Treatment of underground formations for production of hydrogen

Abstract

Implementations include treating water or brine filled or water / brine plus steam (water-vapor) filled porous rock to generate and produce hydrogen through the creation of in-situ reactors wherein fuel and oxidant is added to the porous rock enabling combustion, gasification, steam-reforming, water-gas shift, and aquathermolysis reactions occur. The hydrogen-containing gas may then be produced to the surface.

Description

TREATMENT OF UNDERGROUND FORMATIONS FOR PRODUCTION OF HYDROGENCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 63 / 633,116, filed on 12 April 2024, the entire disclosure of which is hereby incorporated by reference.BACKGROUND

[0002] A large fraction of the Earth comprises rock formations that have porosity containing fluids. These fluids can be petroleum, that is oil or natural gas or other naturally-formed gases containing components such as hydrogen, carbon dioxide, or methane or other gas components. Oil refers to a naturally-occurring, crude petroleum substance consisting of hydrocarbon and other compounds. It can be categorized into heavy oil, extra heavy oil, or bitumen, with distinctions based on their densities and viscosities. Conventionally, oil is upgraded (if heavy oil) and then refined into transportation fuels such as gasoline, diesel, and jet fuel. Natural gas primarily consists of methane and other light hydrocarbons such as ethane and propane and is commonly utilized as a fuel source or as a raw material in chemical processes when extracted from gas reservoirs. Other naturally-formed gases include natural hydrogen that is formed from reactions of steam and rock.

[0003] Another fluid that can be contained in porous rock is brine, an aqueous liquid phase salt solution at the temperature of the formation. If the temperature of a brine system is sufficiently elevated, it can be used as geothermal heat production resources.

[0004] Other fluids that may be contained in sufficiently hot porous rock include gases containing mixtures of water vapor (steam), hydrogen, carbon dioxide, methane, and other gas components. These systems are often at elevated temperature given their depth and as such, can be used as geothermal heat production resources.

[0005] The porosity that exists in rock can take multiple forms including the pore space between rock grains, natural fractures (cracks in rock that have volume), vugs (volume in rock that exists due to dissolution of the rock), and karsted zones (cavernous volume in rock that exists due to dissolved or eroded rock). The fluids (e.g., petroleum, brine, or gas) can be hosted in one or more of these porosity types in the rock at the temperature of the rock formation. The temperature of the rock formation depends on the depth of the formation. Typically, the geothermal gradient over the first few kilometers of the Earth’s surface is equal to about 25°C / km. Insome locations, for example, Iceland, the geothermal gradient can be higher than 50°C / km.

[0006] Porous rock zones are found throughout the world containing fluids at the temperature of the rock formation.

[0007] Human activity has taken advantage of underground porous rock formations for the production of fluids including oil, natural gas, and water or brine (e.g., for dissolved minerals, geothermal, or all).

[0008] There also exist non-porous rock formations in the earth, for example, shale, granitic rock, basalt, volcanic rock, salt, and coal layers. After a well has been drilled into these rock formations, these rock formations can be made porous in the neighbourhood of the wells by using hydraulic fracturing.SUMMARY

[0009] This Summary is intended to introduce, in an abbreviated form, various topics to be elaborated upon below in the Detailed Description. This Summary is not intended to identify key or essential aspects of the claimed invention. This Summary is similarly not intended for use as an aid in determining the scope of the claims.

[0010] In some aspects, the techniques described herein relate to a method, including: providing an underground porous rock formation including water; providing a well disposed at least partially within the underground porous rock formation; injecting, via the well, a hydrogen-generating agent into the underground porous rock formation to produce one or more of combustion, gasification, steam-reforming, water-gas shift, or aquathermolysis reactions to yield a hydrogen-bearing gas in the underground porous rock formation; and producing, via the well, the hydrogenbearing gas to the surface.

[0011] In some aspects, the techniques described herein relate to a method, wherein the underground porous rock formation includes hot porous rock and steam.

[0012] In some aspects, the techniques described herein relate to a method, wherein the hydrogen-generating agent includes a fuel and an oxidant.

[0013] In some aspects, the techniques described herein relate to a method, wherein the fuel includes one or more of methane, natural gas, mixtures of gaseous fuels including hydrogen, hydrocarbons, alcohols, ketones, aldehydes, crude oil, solvent, crude oil fractions, heavy oil, waste oil, plant-based oils (biofuels), or emulsified oils.

[0014] In some aspects, the techniques described herein relate to a method, wherein the oxidant includes one or more of air, oxygen-enriched air, oxygen, nitrous oxide, peroxide, or other compounds that enable oxidation of the fuel.

[0015] In some aspects, the techniques described herein relate to a method, wherein the hydrogen-generating agent includes carbon monoxide.

[0016] In some aspects, the techniques described herein relate to a method, wherein the injecting produces a water-gas shift reaction to yield the hydrogen-bearing gas.

[0017] In some aspects, the techniques described herein relate to a method, wherein the carbon monoxide is produced by combusting a fuel and an oxidant on the surface.

[0018] In some aspects, the techniques described herein relate to a method, further including repeating the injecting and producing operations.

[0019] In some aspects, the techniques described herein relate to a method, wherein the well includes a catalyst disposed around a wellbore of the well.

[0020] In some aspects, the techniques described herein relate to a method, wherein the catalyst includes one or more of platinum, aluminum, iron, magnesium, copper, zinc, cesium, chromium, nickel, oxides of these metals, or mixtures of these metals, or metal oxides.

