CO2 mineralization sequestration and geological hydrogen synergistic enhanced mining method and simulation experiment method

Abstract

The invention discloses a CO2 mineralization sequestration and geological hydrogen synergistic enhanced mining method and a simulation experiment method, which are applied to a geological hydrogen reservoir containing ultra-basic rock, and the method comprises the following steps: screening the ultra-basic rock reservoir rich in magnesium iron minerals, and arranging a bottom injection well and a top recovery well; supercritical CO2 is injected into the bottom injection well, and fracturing is carried out to form a fracture net; a migration channel for CO2 sinking and H2 floating is established; geological hydrogen is extracted, the recovery pressure difference is regulated and controlled to limit upward flowing of CO2, and components and yield of extracted gas are monitored; carrying out CO2 mineralization storage and artificial geological hydrogen supply; and in multiple cycles, the geological hydrogen recovery rate is increased, and CO2 mineralization and storage are completed step by step. According to the method, aiming at the characteristics of low porosity and low permeability and fracture control seepage of the ultra-basic rock reservoir, a supercritical CO2 fracturing technology and CO2 displacement are adopted to improve the permeability and reaction contact area of the reservoir, the geological hydrogen recovery efficiency and the CO2 storage efficiency and economy can be synchronously improved, and cyclic synergistic enhancement of hydrogen energy development and CO2 mineralization storage is realized.

Description

Technical Field

[0001] This invention relates to the field of underground energy development and carbon emission reduction technology, specifically to a method and simulation experiment method for CO2 mineralization and storage and geological hydrogen synergistic enhanced mining, applicable to underground geological systems containing ultramafic rocks. Background Technology

[0002] Hydrogen energy, as an important clean secondary energy source, plays a crucial role in building a low-carbon energy system. Besides industrial hydrogen production, recent years have revealed that naturally occurring geological hydrogen has advantages such as zero carbon emissions and significant resource potential. Natural geological hydrogen is mainly found in special geological environments such as ultramafic rocks and serpentinized rock masses. However, the natural generation rate of geological hydrogen is low, and it is mostly found in fractures, resulting in low overall permeability. Relying solely on natural seepage makes efficient extraction difficult.

[0003] Existing methods for extracting natural geological hydrogen have several limitations: Firstly, the natural generation rate of geological hydrogen is low, and it is mostly found in fractures, exhibiting a dispersed state and limited permeability, making efficient recovery difficult by relying solely on natural seepage. Secondly, ultramafic rock reservoirs have low matrix permeability and insufficient connectivity, requiring measures such as fracturing to improve seepage conditions. Furthermore, from the perspective of continuous hydrogen supply, the ultramafic rock-water reaction is slow and lacks a sustainable supply and enhancement mechanism. In contrast, the ultramafic rock-CO2-water reaction rate is faster, and under suitable temperature and pressure conditions, it is beneficial for CO2 mineral carbon fixation and also holds promise for providing a continuous supply of geological hydrogen; however, related coupled development technologies are still immature.

[0004] Carbon capture, utilization, and storage (CCUS) is an important technological pathway for mitigating greenhouse gas emissions and has been applied in scenarios such as saline aquifers and oil and gas reservoirs. However, traditional CCUS projects mostly focus on CO2 sequestration alone, requiring large engineering investments and relying heavily on policy incentives for economic benefits, resulting in limited overall economic viability. Existing research and patents primarily focus on CO2 geological sequestration or natural geological hydrogen development, and a mature technical approach that couples the CO2 carbon sequestration process with enhanced extraction of natural geological hydrogen within the same system has not yet been established. Therefore, there is an urgent need for a new method that can simultaneously improve geological hydrogen recovery efficiency and achieve stable CO2 sequestration in underground systems. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the prior art by providing a method and simulation experiment method for the synergistic enhancement of CO2 mineralization and sequestration and geological hydrogen mining.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for synergistic enhancement of CO2 mineralization and sequestration and geological hydrogen extraction, the method being applied to geological hydrogen reservoirs containing ultramafic rocks, the method comprising the following steps: Screening for ultramafic rock reservoirs rich in mafic minerals, and deploying at least one bottom injection well and at least one top production well in the ultramafic rock reservoir, wherein the perforated section of the bottom injection well is located at the bottom of the ultramafic rock reservoir, and the perforated section of the top production well is located at the top of the ultramafic rock reservoir; Supercritical CO2 is injected into the bottom injection well. By controlling the injection pressure and injection rate, a fracture network is formed in the ultramafic rock reservoir through supercritical CO2 fracturing, so that CO2 preferentially fills the lower space of the ultramafic rock reservoir. CO2 migrates downward in the ultramafic rock reservoir and forms a lower gas cushion. Under the displacement and buoyancy of this lower gas cushion, geological hydrogen is enriched in the upper part of the ultramafic rock reservoir, establishing a migration channel of CO2 sinking and H2 rising. Geological hydrogen enriched in the upper part of the ultrabasic rock reservoir is extracted through the top production well, the production pressure differential is controlled to limit CO2 upwelling, and the composition and production of the produced gas are monitored. Determine whether the well suffocation triggering conditions are met. If not, continue to the previous step. If yes, enter the well suffocation stage. In the well suffocation stage, based on the CO2-ultrabasic rock-water reaction process, CO2 is in-situ mineralized and sealed using carbonate mineralization, and hydrogen is produced using serpentine action, thus realizing CO2 mineralization and sealing and artificial geological hydrogen replenishment. After the stagnation period reaches the criterion, the bottom injection well is reopened, and the above steps are repeated to improve the geological hydrogen recovery rate and gradually complete CO2 mineralization and storage through multiple cycles.

