Hydrogen-rock microfluidic in-situ testing system and method for simulating underground hydrogen storage

Abstract

The invention relates to a hydrogen-rock microfluidic in-situ test system and method for simulating underground hydrogen storage. The system comprises an environment control module, a reaction type microfluidic chip, a fluid injection module, a back pressure control module, an in-situ test module and a gas chromatographic analysis module, the environment control module provides a high-temperature and high-pressure environment; the reaction type micro-fluidic chip is arranged in the environment control module and provides a hydrogen-rock reaction place; the inlet end of the reaction type micro-fluidic chip is connected with the fluid injection module, and the outlet end of the reaction type micro-fluidic chip is sequentially connected with the back pressure control module and the gas chromatographic analysis module; the back pressure control module is used for maintaining a preset pressure environment; the in-situ test module is used for capturing fluid distribution and mineral form change in the chip; and the gas chromatographic analysis module is used for analyzing the composition and concentration change of a reaction outlet gas-phase product. According to the device and the method, the micromorphological evolution and the macroscopic reaction rate of the hydrogen-rock reaction in the underground reservoir environment are synchronously monitored, and an accurate experimental means is provided for geological hydrogen storage safety evaluation.

Description

Technical Field

[0001] This invention relates to the field of geochemical engineering and testing technology for underground hydrogen storage (UHS), and particularly to a hydrogen-rock microfluidic in-situ testing system and method for simulating underground hydrogen storage. Background Technology

[0002] With the advancement of energy transition, underground hydrogen storage (UHS) has become a key technology for addressing the volatility of renewable energy and the challenges of large-scale energy storage. Its core principle is to inject hydrogen into depleted oil and gas reservoirs, aquifers, and other porous underground media for long-term storage. However, as a highly reactive reducing agent, hydrogen, once injected underground, readily undergoes geochemical reactions with rocks and minerals (such as pyrite, hematite, and carbonate rocks) and formation fluids in the reservoir. This can lead to mineral dissolution and precipitation, altering reservoir porosity and permeability, and even compromising the sealing of the caprock. Furthermore, it may generate hazardous byproducts such as H2S, severely impacting the safety and efficiency of hydrogen storage.

[0003] Existing techniques for studying hydrogen-rock reactions have the following main drawbacks: 1. "Black box" operation, lack of visualization: Traditional high temperature and high pressure reactors and core displacement experiments can only infer the reaction mechanism through the analysis of rock morphology (such as SEM scanning) and fluid properties before and after the reaction. They cannot capture dynamic processes such as mineral dissolution / precipitation and pore throat blockage, and it is difficult to establish the relationship between the reaction location and the degree of reaction. 2. Long experimental cycle and high consumption: Macroscopic experiments require several weeks or even months to reach reaction equilibrium, and consume a large amount of core samples and hydrogen, which is costly and poses a safety hazard of high-pressure hydrogen leakage. 3. Incomplete environmental simulation: The static high-temperature and high-pressure reactor experiment ignores the influence of fluid flow on the reaction rate (the competition between convection and diffusion), making it difficult to reproduce the dynamic seepage scenario of hydrogen injection / extraction. 4. Limited Monitoring Dimensions: Existing high-temperature, high-pressure microfluidic systems focus solely on observing fluid distribution or morphological changes in mineral "disappearance / formation" using optical microscopes, lacking the capability for precise, real-time online analysis of reaction effluents. While simple optical observation can tell researchers that "a change has occurred," it cannot accurately quantify the hydrogen consumption rate or determine what gaseous byproducts have been generated (especially in the early stages of a reaction when byproduct yields are extremely low). The lack of macroscopic quantitative chemical information makes it difficult to effectively translate microscopic morphological observations into macroscopic hydrogen-rock reaction rate models. Summary of the Invention

[0004] This invention provides a hydrogen-rock microfluidic in-situ testing system and method for simulating underground hydrogen storage, in order to solve the above-mentioned technical problems.

