundamentals and mechanisms need to be further investigated for such catalysis.

[0356] Depending on heating methods, biomass pyrolysis can be classified into traditional pyrolysis and microwave pyrolysis. Traditional pyrolysis relies on heat convection through materials via electrical heating. In contrast, microwave is a form of EM radiation with a frequency range of between 300 MHz and 300 GHz, and microwave heating does not necessarily involve heat convection through materials (Foong et al., 2020). During microwave heating, the alternating EM field causes the dipoles of molecules within materials to align with the changing of electric field, resulting in polarization. This process generates frictional heat within the molecular structure (Al-harahsheh and Kingman, 2004), thereby raising the temperature of the material. For microwave pyrolysis, parameters of low temperature, low heating rate, and low microwave power have been shown to contribute to a higher yield of biochar (Foong et al., 2020; Ethaib et al., 2020). Moreover, many carbon-based materials are excellent absorbers of microwaves, which enhances heating efficiency and reduces electricity consumption during biomass pyrolysis.

[0357] Based on differences in heating rates, pyrolysis can be classified into flash pyrolysis, fast pyrolysis, and slow pyrolysis. A low heating rate (slow pyrolysis) typically avoids secondary pyrolysis reactions and ensures minimal thermal cracking of biomass, resulting in a higher yield of biochar. Conversely, a high heating rate can lead to biomass fragmentation and increase the production of gaseous and liquid products, thereby reducing biochar yield (Angin, 2013; Aysu and Kiiguk, 2014). Additionally, the heating rate also influences the elemental content, morphology, and specific surface area of the biochar (Zhao et al., 2018; Ulusal et al., 2021).

[0358] Residence time is closely tied to pyrolysis temperature and heating rate, which makes it challenging to evaluate its role in biochar production. Commonly, a longer residence time at lower temperatures is beneficial for higher biochar yield, as biomass can undergo more repolymerization over extended periods (Lee et al., 2020; Mutsengerere et al., 2019). However, some researchers hold different opinions. Although they agreed residence time can affect the composition of liquid and gaseous products, they suggested its influence on biochar yield is limited (Mohamed et al., 2013). Similarly, there are conflicting observations regarding the impact of residence time on the development of pore structures. While some people observed that longer residence time enhances the pore size of biochar (Tsai et al., 1997), other researchers indicated that the prolonged residence time may damage the pore structure by decreasing the H / C ratios and promoting the formation of highlycondensed aromatic-ring structures in biochar (Akhil et al., 2021). These uncertainties pose challenges in the synthesis of biochar, possibly leading to unstable performance of biochar during its applications.

[0359] Although there are various synthetic methods for biochar, the biochar produced through simple pyrolysis often exhibits drawbacks such as poor surface functionality, low SSA, and limited porosity. These limitations can reduce its effectiveness as both a catalyst and a support in the in-situ hydrogen technology. To enhance its performance in applications, activation and modification techniques are usually employed to optimize these key properties of biochar (Patra et al., 2021).

[0360] The mechanism of activation is to initiate micro-level erosive reactions on the surface of biochar using different agents. This process leads to significant development of pore structures and functional groups. Through activation, biochar can achieve a typical SSA ranging from 400 to 1300 m2 / g, thereby enhancing its catalytic ability and adsorption capacity (Cha et al., 2010; Rambabu et al., 2015; Jiang et al., 2020; Shao et al., 2018; Zhao et al., 2023; Tehrani et al., 2015; Ahmed et al., 2019; Demiral et al., 2015; Shen et al., 2020; Kim et al., 2020; Hayashi et al., 2002). The resulted biochar from this process is referred to as activated biochar or activated carbon. Based on the agent used, activation methods are classified into two categories: physical activation and chemical activation.

[0361] Physical activation usually employs steam, CO2, and air as activating agents within a typical temperature range of 700-900 C (Sajjadi et al., 2019). The fundamental involves the erosion of carbon matrix through reactions associated with water or CO2. There is no corrosive liquid waste produced in the process, making it an environmentally friendly method (Sun et al., 2020). However, physical activation is energy-intensive due to its demand for a high flux of quality gases and high temperatures.

[0362] In contrast, chemical activation is more commonly utilized in activating biochar due to its lower energy consumption and higher efficiency. Chemical activation mainly employs two categories of agents: acids and alkalis (Cha et al., 2010; Rambabu et al., 2015; Jiang et al., 2020; Shao et al., 2018; Zhao et al., 2023; Tehrani et al., 2015; Ahmed et al., 2019; Demiral et al., 2015; Shen et al., 2020; Kim et al., 2020; Hayashi et al., 2002). Reactions between these agents and biochar involve dehydration and oxidation within the temperature range of 500-800 °C. Generally, chemical activation results in a greater SSA and a larger porosity of the activated biochar compared to physical activation (Patra et al., 2021). However, a big issue of chemical activation reagents, such as KOH and ZnCh, istheir highly corrosive nature. These agents have the risk of reacting with facility components during the activation process.

[0363] Modification is another way to enhance the catalytic effectiveness of biochar by incorporating additional functional groups and metal nano-particles into its structure. This approach arises because catalytic activity in materials typically originates from three groups: 1) edge atoms and defect sites (Inyang et al., 2014); 2) functional groups (Zhange et al., 2012); and 3) doped metal atoms (Kong et al., 2020). These features are crucial for biochar in catalyzing natural gas into hydrogen. Common methods employed to modify biochar properties include doping metal nanoparticles and preparing biochar-nanocomposites (Zou et al., 2022). Metal nanoparticles such as Fe, Mn, and Mg possess higher SSA and excellent adsorption abilities, making them effective in many catalytic reactions (Rodriguez-Narvaez et al., 2019). However, these nano-particles are prone to agglomerate due to their high surface energy, leading to rapid deactivation during catalysis. When metal nanoparticles are doped onto the surface of biochar, the biochar structure aids in distributing and stabilizing these nanoparticles (Zhang et al., 2020), thus mitigating agglomeration and improving catalytic stability. Moreover, biochar also acts as a reduction medium that converts metallic oxides into metals or serves as a co-catalyst, further enhancing the catalytic effectiveness (Guo et al., 2019).

[0364] Another approach of modification is incorporating carbon-based nanomaterials such as carbon nanotubes or nanofibers into biochar to create biochar-nanocomposites. The most used method for this approach is wet impregnation, which involves mixing raw biomass materials with a suspension of nanomaterials, followed by dry and decomposition at high temperatures in an inert environment. The resulting biochar-nanocomposites exhibit increased acidic functional groups, larger SSA, and improved thermal stability. These characteristics make biochar highly suitable in catalytic applications.

[0365] While activation and modification significantly enhance the catalytic performance of biochar, these processes come with associated challenges. Activated biochar requires additional energy and operational costs, while modified biochar involves the use of expensive materials such as medals and nanomaterials. These factors can increase the overall cost of biochar, posing a heavy economic burden on its widespread applications.

[0366] Based on the discussion above, the following conclusions can be drawn regarding how different synthesis parameters affect the properties of the resulting biochar: 1) Higher temperatures improve stability but result in a lower yield of synthetic biochar; 2) The heating rate and time maintaina balance between porosity and structural integrity; 3) Feedstock selection impacts the final properties of biochar, influencing its efficiency for methane cracking; 4) Activation and modification increase the specific surface area and functional sites of biochar, enhancing its catalytic performance.

[0367] Biochar has been extensively utilized in pyrolysis of biomass or plastic to produce biooil and hydrogen (Shen et al., 2020; Wang et al., 2021c). Its significant catalytic effect has led to expanding applications in methane conversion to hydrogen. The applications of biochar in catalyzing methane cracking are mainly through 1) incorporating other elements into biochar; 2) activating raw biochar to activated carbon; and 3) utilizing raw biochar (Feng et al, 2023; Zhao et al, 2023; Wang et al., 2020; Kundu et al., 2021; Jarun et al., 2020; Wen et al., 2024; Patel et al., 2020; Haxman et al., 2023; Dufour et al., 2008).

[0368] Incorporating other elements, especially metals, into biochar has shown evident improvements in its catalytic effectiveness. For instance, integrating Fe2Oa into the biochar derived from rice-husk achieves a CFU conversion of 24.4 % at 850 °C with a CPU flowrate of 83.3 ml / min (Feng et al., 2023). Zhao et al. demonstrate that doping phosphorus (P) into enteromorpha prolifera-based (EP) biochar significantly enhances methane conversion, resulting in 5.8 times higher hydrogen output at 950 C compared to the biochar without P element (Zhao et al., 2023). Another study shows that activated carbon doped with Ni, Co, and Fe elements achieves over 80 % CH4 conversion at 850 C (Wang et al., 2020). Remarkably, researchers have achieved the highest CH4 conversion of 95.7 % at 800 °C with a CH4 flowrate of 5 ml / min by impregnating cellulose biochar with an iron nitrate solution (Kundu et al., 2021).