[0021] In some aspects, the techniques described herein relate to a method, further including injecting an alkaline material in an aqueous solution via the well into the underground porous rock formation.

[0022] In some aspects, the techniques described herein relate to a method, wherein the alkaline material includes one or more of calcium hydroxide, potassium hydroxide, magnesium hydroxide, or other alkaline materials.

[0023] In some aspects, the techniques described herein relate to a system, including: a well disposed at least partially within an underground porous rock formation including water configured for: injection of a hydrogen-generating agent into the underground porous rock formation to produce one or more of combustion, gasification, steam-reforming, water-gas shift, or aquathermolysis reactions to yield a hydrogen-bearing gas in the underground porous rock formation; and production of the hydrogen-bearing gas to the surface.

[0024] In some aspects, the techniques described herein relate to a system, wherein the underground porous rock formation includes hot porous rock and steam.

[0025] In some aspects, the techniques described herein relate to a system, wherein the hydrogen-generating agent includes a fuel and an oxidant.

[0026] In some aspects, the techniques described herein relate to a system, wherein the fuel includes one or more of methane, natural gas, mixtures of gaseous fuels including hydrogen, hydrocarbons, alcohols, ketones, aldehydes, crude oil, solvent, crude oil fractions, heavy oil, waste oil, plant-based oils (biofuels), or emulsified oils.

[0027] In some aspects, the techniques described herein relate to a system, wherein the oxidant includes one or more of air, oxygen-enriched air, oxygen, nitrous oxide, peroxide, or other compounds that enable oxidation of the fuel.

[0028] In some aspects, the techniques described herein relate to a system, wherein the hydrogen-generating agent includes carbon monoxide.

[0029] In some aspects, the techniques described herein relate to a system, wherein the injecting produces a water-gas shift reaction to yield the hydrogen-bearing gas.

[0030] In some aspects, the techniques described herein relate to a system, wherein the carbon monoxide is produced by combusting a fuel and an oxidant on the surface.

[0031] In some aspects, the techniques described herein relate to a system, wherein the well is further configured for repeating the injecting and producing operations.

[0032] In some aspects, the techniques described herein relate to a system, further including a catalyst disposed around a wellbore of the well.

[0033] In some aspects, the techniques described herein relate to a system, wherein the catalyst includes one or more of platinum, aluminum, iron, magnesium, copper, zinc, cesium, chromium, nickel, oxides of these metals, or mixtures of these metals, or metal oxides.

[0034] In some aspects, the techniques described herein relate to a system, wherein the well is further configured for injecting an alkaline material in an aqueous solution via the well into the underground porous rock formation.

[0035] In some aspects, the techniques described herein relate to a system, wherein the alkaline material includes one or more of calcium hydroxide, potassium hydroxide, magnesium hydroxide, or other alkaline materials.BRIEF DESCRIPTION OF THE FIGURES

[0036] For a fuller understanding of the nature and objects of the disclosure, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, in which:

[0037] FIG. 1 illustrates a method for producing hydrogen from a porous rock containing water, according to one or more implementations herein.

[0038] FIG. 2 illustrates a method for producing hydrogen from a porous rock containing water and steam, according to one or more implementations herein.

[0039] FIG. 3 illustrates a method for producing hydrogen from a porous rock containing water and steam, according to one or more implementations herein.DETAILED DESCRIPTION

[0040] Various techniques for producing hydrogen and synthesis gas have been disclosed in patents, including U.S. Patent 11 ,530,603, incorporated herein by reference in its entirety, which outlines a method involving the injection of an oxidizing agent into a petroleum reservoir for heating and subsequent hydrogen generation. Another method, described in patent application U.S. Pub. 2021 / 0047905, incorporated herein by reference in its entirety, utilizes in-situ gasification to produce synthesis gas. However, these approaches lack specific guidance on an injection and production method that maximizes hydrogen generation. In a study by Kapadia et al. (2013) [Applied Energy 107:281-296, 2013, D0l:10.1016 / j.apenergy.2013.02.035], incorporated herein by reference in its entirety, steam and oxygen injection into an oil reservoir for in-situ gasification is discussed, demonstrating the feasibility of hydrogen production under steam- oxygen cycles and continuous injection. Nevertheless, the study does not provide an optimal strategy for injection and production. None of these methods are configured for water-filled or steam-filled porous rock zones for hydrogen generation and production.

[0041] Implementations include treating water- or brine-filled or water / brine plus steam (water-vapor)- filled porous rock to generate and produce hydrogen through the creation of in-situ reactors wherein fuel and oxidant is added to the porous rock enabling combustion, gasification, steam-reforming, water-gas shift, and aquathermolysis reactions to occur. The hydrogen-containing gas may then be produced to the surface.

[0042] Components of the method involve wells, number of injection and production wells, types of wells whether vertical, horizontal, deviated, multilateral, multiple-zone perforated wells, arrangement of the wells within the porous rock, and the injection and production operating strategy including the schedule of injection and production and the volumes of materials injected, the volumes of materials produced, thepressure that the fluids in the porous rock achieves during injection, the pressure that the fluids drop to during production, and whether the well is stimulated prior to injection.

[0043] In target formations, the pore space of the porous rock will contain a majority of water or brine (aqueous) phase. Other phases that could be present include gas phase and oil phase. In aquifers, the pore space of the porous rock will be filled with water. In deeper aquifers where the temperature is high enough, the pore space may be filled with saturated steam, where both liquid water and water vapour present.