[0005] To address the aforementioned technical problems, this invention provides a hydrogen-rock microfluidic in-situ testing system for simulating underground hydrogen storage, comprising an environmental control module, a reactive microfluidic chip, a fluid injection module, a back pressure control module, an in-situ testing module, and a gas chromatography analysis module. The reactive microfluidic chip is placed within the environmental control module, which provides the reactive microfluidic chip with a simulated high-temperature and high-pressure environment of an underground reservoir; the reactive microfluidic chip provides a hydrogen-rock reaction site through its built-in simulated pore structure; The fluid injection module is connected to the inlet end of the reactive microfluidic chip, and the outlet end of the reactive microfluidic chip is sequentially connected to the back pressure control module and the gas chromatography analysis module; the back pressure control module is used to maintain a preset pressure environment within the reactive microfluidic chip; The in-situ testing module is used to capture the fluid distribution and mineral morphology changes within the reactive microfluidic chip in real time through the visualization structure of the environmental control module; the gas chromatography analysis module is used for online quantitative analysis of the composition and concentration changes of the gaseous products at the reaction outlet.

[0006] Preferably, the reactive microfluidic chip adopts a "glass-mineral-glass" sandwich bonding structure, the simulated pore structure is a simulated porous media network channel, the simulated porous media network channel is embedded with reservoir characteristic mineral matrix or real reservoir core slices, and transverse irregular fracture channels are constructed in the middle of the core slices.

[0007] Preferably, the fluid injection module includes a set of injection pumps, three sets of intermediate containers, a gas mass flow meter, and a miniature check valve; The three sets of intermediate containers are used to store and inject high-purity hydrogen, simulated formation water, and other reaction fluids, respectively. The injection pump is connected to the intermediate container to control the fluid injection rate; the miniature one-way valve is installed in the pipeline to prevent fluid backflow; and the gas mass flow meter is used to regulate the gas-liquid injection ratio.

[0008] Preferably, the environmental control module includes a transparent microfluidic high-temperature and high-pressure reactor, a heating jacket, and a heat preservation system; The microfluidic high-temperature and high-pressure reactor uses a sapphire window as the visualization structure and has a high-pressure clamping chamber for installing the reactive microfluidic chip. It can withstand fluid pressure of 0-70MPa and provide a constant temperature environment of 20-150℃. The heating jacket is wrapped around the outside of the intermediate container and has a built-in temperature controller and temperature sensor. The insulation system is wrapped around the outside of the intermediate container and the reactants to maintain stable temperature and pressure.

[0009] Preferably, the in-situ testing module includes a microscope and a CCD camera; The microscope employs a long working distance objective lens, positioned above the visualization structure of the environmental control module, and focuses on the porous layer of the reactive microfluidic chip. The CCD camera is installed at the optical path exit of the microscope and connected to a computer image acquisition card. It is used to capture and record in real time the transient changes of fluid and the evolution of mineral morphology within the reactive microfluidic chip.

[0010] Preferably, the back pressure control module includes a back pressure / constant pressure tracking pump, a back pressure valve, a back pressure pump, and a differential pressure sensor; The back pressure / constant pressure tracking pump is connected to the confining pressure interface of the environmental control module to provide confining pressure and automatically track it, so that the confining pressure is always 2-3 MPa higher than the fluid displacement pressure inside the reactive microfluidic chip. The back pressure valve is installed on the fluid outlet pipeline of the reactive microfluidic chip to establish and maintain the internal pore fluid pressure of the reactive microfluidic chip. The high-pressure end of the differential pressure sensor is connected to the inlet pipe of the reactive microfluidic chip, and the low-pressure end is connected to the outlet pipe, which is used to monitor the pressure drop change when the fluid flows through the porous medium in real time.

[0011] Preferably, the gas chromatography analysis module includes a miniature gas-liquid separator and an online gas chromatograph; The miniature gas-liquid separator is located downstream of the back pressure valve of the back pressure control module and is used to separate the gas and liquid of the depressurized fluid. The online gas chromatograph is connected to the micro gas-liquid separator via an automated sampling line and is equipped with a highly sensitive detector for hydrogen and potential byproducts.