[0007] This method for synergistic enhancement of CO2 mineralization and sequestration and geological hydrogen production addresses the characteristics of ultramafic rock reservoirs, which are characterized by low porosity, low permeability, and fracture-controlled seepage. It proposes using supercritical CO2 fracturing technology and CO2 displacement to improve reservoir permeability and reaction contact area, thereby simultaneously enhancing the efficiency and economy of geological hydrogen recovery and CO2 sequestration, achieving a cyclical synergistic enhancement of hydrogen energy development and CO2 mineralization and sequestration.

[0008] Furthermore, when screening the ultramafic rock reservoirs, the reservoir's geothermal temperature, burial depth, original permeability, pore structure, geological hydrogen occurrence characteristics, and mineral composition are evaluated. Magnesium-iron silicate minerals containing olivine, pyroxene, and serpentine, or basalt rich in magnesium-iron minerals, are selected as rock masses to provide reactants for CO2 mineralization and sequestration and serpentinization hydrogen production.

[0009] Furthermore, the perforated section of the bottom injection well is arranged in the lower 1 / 6 to 1 / 2 section of the thickness of the target ultramafic rock reservoir, and the perforated section of the top production well is arranged in the upper 1 / 6 to 1 / 2 section of the thickness of the ultramafic rock reservoir, so as to form a stable CO2 cushion and H2 enrichment zone in the vertical direction and inhibit CO2 from rising to the top production well.

[0010] Furthermore, the supercritical CO2 injection pressure is higher than the fracture initiation pressure of the ultramafic rock reservoir, and multi-level fracture channels are formed by continuous injection, segmented injection, stepped pressurization and / or pulsed injection.

[0011] Furthermore, before injecting supercritical CO2 into the bottom injection well, water or a solution containing a reaction promoter is injected into the bottom injection well. Subsequently, CO2 and water are injected alternately to expand the contact interface between CO2 and minerals in the ultramafic rock reservoir and enhance the mineralization preservation and displacement effects.

[0012] Furthermore, the well-clogging triggering condition includes at least one of the following: (1) Geological hydrogen production showed a continuous downward trend over time; (2) The amount of hydrogen recovered per unit time is lower than the preset recovery threshold; (3) The CO2 concentration in the gas produced by the top production well increases to above the preset concentration threshold.

[0013] Furthermore, the carbonate minerals generated by the CO2-ultrabasic rock-water reaction include at least magnesium carbonate and calcium carbonate, which fill part of the fractures and pores of the fracture network, thus sealing CO2 in mineral form for a long period of time.

[0014] Furthermore, the well-sealing time is determined based on one or a combination of the following: (1) During the well closure period, the rate of change of bottom hole pressure drops to the preset pressure threshold and remains stable within a predetermined time. (2) During the well stagnation period, the rate of change of geochemical parameters of formation fluid at the bottom of the well monitored decreased to the preset threshold and remained stable within a predetermined time. (3) The well closure time reaches the minimum effective reaction time determined according to the reaction kinetics and does not exceed the preset maximum well closure time.