[0044] An example target porous rock would have its pore space filled with water, steam (e.g., water vapor), or both. If there is insufficient water in the pore space of the porous rock, water or steam can be injected into the formation to increase the amount of water within the pore space of the porous rock.

[0045] In some aspects, the techniques described herein relate to a method for treating a porous rock containing water to recover a hydrogen-bearing gas, including the injection of a combustible fuel and an oxidant into a porous rock to initiate combustion reactions that generate heat and carbon oxides including carbon monoxide and carbon dioxide. The temperature in the region of the well may be monitored by using temperature measurement devices such as thermocouples and injection of fuel and oxidant may continue until the temperature exceeds a particular value, after which injection may stop. The combustion reaction may generate steam. The heat generated by the reactions may convert the water in the porous rock to steam. The heat, carbon monoxide, and steam created through in-situ combustion in the porous rock may allow gasification and steam-reforming reactions of the injected fuel as well as the water-gas shift reaction where carbon monoxide and steam react contributing to the generation of hydrogen that accumulates within the pore volume of the porous rock. Thereafter, the hydrogenbearing gas in the pore space may be produced to the surface by using a well until the hydrogen production rate has dropped below a threshold value or the concentration of hydrogen in the produced gas is lower than a threshold value, then gas production is stopped. Thereafter, fuel and oxidant injection may be restarted into the porous rock and the process of in-situ generation and production of hydrogen-bearing gas may resume.

[0046] The injection of the combustible fuel and an oxidant may use a well with vertical, horizontal, deviated, multilateral and other geometric arrangement.

[0047] The production of the hydrogen-bearing gas can may use a well with vertical, horizontal, deviated, multilateral and other geometric arrangement.

[0048] The wells can be used for injection of the combustible fuel and an oxidant or production of the hydrogen-bearing gas or both. If the same well is used for injection and production, then the process can be operated in a cyclic manner. Multiple injection and production wells can be used to create multiple zones where the hydrogen-generating reactions are occurring.

[0049] The injected fuel can be, for example, methane, natural gas, mixtures of gaseous fuels including hydrogen, hydrocarbons, alcohols, ketones, aldehydes, crude oil, solvent, crude oil fractions, heavy oil, waste oil, plant-based oils (biofuels), or emulsified oils.

[0050] The oxidant can be, for example, air, oxygen-enriched air, oxygen, nitrous oxide, peroxide, or other compounds that enable oxidation of the fuel.

[0051] The mixture of injected fuel and oxidant may be injected into the porous rock formation where the ratio of oxidant to fuel is controlled to generate maximum heat, steam (water vapor from the combustion reaction), and carbon oxide within the reservoir. For example, for methane, the molar ratio of oxygen to methane is controlled to be between 0.5 (partial combustion) to 2 (full combustion).

[0052] In another implementation, the injection of combustible fuel and an oxidant may be conducted into a porous rock that contains a hot steam zone. An example of this type of porous system may include a geothermal resource. In this method, the injection of a combustible fuel and an oxidant into a porous rock initiates combustion reactions that generate heat and carbon oxides including carbon monoxide and carbon dioxide. The temperature in the region of the well is monitored by using standard temperature measurement devices such as thermocouples and injection of fuel and oxidant continues until the temperature exceeds a particular value after which injection stops. The combustion reaction generates steam. The generated carbon monoxide and steam, both naturally in the porous rock and that created from the combustion reactions, may allow gasification and steam-reforming reactions of the injected fuel as well as the water-gas shift reaction, where carbon monoxide and steam react, contributing to the generation of hydrogen that accumulates within the pore volume of the porous rock. Thereafter, the hydrogen-bearing gas in the pore space may be produced to the surface by using a well until the hydrogen production rate has dropped below a threshold value or the concentration of hydrogen in the produced gas is lower than a thresholdvalue, then gas production may be stopped. Thereafter, fuel and oxidant injection may be restarted into the porous rock and the process of in-situ generation and production of hydrogen-bearing gas may resume.

[0053] In another implementation, the combustion of the fuel and oxidant may be conducted on the surface and the resulting carbon oxides may be injected into the porous rock that contains a hot steam zone at sufficiently high temperature such as a geothermal resource that is over 200°C. The injected carbon monoxide and steam naturally in the porous rock may allow the water-gas shift reaction where carbon monoxide and steam react leading to the generation of hydrogen that accumulates within the pore volume of the porous rock. After the target volume of carbon oxides has been injected, injection may be stopped and reactions generating hydrogen may continue until the carbon monoxide is consumed. Thereafter, the hydrogen-bearing gas in the pore space may be produced to the surface by using a well until the hydrogen production rate has dropped below a threshold value or the concentration of hydrogen in the produced gas is lower than a threshold value, then gas production may be stopped. Thereafter, the combustion of the fuel and oxidant may be conducted on the surface and the resulting carbon oxides are injected into the porous rock into the porous rock and the process of in- situ generation and production of hydrogen-bearing gas may resume.

[0054] In another implementation, the porous rock may include of a hot dry rock that may be hot enough to be capable of geothermal heat production. In these systems, water or steam can be injected into the porous rock prior to fuel and oxidant injection.

[0055] In another implementation, water or steam can be injected into the porous rock formation prior to the injection of the combustible fuel and oxidant. If water is injected, it may be injected into hot dry rock capable of generating steam.

[0056] In another implementation, the combustible fuel can be injected into porous rock formation prior to the injection of the oxidant.

