Reaction-induced hierarchical fracturing for the recovery of hydrogen, energy, and minerals from geological environments

Abstract

A process for reaction-induced fracturing of a subsurface rock formation includes injecting a fluid comprising water into a subsurface rock formation comprising a Fe2+-containing mineral, inducing metamorphic reactions of the Fe2+-containing mineral with the water to generate volume changes in the subsurface rock formation, and generating microfractures via the volume changes, wherein the volume changes create localized pressures that propagate fractures within the subsurface rock formation.

Description

Atty. Docket No.: GEQ002PCT-8022-00301REACTION-INDUCED HIERARCHICAL FRACTURING FOR THE RECOVERY OF HYDROGEN, ENERGY, AND MINERALS FROM GEOLOGICAL ENVIRONMENTSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. Provisional Application No. 63 / 718,535, filed on November 8, 2024 and entitled, “REACTION-INDUCED HIERARCHICAL FRACTURING FOR THE RECOVERY OF HYDROGEN, ENERGY, AND MINERALS FROM GEOLOGICAL ENVIRONMENTS, " the entire disclosure of which is incorporated herein by reference.FIELD

[0002] This present disclosure relates generally to systems and methods for (e.g., in situ) production, stimulation, and / or recovery' of hydrogen, geothermal energy, amorphous silica, metals, rare earth minerals, and / or other resources from subsurface rock formations and / or other geological environments.BACKGROUND

[0003] Hydrogen is a versatile fuel that produces no greenhouse gas emissions at its point of use and, hence, is a promising source of clean energy. While the use of hydrogen fuel produces no direct greenhouse gases, current methods of production of hydrogen such as natural gas reforming emit a significant amount of CO2, and, as a result, are significantly more CO2- intensive than combusting hydrocarbons themselves. Moreover, production of “green hydrogen”, such as hydrogen produced via electrolysis of water, is impractically expensive, and the transportation and degradation of such green hydrogen pose further challenges that reduce the viability of the widespread use of green hydrogen as an energy' carrier.SUMMARY

[0004] In some embodiments, a process for reaction-induced fracturing of a subsurface rock formation comprises injecting a fluid comprising water into a subsurface rock formation comprising a Fe2+-containing mineral, inducing metamorphic reactions of the Fe2+-containing mineral with the water to generate volume changes in the subsurface rock formation, and generating microfractures via the volume changes, wherein the volume changes create localized pressures that propagate fractures within the subsurface rock formation.

[0005] In some embodiments, a wellbore system comprises: at least one wellbore extending into a subsurface rock formation, wherein the subsurface rock formation comprises aFe2+-containing mineral and comprises microfractures formed by metamorphic reactions thatAtty. Docket No.: GEQ002PCT-8022-00301 convert the Fe2+-containing mineral to reaction products with accompanying volume changes, one or more wellbore tubulars extending through the at least one wellbore and the casing to provide fluid communication with the subsurface rock formation, a fluid injection system configured to inject a fluid comprising water into the subsurface rock formation through the at least one wellbore, and a recovery system configured to recover a fluid produced by the metamorphic reactions in the subsurface rock formation.

[0006] In some embodiments, a process for extraction of metals and minerals from a subsurface geological formation comprises fracturing a subsurface rock formation using reaction-induced fracturing, injecting a solution mining fluid through a wellbore into the fractured subsurface rock formation, wherein the solution mining fluid comprises a brine having a controlled composition, and recovering a fluid from the wellbore, wherein the recovered fluid comprises dissolved metals, dissolved rare earth elements, hydrogen, or any combination thereof. The reaction-induced fracturing comprises injecting a fluid comprising water into the subsurface rock formation to induce metamorphic reactions that generate volume changes and create microfractures.

[0007] In some embodiments, a system for integrated resource extraction from a subsurface geological formation comprises a plurality of wellbores disposed in a subsurface rock formation comprising microfractures formed by metamorphic reactions, wherein the microfractures result from volume changes accompanying conversion of Fe2+-containing minerals to reaction products, a fluid injection system configured to inject solution mining fluids into the subsurface rock formation through at least one of the plurality of wellbores, a brine controller configured to control pH and composition of the solution mining fluids where the brine controller is configured to alternate between injecting high pH brines and low pH brines to perform cyclic leaching, a pressure controller configured to maintain pressure in the subsurface rock formation below a breakdown pressure of the rock formation and to modulate pressure cyclically, a recovery system configured to recover fluid from at least one of the plurality7of wellbores, a separation system configured to separate metals, rare earth elements, hydrogen, heat, silica, or any combination thereof from the recovered fluid, and a control system configured to stage fracturing and resource extraction among the plurality of wellbores such that some wellbores undergo fracturing while other wellbores undergo active resource production simultaneously.

[0008] These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims.Atty. Docket No.: GEQ002PCT-8022-00301BRIEF DESCRIPTION OF THE DRAWINGS

[0009] For a more complete understanding of the present disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description:

[0010] FIG. 1 schematically illustrates a plurality of wellbores completed into a subterranean formation according to some embodiments.

[0011] FIG. 2 A schematically illustrates a wellbore filled with brine under pressure and the resulting brine-filled fractures in a subsurface formation according to some embodiments.

[0012] FIG. 2B schematically illustrates a brine-filled fracture exposing small mineral grains and grain boundaries to water according to some embodiments.

[0013] FIG. 2C schematically illustrates brine penetrating into the grain boundaries in a subsurface formation according to some embodiments.

[0014] FIG. 2D schematically illustrates a serpentinization reaction forming serpentinite along the grain boundaries in a subsurface formation according to some embodiments.

[0015] FIG. 2E schematically illustrates a further serpentinization reaction forming additional serpentinite in a subsurface formation according to some embodiments.

[0016] FIG. 2F illustrates fracturing of a nonreacting mineral (plagioclase) by the expansion caused by serpentinization of a reacting mineral(olivine)

[0017] FIG. 3A illustrates grain boundary reactions at the start of a reaction induced fracturing process according to some embodiments.

[0018] FIG. 3B illustrates grain boundary reactions throughout a reaction induced fracturing process according to some embodiments.

[0019] FIG. 3C illustrates the reaction progress over time for a reaction induced fracturing process according to some embodiments.

[0020] FIG. 4A illustrates a stress profile for a crack during a reaction induced fracturing process.

[0021] FIG. 4B is an image showing the microfractures formed by a reaction induced fracturing process.DETAILED DESCRIPTION

[0022] Presented herein are systems and methods for the production (e.g., in situ production) of geologic hydrogen, geothermal energy (heat), amorphous silica, rare earth minerals, and / or other resource(s), e.g., from geological environments such as subsurface rockAtty. Docket No.: GE0002PCT-8022-00301 formations. A geological environment may include ultramafic rock, such as peridotite, mafic rock containing olivine, such as troctolite, banded iron formations (BIFs), and other Fe2+-rich geological formations including but not limited to formations rich in minerals such as Olivine (Mg,Fe)2SiO4, Orthopyroxene (Mg,Fe)SiOs, Clinopyroxene (Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2Oe, Hedenbergite CaFeSi20e, Pyrite FeS2, Ilmenite FeTiOs, Hercynite (FeA12O4). Siderite (FeCOs), Magnetite (FesO4), Grunerite (Fe?SisO22(OH)2), Lepidocrocite FeO(OH), Glauconite (K,Na)(Mg,Fe,Al)2(Si,Al)40io(OH)2, Chamosite (Mg,Fe)5Al(AlSi30io)(OH)s, Greenalite (Fe2+,Fe3+)2-3Si2Os(OH)4, Minnesotaite (Fe,Mg)3Si40io(OH)2, Vivianite Fe2(PO4)28H2O, and rock formations such as dunites, peridotites, basalts, kimberlites, lamproites, banded iron formations, and greywackes. A geological environment may be suitable for performing serpentinization, for example to form hydrogen from iron-rich rock (e.g., ultramafic rock, including, for example, peridotite, or mafic rock containing olivine and / or pyroxene, including, for example, basalt).