[0015] Furthermore, the chemical parameters include at least Mg. 2+ Ca 2+ and HCO3 - The concentration, pH value, and conductivity.

[0016] A simulation experiment method for CO2 mineralization and sequestration combined with geological hydrogen synergistic enhancement mining is provided to verify the CO2 mineralization and sequestration combined with geological hydrogen synergistic enhancement mining method described above. The simulation experiment method includes at least the following: Basalt was selected, and a CO2-rock-water reaction experiment was carried out at 20℃-25℃ for a duration of no less than 90 days. Basalt was made into powder samples and mixed with CO2-saturated water for continuous reaction for 90 days. Thermogravimetric analysis and X-ray photoelectron spectroscopy were performed on the powder samples before and after the experiment. At the same time, the hydrogen content during the experiment was tested to evaluate the formation of carbonates and the release of hydrogen. Peridotite was selected, and a CO2-rock-water reaction experiment was carried out at 50℃ for one day. Peridotite was made into a powder sample and mixed with CO2-saturated water for continuous reaction. During the experiment, the hydrogen production, the difference in ferrous ion content, and the CO2 content before and after the reaction were detected.

[0017] Compared with existing technologies, the beneficial effects of this invention are as follows: 1. This method of CO2 mineralization and sequestration combined with geological hydrogen synergistic enhancement can simultaneously improve the recovery rate of geological hydrogen and the efficiency and economy of CO2 sequestration, realizing the cyclical synergistic enhancement of hydrogen energy development and CO2 mineralization and sequestration; 2. In the extraction stage, this method addresses the problem of low permeability and difficulty in recovering geological hydrogen in ultramafic rock reservoirs by injecting CO2 for fracturing to induce the formation of a multi-level fracture network, thereby increasing reservoir permeability and reaction area. High-density CO2 drives the upward migration and enrichment of low-density H2, and wells are deployed at the top of the reservoir for recovery; in the well-closing stage, relying on the reaction process of CO2-ultramafic rock-water, long-term stable sequestration of CO2 and continuous generation of hydrogen are achieved, thereby supporting the long-term, multi-round cyclical extraction of geological hydrogen resources; 3. This method can also construct a cyclical underground hydrogen recovery-CO2 sequestration synergistic operation and mutual enhancement system, realizing the integrated operation of hydrogen development and CO2 sequestration, significantly improving overall economy and system efficiency. By embedding the CO2 mineralization and sequestration process into the hydrogen development process, CO2 sequestration can be achieved without additional engineering investment, thereby significantly reducing the overall cost of CCUS; 4. In view of the characteristics of low porosity and low permeability and fracture-controlled seepage in ultrabasic rock reservoirs, this method proposes to use supercritical CO2 fracturing technology and CO2 displacement to improve reservoir permeability and reaction contact area, thereby improving hydrogen generation and recovery efficiency. Attached Figure Description

[0018] Figure 1 This is a schematic flowchart of a method for synergistic enhancement of CO2 mineralization and sequestration and geological hydrogen mining according to the present invention. Figure 2 This is a schematic diagram of the structure of a method for synergistic enhancement of CO2 mineralization and sequestration and geological hydrogen mining according to the present invention; Figure 3 The amount of hydrogen produced by the CO2-basalt-water reaction obtained in the indoor experiments of this invention; Figure 4 The thermogravimetric analysis results curves of the basalt sample before and after the reaction in this invention are shown. Figure 5This is a BSE image of the carbonate minerals generated after the CO2-basalt-water reaction of the present invention; Figure 6 The C1s and Fe2p XPS spectra of basalt before and after the reaction of this invention; Figure 7 The amount of hydrogen produced by the CO2-olivine rock-water reaction obtained in the indoor experiments of this invention; Figure 8 The CO2 content is the CO2 content before and after the CO2-olivine rock-water reaction of this invention. Detailed Implementation

[0019] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In the description of this invention, it should be noted that the terms "middle", "upper", "lower", "left", "right", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0021] Example 1: A method for synergistic enhancement of CO2 mineralization and sequestration with geological hydrogen extraction, wherein the method is applied to geological hydrogen reservoirs containing ultramafic rocks, combined with... Figure 1 and Figure 2 As shown, the method includes the following steps: Step 1, Screening of Ultramafic Rock Reservoirs and Well Network Layout: Screen ultramafic rock reservoirs rich in mafic minerals, and lay at least one bottom injection well and at least one top production well in the ultramafic rock reservoirs to form a three-dimensional well network structure from bottom injection to top production. The perforated section of the bottom injection well is located at the bottom of the ultramafic rock reservoir, and the perforated section of the top production well is located at the top of the ultramafic rock reservoir.