[0057] In another implementation, a catalyst pack can be placed around the sections of the injection well or production well or both wells that are positioned in the target porous rock formation. The catalysts in the pack may enable greater production of hydrogen from the water-gas-shift reaction. The catalyst component may include one or more of platinum, aluminum, iron, magnesium, copper, zinc, cesium, chromium, nickel, oxides of these metals, or mixtures of these metals or metaloxides. The catalyst can be embedded on an inert support or backbone material such as silica for placement as a catalyst pack around the wells.

[0058] In another implementation, alkaline material in aqueous solution may be injected into the porous rock prior to the process or during the process to react with carbon dioxide that is generated from the combustion reactions of the fuel and oxidant, which may subsequently dissolve in the water in the porous rock. This reaction may generate carbonate minerals, reducing the amount of carbon dioxide that is produced to the surface. Examples of alkaline materials include calcium hydroxide, potassium hydroxide, magnesium hydroxide, and other alkaline materials.

[0059] The following figures illustrate example methods and operations thereof. In some implementations, a method illustrated herein may include additional operations, fewer operations, differently arranged operations, or different operations than the operations depicted in the following figures. Moreover, or in the alternative, two or more of the operations depicted in the following figures may be performed at least partially in parallel.

[0060] FIG. 1 illustrates a method 100 for producing hydrogen from a water-filled or brine- filled porous rock, according to one or more implementations herein.

[0061] In an operation 102, a target porous rock containing water or brine may be provided.

[0062] In an operation 104, wells may be placed with the target porous rock where the wells can be set as injection wells or production wells or both. The wells can be, for example, vertical, horizontal, deviated, multiple perforated, multilateral, or another geometric arrangement.

[0063] In an operation 106, fuel and oxidant may be injected into the porous rock. The injection can be done together at the same time or the fuel first and the oxidant second or the oxidant first and the fuel second. The injected fuel can include, for example, methane, natural gas, mixtures of gaseous fuels including hydrogen, hydrocarbons, alcohols, ketones, aldehydes, crude oil, solvent, crude oil fractions, heavy oil, waste oil, plant-based oils (biofuels), and emulsified oils, or mixtures thereof. The oxidant can include, for example, air, oxygen-enriched air, oxygen, nitrous oxide, peroxide, other compounds that enable oxidation of the fuel, or mixtures thereof.

[0064] In an operation 108, the fuel and oxidant may be injected into the porous rock under conditions that promote spontaneous ignition of the fuel within the porous rockwhich in turn generates heat, carbon monoxide, and carbon dioxide. The fuel and oxidant may be fed a ratio where combustion can occur, that is, within the flammability limits of the fuel. There may be an excess of fuel fed into the porous rock such that, when combustion occurs, all of the oxidant is consumed in the porous rock. Also, in such implementations, partial oxidation may occur, which produces carbon monoxide as the dominant carbon oxide. The heat generated by the combustion reactions may convert some fraction of the water in the porous rock to steam. The presence of steam together with the excess fuel within the porous rock may lead to steam reforming with the consequent generation of products such as carbon monoxide and hydrogen. The water-gas shift reaction may also occur where the carbon monoxide and steam react to generate more hydrogen and carbon dioxide. If there is any remaining oxygen, then the fuel, oxygen, and carbon dioxide can react to form hydrogen, carbon monoxide, and steam. With steam, the fuel may react with oxygen and steam to yield more hydrogen and carbon monoxide. The amount of fuel and oxidant injected into the porous rock may be maintained until the temperature around the well has reached, for example, over 400°C and in some implementations over 500°C, after which injection may be stopped.

[0065] For example, if the fuel is methane and oxidant is oxygen, then a set of reactions that can occur include, for example:002(g) + 2 H2O(g)2 CH4(g) + 02(g) 2 00(g) + 4 H2(g)CH4(g) + H2O(g) 00(g) + 2 H2(g) 00(g) + H2O(g) 002(g) + H2(g)2 CH4(g) + 02(g) + 002(4 CH4(g) + 02(g) + 2 H20(g) - 10 H2(g) + 4 CO where x, y, and z are stoichiometric coefficients of the combustion (partial) reaction.

[0066] At an operation 110, after the oxidant is consumed and as a consequence, the heat generation reactions may stop and the temperature may start to drop due to heat losses to the porous rock and inflow of cool fluids. Then, the well may be placed on production and the hydrogen-bearing fluids surrounding the well may be produced to the surface.

[0067] The operation 106, the operation 108, and the operation 110 may be done in some implementations as consecutive steps of the process using a well or multiple wells or in other implementations may be done simultaneously with a well doing, forexample, the operation 106, a well doing the operation 108, and a well doing the operation 110.

[0068] In an operation 112, for a production well, an economic limit of hydrogen recovery may be reached and the recovery process for hydrogen may be stopped in that well. Thereafter, the operation 106, the operation 108, and the operation 110 can be repeated in a well in a cyclic manner. Even if the economic limit is not reached, at any point, the process may return to the operation 106 and / or the operation 108. If the overall hydrogen recovery process may have reached an economic limit, the process can advance to an operation 114. This process can be done in both cyclic manner (e.g., single wells used for both stimulation and production) or a non-cyclic manner (e.g., one or more injection wells and one or more production wells).

[0069] In the operation 114, the recovery process of hydrogen may be stopped.

[0070] In another implementation of the method 100, prior to the operation 106, a well may be stimulated by using hydraulic squeeze or fracturing where proppant or nanocatalyst fluid is placed within the porous rock. The proppant can permanently enhance the permeability of the porous rock. The proppant or nanocatalyst fluid can also contain catalyst particles that enhance the production of hydrogen through the water-gas shift reaction. The catalyst can contain, for example, iron, magnesium, chromium, copper, zinc, and aluminum and combinations thereof or oxides of these metals and combinations thereof. This stimulation can be done multiple times throughout the process.

