Methods for stimulation of natural hydrogen production and extraction thereof from earth's subsurface

Abstract

Disclosed herein are methods and related systems for stimulating hydrogen gas (H2) generation from Earth's subsurface, and extraction thereof. The methods include forming at least one well in contact with a source rock formation, wherein the at least one well is configured to allow the introduction of a fluid composition into the source rock formation, then introducing the fluid composition into the source rock formation. Thereafter, hydrogen gas production is stimulated from the source rock formation through a serpentinization process, and is subsequently extracted.

Description

METHODS FOR STIMULATION OF NATURAL HYDROGEN PRODUCTION AND EXTRACTION THEREOF FROM EARTH’S SUBSURFACECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims benefit under to U.S. Provisional Application Ser. No. 63 / 528809, filed on July 25, 2023, titled, “Approaches For Stimulated Natural Hydrogen Generation And Extraction From The Earths Subsurface”, the entire contents of which are hereby incorporated herein by reference.FIELD OF THE INVENTION

[0002] The present invention relates to methods and systems for stimulating natural H2 production from subsurface rock formations and extracting said hydrogen gas from the Earth’s subsurface.BACKGROUND OF THE INVENTION

[0003] The current process of hydrogen generation suffers from either high greenhouse gas footprint or high cost. For example, the steam methane reforming (SMR) method, producing about 95% H2 (US Fuel Cell Technologies Office, 2018), also generates 9-10 times more carbon dioxide (CO2) than generated H2.

[0004] While green hydrogen produced from water electrolysis using renewable energy is clean, its cost is still very high. Meanwhile, the process needs high energy input and consumes a large amount of fresh water. The next generation of technology needs to be developed to produce clean, affordable hydrogen to meet energy demands and mitigate global warming. Natural hydrogen is carbon-free, and it is generated in the Earth’s subsurface from water or water-rock interactions. It does not need extensive energy input from the surface as the hydrogen is automatically generated in the subsurface at high temperatures. Its cost can potentially be muchlower than $l / kg H2. With about 1017-1018 tons of hydrogen generating rocks in Earth’s crust (top 7 km), it is estimated that 1015 tons of carbon-free or even carbon-negative hydrogen can be generated from rock-water interactions. The hydrogen generating rocks include mafic and ultramafic rocks and various other rocks which are iron-rich. One major mechanism for hydrogen generation is the oxidation of reduced iron (Fe2+) present in the rock minerals through Formula (1) below:Fe2++ H2O Fe3O4+ H2+ H+(1)

[0005] However, the natural hydrogen generation process is very slow with generation rate depending on temperature, pressure, rock composition, availability of water, geology, and so on. Accordingly, there is a need to accelerate or stimulate natural hydrogen generation in the subsurface with the abundant earth rock minerals that are capable of generating hydrogen through water-rock interactions. Meanwhile, the generated hydrogen, either natural or stimulated, needs to be extracted to surface through an efficient and optimized process and system. There remains a need for solutions and methods for efficient generation of subsurface H2and for extracting the generated hydrogen gas from Earth’s subsurface.SUMMARY OF THE INVENTION

[0006] Disclosed herein are methods and related systems for stimulating hydrogen gas (H2) generation from Earth’s subsurface, and extraction thereof. The methods include forming at least one well in contact with a source rock formation, wherein the at least one well is configured to allow the introduction of a fluid composition into the source rock formation, then introducing the fluid composition into the source rock formation. Thereafter, hydrogen gas production isstimulated from the source rock formation through a serpentinization process, and hydrogen gas is subsequently extracted.Selected Definitions

[0007] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0008] The term “targeted formation” or “source rock formation” or “source rocks” or “H2 generating rocks” are used interchangeably and refer to, but not limited to, mafic rocks, ultramafic rocks, olivine-type rocks, or other rocks with and without iron-rich content that can generate hydrogen by reducing water to hydrogen or by other mechanisms.

[0009] The term “gas mixture” refers to a mixture of gases which can contains hydrogen, methane (CH4), steam, and / or any other gases that are naturally generated or stimulated from a subsurface rock formation to the surface.

[0010] The term “well”, as used herein can refer to vertical well, sidetrack wells, horizontal well, deviated well, designer well, multilateral wells, and / or any other advanced well types (such as stacked multi-branch well, dual opposing lateral well, e-entry laterals from a vertical well, and 3D well, etc.), and / or any other type of wells that are drilled to the formation for, but not limited to, water and chemical injection, hydrogen generation stimulation, hydrogen extraction, and / or desired and undesired gas treatment purposes.

[0011] The terms “hydraulic fracture”, “hydraulic fracturing”, and “hydraulic fracture network”, as used herein, are used to refer to the same process and phenomenon. They refer to the rock fractures and / or micro-fractures that are created by injecting fluids and / or by reactions.

[0012] As used herein, the term “fluid” can refer to liquids, gases, a mixture of liquids and gases, or a mixture of liquids with solids, a mixture of gases, liquids and solids, or a combination thereof.

[0013] Various terms are used to refer to particular system components. Different companies may refer to a component by different names - this document does not intend to distinguish between components that differ in name but not function. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or a direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection or through an indirect connection via other devices and connections.

[0014] The terminology used herein is for the purpose of describing particular example embodiments only, and is not intended to be limiting. Following long-standing patent law convention, the terms “a” and “an” mean “one or more” when used in this application, including the claims.