[0022] In this embodiment, an ultramafic rock mass located in a certain region was selected. Geological exploration results indicate that an ultramafic rock reservoir with a thickness of 80 meters, containing minerals such as serpentine, olivine, and pyroxene, exists at a depth of approximately 1800 meters in this region. This reservoir is characterized by low porosity and low permeability, and natural hydrogen is mainly present as trace amounts of gas trapped in pores and microfractures. Two vertical wells are deployed in this target area, namely a bottom injection well and a top production well, with a well spacing of 300 meters. The perforation section of the bottom injection well is located 10 meters from the bottom of the reservoir, and the perforation section of the top production well is located 10 meters from the top of the reservoir. This well deployment method aims to form a three-dimensional channel structure of "bottom injection - top production".

[0023] Step 2, CO2 Injection and Fracturing for Enhanced Permeability: Supercritical CO2 is injected into the bottom injection well. By controlling the injection pressure and injection rate, a fracture network is formed in the ultramafic rock reservoir through supercritical CO2 fracturing, which improves the permeability and connectivity of the ultramafic rock reservoir. This allows CO2 to preferentially fill the lower space of the ultramafic rock reservoir, providing a channel basis for subsequent gas gravity differentiation.

[0024] In this embodiment, supercritical CO2 at a temperature of 35–50°C and a pressure exceeding the fracture pressure of the ultramafic rock reservoir is injected into the injection well. The injection process employs a stepped pressurization method to induce fractures, and fracture monitoring confirms the formation of a multi-level fracture network, thereby improving reservoir permeability and connectivity between injection and production wells. The injection pressure is controlled to exceed the microfracture propagation pressure of the ultramafic rock reservoir, forming a multi-level fracture network and gradually establishing channels connecting the injection and production wells, thus enhancing the permeability of the ultramafic rock reservoir. The injection duration is 5–10 days, and the cumulative injected CO2 volume is determined based on the volume of the ultramafic rock reservoir.

[0025] Step 3, Gas Gravity Differentiation and Displacement: Taking advantage of the difference between the density of CO2 and that of geological hydrogen, CO2 migrates downward in the ultramafic rock reservoir and forms a lower gas cushion. Under the displacement and buoyancy of this lower gas cushion, geological hydrogen is enriched in the upper part of the ultramafic rock reservoir, establishing a migration channel of CO2 sinking and H2 rising. Specifically, as the CO2 injection volume increases, CO2 in the ultramafic rock reservoir begins to migrate downward along the fracture network. Since its density is higher than that of hydrogen, it forms a stable gas cushion at the bottom of the reservoir. At the same time, CO2 displaces and pushes the trace amounts of natural hydrogen in the reservoir. Under the action of buoyancy, hydrogen accumulates at the top of the reservoir and enters the area near the perforated section of the production well.

[0026] Step 4, Geological Hydrogen Recovery: Geological hydrogen enriched in the upper part of the ultrabasic rock reservoir is extracted through the top recovery well. The recovery pressure differential is controlled to prevent CO2 from rising to the recovery well, thereby achieving stable and continuous recovery of geological hydrogen. During the recovery process, the geological hydrogen content, carbon dioxide content, and production changes of the produced gas are monitored.

[0027] In this embodiment, the concentrations of components such as H2, CO2, and CH4 in the produced gas are monitored in real time. Continuous production is initiated when the H2 concentration reaches 70% or higher, and the wellhead pressure differential is controlled to prevent CO2 from overflowing into the production well. The production cycle is set based on the gas production rate. When the H2 concentration in the produced gas drops below 50% and the CO2 concentration rises to 15%, the well shut-in trigger condition is determined to be met.