[0012] This invention also provides an in-situ hydrogen-rock microfluidic testing method for simulating underground hydrogen storage, applied to the above-mentioned system, comprising the following steps: Step 1: Chip pretreatment: The reactive microfluidic chip is evacuated and saturated with simulated formation water; Step 2: Initial state scan: The reactive microfluidic chip is optically scanned using the in-situ testing module to record the initial pore structure and mineral morphology; Step 3: Reaction environment setup: The system is heated and pressurized to the set underground reservoir simulation conditions through the environmental control module, with a temperature range of 20-150℃ and a pressure range of 0-70MPa; Step 4: Reactive fluid injection: Hydrogen gas is injected at a predetermined rate through the fluid injection module to displace the simulated formation water inside the reactive microfluidic chip, forming a gas-liquid two-phase coexistence environment; Step 5: Dynamic testing and observation: The reaction is carried out using either a static or dynamic reaction mode. At set time intervals, the in-situ testing module automatically acquires images of the reactive microfluidic chip, while the gas chromatography analysis module continuously monitors the changes in the composition and concentration of the outlet gas. Step 6: Data processing and analysis: Calculate the rate of change of mineral morphology over time using image processing algorithms, combine the detection data from the gas chromatography analysis module, evaluate the reaction kinetic parameters, and construct a correlation model of "microscopic morphological evolution - macroscopic reaction rate".

[0013] Preferably, in step 5, the static reaction mode is to stop injecting fluid, and the dynamic reaction mode is to maintain an extremely low flow rate when injecting fluid.

[0014] Preferably, in step 6, the reaction kinetic parameters include at least the hydrogen consumption rate, the mineral dissolution / precipitation rate, and the gaseous byproduct formation rate.

[0015] Compared with existing technologies, the hydrogen-rock microfluidic in-situ testing system and method for simulating underground hydrogen storage provided by this invention has the following advantages: 1. Real-time linkage monitoring between micro and macro scales: In the underground hydrogen storage simulation experiment, this invention realizes the combined use of in-situ morphological observation (microscope) at the micropore scale and quantitative chemical analysis (gas chromatography) of macro effluent within the same high-pressure microfluidic system. This solves the technical bottleneck of traditional experiments that "can see morphological changes but cannot accurately quantify reaction rates" and establishes a direct correlation between "micromorphological evolution and macro reaction rate". 2. In-situ dynamic monitoring under real-world conditions: This invention employs a microfluidic chip embedded with real core slices or reservoir characteristic mineral matrix, combined with a high-temperature and high-pressure resistant visual reactor, to fully reproduce the temperature and pressure conditions and seepage environment of the underground reservoir, ensuring the geological authenticity of the reaction. Leveraging the non-destructive observation advantages of a microscope, the dynamic process of the hydrogen-rock reaction can be captured in real time, avoiding the limitations of traditional experiments that only compare the reaction before and after, and achieving uninterrupted monitoring throughout the entire process. 3. Precise quantification of hydrogen loss and safety risks: This invention integrates an online micro gas chromatography analysis module, which can accurately detect changes in the composition of the gas flowing out of the reaction, accurately calculate the amount of irreversible hydrogen loss caused by geochemical reactions, and at the same time capture the generation and concentration changes of trace amounts of hazardous byproducts such as H2S in a timely manner, providing key data support for the safety evaluation of underground hydrogen storage facilities and helping to build a risk early warning system. 4. Significant advantages of high throughput and low consumption: Based on the characteristics of microfluidic technology, the experiment only requires microliter-level fluid and milligram-level rock samples, which shortens the reaction equilibrium time and greatly reduces sample consumption and experimental costs. Compared with the cycle of several weeks of traditional macroscopic experiments, the efficiency is significantly improved, making it suitable for rapid screening and evaluation of reservoir rocks of different strata and lithologies. 5. High experimental safety: The hydrogen content inside the microfluidic chip is extremely low. Even if a leak occurs under high temperature and high pressure experimental conditions, it will not cause safety accidents such as explosion. It is particularly suitable for conventional laboratory environments such as universities and research institutes, which lowers the threshold for technology promotion and application. Attached Figure Description

[0016] Figure 1 This is a system block diagram of a hydrogen-rock microfluidic in-situ testing system for simulating underground hydrogen storage in a specific embodiment of the present invention. Figure 2 This is a schematic diagram of the hardware structure of a hydrogen-rock microfluidic in-situ testing system for simulating underground hydrogen storage in a specific embodiment of the present invention. Figure 3 This is a schematic diagram of the structure of a reactive microfluidic chip in a specific embodiment of the present invention; Figure 4 This is a longitudinal cross-sectional view of a reactive microfluidic chip in a specific embodiment of the present invention.