[0015] As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

[0016] The terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and / or sections; however, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer, or section from another region, layer, or section. Terms such as “first,” “second,” and other numerical terms, when used herein, do notimply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of the example embodiments. The phrase “at least one of,” when used with a list of items, means that different combinations of one or more of the listed items may be used, and only one item in the list may be needed. As used herein, the term “and / or” when used in the context of a listing of entities, refers to the entities being present singly or in combination. Thus, for example, the phrase “A, B, C, and / or D” includes A, B, C, and D individually, but also includes any and all combinations and subcombinations of A, B, C, and D. Accordingly, as an example, “at least one of A, B, and C” includes any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C. In another example, the phrase “one or more” when used with a list of items means there may be one item or any suitable number of items exceeding one.

[0017] Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in this specification are approximations that can vary depending upon the desired properties sought to be obtained by the presently disclosed subject matter.

[0018] As used herein, the term “about” refers to an approximately + / - 15% variation from a given value.

[0019] It will be understood that each of the preferred or optional features of the various embodiments may be combined with other features and features described in combination with one or more particular features may also be combined with one or more other features of the other embodiments.

[0020] These and other features of the invention will become apparent from the following detailed description of the invention, which in conjunction with the drawings disclose various embodiments of the invention.BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The following is a brief description of the drawings in which:

[0022] Fig. 1 illustrates a schematic of a vertical well for a water-based composition injection to a source rock formation for stimulating hydrogen generation, without hydraulic fracking, in accordance with embodiments disclosed herein.

[0023] Fig. 2 illustrates a schematic of a vertical well for a water-based composition injection to a source rock formation for stimulating hydrogen generation, without hydraulic fracturing or a downhole hydrogen membrane separator, in accordance with embodiments disclosed herein.

[0024] Fig. 3 illustrates a schematic depicting hydraulic fracturing using a vertical well to stimulate hydrogen generation without a downhole hydrogen membrane separator, in accordance with embodiments disclosed herein.

[0025] Fig. 4 illustrates a schematic of two vertical wells for a water based composition injection to a source rock formation for stimulating hydrogen generation, without hydraulic fracturing or a downhole hydrogen membrane separator, in accordance with embodiments disclosed herein.

[0026] Fig. 5 illustrates a schematic of two vertical wells for a water based composition injection to a source rock formation for stimulating hydrogen generation, without hydraulic fracturing or a downhole hydrogen membrane separator, in accordance with embodiments disclosed herein.

[0027] Fig. 6 illustrates a schematic of a horizontal well for a water based composition injection to a source rock formation for stimulating hydrogen generation, without hydraulicfracturing or a downhole hydrogen membrane separator, in accordance with embodiments disclosed herein.

[0028] Fig. 7 illustrates a schematic of hydrogen extraction, with hydraulic fracturing but without a downhole hydrogen membrane separator, in accordance with embodiments disclosed herein.

[0029] Fig. 8 illustrates a schematic of hydrogen extraction, with a vertical well and a horizontal well, with hydraulic fracturing but without a downhole hydrogen membrane separator, in accordance with embodiments disclosed herein.

[0030] Fig. 9 illustrates a schematic of extracting water from a shallower aquifer for injection into a source rock formation, in accordance with embodiments disclosed herein.

[0031] Fig. 10(A) illustrates a schematic for cold water injection into a deeper source rock formation, extraction of hot water, and injection of extracted hot water to the source rock formation, in accordance with embodiments disclosed herein.

[0032] Fig. 10(B) illustrates a schematic for hydrogen extraction simultaneously with water injection, in accordance with embodiments disclosed herein.

[0033] Fig. 11(A) illustrates a schematic for a process using a downhole hydrogen membrane separator to extract hydrogen gas to the surface, wherein the hydrogen membrane separator is installed in an upper location of the source rock formation, in accordance with embodiments disclosed herein.

[0034] Fig. 11(B) A illustrates a schematic for a process using a downhole hydrogen membrane separator to extract hydrogen gas to the surface, wherein the hydrogen membrane separator is installed above the source rock formation, in accordance with embodiments disclosed herein.

[0035] Fig. 12 illustrates a schematic of a multiple-stage separation process for hydrogen extraction to the surface, wherein liquids and gases are first separated, followed by the separationof hydrogen gas, from other extracted undesired gases, in accordance with certain embodiments disclosed herein.

[0036] Fig. 13 illustrates a schematic showing extraction of generated hydrogen gas, using a certain number of downhole hydrogen membrane separators, in accordance with embodiments disclosed herein.

[0037] Fig. 14(A) illustrates a schematic of a process using stacked multi -branch well for injection of water into a thicker source rock formation and extraction of generated hydrogen gas from a vertical well.

[0038] Fig. 14(B) illustrates a schematic of a process using stacked multi-branch well for injection of water into a thicker source rock formation and extraction of generated hydrogen gas from a vertical well.

[0039] Fig. 14(C) illustrates a schematic of a process using stacked multi-branch well for injection of water into a thicker source rock formation and extraction of generated hydrogen gas from a vertical well.

[0040] Fig. 15 illustrates the use of a horizontal injection well and a plurality of vertical hydrogen extraction wells, in accordance with embodiments disclosed herein.

[0041] Fig. 16 illustrates a schematic of a branched well for injection of water into the lower branch well and extraction of hydrogen from the upper branch well.