[0369] Activated biochar also exhibits effective catalysis on methane conversion to hydrogen. For example, studies have reported a methane conversion of 71 % at 900 °C with a NaOH-activated biochar from biosolids (Patel et al., 2020). A methane conversion of 51 % at 800 °C after 60 hours using the activated biochar derived from Douglas fir has also been obtained (Harun et al., 2020). Another research demonstrates that a HiPCh-activated biochar has led to a methane conversion of over 90 % at 700 °C under EM heating, along with a weight hourly space velocity (WHSV) of 0.3 L / (h»gcat) and a methane flowrate of 6 ml / min (Wen et al., 2024). The exceptional catalytic performance of activated biochar may stem from the formation of new functional groups, increased pore size, expanded specific surface area, and removal of pore blockages (primarily in micropores) during the activation process (Krzyz'yn'ski and Kozlowski, 2008).

[0370] Typically, activated biochar is preferred as a catalyst for methane conversion due to its higher surface area and superior performance over raw biochar (Feng et al, 2023; Zhao et al, 2023; Wang et al., 2020; Kundu et al., 2021; Jarun et al., 2020; Wen et al., 2024; Patel et al., 2020; Haxman et al., 2023; Dufour et al., 2008). However, the activation process requires more energy and costs. Therefore, the use of raw biochar without activation has recently attracted significant interest. The biochar catalyst derived from palm kernel shell shows a 35 % initial CH4 conversion and the highest initial hydrogen yield of 95 % under 650 °C at a WHSV of 1.2 L / (h»gcat) (Hazman et al., 2023). Patel et al. reported a maximum initial methane conversion of 65.2 % and a final methane conversion of 40 % using raw biochar for methane decomposition at 900 °C (Patel et al., 2020). Other than that, researchers have demonstrated that raw wood biochar contributes to a 70 % methane conversion to hydrogen at 1000 C (Dufour et al., 2008). These results highlight the excellent catalytic activity of raw biochar in promoting hydrogen production from hydrocarbon pyrolysis, even without activation.

[0371] Therefore, biochar products hold great potential for catalyzing methane conversion to hydrogen for in-situ hydrogen production from gas reservoirs. However, it is crucial to note that the methane conversion in these studies is closely linked to methane flow rate and WHSV, with higher conversion rates typically observed at lower methane flow rates and lower WHSV. Considering the gas flow rates in field conditions are much higher than those in lab-scale studies, the feasibility of biochar for field applications requires further evaluations. Moreover, the total cost of activated biochar may significantly increase due to the usage of chemical reagents, metal particles, and electricity in the activation process. Therefore, in terms of economic feasibility, raw biochar may be preferable for practical field applications. However, current research on catalytic methane conversion using raw biochar is very limited, necessitating further studies.

[0372] Normally, excellent EM-absorbing materials should meet four criteria: strong adsorption, wide bandwidth, light weight, and thin thickness (Elmahaishi et al., 2022; Zhang et al., 2018). Due to its exceptional properties such as low density, multiple polarization, excellent durability, and superior dielectric loss (Liu et al., 2008), bio-char has been recognized as an outstanding EM-absorbing material (Zhao et al., 2018). Reflection loss (RL) is a key dielectric parameter for evaluating EM absorption performance. RL measures the extent to which a material reflects EM waves at a specific frequency and is expressed as a negative value. Typically, a higher RL value indicates a lower reflection of EM waves and a stronger EM-absorbing ability (Gu et al., 2023). The frequency range with an RL value of less than - 10 dB is referred to as the effectiveabsorption bandwidth (EAB) of a material. This means at least 90 % of EM energy can be effectively absorbed by the material within this frequency range (Lan et al., 2024).

[0373] Studies indicate that biochar derived from pine sawdust can be heated up to 700 °C under EM irradiation at a frequency of 4.225 GHz and a power of 0.1 kW, demonstrating biochar’s strong EM-absorbing capabilities even with low input powers. Furthermore, the spent bio-char still exhibits excellent EM-absorption with a RL value of - 73.1 dB at a thickness of 2.1 mm (Wen et al., 2024). Another type of biochar synthesized from wooden and bacterial celluloses exhibits a minimum RL of - 57.97 dB and an EAB of 6.28 GHz. Strikingly, this biochar maintains 90 % EM-absorbing capability even after 500 bending-releasing cycles (Yin et al., 2022). Therefore, biochar holds great potential for reducing energy consumption due to its excellent EM-absorbing capabilities during EM heating.

[0374] To further enhance EM-absorbing performance of biochar, researchers integrate magnetic metal particles into biochar to form nanocomposites for optimizing the impedance matching (Elmahaishi et al., 2022). Magnetic alloy nanoparticles such as Fe, Ni, and Co, known for their high permeability, large saturation magnetization, and high Curie temperature, can significantly improve EM-absorbing ability (Yin et al., 2020). For instance, Sun et al. have successfully incorporated Fe, Ni, and Co into pomelo-peel biochar using a physical blending method, resulting in a material with a minimum RL of - 41.6 dB and an EAB of 4.3 GHz at a thickness of 3 mm (Sun et al., 2022). Another study has integrated Fe / FesC into biochar by a chemical impregnation method, achieving a minimum RL of - 50 dB and a EAB of 5.6 GHz (Zhang et al., 2022). These findings, along with the results presented in the figures, have demonstrated that the EM-absorbing properties of biochar can be optimized by adjusting the types and concentrations of magnetic particles. This adjustment consequently enhances heating efficiency ofbiochar under EM irradiation.

[0375] In field applications of in-situ hydrogen technology, the heating efficiency is a challenge due to the poor EM-absorbing ability of reservoir rocks. By incorporating biochar into subsurface formations, the EM-heating efficiency of the biochar-containing rocks could be highly improved, allowing for achieving the required temperatures of natural gas conversion with lower energy input. As a result, utilizing biochar could lead to a substantial reduction in electricity consumption and hydrogen costs, thereby enhancing the economic viability of the proposed technology.

[0376] Feasibility

[0377] Extensive research and large-scale industrial pilots in the oil industry have demonstrated the feasibility of using EM heating in reservoirs (Kasevich et al., 1994; Hiebert et al.1986; Davison, 1995). Pilot tests conducted in shale rocks during the 1980s show that EM heating could raise the temperature of oil shale to 400 °C (Bridges et al., 1983). This temperature could reach higher at a higher power designed for in-situ hydrogen production within petroleum reservoirs. Studies also indicate that EM waves can penetrate rocks into depths of 1-5 m depending on the frequency (Morte et al., 2019; Emissions Reduction Alberta, 2022), with lower frequency penetrating into deeper formation. Considering this, designing a downhole EM antenna distributed along horizontal well could heat a substantial volume of the targeted formation, given the average lateral length of horizontal well in Permian Basin, U.S. is about 3000 m on average. This heated zone can serve as a reactor or generation zone, facilitating sufficient hydrogen production as natural gas flows from reservoirs to wellbores.

[0378] Another efficient approach to convert in-situ natural gas to hydrogen involves installing a synthetic ‘downhole generator’ within gas wells. This generator is purpose-synthesized by highly efficient EM-absorbing materials and catalytic substances like biochar, silicon carbide, and metal elements. The shape of the generator is customized to fit the annular space of the wellbore and the EM antenna. Once installed in boreholes, the synthetic generator (not the surrounding reservoir rocks any more) is heated by EM energy. Due to the excellent EM absorption capability and strong catalytic effect of the generator, facilitating methane conversion to hydrogen with low energy input can be achieved. This method can enhance both heating efficiency and hydrogen production efficiency. However, its successful implementation is determined by advanced fabrication techniques and high-quality chemicals. Further technical evaluations and risk assessments throughout the process are essential.

[0379] Regarding hydrogen separation and extraction, cutting-edge technologies in membrane and material science are pivotal. Hydrogen-selective membranes, including polymer, metallic, and ceramic types, have been used in hydrogen production under surface conditions (Adhikari and Femado, 2006). This experience extends their potential application in subsurface conditions with purpose-built downhole membrane separators. Notably, metallic membranes, such as Pd alloy membranes, can achieve hydrogen purity levels as high as 99.99% (Uemiya, 2004), indicating an exceptional separation efficiency. Moreover, the relatively high downhole pressures and temperatures can be leveraged for running membrane separators. However, challenges such as highcost, susceptibility to sulfur poisoning, contaminants, thermal instability, and failures under harsh conditions may hinder its field applications (Liguori et al., 2020; Ifticene et al., 2023).

[0380] Furthermore, the extensive use of fracturing engineering in the petroleum industry enables the delivery of biochar particles into subsurface reservoirs, allowing for its precise placement within targeted formations (Zhang et al., 2016). In addition, advanced materials science provides the potential for developing highly resistant materials that address corrosion and hydrogen embrittlement issues (Alnaeli et al., 2023). The successful synthesis of superalloys (Balitskii et al., 2023; Balyts’kyi et al., 20189) offers a promising solution for high-quality well constructions specifically designed for hydrogen production, safe-guarding well safety throughout the extraction process. Nevertheless, high cost of quality materials may remain an obstacle during the applications.