[0071] In another implementation of the method 100, prior to the operation 106, in some implementations, the porous rock may be stimulated by using radio frequency stimulation to heat the water within the porous rock. This stimulation can be done multiple times throughout the process.

[0072] In another implementation of the method 100, prior to the operation 106, in some implementations, alkaline solutions, including for example, sodium, magnesium, calcium, potassium, can be injected into the porous rock to mix with the native water within the porous rock. This may provide conditions where dissolved carbon dioxide, in the form of bicarbonate, may react with the cations to produce solid carbonates within the porous rock.

[0073] FIG. 2 illustrates a method 200 for producing hydrogen from a hot porous rock containing (>100°C and in some implementations >200°C) water (brine) and steam, according to one or more implementations herein. In the method 200, in an operation 202, a target hot porous rock containing water (brine) and steam isprovided. The method 200 operates in relation to a hot porous rock where steam is present. Such types of hot porous rock may provide capabilities for geothermal heat recovery. Due to the natural presence of steam within the porous rock, it may react with the injected fuel to form carbon monoxide and hydrogen (reforming reactions). Further, the carbon monoxide together with carbon monoxide generated from oxidation reactions may react with the steam to yield more hydrogen.

[0074] In an operation 204, wells may be placed with the target porous rock where the wells can be set as injection wells or production wells or both. The wells can be, for example, vertical, horizontal, deviated, multiple perforated, multilateral, or another geometric arrangement.

[0075] In an operation 206, fuel and oxidant may be injected into the porous rock. The injection can be done together at the same time or the fuel first and the oxidant second or the oxidant first and the fuel second. The injected fuel can include, for example, methane, natural gas, mixtures of gaseous fuels including hydrogen, hydrocarbons, alcohols, ketones, aldehydes, crude oil, solvent, crude oil fractions, heavy oil, waste oil, plant-based oils (biofuels), and emulsified oils, or mixtures thereof. The oxidant can include, for example, air, oxygen-enriched air, oxygen, nitrous oxide, peroxide, other compounds that enable oxidation of the fuel, or mixtures thereof.

[0076] In an operation 208, the fuel and oxidant may be injected into the porous rock under conditions that promote spontaneous ignition of the fuel within the porous rock which in turn generates heat, carbon monoxide, and carbon dioxide. The fuel and oxidant may be fed a ratio where combustion can occur, that is, within the flammability limits of the fuel. There may be an excess of fuel fed into the porous rock such that, when combustion occurs, all of the oxidant is consumed in the porous rock. Also, in such implementations, partial oxidation may occur, which produces carbon monoxide as the dominant carbon oxide. The heat generated by the combustion reactions may convert some fraction of the water in the porous rock to steam. The presence of steam together with the excess fuel within the porous rock may lead to steam reforming with the consequent generation of products such as carbon monoxide and hydrogen. The water-gas shift reaction may also occur where the carbon monoxide and steam react to generate more hydrogen and carbon dioxide. If there is any remaining oxygen, then the fuel, oxygen, and carbon dioxide can react to form hydrogen, carbon monoxide, and steam. With steam, the fuel may react with oxygen and steam to yield more hydrogen and carbon monoxide. The amount of fuel and oxidant injected into the porous rock may bemaintained until the temperature around the well has reached, for example, over 400°C and in some implementations over 500°C, after which injection may be stopped.

[0077] For example, if the fuel is methane and oxidant is oxygen, then a set of reactions that can occur include, for example:4 CH4(g) + 02(g) + 2 H20(g) - 10 H2(g) + 4 CO where x, y, and z are stoichiometric coefficients of the combustion (partial) reaction.

[0078] At an operation 210, after the oxidant is consumed and as a consequence, the heat generation reactions may stop and the temperature may start to drop due to heat losses to the porous rock and inflow of cool fluids. Then, the well may be placed on production and the hydrogen-bearing fluids surrounding the well may be produced to the surface.

[0079] The operation 206, the operation 208, and the operation 210 may be done in some implementations as consecutive steps of the process using a well or multiple wells or in other implementations may be done simultaneously with a well doing, for example, the operation 206, a well doing the operation 208, and a well doing the operation 210.

[0080] In an operation 212, for a production well, an economic limit of hydrogen recovery may be reached and the recovery process for hydrogen may be stopped in that well. Thereafter, the operation 206, the operation 208, and the operation 210 can be repeated in a well in a cyclic manner. Even if the economic limit is not reached, at any point, the process may return to the operation 206 and / or the operation 208. If the overall hydrogen recovery process may have reached an economic limit, the process can advance to an operation 214. This process can be done in both cyclic manner (e.g., single wells used for both stimulation and production) or a non-cyclic manner (e.g., one or more injection wells and one or more production wells).

[0081] In the operation 214, the recovery process of hydrogen may be stopped.

[0082] In another implementation of the method 200, prior to the operation 206, a well may be stimulated by using hydraulic squeeze or fracturing where proppant ornanocatalyst fluid is placed within the porous rock. The proppant can permanently enhance the permeability of the porous rock. The proppant or nanocatalyst fluid can also contain catalyst particles that enhance the production of hydrogen through the water-gas shift reaction. The catalyst can contain, for example, iron, magnesium, chromium, copper, zinc, and aluminum and combinations thereof or oxides of these metals and combinations thereof. This stimulation can be done multiple times throughout the process.