[0017] In the diagram: 10-Environmental control module, 11-Microfluidic high-temperature and high-pressure reactor, 12-High-pressure clamping chamber, 20-Reactive microfluidic chip, 21-Simulated porous media network channel, 22-Core slice, 23-Fracture channel, 24-Glass substrate, 25-Glass cover, 30-Fluid injection module, 31-Injection pump, 32-Intermediate container, 33-Gas pressurization system, 40-Back pressure control module, 41-Back pressure / constant pressure tracking pump, 50-In-situ testing module, 60-Gas chromatography analysis module, 61-Online gas chromatograph. Detailed Implementation

[0018] To illustrate the technical solutions of the invention in more detail, specific embodiments are listed below to demonstrate the technical effects; it should be emphasized that these embodiments are used to illustrate the invention and not to limit the scope of the invention.

[0019] The present invention provides a hydrogen-rock microfluidic in-situ testing system for simulating underground hydrogen storage, such as... Figures 1 to 4 As shown, it includes an environmental control module 10, a reactive microfluidic chip 20, a fluid injection module 30, a back pressure control module 40, an in-situ testing module 50, and a gas chromatography analysis module 60, wherein: The reactive microfluidic chip 20 is placed inside the environmental control module 10, which provides the reactive microfluidic chip 20 with a simulated high-temperature and high-pressure environment of an underground reservoir. The reactive microfluidic chip 20 provides a hydrogen-rock reaction site through its built-in simulated pore structure. The fluid injection module 30 is connected to the inlet end of the reactive microfluidic chip 20, and the outlet end of the reactive microfluidic chip 20 is sequentially connected to the back pressure control module 40 and the gas chromatography analysis module 60; the back pressure control module 40 is used to maintain a preset pressure environment within the reactive microfluidic chip 20; The in-situ testing module 50 is used to capture the fluid distribution and mineral morphology changes within the reactive microfluidic chip 20 in real time through the visualization structure of the environmental control module 10; the gas chromatography analysis module 60 is used for online quantitative analysis of the composition and concentration changes of the gas phase products at the reaction outlet.

[0020] This invention employs an in-situ testing module 50 to penetrate the environmental control module 10 for microscopic observation, and a gas chromatography analysis module 60 to monitor gaseous products. The two are monitored synchronously to achieve real-time correlation between "microscopic morphological evolution and macroscopic product concentration changes," thus solving the technical problem that traditional offline testing methods cannot capture dynamic reaction processes.

[0021] In some embodiments, please refer to the following: Figure 3 and Figure 4 The reactive microfluidic chip 20 adopts a "glass-mineral-glass" sandwich bonding structure. The simulated pore structure is a simulated porous media network channel 21. The simulated porous media network channel 21 embeds reservoir characteristic mineral matrix (such as calcite, pyrite, etc.) or real reservoir core slices 22, and constructs transverse irregular fracture channels 23 in the core slices 22 to simulate natural fracture morphology. Figure 4 As shown, the sandwich structure of the reactive microfluidic chip 20 is composed of an upper glass cover plate 25, a middle core slice 22, and a lower glass substrate 24 bonded together. The simulated porous media network channel 21 is an etched channel on the surface of the glass substrate 24, which is used to carry the fluid and connect the crack channel 23 of the core slice 22, so that the fluid can fully contact the core slice 22.

[0022] In some embodiments, please refer to the following: Figure 2 The fluid injection module 30 includes a set of high-precision injection pumps 31, three sets of intermediate containers 32, a gas mass flow meter, and a miniature one-way valve, responsible for the injection, transport, and precise control of pore pressure of the experimental fluid. Wherein: The three intermediate containers 32 are used to store and inject high-purity hydrogen, simulated formation water (salt water), and other reaction fluids (such as corrosion inhibitor solutions). Specifically, a gas pressurization system 33 needs to be connected between the high-purity hydrogen storage device and the corresponding intermediate container 32 to pressurize the hydrogen to a preset pressure and then send it into the corresponding intermediate container 32.

[0023] The injection pump 31 is connected to the intermediate container 32 and is a high-precision dual-plunger pump, connected to the bottom of each intermediate container 32 respectively, for controlling the fluid injection rate. The injection pump 31 is configured to deliver multiple media such as oil, water, and gas, and can smoothly inject fluid into the reactive microfluidic chip 20 at an extremely low flow rate. The miniature one-way valve is set in the pipeline to prevent fluid backflow; the gas mass flow meter is used to regulate the gas-liquid injection ratio (e.g., simulating the contact between the cushion gas and formation water).