[0381] Biochar-assisted in-situ hydrogen production from gas reservoirs via EM heating represents a novel interdisciplinary technology that bridges multiple established industries, including petroleum, agriculture, biomass, chemical, physics, hydrogen, and power. By leveraging current resources and expertise from these diverse fields, the efficiency and feasibility of this approach can be significantly enhanced.

[0382] First, biochar is produced from biomass, a cost-effective and abundant resource in agriculture, including various forms of agricultural waste. Using biochar as a subsurface catalyst not only lowers the catalyst cost for in-situ hydrogen production but also addresses agricultural waste issues. The agricultural infrastructure can also contribute to the synthesis of the required biochar. Second, cutting-edge technologies in chemical engineering ensure biochar possess desired properties such as dielectric parameter, size, surface area, durability, and catalytic capability, thereby enhancing its heating efficiency and catalytic performance under EM heating. Third, the expertise and experience in the electrical industry are crucial for improving and deploying downhole EM-tools. Furthermore, leveraging renewable energy like wind and solar power, alongside the local negative wholesale electricity prices for about 25 % of time annually (Seel et al;, 2021), can effectively reduce the cost for both biochar preparation and in-situ EM heating, thereby enhancing the cost-effectiveness of hydrogen production.

[0383] For the petroleum sector, extracting pure hydrogen directly from reservoirs eliminates the need for oil and gas extraction, transportation, separation, and refining processes. This reduces operational costs and mitigates carbon emissions (CI E and CO2) associated with the entire life cycle of the traditional extraction. Importantly, millions of abandoned and orphaned gas wells containingunrecovered hydrocarbons (Cronin et al., 2019) could potentially be repurposed for in-situ hydrogen production, thereby enhancing the asset value of petroleum companies. In addition, leveraging existing infrastructure and dataset in oilfields can enhance the economic viability of the technology. Expertise in petro-physics, logging, reservoir engineering, drilling, completion, and fracturing provide tremendous support for the proposed technology. Meanwhile, the petroleum industry also shows a clear commitment to advancing such hydrogen technologies in the context of energy transition.

[0384] Since the proposed in-situ hydrogen technology is a new concept, no economic feasibility studies have been conducted yet. Nevertheless, the assessments of energy efficiency and techno-economic analysis (TEA) for hydrogen production from methane in the presence of reservoir rocks via EM heating offer some insights into the hydrogen cost. Neufeld evaluated the hydrogen cost at an electricity price of $0.08 / kWh based on the in-situ hydrogen process considering reservoir rocks. The calculated hydrogen cost is $2.67 / kg when 15 kWh of EM-energy is required to produce 1 kg of hydrogen, and $0.89 / kg when 5 kWh of energy is needed for that (Neufeld, 2023). This indicates that the energy or electricity used for each unit of hydrogen under EM heating greatly impacts the hydrogen cost. Considering biochar is more energy efficient under EM heating than reservoir rocks, its application in this process will substantially reduce the required electricity, thus boosting energy efficiency and decreasing the hydrogen cost. Another study shows that a lab-scale system achieves an energy efficiency of 14.6 % at a methane flow rate of 150 seem, and the lowest hydrogen price is $0.86 / kg at an electricity price of $0.03 / kWh (Yan et al., 2024c). This suggests that electricity price is another crucial factor influencing the hydrogen cost. In addition, this study also demonstrates that energy efficiency increases with higher methane flow rates. Given that methane flow rates in reservoir conditions are much higher than those in the lab, the energy efficiency could be significantly improved in field applications. Moreover, deploying effective catalysts to increase the conversion of natural gas to hydrogen offers another pathway for improving energy efficiency. It is worth noting that the above assessments are based on the EM-heating efficiency of reservoir rocks. Consequently, the required energy to produce each unit of hydrogen in these models is relatively high due to the poor EM-absorbing properties of the rocks. If biochar was used in this process, the required EM-heating energy could be lowered due to its excellent EM-absorbing ability, significantly reducing the hydrogen cost. In addition, through leveraging available renewable energies, industrial synergies, and clean hydrogen credits under Section 45V of the Inflation Reduction Act (IRA 45 V), the hydrogen cost could decrease further. Therefore, achieving a hydrogen price of $ 1 / kg by 2031 seems achievable. However,it should be noted that these TEA results are based on ideal assumptions. Practical conditions may introduce uncertainties that could affect the evaluation results.

[0385] The world is striving to achieve a net-zero emissions economy no later than 2050. Concerns about climate change and growing carbon footprint have led to increased public awareness of environmental issues. For instance, research indicates that about 80 % of people suggest that clean energy could offer significant benefits in tackling pollution (Almulhim, 2022). These public opinions and concerns play a crucial role in shaping energy policies and fostering financial development (Oluoch et al., 2021). The resulting policies and financial support are intertwined in driving energy transition and promoting clean hydrogen technologies.

[0386] The development of clean hydrogen technologies has been driven by the increasing allocation of public funds and the implementation of environmental policies. In October 2023, the U.S. government announced $7 billion to establish seven regional clean hydrogen hubs, aiming at boosting the market for low-cost and clean hydrogen. These hubs are expected to leverage over $40 billion in private investment and create tens of thousands of well-paying jobs, resulting in a total investment of nearly $50 billion in hydrogen hubs. There is no doubt that such financial support will significantly accelerate the development of the in-situ hydrogen technology. Another form of support is the adoption and implementation of carbon tax legislation. As of 2024, 37 carbon tax programs have been implemented worldwide. Consequently, global energy companies are reassessing their current resource portfolios to prioritize cleaner energy sources. This undoubtedly increases the chances of hydrogen energy standing out from the realm of alternatives, thus driving the advancement of hydrogen technology.

[0387] As public efforts in the clean hydrogen sector intensify, an increasing number of technical potentials, engineering innovations, and knowledge gaps related to hydrogen are being identified. In turn, these expanding knowledge and accumulated experience further equip policymakers, stakeholders, and professionals to design effective initiatives for advancing clean hydrogen production. Collectively, these elements create a supportive environment for the growth of the proposed technology.

[0388] Limitations and challenges

[0389] Previous discussions have highlighted the potential of extracting carbon-negative hydrogen from gas reservoirs through the application of biochar under EM heating. Although key technical components like hydrocarbon conversion, EM heating, biochar synthesis and applicationare well-developed within their respective domains, integrating them into a new technology exists multiple challenges.

[0390] First, the production efficiency of in-situ hydrogen can be affected by various geological conditions. Unlike natural gas, hydrogen molecules are smaller and lighter, making it easier to diffuse through porous media. Therefore, the quality of caprocks (impermeable layers above reservoirs) is crucial to prevent hydrogen diffusion. Poor sealing ability of caprocks may cause low production efficiency due to hydrogen loss through highly permeable regions. Additionally, seismic faults and natural fractures in formations can lead to further risk of hydrogen leakage. Moreover, high pressure and high flowrate in natural gas reservoirs may decrease the conversion of natural gas to hydrogen, lowering hydrogen production. Therefore, further experimental and simulation works using practical parameters are essential to optimize production strategies and technical parameters for efficient hydrogen production.

[0391] Second, the catalytic efficiency of biochar in converting natural gas to hydrogen remains uncertainties. One consideration is that synthetic biochar may further decompose at high temperatures during EM application. For example, our recent experiments demonstrate that 0.3 g of com stover-derived biochar produces 12.3 ml ofFE, 10.5 ml of CO, 7.0 ml of CO2, and 3.5 ml of CH4 when the temperature is increased from ambient to 550 °C under EM irradiation. This decomposition could alter the biochar’s properties, leading to uncertainties in its catalytic performance. Additionally, the high salinity and impurities (e.g., sulfur) in reservoirs could potentially poison biochar (Argyle and Bartholomew, 2015) and impair the catalytic effect. Moreover, since there is always formation water presented in reservoirs, biochar may react with water to produce syngas at high temperatures (Sun et al., 2024; He et al., 2023), deviating from its intended purpose. Finally, catalytic deactivation over time remains an inevitable challenge during the use of biochar. To address these problems, more investigations into biochar’s catalytic performance under various scenarios are necessary for a commercial hydrogen program.

[0392] There are also challenges in the realm of downhole technologies. Currently, large-scale applications of membrane technology remain theoretical, as there is a lack of sufficient studies to validate their performance under industrial conditions. However, metallic membrane reactors have shown promising potential for small-scale hydrogen production (Liguori et al., 2020). This could lead to a significant advancement in the technological readiness of membrane technology over the next decade. Nevertheless, the high capital investment and maintenance costs may further hinder itswidespread applications. As for the sub-surface applications of EM heating, research on actual temperatures and rock penetration depths under reservoir conditions is still limited, presenting considerable challenges for engineering design. Furthermore, the low EM-heating efficiency of rocks remains another concern. Consequently, field tests and energy-related research are urgently needed to address these knowledge gaps.