[0042] Fig. 17(A)-(D) illustrate various well types and well configurations, in accordance with various embodiments disclosed herein.

[0043] Fig. 18 depicts various well patterns and configurations, in accordance with embodiments disclosed herein.DETAILED DESCRIPTION

[0044] Disclosed herein are various methods for stimulating hydrogen gas generation from the Earth’s subsurface. Also disclosed are methods for extracting the hydrogen gas which was generated or which may already exist in said subsurface rock formations.

[0045] Although there are abundant source rock formations in the Earth’s subsurface, hydrogen may not be generated or generated too slowly due to various factors. These factors include limited access to water, not enough contact between water and rock (all rocks and a proportion of rocks in the formation), secondary minerals deposited on source rock surface that prevent hydrogen generation, rock formation temperature is too low (below 100 °C), or too high (above 400°C or 500 °C), no catalysts to stimulate a reaction, and so on. The stimulated hydrogen generation in this disclosure relates to promoting water-rock interactions to generate more hydrogen in a shorter time. Many reactions and mechanisms are involved and stimulated. One major reaction is the serpentinization of ultramafic rocks in the presence of water at the proper temperature and pressure conditions, discussed in more detail below.

[0046] The source rock formations referred to within this disclosure primarily references but is not limited to rock formations which are capable of generating molecular hydrogen gas (EE) through a serpentinization process or serpentinization reaction between water and the source rock formation. These rock formations include olivine-rich mafic or ultramafic rocks, such as peridotites which produce a serpentinite composition that includes serpentinite, brucite and magnetite when they react with water, with EE liberated as a byproduct. This reaction is represented below by Formula (2):Mgi.8Feo.2Si04+ 1.37H2O 0.5Mg3Si2O5(OH)4+ 0.3Mg(OH)2+ 0.067Fe304+ 0.067H2(2) Olivine Water Serpentine Brucite Magnetite Hydrogen

[0047] According to embodiments disclosed herein, methods for stimulating hydrogen gas (H2) generation from Earth’s subsurface are disclosed. In one embodiment, the method comprises the forming at least one well in contact with a source rock formation. The well is configured to allow the introduction of a fluid composition into the source rock formation. The method further includes the step of introducing the fluid composition into the source rock formation, through the well, and stimulating hydrogen gas production from the source rock formation. In certain embodiments, the stimulation of hydrogen gas production is achieved through a serpentinization process. The fluid composition which is injected into the well can include at least one of carbon dioxide gas (CO2), water (H2O), steam, nitrogen gas (N2), proppants, catalysts, polymeric solutions, or a combination thereof.

[0048] In one example, a serpentinization process refers to the reaction of water with ultramafic rocks at specific temperatures and pressures, to yield released hydrogen, according to the chemical reaction shown in Formula (2) (previously discussed above).

[0049] In one embodiment, the process of stimulating hydrogen gas production from the source rock formation is accomplished with or without a hydraulic fracturing step. Shown in Fig. l is a schematic illustrating a vertical well which is drilled to a depth in Earth’s subsurface, where source rock formation exists (also shown and referenced as H2 generating formation in Fig. 1). As can be seen in the Fig. 1. the further the depth of the rock layers, the higher the temperature of the formations. There are several layers of source rock formations depicted, with a shallower first layer which would exist at a lower temperature, and a deeper source rock formation layer, which has a higher temperature, as compared to the shallower formation. In this embodiment, the fluid injected in the well is water-based. Well perforations are formed, so that cracks can be created in the source rock formation around the well, to create a fluid flow path to and from the well and rock formation surrounding it. The injected fluid also causes perforations in the source rockformation and exposes the source rock to create reactive sites with the water-based fluid injected through the well. The reaction of the water with the reactive areas of the source rock that the water contacts, allows for a serpentinization reaction to occur, to release molecular hydrogen. Therefore, the hydrogen generation is stimulated in this process through the injection of the water-based fluid through the vertical well.

[0050] The water-based fluid can include various other reactants or components which will aid in optimizing the reaction kinetics with the targeted source rock formation. For example, in addition to water, the injected fluid can include pH regulators, proppants, acidic or alkaline chemicals, polymer mixtures, brine, steam, and or other components, or a combination thereof. The water-based fluid is optimized for efficient reaction yields with the particular source rock formation of a certain location where the well is located.

[0051] In certain embodiments, the temperature of the injected fluid is varied, depending on the depth of the well and the depth of the source rock formation. Serpentinization reactions for the generation of hydrogen gas are highly dependent on temperature. As seen in the diagram of Fig.1, temperature of the source rock formation is expected to increase with the depth from the Earth’s surface of that particular formation.