[0024] This embodiment uses a combination of a high-precision injection pump 31 and a gas mass flow meter to achieve nanoliter-level microfluidic injection, meeting the low flow rate requirements of microfluidic chips.

[0025] In some embodiments, the environmental control module 10 includes a transparent microfluidic high-temperature and high-pressure reactor 11, a heating jacket, and a heat preservation system. As the core reaction vessel of the entire system, the shell of the microfluidic high-temperature and high-pressure reactor 11 can be made of corrosion-resistant high-strength alloy steel.

[0026] Specifically, the microfluidic high-temperature and high-pressure reactor 11 uses a sapphire window as the visualization structure to provide a visualization optical path channel; it is equipped with a high-pressure clamping chamber 12 for installing the reactive microfluidic chip 20, which can withstand 0-70MPa fluid pressure and provide a constant temperature environment of 20-150℃, fully covering the real environmental conditions of underground hydrogen storage projects.

[0027] The heating jacket is wrapped around the outside of the intermediate container 32 and has a built-in temperature controller and a high-precision temperature sensor. The insulation system (such as the insulation jacket) is wrapped around the outside of the intermediate container 32 and the reactants to maintain stable temperature and pressure, and is consistent with the microfluidic high-temperature and high-pressure reactor 11. The insulation system can ensure that there is no thermal convection interference in the viewing window area and prevent the lens from fogging.

[0028] In some embodiments, the in-situ testing module 50 includes a high-resolution microscope and a high-speed CCD camera to capture the mineral dissolution or expansion phenomena caused by the hydrogen-mineral reaction, thereby achieving optical monitoring.

[0029] Specifically, the microscope employs a long working distance objective (working distance ≥ 20 mm), positioned above the visualization structure of the environmental control module 10, and focuses on the porous layer of the reactive microfluidic chip 20. Because the viewing window and wall thickness of the microfluidic high-temperature and high-pressure reactor 11 are relatively thick, ordinary microscopes do not provide good focusing. Therefore, this embodiment uses a long working distance (LWD) objective, enabling it to clearly focus on the porous layer of the reactive microfluidic chip 20 inside the reactor body through the thick-walled sapphire viewing window, achieving an imaging accuracy of 2.8 μm.

[0030] The CCD camera is installed at the optical path outlet of the microscope and connected to a computer image acquisition card. It is used to capture and record the transient changes of fluid and the evolution of mineral morphology within the reactive microfluidic chip 20 in real time.

[0031] In this embodiment, a long working distance objective lens is used to adapt to the thickness of the sapphire window of the microfluidic high-temperature and high-pressure reactor 11, so as to achieve in-situ observation without damaging the reactor structure; the high-speed CCD camera can capture the fluid movement dynamics at the millisecond level and record the instantaneous reaction process.

[0032] In some embodiments, the back pressure control module 40 includes a back pressure / constant pressure tracking pump 41, a high-precision back pressure valve (BPR), a back pressure pump, and a high-precision differential pressure sensor.

[0033] The back pressure / constant pressure tracking pump 41 is connected to the confining pressure interface of the microfluidic high-temperature and high-pressure reactor 11 of the environmental control module 10. It is used to provide confining pressure and automatically track it so that the confining pressure is always 2-3 MPa higher than the internal fluid displacement pressure of the reactive microfluidic chip 20, preventing the reactive microfluidic chip 20 from rupturing due to excessive internal and external pressure difference.

[0034] The back pressure valve is located on the fluid outlet pipe of the reactive microfluidic chip 20 to establish and maintain the pore pressure inside the chip, ensuring that carbon dioxide remains in a supercritical high-pressure state throughout the experiment. The back pressure pump works in conjunction with the back pressure valve or is connected to the waste liquid recovery end to assist in regulating the stability of the outlet pressure, eliminating pressure pulsations, and ensuring a smooth displacement process. The high-pressure side of the differential pressure sensor is connected to the inlet pipe of the reactive microfluidic chip 20, and the low-pressure side is connected to the outlet pipe. It is used to monitor the pressure drop changes as the fluid flows through the porous medium in real time, with a range of 1000 psi and an accuracy better than 0.1%, facilitating the calculation of seepage resistance.

[0035] In some embodiments, the gas chromatography analysis module 60 includes a micro gas-liquid separator and an online gas chromatograph 61. The reacted gas is passed into the online gas chromatograph 61 to monitor the consumption of hydrogen and the generation of other gases, thereby completing gas phase monitoring.