[0393] Well safety is another critical issue associated with the proposed technology. When reservoir rocks are heated to temperatures over 600 °C, components such as carbonates may undergo self-decomposition, resulting in the formation of voids, fractures, and macropores in the rock matrix. This thermal degradation can weaken rocks’ strength, potentially causing borehole collapse or even blockage. Additionally, these structures may also cause hydrogen gas leakage under high pressures. Moreover, the harsh subsurface conditions — such as the presence of corrosive substances like EE, H2S, CO2, and high-salinity water — can accelerate the corrosion and failure of well infrastructure such as wellheads, tubing, and subsurface tools. This not only imposes substantial economic costs to maintain well integrity but also introduces potential risks related to hydrogen leakage. This highlights the significance of stricter well integrity standards for hydrogen wells compared to traditional oil and gas wells. Meanwhile, there is a pressing need to develop more advanced and durable techniques specifically tailored for in-situ hydrogen extraction by leveraging high-quality materials and cutting-edge industrial resources.

[0394] Summary

[0395] This work provides technical insights into the viability of an emerging, high-risk, and high-reward technology: biochar-enabled carbon -negative hydrogen production from natural gas reservoirs using EM heating. The technological feasibility is evaluated through assessing synthesized parameters, optimizing properties, evaluating catalytic performance, and exploring the energyenhancing role of biochar from various perspectives. It demonstrates that applying biochar in reservoirs holds great potential to address challenges in the hydrogen, petroleum, and biomass industries, particularly targeting low hydrogen efficiencies and high carbon emissions. Biochar inherently exists strong catalytic effect on hydrocarbon pyrolysis and excellent absorption ability under EM irradiation, which can promote natural gas conversion and EM-heating efficiency, thereby achieving higher hydrogen production efficiency with lower energy input. In addition, introducing biochar into subsurface reservoirs offers significant benefits for enhancing carbon-negative potential.

[0396] The successful implementation of this technology requires engineering techniques, cross-disciplined collaborations, interdisciplinary knowledge, and public support. However, challenges and limitations in areas such as geological risks, downhole technique applications, catalytic efficiency of biochar, and extraction safety still exist, potentially hindering the technological readiness level and impeding on-site applications. It is also important to note that technological innovations require ongoing research and development in both technology and infrastructure, which can result in high capital and operating expenditures. Fortunately, by leveraging renewable energies, carbon tax credits, existing assets across various industries, and other incentives amid the global energy transition, biochar-assisted in-situ hydrogen production and extraction may become economically viable, potentially achieving a hydrogen cost of below $l / kg. Given the highly developed modem industry, the growing demand for clean energy, and strong public efforts toward net-zero emissions, enabling this efficient, cost-effective, and carbon-negative technology is expected to open a new pathway for clean hydrogen and potentially benefit several industries in the future.

[0397] Biochar for Electromagnetic Conversion of Natural Gas to In-Situ Hydrogen Production: Energy Enhancer, Catalyst, and Facilitator

[0398] Biochar-assisted hydrogen generation from natural gas within rock matrix by EM heating will now be discussed. To address the above-mentioned knowledge gaps, a total of 18 experiments were conducted to investigate biochar’s triple role as an energy enhancer, a catalyst, and a hydrogen facilitator under different scenarios. By benchmarking against other supportive material and varying biochar’s loading and particle size, optimal conditions were identified for maximizing hydrogen output while minimizing energy consumption. Isotopic labeling experiments using D2O provide insights into mechanisms of water-biochar / carbon interactions for hydrogen enhancement. Water’s impact on the catalysis of biochar for CH4-to-H2 conversion was also investigated. This work bridges laboratory discovery and field potential by revealing biochar’s synergistic role in enhancing the efficiency and sustainability of EM-driven in-situ hydrogen generation from natural gas reservoirs.

[0399] Experimental

[0400] The materials used in this study include sandstone (Kocurek Industries, Inc.), SiC (Sicat Catalyst), water (H2O), deuterated water (D2O, Sigma-Aldrich Inc.), methane (CH4), Argon (Ar), and biochar. San Saba sandstone, a type of reservoir rocks, is used to fabricate rock matrix. Detailed information of minerology and elementals can be found in previous research14Cubic 3C-SiC (also known as fl-SiC) is used to improve heating efficiency due to its exceptional EM absorption properties. Both sandstone and SiC are crushed into powders with particle sizes ranging from 38 to 100 pm. Two types of water (H2O and D2O) are employed to identify reaction mechanisms and to quantitively evaluate water-biochar / carbon interactions. As an inert gas, Ar is used as carrier gas, which also offers a baseline to calculate gas flow rates during experiments.

[0401] The biochar is produced through microwave-assisted pyrolysis of corn stover (from local farm in Pasco, Washington State). In a typical run, 30 g of com stover is placed in a 500 mL three-necked quartz flask and purged with nitrogen at 400 mL / min for 15 minutes to remove air. Nitrogen is then used as carrier gas at a flow rate of 100 mL / min. Pyrolysis is carried out using a Sineo MAS-II microwave pyrolyzer at 700 W for 40 minutes, yielding approximately 7 g of biochar. The resulting biochar is then ground into three particle size fractions for experimental use: S100 (38-100 pm), S125 (100-125 pm), and S250 (125-250 pm). The SEM images of the synthetic biochar are presented in Fig. 1. Under nano to micro size levels, it is clear that the biochar has numerous interconnected channels, pores, and porous structures, which can provide enough space / surface area and active sites for CFL-to-Fb reactions. At the same time, such structures may enhance heat transfer under EM irradiation.

[0402] The experimental setup used is the identical microwave setup (2.45 GHz, 3 kW) described in previous studies14’41. The samples including sandstone, biochar, and SiC (typically 2.0 grams in total) are uniformly mixed using a pestle and mortar for 15 minutes before loading into the quartz tube (reactor, ID 10 mm, length 360 mm) in the cavity. To remove residual air from the reactor, argon (Ar) is purged at a flow rate of 60 seem for 15 minutes to establish an inert atmosphere. The evolution of temperature is monitored by an infrared (IR) pyrometer with a detective range of 150-1000 °C (Micro-Epsilon). System input power and reflected power are recorded by EM-setup software. The gas composition is detected by a powerful gas analyzer (Extrel Core Mass Spectrometer MAX300-IG) with a detection range of 100 mol.% to 10 ppm. This gas analyzer has the capability of determining gas composition for each sample within 7 seconds, allowing real-time analysis of gas streams produced in the system. More information and calibration details are present in the SI document.

[0403] As summarized in Table 10, a total of 18 experiments is designed to investigate the multiple roles of biochar in enhancing EM-assisted CH4-to-H2 conversion. For the experiments without CH4, only Ar gas is injected into the reactor at a flow rate of 60 seem, where Ar acts as acarrier gas to take gas streams to the gas analyzer for detection. For the experiments with CF , both CH4 and Ar are introduced into the system at a flow rate of 30 seem each, where CH4 acts as the feedstock of hydrogen while Ar plays the same role as carrier gas. As to the experiments involving water, 0.4 grams of water is first saturated into the solid samples for at least 30 minutes prior loading into the reaction tube.

[0404] To understand the reactants’ structural characteristics during reactions, scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analysis, and dispersive Raman microscopy are employed. SEM is conducted by a Hitachi S-4700 field-emission scanning electron microscope (FE-SEM), revealing morphological alterations of samples after experiments. Images are acquired at an accelerating voltage of 2 kV with a working distance of 3 mm. The specific surface area (SBET) is measured by a Quantachrome Autosorb iQ (ASiQ) Micropore Analyzer at LN2 boiling point (77.4 K). Prior to analysis, samples are loaded into glass cells and outgassed at 110 °C under vacuum for 12 h. Pore size distribution is calculated from nitrogen adsorption data using a nonlocal density functional theory based on a slit-pore model. Raman spectroscopy, performed with a Senterra dispersive Raman microscope, is to characterize structural features of biochar and the carbon deposited during methane conversion. Measurements are carried out using a 532 nm excitation laser with an energy setting of 2 pW.

[0405] Results and Discussion

[0406] In this section, six CH4-to-H2 experiments (#.1 - #.6) are conducted under EM heating using different mixtures, to evaluate energy efficiency and hydrogen generation with and without the assistance of biochar. For comparison, SiC is used as a reference EM absorber.

[0407] Figures 49A-49D represent the EM-heating responses of pure sandstone, pure biochar, sandstone-SiC mixtures, and biochar-sandstone mixtures in accordance with one embodiment of the present disclosure. In each case, the red curve denotes the temperature evolution during EM heating, the green curve represents the applied input power, and the blue dashed curve corresponds to the reflected power, which is indicative of impedance matching between the load and the EM system42,43; generally, lower reflected power indicates better EM absorption of the material.

