Submicron analysis method and device for quantitatively evaluating hydrogen sealing capacity of caprock

Abstract

The application provides a sub-micron analysis method and device for quantitatively evaluating hydrogen sealing capacity of a cap rock. The analysis method comprises the following steps: hydrogen saturation treatment is performed on a sample sheet in a micro temperature and pressure reaction pool; the reaction pool is kept sealed, and the whole is integrally transferred to a micro combined device in a fluid state in situ; infrared and Raman spectra of a target micro area are synchronously collected through a window; spatial correlation is performed on hydrogen characteristic peaks of the Raman spectrum and mineral change characteristic peaks of the infrared spectrum, and a direct evidence chain of hydrogen entry and mineral chemical change is established. The application realizes direct, non-destructive and quantitative evaluation of the interaction between hydrogen and the cap rock mineral under in-situ conditions, and greatly improves the accuracy of the evaluation of the hydrogen sealing capacity of the cap rock.

Description

Technical Field

[0001] This invention relates to the field of geological energy evaluation and microscopic analysis technology, specifically to a submicron analysis method and apparatus for quantitatively evaluating the hydrogen sequestration capacity of caprocks. Background Technology

[0002] Underground hydrogen storage is a key technology for achieving large-scale, long-term energy storage. The sealing capacity of the caprock is the primary factor determining whether hydrogen can be safely stored for a long period. Because hydrogen molecules are extremely small, they can easily escape through nanoscale pores and microcracks in the caprock; at the same time, hydrogen has reducing properties and may react chemically with caprock minerals under high temperature and high pressure reservoir conditions, altering the pore structure and affecting long-term sealing performance.

[0003] Currently, the main methods for evaluating the sealing capacity of caprocks are whole-core permeability measurement and conventional petrographic observation. While permeability measurement can provide macroscopic seepage parameters, it cannot reveal the location, migration path, and microscopic chemical reactions of hydrogen in micro- and nano-scale pores. Conventional scanning electron microscopy or X-ray diffraction requires destructive sample preparation and vacuum treatment, making it impossible to capture direct evidence of reactions in situ. Traditional infrared spectroscopy is limited by the diffraction limit, with spatial resolution typically above 10 micrometers, making it unsuitable for submicrometer-scale pore analysis. Although Raman spectroscopy offers high resolution, it provides weak signals for many minerals and is susceptible to fluorescence interference.

[0004] Therefore, there is an urgent need to develop a method and apparatus that can perform in-situ, non-destructive, multimodal chemical composition analysis of capping samples before and after exposure to hydrogen at the micro-nano scale. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of the prior art and provide a submicron analysis method and apparatus for quantitatively evaluating the hydrogen storage capacity of a caprock.

[0006] This application provides an integrated analytical device for quantitatively evaluating the hydrogen sequestration capacity of caprocks. The device includes a first component and a second component that work together. The first component is a micro-thermobaric reaction cell used to saturate rock samples with hydrogen under simulated hydrogen storage conditions. It includes a cell body made of hydrogen-resistant material, a sapphire optical window fixed to the top of the cell body, a finely adjustable sample holder inside the cell body for fixing thin rock sections, and a thermobaric control system. The second component is a non-contact submicron resolution infrared-Raman microscopy device based on photothermal infrared technology. It includes an infrared laser source, a visible light probe laser, a lock-in amplifier, and a spectrometer. It is used to perform simultaneous in-situ analysis of the hydrogen-saturated sample using infrared absorption and Raman scattering spectra with a spatial resolution better than 500 nm through the sapphire optical window. The core design of this device is that after hydrogen saturation, the first component remains sealed and carries the in-situ fluid state, and is transferred as a whole to the sample stage of the second component for fixation. This achieves in-situ spectroscopic analysis that avoids changes in sample state due to depressurization and exposure to the atmosphere.