[0023] In particular, in certain embodiments, presented herein are systems and methods that employ controlled, chemically -induced hierarchical fracturing of rock to increase rock surface area and increase the production and recovery of geologic hydrogen from in-situ sites, e.g., via injection of brine into a volume of rock (e g., an olivine matrix). The chemically- induced reactions can be metamorphic reactions that result in volume changes (e.g., increased volume, decreased volume, etc.) and include reactions such as serpentinization reactions, hydration reactions or the like. In some aspects, the specific reactions can result in temperature changes that can cause differential thermal expansion or stress on the grain boundaries, which can also contribute to the fracture formation. Such controlled, chemically-induced fracturing may be performed subsequent to an initial fracturing process, for example hydraulic fracturing.

[0024] For example, presented is a method that includes fracturing by injecting brine under pressure sufficient to overcome the minimum compressive stress in the rock formation to create an initial fracture network. This fracturing may be created by injecting the brine at a rate sufficient to generate pressures greater than the breakdown pressure of the formation, as in conventional hydraulic fracturing. Alternative, cyclic variation of the pressure of the injected brine below this breakdown pressure may be carried out to generate a more complex fracture network. After a fracture network is generated, the method is augmented by an ongoing chemical reaction (e.g., metamorphic reactions with volume and / or temperature changes such as serpentinization, hydration, etc.) to create further stress and thereby propagate the front controllably. for example according to the brine injection rate and composition.Atty. Docket No.: GEQ002PCT-8022-00301Exothermic reactions (e.g., serpentinization) can generate increased temperatures that augment (or assist) the fracturing. In certain embodiments, an exogenous source such as a pump or heat source (such as an electrically heated wire or other form of injected energy, injection of heated brine, or the like, for example) may be used to control rate of propagation and hydrogen production.

[0025] In certain embodiments, in addition to reaction-based fracturing of rock, the method employs mechanical fracturing (e.g., drilling) as well (e.g., for initial fracturing). Hydraulic fracturing (fracking) techniques may be employed for such mechanical fracturing, for example as are found in the oil and gas arts.

[0026] Referring now to Figure 1 , an example of a wellbore operating environment 100 is shown. In some aspects, exemplary environment 100 includes a wellbore 114 traversing a subterranean formation 102, casing 112 lining at least a portion of wellbore 114. One or more wellbore tubulars can extend through wellbore 114 and casing 112 to provide fluid communication within the wellbore 114 and allow fluid access to the subterranean formation 102 of interest. In some embodiments, the operating environment 100 includes a workover and / or drilling ng positioned at the surface and extending over the wellbore 114.

[0027] In general, the wellbore 114 can be drilled into the subterranean formation 102 using any suitable drilling technique. The wellbore 114 can extend substantially vertically from the earth's surface over a vertical wellbore portion, deviate from vertical relative to the earth's surface over a deviated wellbore portion, and / or transition to a horizontal wellbore portion. In general, all or portions of a wellbore may be vertical, deviated at any suitable angle, horizontal, and / or curved. In addition, the wellbore 114 can be a new wellbore, an existing wellbore, a straight wellbore, an extended reach wellbore, a sidetracked wellbore, a multilateral wellbore, and other types of wellbores for drilling and completing one or more production zones. As illustrated, the wellbore 114 includes a substantially vertical producing section, which can be cased or an open hole completion (i.e., casing 112 does not extend through producing section). In various aspects, sections of wellbores having any orientation, and in open or cased sections of wellbores. Commonly, the casing 112 extends into the wellbore 114 from the surface and is cemented within the wellbore 114 with cement. When present, a wellbore tubular can extend from the surface to the producing zones and generally provides a conduit for fluids to travel between the formation 102 and the surface (e.g., to surface production and handling equipment. In some aspects, a first w ellbore 114 can serve as an injection well, and a second wellbore 111 can serve as a production well. This process can allow- for one well to be fractured as described herein (e.g., using reaction inducted fracturingAtty. Docket No.: GEQ002PCT-8022-00301 with brine injection, etc.) while the other well produces the brine, which can carry products such as hydrogen and / or minerals.

[0028] The current state of the art for generating fractures in the subsurface (e.g., the formation of interest, etc.) to control fluid flow is hydrofracturing. In conventional hydrofracturing, a mixture of fluid and / or solids is injected into the subsurface at a pressure high enough to overcome the preexisting stress caused by the weight of the overburden. The solids can flow into the fractures and maintain the fractures when the fluid pressure is reduced. Fluid pressures can reach as high as ~ 100 MPa in hydrofracturing.

[0029] Disclosed herein is a new method for controlled fracturing of rock that results from the volume changes that accompany the reaction of water with iron-rich rocks in the subsurface, that is. “reaction-based” or “reaction-induced” fracturing, for example, as shown in FIGS. 2A-2E. The process for the controlled fracturing of a subsurface rock formation (e.g., for stimulation and recovery of geologic hydrogen, e.g., as part of a system for geologic hydrogen, geothermal energy, amorphous silica, rare earth mineral, and / or other resource production as presented herein) can comprise injecting a fluid having controlled composition into the subsurface rock formation in a controlled manner (e.g., at controlled temperature, flow rates, and / or pressure cycles such as pressure oscillations in time) and in such a way that fractures and microfractures can be formed and / or expanded, even when the fluid pressure is below the fracturing strength of the formation rock. This process can be referred to in some contexts as “soft fracturing” or “fatiguing” where the pressure remains below the fracturing pressure of the formation rock itself, and the controlled application of pressure (e.g., in a cyclic manner) results in the formation of fractures. The resulting fractures or fracture network may be limited in extent, for example, extending tens of meters from the wellbore.

[0030] The reaction process can begin by injecting brine into the formation using controlled parameters, as shown in FIG. 2A. The brine chemistry, temperature, and pressure can be controlled to create serpentinization reactions. In some aspects, the brine can be circulated through existing fractures, which can be created using traditional hydrofracturing techniques and / or using existing porosity or fractures in the formation.

[0031] As shown in FIG. 2B, brine-filled fractures and microfractures bring the brine into contact with mineral grains and grain boundaries. As shown in FIG. 2C, the brine penetrates into the grain boundaries in the rock in the subsurface formation. As shown in FIG. 2D, an exemplary metamorphic reaction in the form of the serpentinization reaction can occur at the brine-mineral interfaced, and can proceeds as follow:Olivine + H2O — > serpentinite + H2 + heatAtty. Docket No.: GEQ002PCT-8022-00301The reaction results in the formation of serpentinite that has a larger volume than the initial olivine. The serpentinization process exhibits substantial thermodynamic properties that drive the reaction-induced fracturing mechanism, as shown in FIG. 2E. The process generates significant volume changes ranging from about 5% to about 60%, from about 20% to about 50%, or about 35% to about 45%, with some instances showing up to 50% volume changes compared to approximately 1% in conventional extraction methods.

[0032] The associated density reduction provides additional fracturing mechanisms, with initial rock densities ranging from about 2.8 g / cm3to about 4.0 g / cm3, from about 3.2 g / cm3to about 3.6 g / cm3, or about 3.4 g / cm3, transforming to final densities ranging from about 2.0 g / cm3to about 3.0 g / cm3, from about 2.3 g / cm3to about 2.7 g / cm3, or about 2.5 g / cm3.

[0033] The serpentinization process exhibits exothermic characteristics that contribute to self-sustaining fracturing mechanisms. Per cubic meter of serpentinite formation, the process generates thermal energy ranging from about 4 MJ to about 10 MJ, from about 5.5 MJ to about 7.5 MJ, or about 6.6 MJ, depending on the specific composition of the formation and extent of the reaction. Under adiabatic conditions, this energy generation produces temperature increases ranging from about 150°C to about 400°C, from about 200°C to about 320°C, or about 260°C, creating enhanced reaction kinetics and improved fracturing efficiency.

[0034] The serpentinization reaction results in a volume expansion that exerts pressures on a localized scale that substantially exceed those employed in conventional hydrofracturing techniques. Reaction-induced pressures range from about 100 MPa to about 2000 MPa. from about 150 MPa to about 1600 MPa, or from about 200 MPa to about 1500 MPa, compared to approximately 100 MPa in conventional hydrofracturing systems.