[0028] Step 5, Well Sealing and Mineralization Reaction: Determine if the well sealing triggering conditions are met. If not, continue to the previous step. If yes, enter the well sealing stage. In the well sealing stage, based on the CO2-ultrabasic rock-water reaction process, CO2 is in-situ mineralized and sealed using carbonate mineralization, and hydrogen is produced using serpentine action, thus realizing CO2 mineralization and sealing and artificial geological hydrogen replenishment. The stagnation stage achieves CO2 mineralization and hydrogen generation. After hydrogen recovery is completed, the injection well and production well are closed, and the stagnation stage begins. During this stage, CO2 reacts with ultramafic rock and water to generate carbonate minerals, while serpentinization generates new artificial geological hydrogen. The stagnation time will be controlled according to reservoir temperature, pressure conditions, and mineral reaction kinetics to maximize CO2 mineralization and sequestration efficiency. As the mineralization reaction proceeds, some fractures are filled with carbonates, achieving long-term stable CO2 sequestration.

[0029] In this embodiment, when the H2 concentration in the produced gas drops below 50% and the CO2 content rises above 10%, the injection and production wells are shut down, entering the shut-in stage. Under the influence of formation temperature and pressure, CO2 reacts with ultramafic rocks and formation water in the reservoir to generate carbonate minerals such as magnesite and calcite, achieving in-situ mineralization and sequestration of CO2. Simultaneously, serpentinization occurs in the reservoir, releasing new H2 gas. The completion of the reaction is determined by monitoring downhole pressure and geochemical parameters of the produced fluid. The shut-in period is generally 30–90 days. During the reaction, the bottom hole pressure and flowback fluid conductivity, Mg, and other parameters are monitored. 2+ HCO3 - When the rate of change of parameters such as concentration tends to stabilize, the mineralization reaction stage is considered complete.

[0030] Step 6, Synergistic Enhanced Cyclic Operation: After the stalemate time reaches the criterion, the bottom injection well is reopened, and steps 2-5 above are repeated. That is, the cyclic process of "CO2 fracturing and permeability enhancement → CO2 bottom injection displacement → H2 flotation and enrichment → top recovery → stalemate CO2 mineralization and hydrogen production" is executed. In multiple cycles, the geological hydrogen recovery rate is improved and CO2 mineralization and storage are gradually completed.

[0031] Each cycle can sustainably increase reservoir permeability and reactivity, achieving simultaneous improvement in CO2 sequestration capacity and geological hydrogen recovery. After multiple cycles, the reservoir can be partially mineralized and sealed, achieving the goal of long-term CO2 mineralization and sequestration combined with enhanced geological hydrogen extraction.

[0032] This method of synergistic enhancement of CO2 mineralization and sequestration with geological hydrogen can simultaneously improve the recovery rate of geological hydrogen and the efficiency and economy of CO2 sequestration, realizing the cyclical synergistic enhancement of hydrogen energy development and CO2 mineralization and sequestration.

[0033] In the extraction stage, this method addresses the challenges of low permeability and difficulty in recovering geological hydrogen in ultramafic rock reservoirs by injecting CO2 to induce the formation of a multi-level fracture network, thereby increasing reservoir permeability and reaction area. High-density CO2 drives the upward migration and enrichment of low-density H2, which is then extracted by drilling wells at the top of the reservoir. In the well-closing stage, the method relies on the reaction process of CO2-ultramafic rock-water to achieve long-term stable CO2 storage and continuous hydrogen generation, thus supporting the long-term, multi-cycle extraction of geological hydrogen resources.

[0034] This method can also construct a recyclable underground hydrogen harvesting-CO2 storage collaborative operation and mutual enhancement system, realizing the integrated operation of hydrogen development and CO2 storage, significantly improving overall economic efficiency and system efficiency. By embedding the CO2 mineralization and storage process into the hydrogen development process, CO2 storage can be achieved without additional engineering investment, thereby significantly reducing the overall cost of CCUS.

[0035] This method addresses the characteristics of low porosity and low permeability in ultramafic rock reservoirs, where fractures control seepage. It proposes using supercritical CO2 fracturing technology and CO2 displacement to improve reservoir permeability and reaction contact area, thereby enhancing hydrogen generation and recovery efficiency.

[0036] Furthermore, when screening the ultramafic rock reservoirs, the reservoir's geothermal temperature, burial depth, original permeability, pore structure, geological hydrogen occurrence characteristics, and mineral composition are evaluated. Magnesium-iron silicate minerals containing olivine, pyroxene, and serpentine, or basalt rich in magnesium-iron minerals, are selected as rock masses to provide reactants for CO2 mineralization and sequestration and serpentinization hydrogen production.