[0408] The sample of pure sandstone (Figure 49A) displays slow and inefficient heating, with temperatures increasing gradually to 600 °C after 15 minutes with input powers around 450 W. Reflected power is initially high (320 W), significantly dropping after the observed temperature runaway (TR) event at about 15thminute. TR is a phenomenon that occurs in rocks due to enhancedEM absorption caused by mineralogical and conductivity changes under EM heating44This behavior has been fully characterized in previous research, which can result in a sharp drop in input power and a sudden spike in temperature. The temperature exceeds 950 °C and the evident decrease in input power shown in the figure align well with the occurrence of TR.

[0409] The incorporation of 10 wt.% SiC into the sandstone (Figure 49B) markedly altered the heating dynamics. SiC, a well-known EM susceptor, promotes faster heating speed and makes the TR happen earlier at around the 8thminute. The temperature reaches -650 °C at a lower input power of 200 W, while the reflected power decreases significantly during the initial heating phase, indicating improved impedance matching. Compared to the pure sandstone sample, the addition of 10 wt.% SiC results in 56.5% less input power to reach 650 °C. This demonstrates the strong ability of EM absorbers in improving the heating efficiency of rocks under EM heating.

[0410] For pure biochar (Figure 49C), the temperature increases rapidly within the first 5 minutes, reaching 650 °C under a stepwise increase in power from 80 W to 110 W. The reflected power remains consistently low (<30 W), suggesting the excellent EM-absorbing capability of the biochar. Notably, for the mixture of 90 wt.% sandstone and 10 wt.% biochar (Fig. 2d), the heating profile exhibits a similar temperature rise to 650 °C. The reflected power decreases progressively from 50 W to 20 W, indicating that biochar significantly improves the EM-heating efficiency of the otherwise weakly absorbing sandstone matrix.

[0411] Compared to the 100% sandstone sample (Figure 49A), the addition of 10 wt.% biochar (Figure 49D) results in 76.1% less power, demonstrating that biochar contributes an even better heating efficiency compared to SiC. This could be attributed to biochar’s exceptional properties (low reflection loss could be -73. IdB)38, 45. These findings highlight that a small proportion of biochar can efficiently improve the EM-heating behavior and reduce energy consumption of reservoir rocks, which is particularly crucial for in-situ hydrogen production from petroleum reservoirs via EM heating.

[0412] The temperature required for hydrogen generation from natural gas under EM heating is typically over 600 °C46'48. At such temperatures, both reservoir rocks and biochar may undergo decomposition and release gases that may include hydrogen. It is essential to exclude such interventions on the hydrogen production produced from methane in experiments. Therefore, two samples — pure biochar (0.4 g) and SiC-sandstone mixtures (0.4 g SiC and 1.6 g sandstone) — are heated in pure Ar environments to study the decompositions.

[0413] Figures 5OA-5OB present the real-time cumulative gas release and temperature evolution during the decomposition of the solid samples under EM heating in accordance with one embodiment of the present disclosure. In Figure 50A (pure biochar), the rapid temperature rises to 540°C within the first 6 minutes and coincides with obvious gas generation. H2 and carbon monoxide (CO) are the dominant gases, reaching 12.3 cc and 10.5 cc, respectively, while CO2 and CH4 plateau at lower volumes of 7.0 cc and 3.5 cc. In contrast, Figure 50B (80% sandstone and 20% SiC) shows different behavior. The temperature rises more slowly during the initial heating phase, followed by a sharp increase to 740 °C at the 5thminute, corresponding to a TR event. Gas generation in this mixture is slower and lower; H2 and CO reach only 3.0 cc and 7.5 cc, respectively, while CO2 and CH4 remain minimal.

[0414] The results demonstrate that the decomposition of pure biochar under EM heating yields a gas mixture consisting of approximately 37% H2, 32% CO, 21% CO2, and 10% CH4. In contrast, the SiC-sandstone mixture mainly releases CO (-70%) and H2 (-30%), with negligible CO2 and CH4 production. It is worth noting that the generation of CO and H2 from the SiC-sandstone mixture primarily originates from gas release during the TR process of sandstone14These differences highlight the influence of material composition on gas evolution during EM-induced decomposition. These findings serve as a baseline for assessing the extent to which solid-phase decomposition contributes to gas production in subsequent CFU-to-Fh experiments.

[0415] Figures 51A-51B display the cumulative gas production and power consumption of the four samples described above — pure sandstone, sandstone-SiC, pure biochar, and sandstonebiochar. Note: 1) cumulative gas production values correspond to a fixed 10-minute period of EM heating; and 2) the gas release from samples’ decomposition has been subtracted. As shown in Figure 51 A, while CO production remains minimal across all samples, H2 is the dominant gas product in all cases. The highest H2 yield of 139.1 cc is obtained from the sandstone-biochar mixture, followed by the sandstone-SiC mixture (121.6 cc), pure sandstone (61.2 cc), and pure biochar (58.5 cc). Since the hydrogen production from the sandstone-biochar sample is significantly higher than that of either pure sandstone or pure biochar, a synergistic interaction between the two components is likely. This enhancement may be attributed to the inherent catalytic effects present in both the biochar and the sandstone matrixl0‘49

[0416] Figure 5 IB reveals distinct differences in power demand among the samples. Pure sandstone required the highest input power (460 W) to sustain EM heating, reflecting its poor intrinsicdielectric properties. In contrast, pure biochar required only 100 W, highlighting its exceptional EM-absorbing capability. Notably, with only 10 wt.% biochar added, the sandstone-biochar sample consumes over 50% less power (110 W) compared to the sandstone-SiC sample (250 W), indicating that the biochar effectively improves the EM-heating efficiency.

[0417] The results have demonstrated the strong potential of biochar as an energy-efficient additive for hydrogen production from natural gas via EM heating. However, the optimal strategy of biochar for maximizing hydrogen yield remains unclear. In this section, the effect of dosage and particle size of biochar is investigated via purpose-designed experiments to optimize hydrogen production. For comparability, the maximum temperature for the experiments is controlled at approximately 650 °C.

[0418] To evaluate hydrogen production under different biochar dosages, four samples with varying biochar dosages are used to conduct experiments under EM heating. The four samples are (a) pure biochar, (b) 85% sandstone and 15% biochar, (c) 90% sandstone and 10% biochar, and (d) 95% sandstone and 5% biochar. Note that the particle size of biochar for all the samples is the same (SI 00).

[0419] Figures 52A-52D present the real-time profiles of gas generation and temperature evolution for the four samples in accordance with one embodiment of the present disclosure. Although pure biochar is an excellent EM absorber and a proved catalyst, it does not mean that more biochar results in more hydrogen production. Figure 52A shows pure biochar slowly release H2 over the heating period, achieving a modest maximum H2 flow of about 10 seem. By contrast, with the introduction of sandstone into the mixture, H2 production increases by at least two-folder in the case of 85% sandstone and 15% biochar (Figure 52B), reaching peak rates of 30 seem. This further confirms the synergistic interaction between sandstone and biochar.

[0420] Interestingly, reducing the biochar dosage to 10 wt.% (Figure 52C) results in even higher H2 production rates, peaking at 60 seem within 5 minutes. Similarly, at the lowest biochar loading (5 wt.%, Figure 52D), the gas production maintains a similar trend to the 10% case but with slightly reduced peak H2 rates (50 seem). It is worth noting that a minimal amount of CO is produced in both cases; this is attributed to the TR occurrence in sandstone. These results suggest that incorporating a small amount of biochar (5-10 wt.%) into the sandstone matrix can significantly enhance the effectiveness of EM-assisted CH4-to-H2 conversion.

[0421] Both hydrogen yield and energy efficiency are strongly dependent on the biochar dosage in the sandstone-biochar mixtures. As shown in Table 10, the sample containing 90 wt.%sandstone and 10 wt.% biochar achieves the highest hydrogen production (186 cc) with the lowest energy consumption (2.16 MJ / g H2), indicating an optimal balance between catalytic activity and EM energy absorption. A slight increase in biochar dosage to 15 wt.% results in a modest reduction in hydrogen output (158 cc) with a comparable energy consumption of 2.31 MJ / g H2, suggesting that excessive biochar may not further enhance the production efficiency. In contrast, reducing the biochar proportion to 5 wt.% decreases H2 generation (130 cc) and significantly increases the energy requirement to 3.65 MJ / g H2. These findings underscore the critical role of biochar dosage in both optimizing hydrogen production and minimizing energy consumption under EM heating. Under the experimental conditions in this work, a weight ratio of 10% biochar into reservoir rocks is fair enough for balancing efficient EM absorption and catalytic activity for CH4-to-H2 conversion.Table 10 - Hydrogen production and normalized energy consumption by different biochar dosage

[0422] To examine the impact of biochar particle size on hydrogen production and power requirements, three particle sizes (S100, S125, and S250) were incorporated into three mixtures consisting of 90 wt.% sandstone and 10 wt.% biochar. The real-time concentration and cumulative volumes of hydrogen varied with particle size are illustrated in Figures 53A-53C, while the data of input power for the three cases is listed in Figure 53D.