[0035] These elevated pressures are generated locally near reaction sites rather than remotely at subsurface locations, providing enhanced controllability through localized chemical reactions. The localized pressure generation enables fracture propagation control while the bulk pressure in the formation (e.g., at a distance away from the reaction) can remain below' a fracturing pressure. The volume changes associated with these reactions can be very large, for example up to ~ 50% increase in volume in some serpentinization reactions. The accompanying crystallization pressures can be 200 - 1500 MPa in amplitude - far greater than the pressures driving hydrofracturing. In some aspects, these pressures generated by the serpentinization reactions occur locally, not far away from the wellbore as in hydrofracturing. Controlled reaction-induced fracturing is both more powerful and more controllable than hydrofracturing, providing a new process for controlling fracturing in the subsurface. Reaction-induced fracturing may produce fracturing with different characteristics thanAtty. Docket No.: GEQ002PCT-8022-00301 mechanical fracturing, for example having different characteristic channel dimensions (e.g., smaller diameter or thickness).

[0036] The metamorphic reaction process is shown in FIG. 2C - FIG. 2E where serpentinite is formed at the grain interfaces. The serpentinite can create fluid pathways such that the brine can advance as the serpentinite forms and opens a pathway to additional grain boundaries. The resulting stress can fracture the grain boundaries along additional grains and / or through the surrounding rock such that the expansion from the metamorphic reaction causes fracturing in the formation rock. This fracturing can extend between reaction zones and / or along natural grain boundaries. An exemplary' image of the effect of expansion of reacting grains of olivine fracturing adjacent grains of nonreacting grains of plagioclase is shown in FIG. 2F and demonstrates how the reactions can create fractures between reactive zones.

[0037] For serpentinization at the scale of individual olivine grains, hierarchical reaction-induced fracturing is the mechanism by which water penetrates into and reacts with grains (e.g., due to loosened grain boundaries), accompanied by an exponentially increasing reactive surface area. In the method outlined in FIGS. 3A-3C, the initial change in stress and temperature acting on the mineral grains in the walls of the initial brine-filled fracture (FIGS. 2A - 2B) dilates the grain boundaries and may both create and extend microfractures (e.g., as shown in FIG. 3A). Flow of fluid into the grain boundaries sets up chemical reactions that lead to further perturbations in stress and temperature. The grain boundaries and associated microfractures can then connect to increase the permeability7of the rock. As serpentinite is formed and the reaction progresses, the hierarchical fracturing increases the available surface area significantly (e.g., as shown in FIG. 3B). The fracture production rate can increase until the available reactive minerals (e.g., olivine) are consumed (e.g.. as shown in the reaction progress in FIG. 3C). The rate of serpentinite formation and fracture extent can be controlled by controlling the brine circulation rate and properties such as pH, composition (e.g., salinity, etc.), temperature, pressure, and chemical composition.

[0038] In certain embodiments, the method includes controlling the dimensions, strengths, volume changes, and orientations of hydrofractures and the temperature and chemistry of the fluid used to promote stimulation in order to tune the rate at which fractures occur and the rate at which the resulting surface area produces hydrogen and grows (FIG. 3C).

[0039] Reaction-induced volume changes in localized stimulated regions have large effects on the state of stress in the surrounding regions. By controlling the shapes of these localized stimulated regions, the method controls the fracture propagation between and amongAtty. Docket No.: GEQ002PCT-8022-00301 these regions, providing control of the fracture pattern and fluid flow paths to and from the stimulated regions.

[0040] Hydrogen-producing reactions between water and other minerals (e. g., minnesotaite) result in large volume decreases. Engineering such volume decreases via stimulation of a localized region is equivalent to providing negative pressures in hydrofracturing, opening up an entirely new mechanism for generation and control of fractures. It is therefore possible to control the rates and surface areas resulting by engineering the fluid composition, temperature, and the like.

[0041] Other reactions that do not involve production of hydrogen can also lead to large changes in volume, both expansion and contraction. Stimulating these other reactions provides an additional mechanism for controlling fracturing.

[0042] FIGS. 3C through 4B depict modeling fracturing via a mathematical model to control and / or optimize fracture growth and hydrogen production from the site. Note, in FIG. 3C, there is a period of exponential grow th of fractures. FIG. 4A show s a stress profile along a penny-shaped fracture, an example showing extensional microfractures created by volume changes with extension parallel to serpentinite crystals (FIG. 4B), and an example showing extensional microfractures with tangential extension at the boundary of approximately spherical grain of spinel in an olivine matrix (FIG. 3A).

[0043] In some aspects, the controlled fracturing process described herein can use pressure variations to produce the fracture network as part of the reaction based fracture generation, where the injection pressures can change over time. In some aspects, the injection pressures can remain below the breakdow n pressure of the rock itself. In some embodiments, the peak pressure(s) used with the pressure based fatiguing or weathering process can remain below about 0.95 times the breakdown pressure of the rock (Pbreakdown), below about 0.9 Pbreakdown, below about 0.85 Pbreakdown, or below about 0.8 Pbreakdown. In some embodiments, the average injection pressure(s) used wdth the pressure based weathering process can remain below' about 0.95 times the breakdown pressure of the rock (Pbreakdown), below about 0.9 Pbreakdown. below about 0.85 Pbreakdown, or below about 0.8 Pbreakdown. While the average pressure can remain below the Pbreakdown, the injection pressure can cycle above Pbreakdown during the injection process. This can help to hydraulically fracture the rock to allow brine access to additional reaction surface area to help propagate the fracturing process using both mechanisms. The resulting fractures can exhibit higher surface area available for reaction to produce hydrogen in situ. Surface area improvements through reaction-induced fracturing creates increased permeability.Atty. Docket No.: GEQ002PCT-8022-00301

[0044] In certain embodiments, a method of fracturing a formation and produce hydrogen and / or minerals can include alternating brine injection and hydrogen extraction cycles, e.g., akin to a Huff and Puff process. For example, in certain embodiments, high and low pH brines are alternately injected into a mineral deposit (geologic site) to enhance the dissolution of minerals from the rock (e.g., for cyclic leaching). The injection cycles can use a single wellbore with alternating cycles of injection and production. In some aspects, the injection cycles can use a plurality of wellbores with some serving as injection wells while others serve as production wells during a first time period, and then one or more wells switching from producing to injecting and / or injecting to producing during a second time period. The cyclic injection cycles can be used to control the permeability of the formation during a production process.

[0045] In certain embodiments, a geologic site for production of hydrogen can have multiple wells. In certain embodiments, it is advantageous to stage the various wells of the site such that certain wells are being fracked (e.g., via the hydrofracking methods described herein) while others are being used for hydrogen production / harvesting. For example, in certain embodiments, there may be multiple stages of fracks performed such that not all the fractures will be completed at once, due to very high stresses that occur during serpentinization.

[0046] In certain embodiments, first a subset (e.g., one or more) of wells at a site are hydraulically fractured to a stage of fracturing (e.g., a first stage, second stage, or third stage) less than a final stage (e.g., fifth or more stage), then those wells may be used resource (e.g., hydrogen) production / harvesting. Subsequently or simultaneously to the resource production / harvesting another subset of the wells may be hydraulically fractured. Thus, unlike many conventional resource extraction processes (e.g., natural gas extraction) where a well is fully fracked and resource extraction performed before moving on to another well at a site, in some embodiments, a well of a plurality of wells at a site is partially fracked and then resource extraction / production is performed (e.g., before further fracking the well), optionally, before, during, and / or after one or more others of the plurality of wells undergo a similar partial fracking and subsequent resource extraction / production process. Such resource extraction / production processes may be used to control fracture formation (e.g., hierarchical fracture formation) based on chemical-reaction-based control. In this way, energy generation, resource extraction, and rock formation stability' can be improved or optimized.

[0047] Wells at a site may be fractured in stages, where one or more stages are performed using mechanical fracturing (e.g., hydraulic fracturing) and one or more subsequent stages are performed using reaction-based controlled fracturing (e.g., using energy from anAtty. Docket No.: GEQ002PCT-8022-00301 exothermic reaction, such as, for example, a resource extraction, harvesting and / or production reaction, such as, for example, serpentinization). Different wells at a site may be simultaneously fractured at different stages at a same time. Different wells may be in different stages of fracturing at a given time. Multiple wells may be simultaneously fractured at different stages at a same time. Multiple wells may be in different stages of fracturing at a given time. In this way, a site may be used for resource extraction in a non-serial manner, that is, without first exhausting a first well before moving on to a subsequent well.