[0037] Furthermore, the perforated section of the bottom injection well is arranged in the lower 1 / 6 to 1 / 2 section of the target ultramafic rock reservoir thickness, and the perforated section of the top production well is arranged in the upper 1 / 6 to 1 / 2 section of the ultramafic rock reservoir thickness, so as to form a stable CO2 cushion and H2 enrichment zone in the vertical direction, inhibit CO2 from rising to the top production well, thereby reducing the risk of CO2 rising to the top production well.

[0038] Furthermore, the supercritical CO2 injection pressure is higher than the fracture initiation pressure of the ultramafic rock reservoir, and multi-level fracture channels are formed by continuous injection, segmented injection, stepped pressurization and / or pulse injection methods to significantly improve the permeability and inter-well connectivity of the ultramafic rock reservoir.

[0039] Furthermore, before injecting supercritical CO2 into the bottom injection well, water or a solution containing a reaction promoter is injected into the bottom injection well. Subsequently, CO2 and water are injected alternately to expand the contact interface between CO2 and minerals in the ultramafic rock reservoir and enhance the mineralization preservation and displacement effects.

[0040] Furthermore, the well-clogging triggering condition includes at least one of the following: (1) Geological hydrogen production showed a continuous downward trend over time; (2) The amount of hydrogen recovered per unit time is lower than the preset recovery threshold; (3) The CO2 concentration in the gas produced by the top production well increases to above the preset concentration threshold.

[0041] Furthermore, the carbonate minerals generated by the CO2-ultrabasic rock-water reaction include at least magnesium carbonate and calcium carbonate, which fill part of the fractures and pores of the fracture network, thus sealing CO2 in mineral form for a long time, thereby significantly improving the safety and durability of CO2 geological storage.

[0042] Furthermore, the well-sealing time is determined based on one or a combination of the following: (1) During the well closure period, the rate of change of bottom hole pressure drops to the preset pressure threshold and remains stable within a predetermined time. (2) Geochemical parameters of formation fluids at the bottom of the well monitored during the well blockage period (including Mg) 2+ Ca 2+ and HCO3 - The rate of change of the concentration, as well as pH value and conductivity, etc., is reduced to a preset threshold and remains stable within a predetermined time; (3) The well closure time reaches the minimum effective reaction time determined according to the reaction kinetics and does not exceed the preset maximum well closure time.

[0043] This ensures that the CO2-ultrabasic rock-water reaction has sufficient time to proceed, while also preventing the well from being blocked for too long, which would affect the overall development pace.

[0044] Example 2: To further verify the feasibility of CO2 mineralization and hydrogen generation in the "Simulation Experiment Method for Co-enhanced Mining of CO2 and Geological Hydrogen" described in this invention, this example conducts an indoor simulation experiment to evaluate its ability to produce carbonates and release hydrogen after reacting with injected CO2 and water.

[0045] Experiment 1: Since basalt is widely distributed in the shallow crust and is rich in magnesium-iron minerals such as pyroxene and olivine, it is similar to the ultrabasic rock reservoir described in this invention and has good mineralization reaction potential. Therefore, basalt was selected to carry out a 90-day CO2-rock-water reaction experiment.

[0046] The experiment was conducted at 20℃-25℃. Basalt was prepared into powder samples and mixed with CO2-saturated water for a continuous reaction for 90 days. Thermogravimetric analysis (TGA / DTG) and X-ray photoelectron spectroscopy (XPS) were performed on the powder samples before and after the experiment. The hydrogen content during the experiment was also tested to evaluate the formation of carbonates and the release of hydrogen.

[0047] Figure 3 This study demonstrates the H2 production over 7 days via the CO2-rock-water reaction in an experiment. To assess experimental error, each sample was analyzed three times repeatedly, and the relative standard deviation was calculated. The results indicate that basalt can produce H2 at 46.68 ppmd in CO2-saturated water. −1 The average rate of H2 production is 6 days, and the production rate tends to plateau after 6 days.

[0048] Thermogravimetric analysis results are as follows Figure 4 As shown, the sample exhibited a significant weight loss peak at approximately 677°C after the reaction, indicating the occurrence of carbonate thermal decomposition and proving that CO2 was mineralized and fixed during the reaction. The calculated carbonation efficiency was approximately 4.17%, meaning that approximately 41.7 kg of CO2 could be fixed per ton of basalt. Electron probe microanalysis was performed on the basalt powder sample after the reaction, and carbonate minerals (such as...) formed after the CO2-basalt-water reaction were detected. Figure 5 (As shown).