[0423] For the S100 and S125 samples, peak hydrogen concentrations of approximately 81% are both achieved. However, the S100 sample yields a total of 195 cc of hydrogen — 14.7% higher than the 170 cc produced by the S125 sample. This indicates that smaller biochar particles enhance the CH4-to-H2conversion. A plausible explanation is that finer biochar particles possess a larger specific surface area, which improves their catalytic activity50, 51. This is confirmed by the BET measurements of the biochar particles, showing that the SBET of S100 biochar (161.9 m2 / g) is 131%greater than that of S 125 biochar (106.6 m2 / g). In contrast, the largest particle size used in this study — the S250 sample (70.1 m2 / g) — produces lowest hydrogen, leading to a cumulative hydrogen volume below 120 cc over the same heating period. These observations clearly demonstrate that reducing biochar particle size enhances hydrogen production efficiency under EM heating.

[0424] Figure 53D presents the input EM power for samples with three particle sizes. The S100 sample requires the lowest input power (110 W), followed by S125 (130 W), while the S250 particles demand the highest power (140 W) to sustain the reaction temperatures. Although the differences are moderate, this trend indicates that smaller biochar particles not only enhance hydrogen generation but also reduce the energy demand for EM heating. The combination of higher hydrogen yields and lower energy consumption for finer biochar suggests that particle size could be a critical parameter in biochar-assisted hydrogen production.

[0425] Carbon is widely recognized for reacting with water to produce syngas through water-carbon interactions under certain temperatures52‘54. The main reactions in the process are listed in Equations (l)-(3)55‘56. As carbon material, biochar will inevitably react with water during in-situ hydrogen production from natural gas reservoirs, as formation water is always present in reservoirs due to geologic reasons. Therefore, it is essential to investigate the effects of water on biochar’s performance during the process. The presence of water may enhance the process by 1) generating additional hydrogen through water-biochar reactions, and 2) enhancing the catalysis of biochar for CH4-to-H2conversion57. These two aspects are investigated in this section regarding the role of biochar as a hydrogen facilitator and a catalysis enhancer in the presence of water.Coke-gasification reaction (1): C (s) + H2O (g) — ► CO (g) + H2(g)Water-gas shift reaction (2): CO (g) + H2O (g) — ► CO2(g) + H2(g)Boudouard reaction (3): C (s) + CO2(g) —> 2CO (g)

[0426] To elucidate the mechanisms by which biochar facilitates hydrogen production via water-carbon reactions, experiments are conducted under three distinct scenarios. Scenario I employs 0.4 grams of pure biochar, reacting with 0.4 grams of water (HzO) to establish a baseline understanding of water’s impact on biochar under EM heating. This scenario is simplified as PB H2O in the following. Scenario II utilizes 2.0 grams of carbon-containing rock-biochar sample composed of 90 wt.% sandstone and 10 wt.% biochar to react with 0.4 grams of water. Here, “carbon-containing” refers to a sample that has underwent 20 minutes of methane cracking under EM heating before theexperiment, resulting in carbon deposition from methane within the sample. Scenario II is simplified as CCSB H2O for simplification. This design is to investigate the interactions between water and different forms of carbon (carbon in biochar, and carbon formed during methane conversion). Scenario III uses the same carbon-containing rock-biochar sample as in Scenario II but replaced H2O with D2O. The use of D2O enables deeper insights into reaction pathways and enhances experimental repeatability. Scenario 111 is simplified as CCSB D2O.

[0427] Figures 54A-54D compare the gas production of Scenario I and Scenario II at similar temperatures under EM heating in accordance with one embodiment of the present disclosure. In Scenario I (Figure 54A), cumulative hydrogen reaches approximately 133 cc after 25 minutes, accompanied by certain CO and CO2 yields (both during 40-50 cc). In Scenario II (Figure 54B), hydrogen generation rises to 152 cc within 22 minutes, while CO production also increases notably to 95 cc and CO2 yield decreases to 23 cc. Although both scenarios contain biochar, the observed differences in gas production indicate distinct water-carbon reaction pathways between the pure biochar and the carbon-containing biochar sample.

[0428] Gas composition analysis (Figures 54C-54D) further highlights the differences between the two scenarios. For PB H2O, FL accounts for 55.6% of total gas production, followed by CO (23.4%) and CO2 (20.9%). In contrast, the CCSB FLO yields a similar proportion of hydrogen (56.1%) but a much higher CO fraction (35.4%) and lower CO2 fraction (8.5%). The elevated CO content and the suppression of CO2 in Scenario II may result from 1) the structure differences between the carbon in biochar and the carbon generated from methane cracking, leading to different reaction mechanisms when reacting with water; 2) the temperature fluctuations between the two scenarios, leading to a shift toward CO-favoring pathways (i.e., enhanced Boudouard reaction). These two aspects will be further discussed below.

[0429] The SEM images in Figures 55A and 55B depict the morphology of pure biochar after EM heating in Scenario I in accordance with one embodiment of the present disclosure. The surface of the spent biochar exhibits a structural alteration with irregular edges and carbonaceous tubes compared to the fresh biochar presented in Figures 48A-48D, suggesting partial structural collapse due to volatile release during biochar decomposition. Despite this, the bulk carbon structure remained preserved. In contrast, Figures 55C and 55D show the morphology of the carbon deposited from methane cracking in Scenario II. The carbonaceous deposits appear as nodular aggregates (i.e.,spherical and clustered carbon particles) as marked yellow circles in Figure 55C. These carbon forms are different from the carbon in the spent biochar in Scenario I.

[0430] The Raman spectra in Figure 55E further reveals the structural differences in the two types of carbon. Fresh pure biochar (PB Fresh) displays typical D (1350 cm ') and G (1580 cm ') bands with a relatively high intensity ratio of D to G (ID / IG ~ 1.0), representing highly disordered / amorphous carbon58. After EM heating (PB_Spent), the intensity ratio ID / IG remains similar, indicating that structural disorder persists. For the sandstone-biochar sample (SB Fresh), the carbon signals are less intense due to the dilution effect of the rock powders, as biochar only accounts for 10 wt.% in the sample. However, after methane cracking (SB Spent or CCSB), the Raman spectrum shows a moderate intensity ratio ID / IG (0.5-1.0) and a clear 2D peak at 2680 cm’1, suggesting an evident increase in graphitic ordering and graphene layers in the carbon-containing sample41’59Thess observations demonstrate that the carbon deposited from methane cracking is distinctly different from the carbon in biochar.

[0431] Finally, the Raman spectra in Figure 55F compares the carbon structure after water-carbon reactions in Scenario I (PB H2O) and Scenario II (CCSB H2O). Both samples have a high ID / IG ratio (>1.0), indicating that disordered carbon remains dominant after reaction with water in both cases. The missing of 2D peak in CCSB H2O indicates that most of the well-ordered carbon generated from methane cracking has been consumed via water-carbon reactions. This specific pathway is what differentiates Scenario II from Scenario I, contributing to the concentration difference of gas production in the two cases. The SEM and Raman results reveal that the nature of carbon — whether derived from biochar or deposited from methane cracking — plays a critical role in determining the mechanism of water-carbon interactions under EM heating.

[0432] Another factor that may affect the concentration of CO and CO2 in water-carbon interactions is the temperature in the process. This is demonstrated in Scenario III, where H2O is replaced with D2O in the reaction with the carbon-containing sample. As shown in Figures 56A-56B, cumulative D2 production followed a similar trend to that of FE in Scenario II, reaching approximately 131 cc (51.4%) by the end of the reaction in accordance with one embodiment of the present disclosure. Notably, CO evolution, which is closely paralleled D2 production, represents a significantly higher accumulation at 117 cc (45.6%), whereas CO2 decreases to 7 cc (3%). The elevated CO content, combined with the minimal CO2 level, suggests that the isotope substitution (D2O vs. H2O) does not fundamentally alter the carbon-water reaction pathways but may slightlyinfluence the reaction kinetics and dynamics due to the higher temperature (~660°C) in Scenario III than that in Scenario II (580°C)56, 60-61. This is because higher temperatures favor CO production while reducing CO2 yield via enhancing the Boudouard reaction60.

[0433] These results also demonstrate that isotopic labeling with D2O effectively identify hydrogen (here, deuterium) generation pathways in carbon-containing rock systems. The comparable D2 yield in Scenario III to the H2 yield in Scenario II confirms that water-carbon reactions remain the primary pathway for hydrogen production. This finding reinforces the conclusion that biochar acts as a facilitator, enhancing hydrogen generation in the presence of water. Temperature, biochar, and carbon deposition collectively shape the distinct reaction mechanism, which in turn lead to shifts in the ratio of CO and CO2 production at different conditions.