[0048] The systems and methods as disclosed herein can use multiple time-dependent variables to improve production efficiency. Pressure modulation can follow predetermined profiles where pressure as a function of time (P(t)) in the formation ranges from about the magnitude of the least compressive stress to about the breakdown pressure, from about the magnitude of the least compressive stress to about 90% of the breakdown pressure, or from about the magnitude of the least compressive stress to about 80% of the breakdown pressure.

[0049] The pH control as a function of time (pH(t)) represents a controllable parameter, with pH values ranging from about 2 to about 13, from about 4 to about 11, or from about 6 to about 9. The pH modulation prevents reaction suppression while maintaining dissolution kinetics.

[0050] Water-to-rock ratio optimization (WRR(t)) controls reaction stoichiometry and mass transfer efficiency. Water-to-rock ratios range from about 0.1 to about 5.0, from about 0.2 to about 2.0, or from about 0.3 to about 1.0.

[0051] The cyclic stimulation process comprises a controlled hydraulic method that operates at pressures less than the breakdown pressure (Pbreakdown) of the subsurface formation, because pressures in the brine must overcome the minimum compressive stress (S_min) in the formation to allow a fracture to open, the pressure is controlled to oscillate between the minimum stress (S_min) and a pressure maintained below the breakdown pressure of the rock formation. Both the minimum compressive stress and the breakdown pressure increase with depth at a rate proportional to the density of the rock formation.

[0052] In contrast to conventional hydrofracking methods that inject fluids at pressures exceeding the breakdown pressure using massive volumes delivered as rapidly as possible, the disclosed cyclic stimulation process utilizes fracture formation via rock fatigue with accumulating damage at lower pressures. The process operates using fracture formation mechanisms that rely on repeated stress cycling rather than single catastrophic fracture events, thereby achieving controlled fracture network development with significantly reduced water and energy requirements.Atty. Docket No.: GEQ002PCT-8022-00301

[0053] The cycle duration for the pressure oscillation operates with a period that depends on properties of the formation. For example, the breakdown pressure can vary based on the type of formation, the depth, and any fluids or other materials present. Periods of approximately one day might be typical. A typical amplitude of the pressure variation might be 5 MPa, added to an approximately constant pressure equal to S_min. In some aspects, the pressure can be varied between about 0.6 to about 0.99 of the breakdown pressure, and the variations may have a variation of between about 0.01 and about 0.2, or between about 0.05 and about 0.15 of the breakdown pressure. The process employs a multi-frequency approach wherein high frequency fluid action weakens the rock structure and allows infdtration between mineral grains, while low frequency cycles remove and reinject water into the formation to extract hydrogen-rich water from the subsurface.

[0054] As an example, over an operational window of approximately 80 to 100 hours, the system can maintain flow rate cycling that varies between positive injection phases and negative extraction phases, executing multiple injection and extraction cycles throughout the operational period. The pressure cycling can maintain pressures between S_min and a pressure about 1 MPa below the breakdown pressure, or between about 0.6 and about 0.99 of the breakdown pressure, with regular oscillation patterns, wherein the pressure modulation cycles multiple times within the operational window.

[0055] The cyclic pressure variation creates rock fatigue with accumulating damage rather than inducing single rapid fracturing events, facilitates grain boundary infiltration through high-frequency fluid action, generates controlled fracture networks with substantially higher surface area compared to conventional hydrofracturing, and produces comminution via fatigue mechanisms resulting from oscillating stress conditions within the rock formation.

[0056] In certain embodiments, the brine itself is used as an underground hydrogen storage medium. For example, hydrogen may be dissolved in the brine and stored in a dissolved state, for later extraction from the brine (e.g., upon bringing the brine to the surface). In certain embodiments, the production and / or harvesting of hydrogen and the production and / or harvesting of heat are staged in the various wells of the geologic site.

[0057] In addition to, or in place of, hydrogen production, the resulting formation can be used to extract products including metals such as rare earth metals. The systems and methods described herein enable the extraction and recovery of metals and rare earth elements from subsurface geological formations, including but not limited to iron (Fe), copper (Cu), uranium (U). aluminum (Al), cobalt (Co), nickel (Ni), chromium (Cr), zinc (Zn), and rare earth elements including the lanthanides, scandium, and yttrium. The extraction processes can beAtty. Docket No.: GEQ002PCT-8022-00301 performed in conjunction with hydrogen production or as standalone metal recovery operations.

[0058] Metal extraction can be accomplished through solution mining processes, wherein brines having varying compositions are used to recover minerals from the formation. Solution mining can be used to recover metals, rare earths, and other species resulting from any water-rock reaction that has negative Gibbs Free Energy accompanied by a density change of greater than a few percent. The rate of extraction can be increased by the increase of surface area resulting from fracturing driven by fatiguing and weathering processes including pressure- induced weathering, temperature-induced weathering, and / or reaction-induced fracturing as described herein.

[0059] Brines having different properties can be alternately injected into the mineral deposit to enhance the dissolution of metals from the rock through a process known as cyclic leaching. The brine properties such as temperature, pressure, salinity, and composition (e.g., pH, additive compositions, etc.) can be used to enhance the extraction of metals. For example, the cyclic processing can take advantage of the alternating chemical reactions that occur under different pH conditions to improve the recovery of target metals. In high pH brines (alkaline conditions), the brines can be used to dissolve minerals containing potassium or sodium by increasing their solubility at high pH levels. In low pH brines (acidic conditions), the acids help to dissolve other minerals, especially those that are more soluble at lower pH, such as those containing calcium, magnesium, and metal oxides.

[0060] The alternating of brine composition in different cycles creates conditions where different metals are more readily dissolved and extracted in each cycle. This leads to a more efficient and thorough leaching process, allowing more of the target metal to be recovered. Different pH levels can selectively dissolve specific minerals, which helps in selectively recovering the desired metal while minimizing contamination from others. Cyclic leaching also prevents the build-up of scale or precipitates in the well, which can happen when certain minerals re-precipitate under constant pH conditions. Alternating pH breaks up these deposits, keeping the flow channels clear.

[0061] Mineral recovery of metals such as Fe, Cu, U, Al, Co, and / or Ni may be used as indicators regarding reaction efficiency. Continuous data may be obtained during the process including temperature, pH, pressure, H2 saturation, and / or composition, and fed as input to a neural network to estimate improvements of the free energy and reaction rates.

[0062] The solution used for solution mining can be supplied at a mean pressure sufficient to maintain the fractures in an accessible state, which allows the solution miningAtty. Docket No.: GEQ002PCT-8022-00301 process to proceed at or above a desired reaction rate based on a reaction rate per unit volume of rock. The pressure can be modulated during the solution mining process to maintain the fractures and / or create new fractures during the process. In some aspects, the pressure can be maintained and / or cycled during the weathering and solution mining process in any of the processes described herein.

[0063] The production rate from solution mining may be further increased by adjustment of the pH, temperature, and composition to increase the rate of chemical dissolution of the rock matrix and desired species. The species going into solution as a result may be produced with the water and subsequently separated at the surface. The solution mining can occur in formations that have been subjected to fracturing or weathering processes, including pressure-induced weathering, temperature-induced weathering, and / or reaction-induced fracturing, which allows the solution mining process to access the rock formation surfaces for increased extraction.

[0064] In some embodiments, a low pH solution can be used to leach minerals for recovery. Acid leaching represents a straightforward method for extracting metals including Fe2+ and other metallic species. The process involves contacting a formation with a strong acid to dissolve metal ions into solution. The source material may be fracked in situ as described herein to increase the surface area. The material is contacted with an acidic aqueous solution under controlled temperature and pressure conditions to leach the metals. The ions can be dissolved into the solution forming soluble complexes that can be processed at the surface to recover the metals. Specific acids that can be used to acidify the extraction fluid include, but are not limited to, carbonic acid from dissolution of CO2 in water, mineral acids such as sulfuric acid (H2SO4), hydrochloric acid (HC1), and / or nitric acid (HNO3), and organic acids such as acetic acid (CH3COOH). citric acid, sugar acids, or the like. The acids can facilitate the dissolution of metals from iron-rich and metal-bearing minerals by protonating and breaking down the mineral structure.