[0049] like Figure 6 As shown, XPS detection results further indicate that the C=O functional group in the sample increased significantly after the reaction, from 6.49% before the reaction to 13.23%, which may be due to the initial CO2 being fixed as carbonate on the basalt surface. At the same time, the proportion of Fe(II) decreased from 54.03% to 28.41%, while the proportion of Fe(III) increased from 45.97% to 71.59%, indicating that ferrous ions participated in the reduction reaction during the reaction, providing an electron source for hydrogen release.

[0050] Experiment 2: To verify the short-cycle carbon fixation and hydrogen production effect of the method described in this invention in ultramafic rocks, a CO2-rock-water reaction experiment was carried out on peridotite samples for 1 day at 50 °C.

[0051] The experiment focused on hydrogen production and the amount of ferrous ions (Fe) under different experimental conditions. 2+The differences in hydrogen content and the CO2 content before and after the reaction were detected. The results showed that the hydrogen production reached 5575 ppm after one day of the CO2-rock-water reaction (e.g., ...). Figure 7 (As shown); without CO2, the Fe in the reaction system 2+ The content was 0.07 Mm, and when CO2 participated in the reaction, Fe 2+ The content increased to 0.23 Mm, indicating that Fe 2+ It participates in the reaction as an electron donor; at the same time, the CO2 content before and after the reaction decreased from 5882 ppm to 2642 ppm (e.g. Figure 8 As shown in the figure, CO2 is consumed and participates in the mineralization process. The above results indicate that CO2 consumption and hydrogen production response can also be achieved in the peridotite system within a short time scale, thereby further verifying the coupling mechanism of the present invention "CO2 mineralization and sequestration and geological hydrogen synergistic enhanced exploitation" and its applicability to ultramafic reservoirs.

[0052] Experiments 1 and 2 demonstrate that the CO2 mineralization and sequestration and geological hydrogen synergistic enhancement mining mechanism proposed in this invention is applicable not only to typical ultramafic rock reservoirs, but also to basalt systems with similar mineral composition and reaction characteristics. This verifies the wide applicability and engineering feasibility of the method in various natural mafic rock masses.

[0053] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for synergistic enhancement of CO2 mineralization and sequestration with geological hydrogen extraction, characterized in that, The method is applied to geological hydrogen reservoirs containing ultramafic rocks, and the method includes the following steps: Screening for ultramafic rock reservoirs rich in mafic minerals, and deploying at least one bottom injection well and at least one top production well in the ultramafic rock reservoir, wherein the perforated section of the bottom injection well is located at the bottom of the ultramafic rock reservoir, and the perforated section of the top production well is located at the top of the ultramafic rock reservoir; Supercritical CO2 is injected into the bottom injection well. By controlling the injection pressure and injection rate, a fracture network is formed in the ultramafic rock reservoir through supercritical CO2 fracturing, so that CO2 preferentially fills the lower space of the ultramafic rock reservoir. CO2 migrates downward in the ultramafic rock reservoir and forms a lower gas cushion. Under the displacement and buoyancy of this lower gas cushion, geological hydrogen is enriched in the upper part of the ultramafic rock reservoir, establishing a migration channel of CO2 sinking and H2 rising. Geological hydrogen enriched in the upper part of the ultrabasic rock reservoir is extracted through the top production well, the production pressure differential is controlled to limit CO2 upwelling, and the composition and production of the produced gas are monitored. Determine whether the well suffocation triggering conditions are met. If not, continue to the previous step. If yes, enter the well suffocation stage. In the well suffocation stage, based on the CO2-ultrabasic rock-water reaction process, CO2 is in-situ mineralized and sealed using carbonate mineralization, and hydrogen is produced using serpentine action, thus realizing CO2 mineralization and sealing and artificial geological hydrogen replenishment. After the stagnation period reaches the criterion, the bottom injection well is reopened, and the above steps are repeated to improve the geological hydrogen recovery rate and gradually complete CO2 mineralization and storage through multiple cycles.