[0434] Since biochar can facilitate hydrogen production in the presence of water, whether water has a positive influence on the catalytic activity of spent biochar (after reacting with water) is essential for natural gas conversion to hydrogen. To understand this, two methane-cracking experiments are conducted on biochar-sandstone samples (90% sandstone and 10% biochar) before and after water reaction, respectively. The maximum temperature set in both experiments is controlled within the same level around 670°C. The evolution of hydrogen production from methane in the two cases is presented in Figure 57 in accordance with one embodiment of the present disclosure.

[0435] While the temperature evolution in both cases (before and after) shows a similar trend, it is obvious that the hydrogen production (up to 30 seem) from the biochar sample after reacting with water is three times higher than that (below 10 seem) from the sample before reacting with water. This suggests that the biochar after reacting with water demonstrates a positive role in promoting higher methane conversion to hydrogen, compared to the biochar without reacting with water. In other words, after water-carbon / biochar reactions, biochar’s catalytic effect on CEU-to-FE conversion is enhanced.

[0436] This is evidenced by the comparisons of SEM images and BET tests between the biochar samples before and after reacting with water. The microstructure of the biochar after reaction with water exhibits a highly porous network with filamentous and fibrous features, indicating the partial gasification and structural breakdown of the carbon matrix. When comparing Figures 58B with Figure 55B, it can be observed that etching happened on the biochar matrix after reacting with water. This is likely caused by the reaction-induced carbon consumption such as coke gasification reaction. BET tests show that the SBET of biochar after reaction with water is 375.3 m2 / g, approximately 132%higher than that of biochar before reaction (161.9 m2 / g). Therefore, one may conclude that these additional reactive surface areas created by water-carbon reactions enhance the catalysis of biochar in stimulating natural gas conversion to hydrogen.

[0437] CONCLUSIONS

[0438] The comprehensive findings highlight three complementary roles of biochar as a multifunctional additive: (i) a highly efficient EM absorber, reducing energy consumption by up to 76%, and outperforming SiC in heating efficiency; (ii) a catalyst that synergistically interacts with rock matrix to promote natural gas conversion, achieving optimal hydrogen yields and superior energy efficiency at a 5-10 wt.% loading; and (iii) a hydrogen facilitator in the presence of water, which not only contributes to extra hydrogen but also enhances the catalytic activity for CEL-to-Jfc conversion. Parametric investigations identify 10 wt.% biochar with particle size of 38-100 pm as an optimal configuration. Reaction mechanism investigation indicates that carbon structure is a key factor governing the gas composition produced via water-carbon reactions under EM heating. This work provides insights into tailoring biochar loading, particle size, and water utilization to bridge knowledge gaps between lab-scale study and field applications for in-situ hydrogen technology. The demonstrated energy savings, hydrogen production enhancement, and adaptability to rocks highlight the promise of biochar-enhanced EM heating as a strategy for energy-efficient, carbon-negative hydrogen production from natural gas reservoirs.

[0439] It will be understood that particular embodiments described herein are shown by way of illustration and not as limitations of the invention. The principal features of this invention can be employed in various embodiments without departing from the scope of the invention. Those skilled in the art will recognize or be able to ascertain using no more than routine experimentation, numerous equivalents to the specific procedures described herein. Such equivalents are considered to be within the scope of this invention and are covered by the claims.

[0440] All publications and patent applications mentioned in the specification are indicative of the level of skill of those skilled in the art to which this invention pertains. All publications and patent applications are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.

[0441] The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and / or the specification may mean “one,” but it is also consistent with the meaning of“one or more,” “at least one,” and “one or more than one.” The use of the term “or” in the claims is used to mean “and / or” unless explicitly indicated to refer to alternatives only or the alternatives are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and “and / or.” Throughout this application, the term “about” is used to indicate that a value includes the inherent variation of error for the device, the method being employed to determine the value, or the variation that exists among the study subjects.

[0442] As used in this specification and claim(s), the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “includes” and “include”) or “containing” (and any form of containing, such as “contains” and “contain”) are inclusive or open-ended and do not exclude additional, unrecited features, elements, components, groups, integers, and / or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and / or steps. In embodiments of any of the compositions and methods provided herein, “comprising” may be replaced with “consisting essentially of’ or “consisting of’. As used herein, the term “consisting” is used to indicate the presence of the recited integer (e.g., a feature, an element, a characteristic, a property, a method / process step or a limitation) or group of integers (e.g., feature(s), element(s), characteristic(s), property(ies), method / process steps or limitation(s)) only. As used herein, the phrase “consisting essentially of’ requires the specified features, elements, components, groups, integers, and / or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and / or steps as well as those that do not materially affect the basic and novel characteristic(s) and / or function of the claimed invention.

[0443] The term “or combinations thereof’ as used herein refers to all permutations and combinations of the listed items preceding the term. For example, “A, B, C, or combinations thereof’ is intended to include at least one of: A, B, C, AB, AC, BC, or ABC, and if order is important in a particular context, also BA, CA, CB, CBA, BCA, ACB, BAC, or CAB. Continuing with this example, expressly included are combinations that contain repeats of one or more item or term, such as BB, AAA, AB, BBC, AAABCCCC, CBBAAA, CABABB, and so forth. The skilled artisan will understand that typically there is no limit on the number of items or terms in any combination, unless otherwise apparent from the context.

[0444] As used herein, words of approximation such as, without limitation, “about”, “substantial” or “substantially” refers to a condition that when so modified is understood to notnecessarily be absolute or perfect but would be considered close enough to those of ordinary skill in the art to warrant designating the condition as being present. The extent to which the description may vary will depend on how great a change can be instituted and still have one of ordinary skill in the art recognize the modified feature as still having the required characteristics and capabilities of the unmodified feature. In general, but subject to the preceding discussion, a numerical value herein that is modified by a word of approximation such as “about” may vary from the stated value by at least ±1, 2, 3, 4, 5, 6, 7, 10, 12 or 15%.

[0445] All of the compositions and / or methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the compositions and methods of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the compositions and / or methods and in the steps or in the sequence of steps of the method described herein without departing from the concept, spirit and scope of the invention. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined by the appended claims.

[0446] To aid the Patent Office, and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants wish to note that they do not intend any of the appended claims to invoke paragraph 6 of 35 U.S.C. § 112, U.S.C. § 112 paragraph (f), or equivalent, as it exists on the date of filing hereof unless the words “means for” or “step for” are explicitly used in the particular claim.

[0447] For each of the claims, each dependent claim can depend both from the independent claim and from each of the prior dependent claims for each and every claim so long as the prior claim provides a proper antecedent basis for a claim term or element.

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Claims

1. CLAIMSWhat is claimed is:

1. A method of producing hydrogen from a petroleum reservoir comprising:providing a porous configuration of catalyst particles within one or more wellbores in the petroleum reservoir;heating the catalyst particles using one or more electromagnetic wave generators such that hydrocarbons passing through or near the porous configuration of catalyst particles react with the heated catalyst particles and generate syngas, wherein the porous configuration of catalyst particles is disposed only within the one or more wellbores proximate to the one or more electromagnetic wave generators; andseparating and extracting the hydrogen from the syngas at the surface or within the one or more wellbores.

2. The method as recited in claim 1, wherein the porous configuration of catalyst particles comprise metal-based catalytic particles integrated into silicon carbide particles.

3. The method as recited in claim 2, wherein the silicon carbide particles comprise beta-phase (P-phase) silicon carbide particles.

4. The method as recited in claim 2, wherein the metal-based catalytic particles contain Fe, Ti, K, Mn, Ni, Co, or a combination thereof.

5. The method as recited in claim 2, wherein a weight percentage of metal -based catalytic particles is between 0.1% and 50% of a total weight of the porous configuration of catalyst particles.

6. The method as recited in claim 2, wherein:a size of the metal-based catalytic particles is less than or equal to 500 nanometers; or a shape of metal -based catalytic particles comprises tri-lobe, spherical, or agglomerated.

7. The method as recited in claim 2, further comprising manufacturing the porous configuration of catalyst particles by:integrating the metal-based catalytic particles into the silicon carbide particles; customizing a permeability of the porous configuration of catalyst particles to be 0.01 to 100 Darcys; andconfiguring the catalyst particles into a substantially annular cylinder having an inner diameter larger than an outer diameter of the one or more electromagnetic wave generators and an outer diameter smaller than a diameter of the one or more wellbores.

8. The method as recited in claim 2, wherein one or more support materials are also integrated into the silicon carbide particles.

9. The method as recited in claim 8, wherein the one or more support materials comprise AI2O3, SiO2, activated carbon, or Zeolites.

10. The method as recited in claim 8, further comprising varying a ratio of the one or more support materials to the silicon carbide particles to: increase a material strength of the porous configuration of catalyst particles, adjust a permeability of the porous configuration of catalyst particles, or reduce a cost of the porous configuration of catalyst particles.

11. The method as recited in claim 8, wherein a size of the one or more support materials and the silicon carbide particles is less than or equal to 100 micrometers.

12. The method as recited in claim 8, further comprising coating or doping the metal-based catalytic particles on the one or more support materials and the silicon carbide particles.