[0007] In this integrated analytical device, the micro-thermo-pressure reaction cell provides a hydrogenation environment for rock samples that closely resembles real reservoir conditions. Simultaneously, its top sapphire optical window exhibits excellent transmittance and high mechanical strength across a wide wavelength range from visible to mid-infrared, providing an effective physical channel and optical quality support for the non-contact optical probe. The non-contact submicron resolution infrared-Raman microscopy-guided device employs the photothermal infrared (O-PTIR) detection principle. Its spatial resolution is determined by the focused spot size of the visible light probe, rather than the wavelength of the infrared laser, thus breaking through the optical diffraction limit of traditional infrared microscopes and achieving submicron-level spectral acquisition. This application configures the objective lens of the O-PTIR system with a sufficient numerical aperture to focus on the sample surface and collect spectral signals through the sapphire window, solving the problem of high-resolution chemical analysis under high-pressure fluid conditions in existing technologies. More importantly, by sealing and transferring the micro thermo-pressure reaction cell after the reaction to the sample stage of the analytical device, the changes in sample state caused by the need to remove the sample for analysis in traditional methods (such as gas escape caused by pressure release, oxidation or adsorption contamination caused by exposure to air) are completely avoided. This ensures that the spectral analysis results can truly reflect the interaction between hydrogen and caprock under in-situ conditions.

[0008] Furthermore, the temperature and pressure control system includes heating elements and a temperature controller located around the perimeter of the pool, an air inlet and an air outlet located on the side wall of the pool, a high-pressure booster pump and a mass flow meter connected to the air inlet, and a back pressure valve and a pressure sensor connected to the air outlet. Specifically, the heating element can be selected from either a ceramic heating belt or a cylindrical heater, the temperature controller has a temperature control accuracy of ±0.5℃, and the pressure sensor has an accuracy of ±0.1%FS.

[0009] Furthermore, the second component also includes a reflective Cassegrain objective or a refractive objective with a numerical aperture greater than or equal to 0.78; a visible light probe laser with a wavelength of 532 nm or 785 nm; and an infrared laser source that is a quantum cascade laser or an optical parametric oscillator with a tuning range covering 800 cm. -1 Up to 1800cm -1 and / or 2800cm -1 Up to 3600cm -1 Specifically, the reflective Cassegrain objective is 40x with a numerical aperture of 0.78, and the refracting objective is 50x with a numerical aperture of 0.8. This optical configuration ensures that the focused spot diameter of the visible light probe on the sample surface is less than 500 nm after passing through the sapphire window, thus achieving submicron spatial resolution.

[0010] Furthermore, the sapphire optical window has a thickness of 1.0 mm to 2.0 mm, and both sides are precision polished with a flatness better than λ / 10 (λ=632.8 nm). The height fine-tuning function of the sample holder is configured to set the distance between the polished surface of the rock section and the inner surface of the sapphire optical window to 50 μm to 200 μm. This distance is configured to be less than the working distance of the microscope objective used to ensure that the probe beam can be effectively focused on the sample surface, while reserving a small space for fluid circulation.

[0011] On the other hand, this application also provides a submicron analysis method for quantitatively evaluating the hydrogen storage capacity of a caprock using the aforementioned integrated analysis device, comprising the following steps: Step S1: Prepare the target caprock sample into a thin section, mount it on the sample holder in the micro thermobaric reaction cell and adjust it to face the sapphire optical window; Step S2: Hydrogen gas is introduced into the reaction tank through the temperature and pressure control system, and the temperature and pressure conditions of the target reservoir are set to saturate the sheet with hydrogen. Step S3: While keeping the micro thermo-pressure reaction cell sealed and its interior under hydrogen pressure, transfer and fix it as a whole onto the sample stage of the non-contact submicron resolution infrared Raman microscope. Step S4: Start the microscope-microscopy system and simultaneously acquire infrared absorption and Raman scattering spectra with a spatial resolution better than 500 nm for one or more target micro-regions on the processed thin slice through the sapphire optical window. Step S5: Analyze the spectral data, and in the Raman scattering spectrum at 4156±10 cm⁻¹ -1 The detection of characteristic peaks serves as evidence of the presence of hydrogen. Infrared absorption spectra are used to detect changes in the intensity or shift of characteristic peaks of minerals as evidence of mineral chemical changes. The two are spatially correlated to determine the microscopic spatial correspondence of hydrogen entering the caprock and causing chemical changes in minerals.