2. The method for CO2 mineralization and sequestration combined with enhanced geological hydrogen extraction according to claim 1, characterized in that, When screening the ultramafic rock reservoirs, the reservoir's geothermal temperature, burial depth, original permeability, pore structure, geological hydrogen occurrence characteristics, and mineral composition are evaluated. Magnesium-iron silicate minerals containing olivine, pyroxene, and serpentine, or basalt rich in magnesium-iron minerals, are selected as the rock mass to provide reactants for CO2 mineralization and sequestration and serpentinization hydrogen production.

3. The method for CO2 mineralization and sequestration combined with enhanced geological hydrogen extraction according to claim 1, characterized in that, The perforated section of the bottom injection well is located in the lower 1 / 6 to 1 / 2 of the thickness of the target ultramafic rock reservoir, and the perforated section of the top production well is located in the upper 1 / 6 to 1 / 2 of the thickness of the ultramafic rock reservoir, so as to form a stable CO2 cushion and H2 enrichment zone in the vertical direction and inhibit CO2 from rising to the top production well.

4. The method for CO2 mineralization and sequestration combined with geological hydrogen synergistic enhancement mining according to claim 1, characterized in that, The supercritical CO2 injection pressure is higher than the fracture initiation pressure of the ultramafic rock reservoir, and multi-level fracture channels are formed by continuous injection, segmented injection, stepped pressurization and / or pulse injection.

5. The method for CO2 mineralization and sequestration combined with enhanced geological hydrogen extraction according to claim 1, characterized in that, Before injecting supercritical CO2 into the bottom injection well, water or a solution containing a reaction promoter is injected into the bottom injection well. Subsequently, CO2 and water are injected alternately to expand the contact interface between CO2 and minerals in the ultramafic rock reservoir and enhance the mineralization preservation and displacement effects.

6. The method for CO2 mineralization and sequestration combined with enhanced geological hydrogen extraction according to claim 1, characterized in that, The well blockage triggering conditions include at least one of the following: (1) Geological hydrogen production showed a continuous downward trend over time; (2) The amount of hydrogen recovered per unit time is lower than the preset recovery threshold; (3) The CO2 concentration in the gas produced by the top production well increases to above the preset concentration threshold.

7. The method for CO2 mineralization and sequestration combined with enhanced geological hydrogen extraction according to claim 1, characterized in that, The carbonate minerals generated by the reaction of CO2 with ultramafic rocks and water include at least magnesium carbonates and calcium carbonates, which fill part of the fractures and pores of the fracture network, thus sealing CO2 in mineral form for a long time.

8. The method for CO2 mineralization and sequestration combined with enhanced geological hydrogen extraction according to claim 1, characterized in that, The well stagnation time is determined according to one or a combination of the following: (1) During the well closure period, the rate of change of bottom hole pressure drops to the preset pressure threshold and remains stable within a predetermined time. (2) During the well stagnation period, the rate of change of geochemical parameters of formation fluid at the bottom of the well monitored decreased to the preset threshold and remained stable within a predetermined time. (3) The well closure time reaches the minimum effective reaction time determined according to the reaction kinetics and does not exceed the preset maximum well closure time.

9. The method for CO2 mineralization and sequestration combined with enhanced geological hydrogen extraction according to claim 8, characterized in that, The chemical parameters include at least Mg. 2+ Ca 2+ and HCO3 - The concentration, pH value, and conductivity.

10. A simulation experiment method for CO2 mineralization and sequestration combined with geological hydrogen synergistic enhancement, used to verify the method for CO2 mineralization and sequestration combined with geological hydrogen synergistic enhancement as described in any one of claims 1-9, characterized in that, The simulation experiment method includes at least the following: Basalt was selected, and a CO2-rock-water reaction experiment was carried out at 20℃-25℃ for a duration of no less than 90 days. Basalt was made into powder samples and mixed with CO2-saturated water for continuous reaction for 90 days. Thermogravimetric analysis and X-ray photoelectron spectroscopy were performed on the powder samples before and after the experiment. At the same time, the hydrogen content during the experiment was tested to evaluate the formation of carbonates and the release of hydrogen. Peridotite was selected, and a CO2-rock-water reaction experiment was carried out at 50℃ for one day. Peridotite was made into a powder sample and mixed with CO2-saturated water for continuous reaction. During the experiment, the hydrogen production, the difference in ferrous ion content, and the CO2 content before and after the reaction were detected.

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