[0036] Specifically, the micro gas-liquid separator is located downstream of the back pressure valve of the back pressure control module 40. The outlet fluid enters the separator after being depressurized by the back pressure valve. Separation is achieved by utilizing the gas-liquid density difference. The separated gas enters the online gas chromatograph (Micro-GC) 61 through the automatic sampling pipeline, while the liquid is collected in the waste liquid bottle.

[0037] The online gas chromatograph 61 is connected to the micro gas-liquid separator via an automatic sampling line. The online gas chromatograph 61 is also equipped with a highly sensitive detector for hydrogen and potential byproducts (such as H2S, CH4, etc.). Through rapid, periodic, and automatic sampling, it accurately quantifies the unreacted H2 content in the outlet fluid and monitors whether new gas components are generated and their concentration changes over time, thereby calculating the geochemical consumption rate of hydrogen.

[0038] This invention also provides an in-situ hydrogen-rock microfluidic testing method for simulating underground hydrogen storage, applied to the above-mentioned system, comprising the following steps: Step 1: Chip pretreatment: The reactive microfluidic chip 20 is evacuated and saturated with simulated formation water.

[0039] Step 2: Initial state scan: The reactive microfluidic chip 20 is optically scanned by the in-situ testing module 50 to record the initial pore structure and mineral morphology as baseline data.

[0040] Step 3: Reaction Environment Setup: The system is heated and pressurized to the set underground reservoir simulation conditions using the environmental control module 10. The temperature range is 20-150°C, and the pressure range is 0-70 MPa. In this embodiment, 40°C and 10 MPa are used. Specifically, the temperature control system of the environmental control module 10 heats the reactor to the set temperature; the back pressure / constant pressure tracking pump 41 applies confining pressure; and the back pressure valve sets the internal pore pressure of the chip to simulate the temperature and pressure conditions of the target reservoir.

[0041] Step 4: Reaction fluid injection: Hydrogen gas is injected at a predetermined rate through the fluid injection module 30 to displace the simulated formation water inside the reactive microfluidic chip 20, forming a gas-liquid two-phase coexistence environment. The amount of hydrogen injected is monitored in real time by a gas mass flow meter.

[0042] Step 5: Dynamic Testing and Observation: The reaction is conducted using either a static reaction mode (injection stopped) or a dynamic reaction mode (maintaining an extremely low flow rate). At set time intervals (e.g., every hour), images within the reactive microfluidic chip 20 are automatically acquired by the in-situ testing module 50, while the gas chromatography analysis module 60 continuously monitors changes in the composition and concentration of the outlet gas. Specifically, for the static reaction mode: the syringe pump 31 is turned off, the injection fluid is stopped, and the temperature and pressure conditions are maintained. Images are acquired every 30 minutes via the in-situ testing module 50, and the outlet gas composition is detected by the gas chromatography analysis module 60. For the dynamic reaction mode: hydrogen is injected at an extremely low flow rate (e.g., 0.01 mL / min) using the syringe pump 31, and changes in images and gas composition are continuously monitored.

[0043] Step 6: Data Processing and Analysis: Calculate the rate of change of mineral morphology over time using image processing algorithms, and combine the detection data from the gas chromatography analysis module 60 to evaluate reaction kinetic parameters (hydrogen consumption rate, mineral dissolution / precipitation rate, and gaseous byproduct generation rate, etc.) and construct a correlation model of "microscopic morphological evolution - macroscopic reaction rate".

[0044] The following section investigates the H2S generation reaction induced by hydrogen injection into anhydrite (CaSO4) carbonate reservoir. The specific experimental procedure is as follows: Preparation: Fabricate a reactive microfluidic chip 20 containing real anhydrite mineral particles and calcite matrix, and load the reactive microfluidic chip 20 into a microfluidic high-temperature and high-pressure reactor 11 with a sapphire window.

[0045] Parameter settings: Heat the microfluidic high-temperature and high-pressure reactor 11 to 90°C, and maintain the system pressure at 15 MPa through the back pressure valve.

[0046] Initial state: The chip was saturated with simulated formation water (saltwater). Under a microscope, anhydrite particles (long columnar or plate-like) were clearly observed embedded in the matrix, and the initial image was recorded.

[0047] Reaction process: High-purity hydrogen gas is continuously injected at an extremely low flow rate to displace the brine.