[0052] A hydrogen production window exists between the shallowest depth containing serpentinizing peridotite and the deepest depth at which the absence of water impedes H2 formation. Since temperature affects the reaction kinetics, mineral stability, redox reactions, and water availability, it plays a crucial role in controlling the H2 production window during serpentinization. For instance, ultramafic minerals remain thermodynamically stable at elevated temperatures and pressures in the earth’s mantle. This implies that as temperature increases, the rate of serpentinization reduces, and the minerals precipitated may transform into other mineral phases. Although ultramafic rocks primarily form in the high temperature Earth’s mantle, they can move toward the surface through tectonic processes such as uplift and erosion. This willencourage serpentinization in ultramafic rocks under relatively low temperatures and pressures in various geologic settings such as mid-ocean ridges, subduction zones, and ophiolites. It has been reported that the main factors that control H2 production are a function of temperature. These include thermodynamic constraints on mineral stability and Fe distribution among mineral alteration products. To stimulate H2 production, serpentinization should be sustained within a temperature range that favors the rapid release of Fe(II) from olivine and inhibits Fe(II) partitioning into brucite (or serpentine). This will increase the amount of magnetite formed due to the oxidation of the available ferrous Fe(II) in the aqueous fluid to ferric Fe(III), increasing H2 generation. This is because the rate of H2 production is reduced at low temperatures due to the low Fe(II) release rate from olivine and the partitioning of dissolved Fe(II) into brucite. The reduced amount of produced H2 from serpentinization occurs mainly due to decreased magnetite formation as temperature declines.

[0053] In certain embodiments, the temperature range of 200 to 350 °C is achieved and / or maintained in the source rock formation, through the injection of hot water or steam.

[0054] In some embodiments, cold water is injected if the temperature of the targeted source rock formation is high enough, (i.e., above 350 °C) in order to create thermal stress, fractures, and fracture network to increase reactive surface areas for stimulated hydrogen generation.

[0055] Shown in Fig. 2 is a schematic for pumping or extracting hydrogen, gas mixtures, or other fluids from an upper perforation zone after hydrogen is generated and accumulated at an upper layer of the source rock formation. The small hydrogen molecules will accumulate there because of the existence of low-permeability rock like seals or because of capillary trapping mechanisms. Depending on the hydrogen generation rate and economic assessment, different operating schemes can be used.

[0056] In some embodiments, one or more packers between the water injection zone and hydrogen extraction zone are used to prevent water extraction from the lower formation while ensuring hydrogen and desired fluids extracted from the upper perforation zone.

[0057] In some embodiments, hydrogen and desired fluids are extracted from the production casing in the upper perforation zone (i.e., hydrogen accumulation zone) while water and other chemicals are injected through the tubing in the lower perforation zone (i.e., hydrogen generation zone).

[0058] In one embodiment, the step of introducing the fluid composition comprises a first injection of a CCh-based fluid composition for fracturing of the source rock formation and a second injection of water. The CO2 content in the first injection CO2 based fluid composition can vary from 0% to 100%, or 10 % to 100%, or 20% to 100%, or 30% to 100%, or 40% to 100%, or 50% to 100%, or 60% to 100%, or 70% to 100%, or 80% to 100%, or 90% to 100%, or 10% to 90%, 20% to 80%, or 30% to 70%, 40% to 60%, or any range or value there between. The content of the first injection for fracturing can be pure CO2 gas or it can be a mixture of CO2 dissolved in water. Referring now to Figure 3, illustrated therein is the schematic for using a first injection of CCh-based fluids to create more fractures and reactive surface areas and then inject water to stimulate hydrogen generation without a downhole hydrogen membrane separator. Thus, in one embodiment, CCh-based fluids are used for hydraulic fracturing. In other embodiments, polymer solutions with proppants and / or catalysts are used for hydraulic fracturing. The polymer solutions are then pumped back to the surface, while the proppants and catalysts stay in formation to prevent the closure of the fractures and to catalyze the hydrogen generation reactions.

[0059] In certain embodiments, the step of stimulating hydrogen gas production comprises injection of at least one of water, steam, CO2 based fluid, proppants, catalysts, polymeric solutions, or a combination thereof.

[0060] In some embodiments, catalysts are used to promote the reactions which yield hydrogen gas as a product, or they can also be used as proppants to prevent the closure of fractures while also promoting hydrogen generation. The catalytic phases can act as real catalysts or reactants whose alteration can produce H2 or promote olivine dissolution, and these catalysts may be introduced as solids such as Cr-spinel, magnetite, chromite, Ni- or Fe-bearing minerals or alloys, or produced during serpentinization, for example, spinel or magnetite. For instance, studies have shown that Ni2+ stimulates H2 generation. Studies have indicated that Fe-bearing phases that contain Fe(II) and Fe(III) compounds tend to result in the highest H2 generation, followed by Ni bearing and then magnetite, whereas spinel can enhance H2 generation at low-pressure, low- temperature conditions. When aqueous Fe(II) interacts with spinel, there is the oxidation of sorbed Fe(II) because of the electron transfer from the aqueous Fe(II) and the spinel substrate. The oxidation of Fe(II) in magnetite and Ni or the reduction of sulfur in Ni-bearing phases (e.g., sulfides and alloys) may naturally enhance H2 production without exhibiting a true catalytic effect. Similarly, aluminum (Al) in solution could speed up olivine serpentinization, although it delays the serpentinization of orthopyroxene. It has also been reported that Al increases olivine dissolution and promotes the formation of aluminous serpentine. They demonstrated that the onset of serpentinization correlates with the dissolution of AI2O3 microspheres at 300 °C, with the first serpentine grains appearing simultaneously on the surface of olivine grains and AI2O3 microspheres. They also showed that A1(OH)4 - was the dominant aluminum species in solution at 2 kbar and 340 °C, and Al could reach concentrations of ca. 200 ppm. Thus, Al(0H)4 - can be adsorbed on the positively charged olivine surface, dissolving the interface and releasing Mg2+ and silicate groups F SiC .