[0083] In another implementation of the method 200, prior to the operation 206, in some implementations, the porous rock may be stimulated by using radio frequency stimulation to heat the water within the porous rock. This stimulation can be done multiple times throughout the process.

[0084] In another implementation of the method 200, prior to the operation 206, in some implementations, alkaline solutions, including for example, sodium, magnesium, calcium, potassium, can be injected into the porous rock to mix with the native water within the porous rock. This may provide conditions where dissolved carbon dioxide, in the form of bicarbonate, may react with the cations to produce solid carbonates within the porous rock.

[0085] FIG. 3 illustrates a method 300 for producing hydrogen from a hot porous rock containing (>100°C and in some implementations >200°C) water (brine) and steam, according to one or more implementations herein. In the method 300, at an operation 302, a target hot porous rock containing water (brine) and steam is provided. The method 300 may include injection of carbon monoxide into the porous rock, which in turn may react with the steam within the porous rock to form hydrogen under a water-gas shift reaction.

[0086] In an operation 304, wells may be placed with the target porous rock where the wells can be set as injection wells or production wells or both. The wells can be, for example, vertical, horizontal, deviated, multiple perforated, multilateral, or another geometric arrangement.

[0087] In an operation 306, fuel and oxidant may be injected into the porous rock. The injection can be done together at the same time or the fuel first and the oxidant second or the oxidant first and the fuel second. The injected fuel can include, for example, methane, natural gas, mixtures of gaseous fuels including hydrogen, hydrocarbons, alcohols, ketones, aldehydes, crude oil, solvent, crude oil fractions, heavy oil, waste oil, plant-based oils (biofuels), and emulsified oils, or mixtures thereof. The oxidant can include, for example, air, oxygen-enriched air, oxygen,nitrous oxide, peroxide, other compounds that enable oxidation of the fuel, or mixtures thereof.

[0088] In an operation 308, the fuel and oxidant may be injected into the porous rock under conditions that promote spontaneous ignition of the fuel within the porous rock which in turn generates heat, carbon monoxide, and carbon dioxide. The fuel and oxidant may be fed a ratio where combustion can occur, that is, within the flammability limits of the fuel. There may be an excess of fuel fed into the porous rock such that, when combustion occurs, all of the oxidant is consumed in the porous rock. Also, in such implementations, partial oxidation may occur, which produces carbon monoxide as the dominant carbon oxide. The heat generated by the combustion reactions may convert some fraction of the water in the porous rock to steam. The presence of steam together with the excess fuel within the porous rock may lead to steam reforming with the consequent generation of products such as carbon monoxide and hydrogen. The water-gas shift reaction may also occur where the carbon monoxide and steam react to generate more hydrogen and carbon dioxide. If there is any remaining oxygen, then the fuel, oxygen, and carbon dioxide can react to form hydrogen, carbon monoxide, and steam. With steam, the fuel may react with oxygen and steam to yield more hydrogen and carbon monoxide. The amount of fuel and oxidant injected into the porous rock may be maintained until the temperature around the well has reached, for example, over 400°C and in some implementations over 500°C, after which injection may be stopped.

[0089] For example, if the fuel is methane and oxidant is oxygen, then a set of reactions that can occur include, for example:002(g) + 2 H2O(g)2 CH4(g) + 02(g) 2 00(g) + 4 H2(g)CH4(g) + H2O(g) 00(g) + 2 H2(g) 00(g) + H2O(g) 002(g) + H2(g) 2 CH4(g) + 02(g) + 002(4 CH4(g) + 02(g) + 2 H20(g) — 10 H2(g) + 4 CO where x, y, and z are stoichiometric coefficients of the combustion (partial) reaction.

[0090] At an operation 310, after the oxidant is consumed and as a consequence, the heat generation reactions may stop and the temperature may start to drop due to heat losses to the porous rock and inflow of cool fluids. Then, the well may be placed onproduction and the hydrogen-bearing fluids surrounding the well may be produced to the surface.

[0091] The operation 306, the operation 308, and the operation 310 may be done in some implementations as consecutive steps of the process using a well or multiple wells or in other implementations may be done simultaneously with a well doing, for example, the operation 306, a well doing the operation 308, and a well doing the operation 310.

[0092] In an operation 312, for a production well, an economic limit of hydrogen recovery may be reached and the recovery process for hydrogen may be stopped in that well. Thereafter, the operation 306, the operation 308, and the operation 310 can be repeated in a well in a cyclic manner. Even if the economic limit is not reached, at any point, the process may return to the operation 306 and / or the operation 308. If the overall hydrogen recovery process may have reached an economic limit, the process can advance to an operation 314. This process can be done in both cyclic manner (e.g., single wells used for both stimulation and production) or a non-cyclic manner (e.g., one or more injection wells and one or more production wells).

[0093] In the operation 314, the recovery process of hydrogen may be stopped.

[0094] In another implementation of the method 300, prior to the operation 306, a well may be stimulated by using hydraulic squeeze or fracturing where proppant or nanocatalyst fluid is placed within the porous rock. The proppant can permanently enhance the permeability of the porous rock. The proppant or nanocatalyst fluid can also contain catalyst particles that enhance the production of hydrogen through the water-gas shift reaction. The catalyst can contain, for example, iron, magnesium, chromium, copper, zinc, and aluminum and combinations thereof or oxides of these metals and combinations thereof. This stimulation can be done multiple times throughout the process.