[0048] Microscopic observation: After the reaction had proceeded for several hours to tens of hours, under an optical microscope, the edges of the anhydrite particles gradually became rough and blurred, and the overall volume of the particles gradually decreased over time, indicating that a dissolution reaction had occurred. Simultaneously, the distribution changes of the gas and water phases were observed.

[0049] Online chromatographic analysis: After the reaction begins, the online gas chromatograph 61 automatically samples and analyzes the outlet gas at regular intervals (1 hour). Initially, the outlet gas mainly consists of background gases present before displacement. As hydrogen breaks through, the online gas chromatograph 61 detects a high concentration of H2. After the reaction has proceeded for some time, the sulfur-sensitive detector channel of the online gas chromatograph 61 begins to detect trace amounts of H2S gas signals, and its concentration slowly increases over time, indicating that the hydrogen reduction of anhydrite is underway.

[0050] Through the combined analysis described above, microscopy provided direct evidence and locational information of the dissolution of anhydrite minerals, while online gas chromatography-61 provided precise quantitative data on the H2S generation rate. Together, these methods fully revealed the dynamic process and potential risks of the reaction between hydrogen and anhydrite under these temperature and pressure conditions.

[0051] In summary, the hydrogen-rock microfluidic in-situ testing system and method for simulating underground hydrogen storage provided by this invention constructs a realistic reservoir temperature and pressure environment through the environmental control module 10, realizes the in-situ reaction of hydrogen-rock using the reactive microfluidic chip 20, and obtains microscopic morphology and macroscopic quantitative data by combining the in-situ testing module 50 and the gas chromatography analysis module 60. This solves the technical problem that traditional testing methods are difficult to simultaneously observe the reaction process and quantitatively analyze the products, and provides a precise experimental means for assessing the safety and effectiveness of underground hydrogen storage.

[0052] Obviously, those skilled in the art can make various modifications and variations to the invention without departing from the spirit and scope of the invention. Therefore, if these modifications and variations fall within the scope of the claims of the invention and their equivalents, the invention is also intended to include these modifications and variations.

Claims

1. A hydrogen-rock microfluidic in-situ testing system for simulating underground hydrogen storage, characterized in that, It includes an environmental control module, a reactive microfluidic chip, a fluid injection module, a back pressure control module, an in-situ testing module, and a gas chromatography analysis module; The reactive microfluidic chip is placed within the environmental control module, which provides the reactive microfluidic chip with a simulated high-temperature and high-pressure environment of an underground reservoir; the reactive microfluidic chip provides a hydrogen-rock reaction site through its built-in simulated pore structure; The fluid injection module is connected to the inlet end of the reactive microfluidic chip, and the outlet end of the reactive microfluidic chip is sequentially connected to the back pressure control module and the gas chromatography analysis module; the back pressure control module is used to maintain a preset pressure environment within the reactive microfluidic chip; The in-situ testing module is used to capture the fluid distribution and mineral morphology changes within the reactive microfluidic chip in real time through the visualization structure of the environmental control module; the gas chromatography analysis module is used for online quantitative analysis of the composition and concentration changes of the gaseous products at the reaction outlet.

2. The hydrogen-rock microfluidic in-situ testing system for simulating underground hydrogen storage as described in claim 1, characterized in that, The reactive microfluidic chip adopts a "glass-mineral-glass" sandwich bonding structure. The simulated pore structure is a simulated porous media network channel. The simulated porous media network channel is embedded with reservoir characteristic mineral matrix or real reservoir core slices, and transverse irregular fracture channels are constructed in the middle of the core slices.

3. The hydrogen-rock microfluidic in-situ testing system for simulating underground hydrogen storage as described in claim 1, characterized in that, The fluid injection module includes a set of injection pumps, three sets of intermediate containers, a gas mass flow meter, and a miniature check valve. The three sets of intermediate containers are used to store and inject high-purity hydrogen, simulated formation water, and other reaction fluids, respectively. The injection pump is connected to the intermediate container to control the fluid injection rate; the miniature one-way valve is installed in the pipeline to prevent fluid backflow; and the gas mass flow meter is used to regulate the gas-liquid injection ratio.