[0061] In some embodiments, a soak stage is be implemented in which the well is shut down to allow for longer period of hydrogen generation from the source rock formation. The soak stagecan be implemented as an additional step, after injection of the fluid for stimulating the generation of H2 gas.

[0062] In some embodiments, multiple hydraulic fracturing steps can be conducted when the hydrogen extraction rate declines too fast, followed by the multiple water injection steps. The interval between different fracturing operations depends on the declining rate of hydrogen extraction and the concentration. It may vary from weeks to tens of years.

[0063] In some embodiments, proppants and / or catalyst can be injected during and after hydraulic fracturing processes. In some embodiments, water injection rates will be optimized to enhance the propagation of catalyst particles into the unreacted regions to stimulate hydrogen generation from rock-water reactions. Referring now to Figure 4, two vertical wells are used for stimulated hydrogen generation and extraction without hydraulic fracturing or downhole hydrogen membrane separator. One well is used as an injection well, for injecting fluids for fracturing and / or injecting fluids for stimulation of H2 generation. The other well is used as an extraction well, wherein generated or existing H2 and other generated or existing gases can be extracted.

[0064] In some embodiments, water is injected into the targeted source rock formation. Because of the perforation zone, water may be inj ected into a proportion of or the whole formation. In some embodiments, soak stage may be needed to allow water-rock reaction for hydrogen generation. Generated hydrogen will propagate upward and to the direction with lower pressure because of the pressure gradient. In some embodiments, the extraction well will be open for extracting generated hydrogen to surface, while water and other chemicals are continuously injected through the injection well. In other embodiments, the extraction well will be shut down if hydrogen extraction rate or concentration is too low and / or water breakthrough happens.

[0065] Shown in Fig. 5 is a schematic for using hydraulic fracturing and two vertical wells for stimulating hydrogen generation and extraction without a downhole hydrogen membraneseparator. CCh-based fluids will be injected first to generate more fractures and reactive surface areas and then water is injected to stimulate hydrogen generation. In some embodiments, similar to Figure 3, proppants and catalysts are used for preventing the closure of fractures and enhancing hydrogen generation by catalytic effects. A larger proportion of the targeted formation can be swept by the injected water to maximize water-rock contact and reactions. In some embodiments, similar operations, including multiple fracturing processes, will be used for injection well and extraction well as discussed for Figure 4 without hydraulic fracturing. In some embodiments, the hydraulic fracturing will also be conducted for the extraction well to improve the permeability of the formation and enhance hydrogen transport to the extraction well.

[0066] A gel that can tolerate high temperature conditions is used to reduce the natural heterogeneity and those caused by reactions to ensure a large volume of iron-rich rocks is swept for hydrogen generation. In some embodiments, tracers that can tolerate high temperatures are used to monitor injected water fronts. In some embodiments, the right well in Figure 5 can be converted to an injection well and the injection well on the left side in Figure 5 can be converted to an extraction well to maximize the reaction of rock and water in the formation.

[0067] Figure 6 illustrates a schematic wherein a vertical well has tens of meters to thousands of meters extension in the horizontal direction, within a zone where source rock formations are located. In this embodiment, a first step of injecting CCh-based fluids to create more fractures and reactive surface areas is conducted, followed by a second step of injecting water through the horizontal well to stimulate hydrogen generation with hydraulic fracturing but without downhole hydrogen membrane separator. In some embodiments, the distance of horizontal well with the upper non-hydrogen generation formation can be meters to tens of thousands of meters. In some embodiments, hydraulic fracturing process is not needed for the horizontal well. In some embodiments, if hydraulic fracturing is conducted, the common operations for vertical wells after hydraulic fracturing will be implemented. In some embodiments, the fracture half-length can varyfrom meters to hundreds of meters, for example from 1 meter to 500 meters or more, depending on the geology, operators, and technology level. In some embodiments, water will be injected through the whole horizontal well or through only a proportion of the horizontal well for stimulated hydrogen generation.

[0068] In one example, steam is injected into the targeted formation to initiate or accelerate the reaction and control the formation in the optimal temperature range (200-350 °C) for hydrogen generation. In some embodiments, the well will be shut down to allow the soak stage, which is needed to allow a more complete reaction between injected water and rock and to consume water in the formation. In certain conditions, cold water is injected if the temperature of the targeted formation is too high, i.e., above 350 °C in order to create thermal stress, fractures, and fracture network to increase reactive surface areas for stimulated hydrogen generation.

[0069] Turning now to Fig. 7, illustrated therein, is a schematic for a hydrogen extraction process using the same horizontal well used for injection, under a pressure gradient. In some embodiments, hydrogen is extracted after each fracturing and soak period. In other embodiments, hydrogen can be extracted after multiple fracturing processes, water injection, and soak periods.