[0065] Chelating agents form stable complexes with metals, preventing their precipitation and enhancing their solubility. The chelating agents can be added to the brine during the recovery process. Chelating agents suitable for metal extraction include, ethylenediaminetetraacetic acid (EDTA), organic chelators derived from citric acid, oxalic acid, and / or aldonic acids, phosphates, and amino acids including histidine. These chelating agents stabilize dissolved metals in solution, facilitating their transport to the surface for recovery.Atty. Docket No.: GEQ002PCT-8022-00301

[0066] Elevated temperatures can enhance reaction kinetics, increasing metal extraction rates. Temperature ranges from 50-350 °C can be utilized for metal extraction processes. Implementation of heat exchangers to recover and reuse thermal energy within the process can be deployed for energy efficiency. High-pressure conditions can improve mass transfer rates, facilitating the dissolution of metals. The transport liquid containing chelate and acid can be recycled for greater process efficiency. In some aspects, the serpentinization reactions can release heat. The use of a controlled serpentinization reaction using, for example, a controlled injection of brine, can be used to maintain a reaction temperature within the formation to enhance the reaction kinetics.

[0067] The pressure can be maintained such that the water remains a liquid within the formation and the conditions are controlled to increase the dissolution rate of metals into solution. The conditions that can be controlled include pH, which can be maintained at approximately 4-6 for certain metal extraction processes by dissolution of CO2 to form carbonic acid, or at other pH ranges depending on the specific metal being targeted, the temperature, the brine pressure, and the composition of additives such as chelating agents. The CO2 may be dissolved into the liquid at the surface or injected with the liquid.

[0068] Ferrous iron (Fe2+) in iron-rich rocks represents a significant chemical potential that can be harnessed through various processes. Minerals such as Olivine (Mg,Fe)2SiO4, Orthopyroxene (Mg.FejSiOs, Clinopyroxene (Ca,Na)(Mg,Fe,Al.Ti)(Si,Al)2Oe, Hedenbergite CaFeSi2Oe, Pyrite FeS2, Ilmenite FeTiOs, Hercynite (FeAhO4), Siderite (FeCOs), Magnetite (FesO4), Grunerite (Fe7SisO22(OH)2), Lepidocrocite FeO(OH), Glauconite (K,Na)(Mg,Fe,Al)2(Si,Al)40w(0H)2, Chamosite (Mg,Fe)sAl(AlSi30io)(OH)s, Greenalite (Fe2+,Fe?+)2-3Si2O5(OH)4, Minnesotaite (Fe,Mg)3Si40io(OH)2, Vivianite Fe2(PO4)28H2O are abundant in the Earth's crust and contain substantial amounts of Fe2+. making them suitable candidates for iron extraction and energy-related applications. Further, Fe2+is found in other geologic formations including certain sandstones where the same approaches are applicable.

[0069] Strategies for utilizing the chemical potential of Fe2+can include in situ hydrogen generation facilitated by subsurface reactions that generate hydrogen by leveraging the redox properties of Fe2+in iron-rich rocks, and ex situ conversion via leaching and transport to the surface that allows for extraction of Fe2+from iron-rich minerals through chemical leaching for subsequent applications in surface conversion systems.

[0070] The systems and methods described herein enable the extraction of rare earth minerals and elements from subsurface geological formations. Rare earth elements include theAtty. Docket No.: GEQ002PCT-8022-00301 lanthanides, scandium, and yttrium. The extraction of rare earth minerals can be accomplished through solution mining processes as described herein to enhance dissolution of rare earthcontaining minerals from the rock.

[0071] The production and extraction of rare earth minerals can be improved through controlled brine composition and conditions such as pH modulation ranging from about 2 to about 13, temperature control ranging from about 50°C to about 500°C, and pressure modulation. The rare earth minerals may be co-produced with hydrogen, geothermal energy, amorphous silica, and / or other metals in an integrated extraction process.

[0072] The extraction processes described herein are applicable to cobalt (Co) and nickel (Ni) recover}' from subsurface formations. Cobalt and nickel may be present in ultramafic and mafic rock formations, including those containing olivine and pyroxene. The cyclic leaching process using alternating pH conditions can selectively dissolve and recover cobalt and nickel. Mineral recover7of metals including Co and Ni may be used as indicators of reaction efficiency and may be monitored continuously during the extraction process.

[0073] The solution mining processes disclosed herein can be used to recover copper (Cu), uranium (U). aluminum (Al), and zinc (Zn) from geological formations. These metals can be extracted through acid leaching combined with chelating agents, with pH control optimized for each specific metal. The extraction rates can be increased by fracturing driven by weathering processes to increase surface area, and by adjustment of pH and temperature to increase the rate of chemical dissolution of the rock matrix and desired metal species.

[0074] The controlled conditions for metal extraction comprise operating temperatures in a range between 50°C to about 500°C, operating pressures in a range of 1 bar to about 4000 bar, and pH control in a range from about 2 to about 13. Cycle durations for alternating injection and extraction cycles can range from about 0.5 hours to about 48 hours, from about 2 hours to about 24 hours, or from about 6 hours to about 12 hours. Water-to-rock ratios can range from about 0.1 to about 5.0, from about 0.2 to about 2.0, or from about 0.3 to about 1.0.

[0075] Chemical injection protocols for metal extraction can include pH adjusters (e.g., carbonates) at concentrations ranging from about 0.01 M to about 1.0 M, CO2 at injection rates ranging from about 10 kg / hr to about 1000 kg / hr, acids in concentrations from about 0.1 M to about 1.0 M, and chelating agents in concentrations from about 0.01 M to about 0.5 M, each selected to provide a desired pH control, metal solubilization, and enhanced reaction kinetics.

[0076] Having described various systems, methods, and reaction processes, certain aspects can include, but are not limited to:Atty. Docket No.: GEQ002PCT-8022-00301

[0077] In a first aspects, a process for reaction-induced fracturing of a subsurface rock formation comprises: injecting a fluid comprising water into a subsurface rock formation comprising a Fe2+-containing mineral; inducing metamorphic reactions of the Fe2+-containing mineral with the water to generate volume changes in the subsurface rock formation; and generating microfractures via the volume changes, wherein the volume changes create localized pressures that propagate fractures within the subsurface rock formation.

[0078] A second aspect can include the process of the first aspect, wherein the Feecontaining mineral is selected from the group consisting of Olivine (Mg,Fe)2SiO4, Orthopyroxene (Mg,Fe)SiO3, Clinopyroxene (Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2O6, Hedenbergite CaFeSi20e, Pyrite FeS2, Ilmenite FeTiOs. Hercynite (FeAhOr), Siderite (FeCCh), Magnetite (FesOr), Grunerite (Fe7SisO22(OH)2), Lepidocrocite FeO(OH), Glauconite (K,Na)(Mg,Fe,Al)2(Si,Al)40io(OH)2, Chamosite (Mg,Fe)sAl(AlSi 0io)(OH)s, Greenalite (Fe2+,Fe3+)2-3Si2Os(OH)4, Minnesotaite (Fe,Mg)3Si40io(OH)2, Vivianite Fe2(PO4)28H2O, dunites, peridotites, basalts, kimberlites, lamproites, banded iron formations, greywackes, or any combinations thereof.

[0079] A third aspect can include the process of the first or second aspect, wherein the volume changes comprise a volume increase in a range of from about 5% to about 60%.

[0080] A fourth aspect can include the process of any one of the first to third aspects, wherein the localized pressures range from about 100 MPa to about 2000 MPa, and wherein the localized pressures from the metamorphic reaction are generated near reaction sites.

[0081] A fifth aspect can include the process of any one of the first to fourth aspects, wherein the metamorphic reactions are exothermic and generate thermal energy ranging from about 4 MJ to about 10 MJ per cubic meter of reaction product formation.

[0082] A sixth aspect can include the process of any one of the first to fifth aspects, wherein the fluid is injected at a pressure belowfa breakdown pressure of the subsurface rock formation.

[0083] A seventh aspect can include the process of any one of the first to sixth aspects, wherein the controlled conditions comprise: an operating temperature in a range from about 150 °C to about 500 °C; an operating pressure in a range from about 50 bar to about 4000 bar; and a pH in a range from about 2 to about 13.