[0095] In another implementation of the method 300, prior to the operation 306, in some implementations, the porous rock may be stimulated by using radio frequency stimulation to heat the water within the porous rock. This stimulation can be done multiple times throughout the process.

[0096] In another implementation of the method 300, prior to the operation 306, in some implementations, alkaline solutions, including for example, sodium, magnesium, calcium, potassium, can be injected into the porous rock to mix with the native water within the porous rock. This may provide conditions where dissolved carbondioxide, in the form of bicarbonate, may react with the cations to produce solid carbonates within the porous rock.

[0097] Other implementations of the method 100, 200, or 300 may be done in hot dry rock with temperatures greater than 100°C and in some implementations above 200°C. Such hot dry rocks may be porous. These rock formations may be considered targets for geothermal heat recovery. In such systems, water or steam can be injected into the porous rock prior to fuel and oxidant injection.

[0098] In other implementations, the method 100, 200, or 300 can be operated in porous rock containing hydrocarbons.

[0099] The following clauses may provide additional context for the present disclosure but should be taken in no way as limiting.

[0100] Clause 1. A method, comprising: providing an underground porous rock formation comprising water; providing a well disposed at least partially within the underground porous rock formation; injecting, via the well, a hydrogen-generating agent into the underground porous rock formation to produce one or more of combustion, gasification, steam-reforming, water-gas shift, or aquathermolysis reactions to yield a hydrogen-bearing gas in the underground porous rock formation; and producing, via the well, the hydrogen-bearing gas to a surface of the earth.

[0101] Clause 2. The method of clause 1 , wherein the underground porous rock formation comprises hot porous rock and steam.

[0102] Clause 3. The method of clause 1, wherein the hydrogen-generating agent comprises a fuel and an oxidant.

[0103] Clause 4. The method of clause 3, wherein the fuel comprises one or more of methane, natural gas, mixtures of gaseous fuels including hydrogen, hydrocarbons, alcohols, ketones, aldehydes, crude oil, solvent, crude oil fractions, heavy oil, waste oil, plant-based oils (biofuels), or emulsified oils.

[0104] Clause 5. The method of clause 3, wherein the oxidant comprises one or more of air, oxygen-enriched air, oxygen, nitrous oxide, peroxide, or other compounds that enable oxidation of the fuel.

[0105] Clause 6. The method of clause 1 , wherein the hydrogen-generating agent comprises carbon monoxide.

[0106] Clause 7. The method of clause 6, wherein the injecting produces a water-gas shift reaction to yield the hydrogen-bearing gas.

[0107] Clause 8. The method of clause 6, wherein the carbon monoxide is produced by combusting a fuel and an oxidant on the surface.

[0108] Clause 9. The method of clause 1, further comprising repeating the injecting and the producing.

[0109] Clause 10. The method of clause 1, wherein the well comprises a catalyst disposed around a wellbore of the well.

[0110] Clause 11. The method of clause 10, wherein the catalyst comprises one or more of platinum, aluminum, iron, magnesium, copper, zinc, cesium, chromium, nickel, oxides of these metals, or mixtures of these metals, or metal oxides.

[0111] Clause 12. The method of clause 1 , further comprising injecting an alkaline material in an aqueous solution via the well into the underground porous rock formation.

[0112] Clause 13. The method of clause 12, wherein the alkaline material comprises one or more of calcium hydroxide, potassium hydroxide, magnesium hydroxide, or other alkaline materials.

[0113] Clause 14. A system, comprising: a well disposed at least partially within an underground porous rock formation comprising water configured for: injection of a hydrogen-generating agent into the underground porous rock formation to produce one or more of combustion, gasification, steam-reforming, water-gas shift, or aquathermolysis reactions to yield a hydrogen-bearing gas in the underground porous rock formation; and production of the hydrogen-bearing gas to a surface of the earth.

[0114] Clause 15. The system of clause 14, wherein the underground porous rock formation comprises hot porous rock and steam.

[0115] Clause 16. The system of clause 14, wherein the hydrogen-generating agent comprises a fuel and an oxidant.

[0116] Clause 17. The system of clause 16, wherein the fuel comprises one or more of methane, natural gas, mixtures of gaseous fuels including hydrogen, hydrocarbons, alcohols, ketones, aldehydes, crude oil, solvent, crude oil fractions, heavy oil, waste oil, plant-based oils (biofuels), or emulsified oils.

[0117] Clause 18. The system of clause 16, wherein the oxidant comprises one or more of air, oxygen-enriched air, oxygen, nitrous oxide, peroxide, or other compounds that enable oxidation of the fuel.

[0118] Clause 19. The system of clause 14, wherein the hydrogen-generating agent comprises carbon monoxide.

[0119] Clause 20. The system of clause 19, wherein the injecting produces a water-gas shift reaction to yield the hydrogen-bearing gas.

[0120] Clause 21. The system of clause 19, wherein the carbon monoxide is produced by combusting a fuel and an oxidant on the surface.

[0121] Clause 22. The system of clause 14, wherein the well is further configured for repeating the injecting and the producing.

[0122] Clause 23. The system of clause 14, further comprising a catalyst disposed around a wellbore of the well.

[0123] Clause 24. The system of clause 23, wherein the catalyst comprises one or more of platinum, aluminum, iron, magnesium, copper, zinc, cesium, chromium, nickel, oxides of these metals, or mixtures of these metals, or metal oxides.

[0124] Clause 25. The system of clause 14, wherein the well is further configured for injecting an alkaline material in an aqueous solution via the well into the underground porous rock formation.