[0070] Referring now to Figure 8, illustrated therein, is a schematic which shows one vertical well and one horizontal well. The vertical well is used for extracting generated hydrogen after water has been injected and reacts with the source rock formation. The vertical well may need to be drilled if too much hydrogen gas is accumulated in an upper location of the source rock formation and the horizontal well cannot be used extract H2 efficiently. In some embodiments, the horizontal well and vertical well are drilled at the same time. In other embodiments, the horizontal well is drilled first, followed by hydraulic fracturing and water injection. The vertical well is drilled later to maximize hydrogen recovery. In some embodiments, hydrogen is extracted from the vertical well while the horizontal well is shut down. In some embodiments, after a period of time of hydrogen extraction from the vertical well, water is injected in the horizontal well whilethe vertical well continues to extract hydrogen at a controllable rate. In other embodiments, the horizontal well can be used for extracting hydrogen if water is consumed and more hydrogen occupies the pore space or fracturing network near the horizontal well. In some embodiments, hydrogen is extracted from the vertical well while water is continuously injected from the horizontal well. In other embodiments, the vertical well is converted to injection well to allow water injection into the upper location of the targeted formation for more hydrogen generation. The downward flow of inj ected water under gravity can maximize the contact of the inj ected water with rock to maximize hydrogen generation. In some embodiments, hydraulic fracturing can be conducted to the vertical well to maximize hydrogen generation and extraction. In some embodiments, multiple fracturing processes will be performed to maximize the hydrogen generation and extraction.

[0071] Figure 9 illustrates a schematic for extracting water from a shallower existing aquifer and then injecting it into the targeted source rock formation for hydrogen generation and extraction. In some embodiments, fresh water from the surface will not be used. Instead, the water from aquifer, either near surface or relatively deeper, is used for stimulating hydrogen generation. In some embodiments, the aquifer water is directly injected into the source rock formation. In other embodiments, the aquifer water is first extracted to surface for certain treatment and then reinjected into the source rock formation for stimulated hydrogen generation. In some embodiments, the water may be heated to a certain temperature prepared with desired chemicals to accelerate the hydrogen generation process. In some embodiments, the operations for water injection and hydrogen extraction are similar to those in Figure 8. The vertical well may also be used to first extract aquifer water and inj ect water to the targeted formation. In some embodiments, the produced water may be used for geothermal recovery and / or reinjection for stimulated hydrogen generation.

[0072] Turning to Figs. 10(A) and 10(B), illustrated therein, is a schematic for using deeper geothermal energy and water to stimulate natural hydrogen generation and extraction process. A vertical well is first drilled into the much deeper source rock formation, followed by a sidetrack horizontal well, as shown in Fig. 10(A). Hydraulic fracturing may or may not be conducted for the horizontal well. In some embodiments, cold water, either surface fresh water or extracted water from shallower aquifer, is first injected into the deeper formation and is heated by geothermal energy existing in the deeper formation. In some embodiments, a soak stage will be needed from days to years to make sure the injected water is heated to a high enough temperature for maximize hydrogen generation. In some embodiments, after a target temperature of water is achieved in the deeper formation, that water is extracted and re-injected into the targeted source rock formation for stimulated hydrogen generation to occur. In some embodiments, the other operations for hydrogen generation, soaking, and extraction are similar to those discussed in Figures 8 and 9. The steps of heating the water using the geothermal energy, then re-injection into the targeted source rock formation, and extraction of hydrogen may be repeated twice to an unlimited amount of times, if the source rocks are still available and it is still economic for stimulated hydrogen generation and extraction.

[0073] Figures 11 (A) and (B), show an embodiment wherein a downhole hydrogen membrane separator is used to extract hydrogen and desired gases to the surface. The materials for downhole hydrogen membrane separators can be polymer, microporous ceramic, metallic, porous carbon, and dense ceramic materials as long as they can tolerate the high temperature high pressure conditions in subsurface. The hydrogen concentration, from 0 to nearly 100%, after downhole hydrogen membrane separator can be controlled and adjusted to obtain the desired hydrogen concentration at the surface for transportation purposes. In some embodiments, small molecules such as hydrogen and methane gas mixtures are obtained using proper downhole membrane separators. The downhole hydrogen membrane separator can be installed at an upper location ofthe targeted source rock formation but below the seal. In other embodiments, the downhole hydrogen membrane separator is installed at a different formation above the targeted source rock formation, as shown in Fig. 11(B). In this case, the undesired gases will be emitted into the designed formation for sequestration, while the hydrogen gas and other desired gases at controllable concentration will be extracted to the surface. In some embodiments, one or more downhole membrane separators will be used. For example, two or more downhole hydrogen membrane separators can be installed in an upper location of the targeted source rock formation and a rock formation above the targeted source rock formation.

[0074] In other embodiments, a downhole hydrogen membrane separator is not used. Instead, the gas mixtures are first extracted to the surface to separate hydrogen from other gases. The undesired gases or liquids are then re-injected into the subsurface. Turning to Fig. 12, illustrated therein, is a schematic for a multiple-stage separation process for hydrogen extraction to surface using downhole hydrogen membrane separators. In some embodiments, liquids and gases are first separated before entering the downhole hydrogen membrane separators, such as by use of a downhole liquid-gas separator. In some embodiments, the gas mixtures, after the liquid-gas separation process, will flow into the downhole hydrogen membrane separators so that the hydrogen and desired gases will be obtained and extracted to surface. If too much water flows towards the extraction well, the extraction well will be shut down and the soak stage starts. After all or most of water is consumed by water-rock reactions, the extraction well will then be opened for extracting desired gases.

[0075] Fig. 13 illustrates extraction of generated hydrogen using a certain number of downhole hydrogen membrane separators using a horizontal well. In some embodiments, one or more downhole membrane separators will be installed at different locations along the horizontal well. In some embodiments, one or more downhole membrane separators will be in on / off modeand may change with time, depending on the distribution of hydrogen in the formation and water content or other considerations.