[0084] An eighth aspect can include the process of any one of the first to seventh aspects, further comprising modulating pressure of the injected fluid as a function of time P(t) in frequency, amplitude, or relative phases of any different frequencies.Atty. Docket No.: GEQ002PCT-8022-00301

[0085] A ninth aspect can include the process of the eighth aspect, wherein modulating the pressure occurs between approximately 0.6 to 0.99 of the breakdown pressure of the subsurface rock formation with a cycle duration of approximately 16 hours.

[0086] A tenth aspect can include the process of any one of the first to ninth aspects, further comprising: creating an initial fracture network using conventional hydraulic fracturing; and subsequently propagating additional microfractures through the metamorphic reactions.

[0087] An eleventh aspect can include the process of any one of the first to tenth aspects, wherein the fluid further comprises one or more of acid, base, salt, catalyst, or surfactant.

[0088] A twelfth aspect can include the process of any one of the first to eleventh aspects, wherein the inducing of the metamorphic reactions further generates temperature changes in the subsurface rock formation.

[0089] A thirteenth aspect can include the process of any one of the first to twelfth aspects, wherein the metamorphic reactions comprise serpentinization reactions, hydration reactions, or a combination thereof.

[0090] In a fourteenth aspect, a wellbore system comprises: at least one wellbore extending into a subsurface rock formation, wherein the subsurface rock formation comprises aFe2+-containing mineral and comprises microfractures formed by metamorphic reactions that convert the Fe2+-containing mineral to reaction products with accompanying volume changes; one or more wellbore tubulars extending through the at least one wellbore and the casing to provide fluid communication with the subsurface rock formation; a fluid injection system configured to inject a fluid comprising water into the subsurface rock formation through the at least one wellbore; and a recovery system configured to recover a fluid produced by the metamorphic reactions in the subsurface rock formation.

[0091] A fifteenth aspect can include the wellbore system of the fourteenth aspect, wherein the microfractures comprise hierarchical fracture networks.

[0092] A sixteenth aspect can include the wellbore system of the fourteenth or fifteenth aspect, wherein the metamorphic reactions generate localized crystallization pressures ranging from about 100 MPa to about 2000 MPa that create the microfractures while bulk pressure in the subsurface rock formation remains below a breakdown pressure of the subsurface rock formation.

[0093] A seventeenth aspect can include the wellbore system of any one of the fourteenth to sixteenth aspects, further comprising: a pressure controller configured to maintain fluid pressure in the subsurface rock formation below the breakdown pressure of the subsurfaceAtty. Docket No.: GEQ002PCT-8022-00301 rock formation and to modulate pressure cyclically; a chemical injection unit for delivering pH control agents; and a temperature control system for maintaining operating temperatures ranging from about 150 °C to about 500 °C.

[0094] An eighteenth aspect can include the wellbore system of any one of the fourteenth to seventeenth aspects, further comprising a control system configured to execute alternating injection and extraction cycles wherein: the at least one wellbore receives fluid during injection cycles; and the at least one wellbore extracts fluid during extraction cycles, wherein cycle durations range from about 0.5 hours to about 48 hours.

[0095] A nineteenth aspect can include the wellbore system of any one of the fourteenth to eighteenth aspects, wherein the at least one wellbore comprises a plurality of wellbores, wherein the plurality of wellbores are operated such that: a first subset of the plurality of wellbores undergo fracturing during a first time period while a second subset of the plurality of wellbores undergo hydrogen production during the first time period; and wherein different wellbores are simultaneously at different stages of fracturing.

[0096] A twentieth aspect can include the wellbore system of the nineteenth aspect, wherein the plurality of wellbores comprise: at least one injection wellbore configured to inject brine into the subsurface rock formation; and at least one production wellbore configured to extract hydrogen-rich fluid from the subsurface rock formation.

[0097] A twenty first aspect can include the wellbore system of any one of the fourteenth to twentieth aspects, wherein the subsurface rock formation is selected from the group consisting of mafic rock formations and ultramafic rock formations containing olivine and / or pyroxene, banded iron formations (BIFs), and formations rich in Fe2+-containing minerals.

[0098] In a twenty second aspect, a process for extraction of metals and minerals from a subsurface geological formation comprises: fracturing a subsurface rock formation using reaction-induced fracturing, wherein the reaction-induced fracturing comprises injecting a fluid comprising water into the subsurface rock formation to induce metamorphic reactions that generate volume changes and create microfractures; injecting a solution mining fluid through a wellbore into the fractured subsurface rock formation, wherein the solution mining fluid comprises a brine having a controlled composition; and recovering a fluid from the wellbore, wherein the recovered fluid comprises dissolved metals, dissolved rare earth elements, hydrogen, or any combination thereof.

[0099] A twenty third aspect can include the process of the twenty second aspect, wherein the metals comprise iron (Fe), copper (Cu), uranium (U), aluminum (Al), cobalt (Co),Atty. Docket No.: GEQ002PCT-8022-00301 nickel (Ni), chromium (Cr), zinc (Zn), or any combination thereof, and wherein the rare earth elements comprise lanthanides, scandium, yttrium, or any combination thereof.

[0100] A twenty fourth aspect can include the process of the twenty second or twenty third aspect, wherein injecting the solution mining fluid comprises alternately injecting high pH brines and low pH brines into the subsurface rock formation to perform cyclic leaching, wherein: the high pH brines dissolve minerals containing potassium or sodium; and the low pH brines dissolve minerals containing calcium, magnesium, and metal oxides.

[0101] A twenty fifth aspect can include the process of any one of the twenty second to twenty fourth aspects, wherein the solution mining fluid comprises: an acid selected from the group consisting of carbonic acid formed from dissolution of CO2 in water, sulfuric acid (H2SO4), hydrochloric acid (HC1). nitric acid (HNO3), and organic acids selected from acetic acid, citric acid, and sugar acids; and a chelating agent selected from the group consisting of ethylenediaminetetraacetic acid (EDTA), citric acid, oxalic acid, aldonic acids, phosphates, and amino acids.

[0102] A twenty sixth aspect can include the process of any one of the twenty second to twenty fifth aspects, wherein the controlled pH ranges from about 2 to about 13, the operating temperature ranges from about 50 °C to about 500 °C, and the operating pressure ranges from about 1 bar to about 4000 bar.

[0103] A twenty seventh aspect can include the process of any one of the twenty second to twenty sixth aspects, wherein the solution mining fluid is maintained at a mean pressure sufficient to maintain the microfractures in an accessible state, and wherein the pressure is modulated during solution mining to maintain existing microfractures and create new microfractures.

[0104] A twenty eighth aspect can include the process of any one of the twenty second to twenty seventh aspects, wherein injecting the solution mining fluid comprises operating in alternating injection and extraction cycles, wherein cycle durations range from about 0.5 hours to about 48 hours, and wherein a water-to-rock ratio ranges from about 0.1 to about 5.0.

[0105] A twenty ninth aspect can include the process of any one of the twenty second to twenty eighth aspects, further comprising separating the dissolved metals and dissolved rare earth elements from the recovered fluid at a surface processing unit.

[0106] A thirtieth aspect can include the process of any one of the twenty second to twenty ninth aspects, wherein recovering the fluid comprises co-producing hydrogen gas, geothermal heat, amorphous silica, metals, rare earth minerals, or any combination thereof from the subsurface rock formation.Atty. Docket No.: GEQ002PCT-8022-00301

[0107] A thirty first aspect can include the process of any one of the twenty second to thirtieth aspects, wherein fracturing the subsurface rock formation using reaction-induced fracturing comprises: performing a first stage of mechanical fracturing using hydraulic fracturing to create an initial fracture network; performing a first stage of resource production from the subsurface rock formation; and performing a second stage of fracturing using reactionbased controlled fracturing through metamorphic reactions while performing ongoing resource production.

[0108] A thirty second aspect can include the process of any one of the twenty second to thirty first aspects, further comprising controlling at least one of: pH of the solution mining fluid as a function of time pH(t) ranging from about 2 to about 13; pressure of the solution mining fluid as a function of time P(t) ranging from about the magnitude of least compressive stress to about 99% of breakdown pressure; temperature of the solution mining fluid as a function of time T(t); water-to-rock ratio as a function of time WRR(t) ranging from about 0.1 to about 5.0; and composition of the solution mining fluid as a function of time including concentrations of acids ranging from about 0. 1 M to about 1.0 M and chelating agents ranging from about 0.01 M to about 0.5 M.