[0125] Clause 26. The system of clause 25, wherein the alkaline material comprises one or more of calcium hydroxide, potassium hydroxide, magnesium hydroxide, or other alkaline materials.

[0126] The invention is limited only by the appended claims. Variations, characteristics, advantages, implementations, constructions, arrangements, terminology, materials, dimensions, embodiments, illustrations, depictions, and examples composing the above description and accompanying drawings show some possible implementations of the invention without limiting the invention. It is not necessary that every implementation of the invention achieve or possess every advantage, purpose, or characteristic identified herein, and as such, one skilled in the art may effect various additions, changes, modifications, or omissions without departing from the scope or spirit of the invention or its legal equivalents.

[0127] All ranges are inclusive of the stated limits, the orders of magnitude thereof, and all values and ranges substantially therebetween unless otherwise defined. Unless otherwise stated, every use of “and” forms an inclusive list comprising at least the conjoined elements, and every use of “or” forms an inclusive list comprising at least one element of conjoined elements. Unless otherwise stated, singular usage (e.g., 'a', 'an', or 'the') includes plurals of the same.

[0128] The order of recitations in a claim do not imply a temporal or ordered relationship unless unavoidable by the plain language of that claim. No claim may be interpreted to invoke 35 U.S.C. § 112(f) unless that claim recites “means for” or “step for.”

Claims

CLAIMSWe claim:

1. A method, comprising: providing an underground porous rock formation comprising water; providing a well disposed at least partially within the underground porous rock formation; injecting, via the well, a hydrogen-generating agent into the underground porous rock formation to produce one or more of combustion, gasification, steam-reforming, water-gas shift, or aquathermolysis reactions to yield a hydrogen-bearing gas in the underground porous rock formation; and producing, via the well, the hydrogen-bearing gas to a surface of the earth.

2. The method of claim 1, wherein the underground porous rock formation comprises hot porous rock and steam.

3. The method of claim 1, wherein the hydrogen-generating agent comprises a fuel and an oxidant.

4. The method of claim 3, wherein the fuel comprises one or more of methane, natural gas, mixtures of gaseous fuels including hydrogen, hydrocarbons, alcohols, ketones, aldehydes, crude oil, solvent, crude oil fractions, heavy oil, waste oil, plant-based oils (biofuels), or emulsified oils.

5. The method of claim 3, wherein the oxidant comprises one or more of air, oxygen- enriched air, oxygen, nitrous oxide, peroxide, or other compounds that enable oxidation of the fuel.

6. The method of claim 1, wherein the hydrogen-generating agent comprises carbon monoxide.

7. The method of claim 6, wherein the injecting produces a water-gas shift reaction to yield the hydrogen-bearing gas.

8. The method of claim 6, wherein the carbon monoxide is produced by combusting a fuel and an oxidant on the surface.

9. The method of claim 1 , further comprising repeating the injecting and the producing.

10. The method of claim 1, wherein the well comprises a catalyst disposed around a wellbore of the well.

11. The method of claim 10, wherein the catalyst comprises one or more of platinum, aluminum, iron, magnesium, copper, zinc, cesium, chromium, nickel, oxides of these metals, or mixtures of these metals, or metal oxides.

12. The method of claim 1 , further comprising injecting an alkaline material in an aqueous solution via the well into the underground porous rock formation.

13. The method of claim 12, wherein the alkaline material comprises one or more of calcium hydroxide, potassium hydroxide, magnesium hydroxide, or other alkaline materials.

14. A system, comprising: a well disposed at least partially within an underground porous rock formation comprising water configured for: injection of a hydrogen-generating agent into the underground porous rock formation to produce one or more of combustion, gasification, steamreforming, water-gas shift, or aquathermolysis reactions to yield a hydrogenbearing gas in the underground porous rock formation; and production of the hydrogen-bearing gas to a surface of the earth.

15. The system of claim 14, wherein the underground porous rock formation comprises hot porous rock and steam.

16. The system of claim 14, wherein the hydrogen-generating agent comprises a fuel and an oxidant.

17. The system of claim 16, wherein the fuel comprises one or more of methane, natural gas, mixtures of gaseous fuels including hydrogen, hydrocarbons, alcohols, ketones, aldehydes, crude oil, solvent, crude oil fractions, heavy oil, waste oil, plant-based oils (biofuels), or emulsified oils.

18. The system of claim 16, wherein the oxidant comprises one or more of air, oxygen- enriched air, oxygen, nitrous oxide, peroxide, or other compounds that enable oxidation of the fuel.

19. The system of claim 14, wherein the hydrogen-generating agent comprises carbon monoxide.

20. The system of claim 19, wherein the injecting produces a water-gas shift reaction to yield the hydrogen-bearing gas.

21. The system of claim 19, wherein the carbon monoxide is produced by combusting a fuel and an oxidant on the surface.

22. The system of claim 14, wherein the well is further configured for repeating the injecting and the producing.

23. The system of claim 14, further comprising a catalyst disposed around a wellbore of the well.

24. The system of claim 23, wherein the catalyst comprises one or more of platinum, aluminum, iron, magnesium, copper, zinc, cesium, chromium, nickel, oxides of these metals, or mixtures of these metals, or metal oxides.

25. The system of claim 14, wherein the well is further configured for injecting an alkaline material in an aqueous solution via the well into the underground porous rock formation.

26. The system of claim 25, wherein the alkaline material comprises one or more of calcium hydroxide, potassium hydroxide, magnesium hydroxide, or other alkaline materials.

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