[0076] Referring now to Fig. 14(A) - (C), illustrated therein is a schematic for using stacked multi-branch wells to inject water into the thicker targeted formation to stimulate hydrogen generation and extract generated hydrogen from a horizontal well. In some embodiments, one or unlimited number of horizontal wells are drilled for the stacked multi-branch wells, depending on the thickness of the source rock formation and the suitable temperature range for stimulated hydrogen generation. Three branches are shown in the embodiment depicted in Fig. 14(A), (B) and (C), although this number is not intended to be limited. The stacked multi-branch wells are drilled at the same time or at different times. The length of each branch well can be the same or different, depending on the size and configuration of the source rock formation. In some embodiments, water and other chemicals are first injected into the upper branch of the well (as seen in Fig. 14 (A)), or any other well. In some embodiments, water and other chemicals are simultaneously injected into any one of the branches of the well (see Fig. 14 (C)). In some embodiments, one or more horizontal wells, as shown in Figs. 14(A) and (B) may also be converted to extraction wells to extract generated hydrogen when it flows upwards. In some embodiments, downhole hydrogen membrane separators are installed in the vertical extraction well . In some embodiments, the lower well(s) at the deeper formation may be used to heat inj ected cold water and then re-injected to the shallower branch well for stimulated hydrogen generation.

[0077] Referring now to Figure 15, illustrated therein is a schematic for extracting generated hydrogen with one horizontal well and at least one or a plurality of vertical wells. In some embodiments, one or more vertical wells will be drilled at the same time or at different times to extract more hydrogen to surface if the source rock formation is large. In some embodiments, hydraulic fracturing may be conducted for one or more vertical wells to maximize the stimulation of hydrogen generation and extraction. In some embodiments, one or more vertical wells will beopen or shut down depending on the amount of hydrogen generated and its distribution in the formation. The extraction rate of the hydrogen from each vertical well will be designed and optimized for its particular location. In some embodiments, the horizontal well can also be used for extracting generated hydrogen if enough hydrogen is generated and available for extraction. The extraction wells can be converted to hydrogen injection wells if a good seal is identified. In this case, the reservoir can be repurposed for underground hydrogen storage to meet the seasonal need for hydrogen energy. The reservoir, therefore, can be integrated hydrogen generation and storage site.

[0078] Fig. 16 illustrates a schematic for extracting generated hydrogen from the above side well. In some embodiments, drilling a horizontal multi -branch well, with a well branch above a water injection well branch, instead of one or more vertical well, will make the process more economic and more hydrogen may be able to be extracted. In some embodiments, one or both horizontal wells will serve as an extraction well if a large amount of hydrogen is generated in the targeted source rock formation. In some embodiments, hydrogen is extracted from the upper well while water is injected through the lower well, either continuously or pulsed. The upper horizontal well may be converted to an injection well to stimulate hydrogen generation in the upper formation. In some embodiments, many other types of wells, such as sidetrack wells, deviated well, designer well, multilateral wells, and / or any other advanced well types (including but not limited to the stacked multi-branch well, dual opposing lateral well, e-entry laterals from a vertical well, and 3D well, etc.), are drilled in the targeted formation for, but not limited to, water and chemical injection, hydrogen generation stimulation, hydrogen extraction, and / or desired and undesired gas treatment purposes.

[0079] Referring now to Fig. 17 (A)-(D), illustrated therein is a schematic for using different advanced well types to stimulate and extract hydrogen from the targeted formation, consisting of, but not limited to, dual opposing lateral well, multilateral from a vertical well, multilateral from ahorizontal well, and a multi -branch well. In some embodiments, water and other chemicals are injected into the targeted formation and hydrogen and / or desired gases and fluids are extracted from the same well. In some embodiments, the well has two or more lateral and / or branch wells and is not limited to the ones depicted in Figure 17. In some embodiments, one or more or all lateral wells and branch wells can be converted from a water injection well to hydrogen extraction well, or vice versa. Hydraulic fracturing can be conducted in one or more or all lateral wells and branch wells.

[0080] Fig. 18 illustrates different well patterns for stimulating and extracting hydrogen from the targeted source rock formation, particularly for large source rock formations. The well type in Fig. 18 can be vertical well, horizontal well, or any other well type. In some embodiments, the direct line pattern with alternating injection well and extraction well is used for the targeted formation. In other embodiments, the other types of well patterns such as four-spot pattern, five- spot pattern, seven-spot pattern, nine-spot pattern, and other regular and irregular patterns are used for stimulating hydrogen generation and extraction. In some embodiments, one or more injection wells will be open or shut down. In some embodiments, the reversed well patterns, converting injection wells to extraction wells and vice versa, are used for stimulating hydrogen generation and extraction. The water injection rate and gas extraction rate in these wells will change with time and be optimized with the development of the targeted formation. After the source rocks lose their ability for hydrogen generation or if the process becomes non-economic, those wells can also be used for storage of undesired gases. In some embodiments, if rare minerals are found in the water during and / or after water-rock interactions, these wells can also be used to extract water for rare mineral recovery purposes.