13. The method as recited in claim 1, wherein:the one or more wellbores comprise one or more vertical wellbores, one or more horizontal wellbores, one or more multilateral wellbores, or a combination thereof;the petroleum reservoir comprises a conventional, an unconventional, a new, a depleted or an abandoned oil and gas reservoir; orthe syngas comprises the hydrogen, methane, carbon monoxide, carbon dioxide, and other light hydrocarbons.

14. The method as recited in claim 1, wherein providing the porous configuration of catalyst particles comprises embedding the porous configuration of catalyst particles to an outside of the one or more electromagnetic wave generators.

15. The method as recited in claim 1, wherein the porous configuration of catalyst particles comprises an annular cylinder having an inner diameter larger than an outer diameter of the one or more electromagnetic wave generators and an outer diameter smaller than an inner diameter of the one or more wellbores.

16. The method as recited in claim 1, wherein the porous configuration of catalyst particles has a substantially similar length as the one or more electromagnetic wave generators.

17. The method as recited in claim 1, wherein a thickness of the porous configuration of catalyst particles varies according to a size of the one or more electromagnetic wave generators and the one or more wellbores.

18. The method as recited in claim 1, wherein:the catalyst particles are heated to a temperature range of 250 to 1000°C; andthe catalyst particles are heated for a time period of hours, days, seasons or years.

19. The method as recited in claim 1, wherein electromagnetic waves generated by the one or more electromagnetic wave generators are continuous, pulsed, intermittent, time dependent or time independent.

20. The method as recited in claim 1, further comprising adjusting a frequency of the one or more electromagnetic wave generators to optimize a heating efficiency of the catalyst particles or the generation of the hydrogen.

21. The method as recited in claim 1, further comprising using off-peak electricity from one or more renewable energy sources to power the one or more electromagnetic wave generators.

22. The method as recited in claim 1, further comprising:positioning one or more one or more electromagnetic wave generators within the one or more wellbores;connecting the one or more electromagnetic wave generators to a power source; and generating electromagnetic waves using one or more electromagnetic wave generators.

23. The method as recited in claim 1, further comprising removing carbon deposited on the catalyst particles and regenerating the catalyst particles in-situ using water or steam.

24. The method as recited in claim 23, wherein:the water is pre-existing within the petroleum reservoir or injected into the one or more wellbores; orthe steam is injected into the one or more wellbores.

25. The method as recited in claim 1, further comprising sequestrating carbon oxides from the one or more wellbores into a sequestration formation using a production packer.

26. The method as recited in claim 25, further comprising improving an injection of the carbon oxides into the sequestration formation using surface compressors or downhole pumps.

27. The method as recited in claim 1, further comprising injecting water into the one or more wellbores to increase a production and a purity of the hydrogen.

28. The method as recited in claim 27, wherein the water is injected into the one or more wellbores to have an approximate ratio of one to one with the hydrocarbons within the one or more wellbores or proximate to the porous configuration of catalyst particles.

29. The method as recited in claim 27, wherein the injected water approximately doubles the production of the hydrogen and increases the purity of the hydrogen to approximately 50% or more.

30. The method as recited in claim 1, wherein:the porous configuration of catalyst particles further comprises biochar; orthe biochar is in injected into the one or more wellbores.

31. The method as recited in claim 30, wherein the biochar comprises approximately 5 to 10 wt% of the catalyst particles.

32. The method as recited in claim 30, wherein a particle size of the biochar comprises approximately 38-100 .m.

33. The method as recited in claim 30, wherein the method is carbon negative.

34. A system for generating hydrogen within a petroleum reservoir comprising:one or more wellbores into the petroleum reservoir;a power source at a surface above the petroleum reservoir;a porous configuration of catalyst particles within the one or more wellbores;one or more electromagnetic wave generators within the one or more wellbores and connected to the power source, wherein the one or more electromagnetic wave generators heat the catalyst particles such that hydrocarbons passing through or near the porous configuration of catalyst particles react with the heated catalyst particles and generate syngas, and the porous configuration of catalyst particles is disposed only within the one or more wellbores proximate to the one or more electromagnetic wave generators; andone or more hydrogen separators located within the one or more wellbores or at the surface that separate and extract the hydrogen from the syngas.

35. The system as recited in claim 34, wherein the porous configuration of catalyst particles comprise metal-based catalytic particles integrated into silicon carbide particles.

36. The system as recited in claim 35, wherein the silicon carbide particles comprise beta-phase (P-phase) silicon carbide particles.

37. The system as recited in claim 35, wherein the metal-based catalytic particles contain Fe, Ti, K, Mn, Ni, Co, or a combination thereof.

38. The system as recited in claim 35, wherein a weight percentage of metal-based catalytic particles is between 0.1% and 50% of a total weight of the porous configuration of catalyst particles.

39. The system as recited in claim 35, wherein:a size of the metal-based catalytic particles is less than or equal to 500 nanometers; ora shape of metal-based catalytic particles comprises tri-lobe, spherical, or agglomerated.

40. The system as recited in claim 35, wherein the porous configuration of catalyst particles has a permeability of 0.01 to 100 Darcys.

41. The system as recited in claim 35, wherein the porous configuration of catalyst particles is a substantially annular cylinder having an inner diameter larger than an outer diameter of the one or more electromagnetic wave generators and an outer diameter smaller than a diameter of the one or more wellbores.

42. The system as recited in claim 35, wherein one or more support materials are also integrated into the silicon carbide particles.

43. The system as recited in claim 35, wherein the one or more support materials comprise AI2O3, SiC>2, activated carbon, or Zeolites.

44. The system as recited in claim 35, wherein a ratio of the one or more support materials to the silicon carbide particles is varied to: increase a material strength of the porous configuration of catalyst particles, adjust a permeability of the porous configuration of catalyst particles, or reduce a cost of the porous configuration of catalyst particles.

45. The system as recited in claim 35, wherein a size of the one or more support materials and the silicon carbide particles is less than or equal to 100 micrometers.

46. The system as recited in claim 35, wherein the metal -based catalytic particles are coated or doped on the one or more support materials and the silicon carbide particles.

47. The system as recited in claim 34, wherein:the one or more wellbores comprise one or more vertical wellbores, one or more horizontal wellbores, one or more multilateral wellbores, or a combination thereof;the petroleum reservoir comprises a conventional, an unconventional, a new, a depleted or an abandoned oil and gas reservoir; orthe syngas comprises the hydrogen, methane, carbon monoxide, carbon dioxide, and other light hydrocarbons.

48. The system as recited in claim 34, wherein the porous configuration of catalyst particles is embedded to an outside of the one or more electromagnetic wave generators.

49. The system as recited in claim 34, wherein the porous configuration of catalyst particles has a substantially similar length as the one or more electromagnetic wave generators.

50. The system as recited in claim 34, wherein a thickness of the porous configuration of catalyst particles varies according to a size of the one or more electromagnetic wave generators and the one or more wellbores.

51. The system as recited in claim 34, wherein:the catalyst particles are heated to a temperature range of 250 to 1000°C; andthe catalyst particles are heated for a time period of hours, days, seasons or years.

52. The system as recited in claim 34, wherein electromagnetic waves generated by the one or more electromagnetic wave generators are continuous, pulsed, intermittent, time dependent or time independent.

53. The system as recited in claim 34, wherein a frequency of the one or more electromagnetic wave generators is adjusted to optimize a heating efficiency of the catalyst particles or the generation of the hydrogen.

54. The system as recited in claim 34, wherein the power source comprises off-peak electricity from one or more renewable energy sources.

55. The system as recited in claim 34, wherein carbon deposited on the catalyst particles is removed and the catalyst particles are regenerated in-situ using water or steam.

56. The system as recited in claim 55, wherein:the water is pre-existing within the petroleum reservoir or injected into the one or more wellbores; orthe steam is injected into the one or more wellbores.

57. The system as recited in claim 34, wherein carbon oxides from the one or more wellbores are injected into a sequestration formation using a production packer.

58. The system as recited in claim 57, wherein the injection of the carbon oxides into the sequestration formation is improved using surface compressors or downhole pumps.

59. The system as recited in claim 34, wherein water is injected into the one or more wellbores to increase a production and a purity of the hydrogen.

60. The system as recited in claim 59, wherein the water is injected into the one or more wellbores to have an approximate ratio of one to one with the hydrocarbons within the one or more wellbores or proximate to the porous configuration of catalyst particles.

61. The system as recited in claim 59, wherein the injected water approximately doubles the production of the hydrogen and increases the purity of the hydrogen to approximately 50% or more.

62. The system as recited in claim 34, wherein:the porous configuration of catalyst particles further comprises biochar; orthe biochar is in injected into the one or more wellbores.

63. The system as recited in claim 62, wherein the biochar comprises approximately 5 to 10 wt% of the catalyst particles.

64. The system as recited in claim 62, wherein a particle size of the biochar comprises approximately 38-100 ^m.

65. The system as recited in claim 62, wherein the system provides a carbon negative process.

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