4. The hydrogen-rock microfluidic in-situ testing system for simulating underground hydrogen storage as described in claim 3, characterized in that, The environmental control module includes a transparent microfluidic high-temperature and high-pressure reactor, a heating jacket, and a heat preservation system; The microfluidic high-temperature and high-pressure reactor uses a sapphire window as the visualization structure and has a high-pressure clamping chamber for installing the reactive microfluidic chip. It can withstand fluid pressure of 0-70MPa and provide a constant temperature environment of 20-150℃. The heating jacket is wrapped around the outside of the intermediate container and has a built-in temperature controller and temperature sensor. The insulation system is wrapped around the outside of the intermediate container and the reactants to maintain stable temperature and pressure.

5. The hydrogen-rock microfluidic in-situ testing system for simulating underground hydrogen storage as described in claim 1, characterized in that, The in-situ testing module includes a microscope and a CCD camera; The microscope employs a long working distance objective lens, positioned above the visualization structure of the environmental control module, and focuses on the porous layer of the reactive microfluidic chip. The CCD camera is installed at the optical path exit of the microscope and connected to a computer image acquisition card. It is used to capture and record in real time the transient changes of fluid and the evolution of mineral morphology within the reactive microfluidic chip.

6. The hydrogen-rock microfluidic in-situ testing system for simulating underground hydrogen storage as described in claim 1, characterized in that, The back pressure control module includes a back pressure / constant pressure tracking pump, a back pressure valve, a back pressure pump, and a differential pressure sensor. The back pressure / constant pressure tracking pump is connected to the confining pressure interface of the environmental control module to provide confining pressure and automatically track it, so that the confining pressure is always 2-3 MPa higher than the fluid displacement pressure inside the reactive microfluidic chip. The back pressure valve is installed on the fluid outlet pipeline of the reactive microfluidic chip to establish and maintain the internal pore fluid pressure of the reactive microfluidic chip. The high-pressure end of the differential pressure sensor is connected to the inlet pipe of the reactive microfluidic chip, and the low-pressure end is connected to the outlet pipe, which is used to monitor the pressure drop change when the fluid flows through the porous medium in real time.

7. The hydrogen-rock microfluidic in-situ testing system for simulating underground hydrogen storage as described in claim 6, characterized in that, The gas chromatography analysis module includes a miniature gas-liquid separator and an online gas chromatograph; The miniature gas-liquid separator is located downstream of the back pressure valve of the back pressure control module and is used to separate the gas and liquid of the depressurized fluid. The online gas chromatograph is connected to the micro gas-liquid separator via an automated sampling line and is equipped with a highly sensitive detector for hydrogen and potential byproducts.

8. A method for in-situ microfluidic testing of hydrogen-rock microfluidics to simulate underground hydrogen storage, characterized in that, The system applied to any one of claims 1-7 comprises the following steps: Step 1: Chip pretreatment: The reactive microfluidic chip is evacuated and saturated with simulated formation water; Step 2: Initial state scan: The reactive microfluidic chip is optically scanned using the in-situ testing module to record the initial pore structure and mineral morphology; Step 3: Reaction environment setup: The system is heated and pressurized to the set underground reservoir simulation conditions through the environmental control module, with a temperature range of 20-150℃ and a pressure range of 0-70MPa; Step 4: Reactive fluid injection: Hydrogen gas is injected at a predetermined rate through the fluid injection module to displace the simulated formation water inside the reactive microfluidic chip, forming a gas-liquid two-phase coexistence environment; Step 5: Dynamic testing and observation: The reaction is carried out using either a static or dynamic reaction mode. At set time intervals, the in-situ testing module automatically acquires images of the reactive microfluidic chip, while the gas chromatography analysis module continuously monitors the changes in the composition and concentration of the outlet gas. Step 6: Data processing and analysis: Calculate the rate of change of mineral morphology over time using image processing algorithms, combine the detection data from the gas chromatography analysis module, evaluate the reaction kinetic parameters, and construct a correlation model of "microscopic morphological evolution - macroscopic reaction rate".

9. The in-situ hydrogen-rock microfluidic testing method for simulating underground hydrogen storage as described in claim 8, characterized in that, In step 5, the static reaction mode is to stop injecting fluid, and the dynamic reaction mode is to maintain an extremely low flow rate when injecting fluid.

10. The in-situ hydrogen-rock microfluidic testing method for simulating underground hydrogen storage as described in claim 8, characterized in that, In step 6, the reaction kinetic parameters include at least the hydrogen consumption rate, the mineral dissolution / precipitation rate, and the gaseous byproduct formation rate.

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