[0081] Also disclosed are systems for stimulating and extracting hydrogen gas generated from Earth’s subsurface. In accordance with above embodiments, the systems comprise at least one well in contact with a source rock formation; a fluid composition configured to be introduced intothe source rock formation, through the at least one well for stimulating hydrogen gas production from the source rock formation. The system optionally includes an extraction component for extracting the stimulated hydrogen gas produced from the source rock formation wherein the fluid composition comprises at least one of carbon dioxide gas (CO2), water (H2O), steam, nitrogen gas (N2), proppants, catalysts, polymeric solutions, or a combination thereof. The at least one well can include at least one vertical well, at least one horizontal well, or a combination thereof, similar with embodiments described above and detailed in the figures. The extraction component can include at least one downhole hydrogen membrane separator, and / or at least one extraction well. In one embodiment, the extraction component can comprise multiple downhole hydrogen membrane separators. In a further embodiment, the extraction component is located either within the source rock formation, or at a location above the source rock formation, in accordance with prior embodiments described above.

[0082] In certain embodiments, the fluid composition comprises at least one of or a combination of water and CO2 based fluids for hydraulic fracturing.

[0083] The above description of the preferred embodiments is not to be deemed as limiting the invention, which is defined by the appended claims. The disclosure is intended to enable the artisan of ordinary skill to practice variants of the invention described without departing from the scope of the invention. Numerical limitations herein, in the specification and in the claims, are understood to be limited by the modifier “about,” such that minor departures yielding equivalent results is within the scope of the invention.

[0084] Features or dependent claim limitations disclosed in connection with one embodiment or independent claim may be combined in another embodiment or with a different independent claim without departing from the scope of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one skilled in the art to which this invention belongs. Although any methods and materials similar orequivalent to those described herein can also be used in the practice or testing of the present invention, the preferred methods and materials are now described. All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and / or materials in connection with which the publications are cited.

[0085] Consistent with the above disclosure, the examples of systems and methods enumerated in the following clauses are specifically contemplated and are intended as a non-limiting set of examples.

Claims

CLAIMS1. A method for stimulating hydrogen gas (H2) generation from Earth’s subsurface, the method comprising the steps of: forming at least one well in contact with a source rock formation, wherein the at least one well is configured to allow the introduction of a fluid composition into the source rock formation; introducing the fluid composition into the source rock formation, through the at least one well; and stimulating hydrogen gas production from the source rock formation through a serpentinization process; wherein the fluid composition comprises at least one of carbon dioxide gas (CO2), water (H2O), steam, nitrogen gas (N2), proppants, catalysts, polymeric solutions, or a combination thereof.

2. The method of claim 1, wherein the step of introducing the fluid composition comprises a first injection of a CO2 based fluid composition for fracturing of the source rock formation and a second injection of water.

3. The method of claim 1, wherein the step of stimulating hydrogen gas production comprises injection of at least one of water, steam, CO2 based fluid, proppants, catalysts, polymeric solutions, or a combination thereof.

4. The method of claim 2, wherein the first injection of a CO2 based fluid composition does not comprise hydraulic fracturing.

5. The method of claim 1, wherein the step of introducing a fluid composition into the well comprises injection of a combination of water and CO2 based fluids for hydraulic fracturing.

6. A method of claim 1, wherein the step of stimulating hydrogen gas production from the source rock formation comprises injection of at least one of cold water, warm water, hot water, steam or a combination thereof, in order to maintain a temperature of 200 to 350 °C in the source rock formation.

7. The method of claim 1, further comprising a step of hydrogen gas extraction, through the use of at least one of a hydrogen membrane separator.

8. The method of claim 1, wherein the at least one well comprises at least one vertical well, at least one horizontal well, or a combination thereof.

9. The method of claim 8, wherein the at least one horizontal well comprises a multibranched configuration, wherein multiple horizontal branches of the at least one well are located at varying depths within the source rock formation.

10. The method of claim 1, further comprising a conducting or forming perforations in at least one or at varying locations within the source rock formation.

11. The method of claim 1, wherein cold water is injected into a deeper source rock formation having a temperature of about 350 °C, for creating fractures, a fracture network, or reactive surface areas within the source rock formation, by thermal-induced fracturing.

12. The method of claim 1, wherein the step of introducing the fluid into the source rock formation comprises multiple hydraulic fracturing steps.

13. The method of claim 1, wherein the fluid can comprise water obtained from an aquifer.

14. The method of claim 13, wherein surface water or aquifer water is introduced into a deeper source rock formation to be heated and then re-injected into a shallower source rock formation, at a lower temperature.

15. The method of claim 1, further comprising extraction of generated hydrogen gas, through a downhole hydrogen membrane separator which is installed in the source rock formation of a formation residing above the source rock formation.

16. A system for stimulating and extracting hydrogen gas (H2) generation from Earth’s subsurface, the system comprising: at least one well in contact with a source rock formation; a fluid composition configured to be introduced into the source rock formation, through the at least one well for stimulating hydrogen gas production from the source rock formation optionally an extraction component for extracting the stimulated hydrogen gas produced from the source rock formation wherein the fluid composition comprises at least one of carbon dioxide gas (CO2), water (H2O), steam, nitrogen gas (N2), proppants, catalysts, polymeric solutions, or a combination thereof.

17. The system of claim 16, wherein the at least one well comprises at least one vertical well, at least one horizontal well, or a combination thereof.

18. The system of claim 16, wherein the extraction component comprises at least one downhole hydrogen membrane separator.

19. The system of claim 16, wherein the fluid composition comprises at least one of or a combination of water and CO2 based fluids for hydraulic fracturing.

20. The system of claim 16, wherein the extraction component is located either within the source rock formation, or at a location above the source rock formation.

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