[0109] In a thirty third aspect, a system for integrated resource extraction from a subsurface geological formation comprises a plurality of w ellbores disposed in a subsurface rock formation comprising microfractures formed by metamorphic reactions, wherein the microfractures result from volume changes accompanying conversion of Fe2+-containing minerals to reaction products; a fluid injection system configured to inject solution mining fluids into the subsurface rock formation through at least one of the plurality of wellbores; a brine controller configured to control pH and composition of the solution mining fluids, wherein the brine controller is configured to alternate between injecting high pH brines and low7pH brines to perform cyclic leaching; a pressure controller configured to maintain pressure in the subsurface rock formation below7a breakdown pressure of the rock formation and to modulate pressure cyclically7; a recovery system configured to recover fluid from at least one of the plurality of wellbores; a separation system configured to separate metals, rare earth elements, hydrogen, heat, silica, or any combination thereof from the recovered fluid; and a control system configured to stage fracturing and resource extraction among the plurality of wellbores such that some wellbores undergo fracturing while other wellbores undergo active resource production simultaneously.

[0110] Additional aspects can include:Atty. Docket No.: GEQ002PCT-8022-00301

[0111] In a first aspect, a process for in-situ generation of hydrogen gas from a subsurface geologic formation (e.g., and, optionally, production of geothermal heat and / or amorphous silica and / or a rare earth mineral), comprises injecting brine into the subsurface geologic formation (e.g., wherein the formation comprises an olivine matrix) [e.g., wherein the formation is iron-rich (e.g., comprises olivine and / or peridotite) (e.g., of mafic rock)] [e.g., a banded iron formation (BIF), e.g., iron-rich hematite and / or magnetite, with adjacent silica- rich layers], and recovering generated hydrogen gas (e.g., and, optionally, recovering heat produced from exothermic reaction, and, optionally, recovering amorphous silica) (e.g., wherein the process comprises applying pressure modulated hydraulics and geochemical control for enhanced chemical and heat recovery' by facilitating dissolution of Fe(2+) from the rock formation).

[0112] A second aspect can include the process of the first aspect, comprising performing hierarchical fracturing of rock in the subsurface geologic formation.

[0113] A third aspect can include the process of the first or second aspect, comprising utilizing energy from (e.g.. the) exothermic reaction to control fracturing of rock in the subsurface geologic formation.

[0114] A fourth aspect can include the process of any one of the first to third aspects, wherein the process comprises establishing a plurality' of wells at a given site of the subsurface geologic formation, and staging fracking and hydrogen harvesting / extraction at the wells (e.g., such that some wells are fracked while others are used for active H2 production and extraction, e.g., not all fracks are performed for a given well at once, e.g., not all stages of fracking are performed for a given well before moving on to another well).

[0115] A fifth aspect can include the process of any one of the first to fourth aspects, comprising first performing mechanical fracturing (e.g.. hydraulic fracturing (fracking)) of the subsurface geologic formation and subsequently controlling fracture formation using reactionbased fracturing [e.g., using energy released from an exothermic chemical reaction occurring (e.g., induced) in the subsurface geologic formation (e.g., using brine)].

[0116] Unless otherwise specified, any use of any form of the terms “connect,” “engage,” “couple,” “attach,” or any other term describing an interaction between elements is not meant to limit the interaction to direct interaction between the elements and may also include indirect interaction between the elements described. 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 . . . “. Reference to up or down will be made for purposes of description with “up,” “upper,” “upward,” “upstream,” or “above”Atty. Docket No.: GE0002PCT-8022-00301 meaning toward the surface of the wellbore and with "down." “low er,” "downward." “downstream,” or “below” meaning toward the terminal end of the well, regardless of the w ellbore orientation. Reference to inner or outer will be made for purposes of description with “in,” “inner,” or “inward” meaning towards the central longitudinal axis of the wellbore and / or wellbore tubular, and “out,” “outer,” or “outward” meaning tow ards the wellbore wall. As used herein, the term “longitudinal” or “longitudinally” refers to an axis substantially aligned with the central axis of the wellbore tubular, and “radial” or “radially” refer to a direction perpendicular to the longitudinal axis. The various characteristics mentioned above, as well as other features and characteristics described in more detail below, will be readily apparent to those skilled in the art with the aid of this disclosure upon reading the following detailed description of the embodiments, and by referring to the accompanying drawings.

[0117] Additionally, the section headings used herein are provided for consistency with the suggestions under 37 C.F.R. 1.77 or to otherwise provide organizational cues. These headings shall not limit or characterize the invention(s) set out in any claims that may issue from this disclosure. Specifically, and by way of example, although the headings might refer to a “Field,” the claims should not be limited by the language chosen under this heading to describe the so-called field. Further, a description of a technology in the “Background” is not to be construed as an admission that certain technology' is prior art to any invention(s) in this disclosure. Neither is the “Summary” to be considered as a limiting characterization of the invention(s) set forth in issued claims. Furthermore, any reference in this disclosure to “invention” in the singular should not be used to argue that there is only a single point of novelty' in this disclosure. Multiple inventions may be set forth according to the limitations of the multiple claims issuing from this disclosure, and such claims accordingly define the invention(s), and their equivalents, that are protected thereby. In all instances, the scope of the claims shall be considered on their own merits in light of this disclosure, but should not be constrained by the headings set forth herein.

[0118] Use of broader terms such as comprises, includes, and having should be understood to provide support for narrower terms such as consisting of, consisting essentially of, and comprised substantially of. Use of the term “optionally,” “may,” “might,” “possibly,” and the like with respect to any element of an embodiment means that the element is not required, or alternatively, the element is required, both alternatives being within the scope of the embodiment(s). Also, references to examples are merely provided for illustrative purposes, and are not intended to be exclusive.Atty. Docket No.: GE0002PCT-8022-00301

[0119] While preferred embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teachings herein. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the systems, apparatus, and processes described herein are possible and are within the scope of the disclosure. For example, the relative dimensions of various parts, the materials from which the various parts are made, and other parameters can be varied. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims. Unless expressly stated otherwise, the steps in a method claim may be performed in any order. The recitation of identifiers such as (a), (b), (c) or (1), (2), (3) before steps in a method claim are not intended to and do not specify a particular order to the steps, but rather are used to simplify subsequent reference to such steps.

[0120] Also, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate component, whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein.

Claims

Atty. Docket No.: GEQ002PCT-8022-00301CLAIMSWhat is claimed is:

1. A process for reaction-induced fracturing of a subsurface rock formation, the process comprising: injecting a fluid comprising water into a subsurface rock formation compnsing a Feecontaining mineral; inducing metamorphic reactions of the Fe2+-containing mineral with the water to generate volume changes in the subsurface rock formation; and generating microfractures via the volume changes, wherein the volume changes create localized pressures that propagate fractures within the subsurface rock formation.

2. The process of claim 1. wherein the Fe2+-containing mineral is selected from the group consisting of Olivine (Mg,Fe)2SiO4, Orthopyroxene (Mg,Fe)SiO?, Clinopyroxene (Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2Oe, Hedenbergite CaFeSi20e, Pyrite FeS2, Ilmenite FeTiOs, Hercynite (FeAhO4), Siderite (FeCOs), Magnetite (FesO4), Grunerite (Fe7SisO22(OH)2), Lepidocrocite FeO(OH), Glauconite(K,Na)(Mg,Fe,Al)2(Si,Al)40io(OH)2, Chamosite (Mg,Fe)5Al(AlSi30io)(OH)8, Greenalite (Fe2+,Fe3+)2-3Si2Os(OH)4, Minnesotaite (Fe,Mg)3Si40io(OH)2, Vivianite Fe2(PO4)28H2O, dunites, peridotites, basalts, kimberlites, lamproites, banded iron formations, greywackes, or any combinations thereof.

3. The process of claim 1, wherein the volume changes comprise a volume increase in a range of from about 5% to about 60%.

4. The process of claim 1, wherein the localized pressures range from about 100 MPa to about 2000 MPa, and wherein the localized pressures from the metamorphic reaction are generated near reaction sites.

5. The process of claim 1 , wherein the metamorphic reactions are exothermic and generate thermal energy ranging from about 4 MJ to about 10 MJ per cubic meter of reaction product formation.Atty. Docket No.: GE0002PCT-8022-003016. The process of claim 1, wherein the fluid is injected at a pressure below a breakdown pressure of the subsurface rock formation.

7. The process of claim 1, wherein the controlled conditions comprise: an operating temperature in a range from about 150 °C to about 500 °C; an operating pressure in a range from about 50 bar to about 4000 bar; and a pH in a range from about 2 to about 13.

8. The process of claim 1, further comprising modulating pressure of the injected fluid as a function of time P(t) in frequency, amplitude, or relative phases of any different frequencies.

9. The process of claim 8, wherein modulating the pressure occurs between approximately 0.6 to 0.99 of the breakdown pressure of the subsurface rock formation with a cycle duration of approximately 16 hours.

10. The process of claim 1, further comprising: creating an initial fracture network using conventional hydraulic fracturing; and subsequently propagating additional microfractures through the metamorphic reactions.1 1 . The process of claim 1 , wherein the fluid further comprises one or more of acid, base, salt, catalyst, or surfactant.

12. The process of claim 1, wherein the inducing of the metamorphic reactions further generates temperature changes in the subsurface rock formation.

13. The process of claim 1, wherein the metamorphic reactions comprise serpentinization reactions, hydration reactions, or a combination thereof.

14. A wellbore system comprising: at least one wellbore extending into a subsurface rock formation, wherein the subsurface rock formation comprises a Fe2+-containing mineral and comprises microfractures formed by metamorphic reactions that convert the Fe2 t- containing mineral to reaction products with accompanying volume changes;Atty. Docket No.: GEQ002PCT-8022-00301 one or more wellbore tubulars extending through the at least one wellbore and the casing to provide fluid communication with the subsurface rock formation; a fluid injection system configured to inject a fluid comprising water into the subsurface rock formation through the at least one wellbore; and a recover}' system configured to recover a fluid produced by the metamorphic reactions in the subsurface rock formation.

15. The wellbore system of claim 14, wherein the microfractures comprise hierarchical fracture networks.

16. The wellbore system of claim 14. wherein the metamorphic reactions generate localized crystallization pressures ranging from about 100 MPa to about 2000 MPa that create the microfractures while bulk pressure in the subsurface rock formation remains below a breakdown pressure of the subsurface rock formation.

17. The wellbore system of claim 14, further comprising: a pressure controller configured to maintain fluid pressure in the subsurface rock formation below the breakdow n pressure of the subsurface rock formation and to modulate pressure cyclically; a chemical injection unit for delivering pH control agents; and a temperature control system for maintaining operating temperatures ranging from about 150 °C to about 500 °C.

18. The wellbore system of claim 14. further comprising a control system configured to execute alternating injection and extraction cycles wherein: the at least one wellbore receives fluid during injection cycles; and the at least one wellbore extracts fluid during extraction cycles, wherein cycle durations range from about 0.5 hours to about 48 hours.

19. The wellbore system of claim 14, wherein the at least one wellbore comprises a plurality of wellbores, wherein the plurality of wellbores are operated such that: a first subset of the plurality of w ellbores undergo fracturing during a first time period while a second subset of the plurality of wellbores undergo hydrogen production during the first time period; and w herein different wellbores are simultaneously at different stages of fracturing.Atty. Docket No.: GE0002PCT-8022-0030120. The wellbore system of claim 19, wherein the plurality of wellbores comprise: at least one injection wellbore configured to inject brine into the subsurface rock formation; and at least one production wellbore configured to extract hydrogen-rich fluid from the subsurface rock formation.

21. The wellbore system of claim 14, wherein the subsurface rock formation is selected from the group consisting of mafic rock formations and ultramafic rock formations containing olivine and / or pyroxene, banded iron formations (BIFs), and formations rich in Fe2 t-containing minerals.

22. A process for extraction of metals and minerals from a subsurface geological formation, the process comprising: fracturing a subsurface rock formation to generate the microfractures using the process of any one of claims 1-13; injecting a solution mining fluid through a wellbore into the fractured subsurface rock formation, wherein the solution mining fluid comprises a brine having a controlled composition; and recovering a fluid from the wellbore, wherein the recovered fluid comprises dissolved metals, dissolved rare earth elements, hydrogen, or any combination thereof.

23. The process of claim 22, wherein the metals comprise iron (Fe), copper (Cu). uranium (U), aluminum (Al), cobalt (Co), nickel (Ni), chromium (Cr), zinc (Zn), or any combination thereof, and wherein the rare earth elements comprise lanthanides, scandium, yttrium, or any combination thereof24. The process of claim 22, wherein injecting the solution mining fluid comprises alternately injecting high pH brines and low pH brines into the subsurface rock formation to perform cyclic leaching, wherein: the high pH brines dissolve minerals containing potassium or sodium; and the low pH brines dissolve minerals containing calcium, magnesium, and metal oxides.

25. The process of claim 22, wherein the solution mining fluid comprises:Atty. Docket No.: GEQ002PCT-8022-00301 an acid selected from the group consisting of carbonic acid formed from dissolution of CO2 in water, sulfuric acid (H2SO4), hydrochloric acid (HC1), nitric acid (HNO3), and organic acids selected from acetic acid, citric acid, and sugar acids; and a chelating agent selected from the group consisting of ethylenediaminetetraacetic acid (EDTA), citric acid, oxalic acid, aldonic acids, phosphates, and amino acids.

26. The process of claim 22, wherein the controlled pH ranges from about 2 to about 13, the operating temperature ranges from about 50 °C to about 500 °C, and the operating pressure ranges from about 1 bar to about 4000 bar.

27. The process of claim 22, wherein the solution mining fluid is maintained at a mean pressure sufficient to maintain the microfractures in an accessible state, and wherein the pressure is modulated during solution mining to maintain existing microfractures and create new microfractures.

28. The process of claim 22, wherein injecting the solution mining fluid comprises operating in alternating injection and extraction cycles, wherein cycle durations range from about 0.5 hours to about 48 hours, and wherein a water-to-rock ratio ranges from about 0.1 to about 5.0.

29. The process of claim 22, further comprising separating the dissolved metals and dissolved rare earth elements from the recovered fluid at a surface processing unit.

30. The process of claim 22, wherein recovering the fluid comprises co-producing hydrogen gas, geothermal heat, amorphous silica, metals, rare earth minerals, or any combination thereof from the subsurface rock formation.

31. The process of claim 22, wherein fracturing the subsurface rock formation using reaction-induced fracturing comprises: performing a first stage of mechanical fracturing using hydraulic fracturing to create an initial fracture network; performing a first stage of resource production from the subsurface rock formation; and performing a second stage of fracturing using reaction-based controlled fracturing through metamorphic reactions while performing ongoing resource production.Atty. Docket No.: GEQ002PCT-8022-0030132. The process of claim 22, further comprising controlling at least one of: pH of the solution mining fluid as a function of time pH(t) ranging from about 2 to about 13; pressure of the solution mining fluid as a function of time P(t) ranging from about the magnitude of least compressive stress to about 99% of breakdown pressure; temperature of the solution mining fluid as a function of time T(t); water-to-rock ratio as a function of time WRR(t) ranging from about 0.1 to about 5.0; and composition of the solution mining fluid as a function of time including concentrations of acids ranging from about 0. 1 M to about 1.0 M and chelating agents ranging from about 0.01 M to about 0.5 M.

33. A system for integrated resource extraction from a subsurface geological formation, the system comprising: a plurality of wellbores disposed in a subsurface rock formation comprising microfractures formed by metamorphic reactions, wherein the microfractures result from volume changes accompanying conversion of Fe2+-containing minerals to reaction products; a fluid injection system configured to inject solution mining fluids into the subsurface rock formation through at least one of the plurality of wellbores; a brine controller configured to control pH and composition of the solution mining fluids, wherein the brine controller is configured to alternate between injecting high pH brines and low pH brines to perform cyclic leaching; a pressure controller configured to maintain pressure in the subsurface rock formation below a breakdown pressure of the rock formation and to modulate pressure cyclically; a recovery system configured to recover fluid from at least one of the plurality of wellbores; a separation system configured to separate metals, rare earth elements, hydrogen, heat, silica, or any combination thereof from the recovered fluid; and a control system configured to stage fracturing and resource extraction among the plurality of wellbores such that some wellbores undergo fracturing while other wellbores undergo active resource production simultaneously.

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