[0012] In this analytical method, steps S1 to S3 constitute a complete integrated "in-situ reaction-in-situ transfer-in-situ detection" process, ensuring the fidelity of the sample's chemical state throughout the entire process from reaction to analysis. Step S4 utilizes the simultaneous multimodal spectral acquisition capability of the O-PTIR system to acquire Raman and infrared spectra at the same site in a single focusing, avoiding spatial alignment errors caused by switching between different instruments. More importantly, step S5 spatially correlates two complementary spectral evidences: Raman spectroscopy has extremely high sensitivity to nonpolar hydrogen molecules, with a sensitivity of 4156 cm⁻¹. -1 Characteristic peaks are the "gold standard" for the presence of hydrogen; infrared spectroscopy is sensitive to changes in polar chemical bonds (such as Fe-O, SO, OH) in minerals. The joint detection of the two spectra at the same site can directly establish a deterministic causal chain of evidence at the submicron scale that "hydrogen has reached this location" and "the mineral here has been reduced," which is impossible to achieve with existing methods that rely solely on single-spectral analysis.

[0013] Furthermore, in step S2, the target reservoir temperature is room temperature to 150°C, the target reservoir pressure is 0.1 MPa to 30 MPa, and the hydrogen saturation treatment time is 24 hours to 7 days.

[0014] Furthermore, step S2 also includes: before performing hydrogen saturation treatment, introducing an inert gas into the micro thermo-pressure reaction cell for an airtightness check, followed by purging the cell multiple times with high-purity hydrogen to replace the air. Specifically, the inert gas used for the airtightness check is helium, and the check pressure is 5 MPa; the purity of the high-purity hydrogen is ≥99.999%, and the dew point is ≤-70℃; the purging and gas replacement are repeated no less than three times.

[0015] Furthermore, step S4 also includes: selecting a specific infrared absorption wavenumber to perform point-by-point scanning on at least one of the one or more target micro-regions to generate a pseudo-color image showing the spatial distribution of a specific chemical component, wherein the pixel size of the point-by-point scan is less than 500 nm.

[0016] Furthermore, the evidence for the mineral chemical changes in step S5 is selected from one or more of the following: changes in the intensity ratio of the Fe-O vibrational peak in iron oxides, a shift in the peak position or an intensity decrease in the hydroxyl stretching vibrational peak in clay minerals, and a weakening of the SO stretching vibrational peak in sulfate minerals or the appearance of new characteristic peaks of sulfides. Specifically, the Fe-O vibrational peak in iron oxides is located at 540 cm⁻¹. -1 and 570cm -1 The hydroxyl stretching vibration peak in clay mineral structure is located at 3620 cm⁻¹. -1 and 3420cm -1 The SO stretching vibration peak of sulfate minerals is located at 1100 cm⁻¹. -1 Up to 1000cm -1 .

[0017] Furthermore, the method also includes step S6: statistically quantifying the degree of mineral chemical changes in multiple different micro-regions obtained in step S5 to obtain microscopic reaction characteristic parameters, and coupling these microscopic reaction characteristic parameters with macroscopic permeability change data of rock samples measured through independent core displacement experiments to establish a quantitative evaluation model with the microscopic reaction characteristic parameters as independent variables and the macroscopic permeability change rate as dependent variable. Specifically, the microscopic reaction characteristic parameters can be selected from any one or more of alteration zone thickness, mineral conversion rate, and characteristic peak intensity ratio; the quantitative evaluation model can be a fitting equation or an evaluation chart. Compared with the prior art, the present invention has the following beneficial effects: This application integrates a micro thermo-pressure reaction cell with a non-contact submicron resolution infrared Raman microscope and adopts an integrated operation process of "in-situ reaction-sealed transfer-in-situ analysis" to achieve non-destructive, high-resolution detection of hydrogen fluid and surrounding minerals in nano- to submicron scale pores of caprock under in-situ formation conditions.

[0018] This application utilizes the simultaneous acquisition of Raman and infrared absorption spectra in the same micro-region, and takes advantage of the characteristic hydrogen peak (4156 cm⁻¹) in the Raman spectrum. -1 By spatially correlating the changes in characteristic peaks of minerals in infrared spectra, definitive evidence can be obtained directly of hydrogen entering specific nanopores and triggering mineral reduction reactions, fundamentally solving the drawback of traditional methods that can only infer from indirect phenomena.

[0019] This application establishes a quantitative evaluation model from microscopic reaction mechanisms to macroscopic seepage properties by cross-scale coupling and correlation between submicron-scale mineral reaction characteristics (such as alteration zone thickness) and macroscopic core permeability variation data, thereby significantly improving the accuracy and reliability of evaluating the caprock's ability to long-term store hydrogen. Attached Figure Description

[0020] Figure 1 This is an overall flowchart of the submicron analysis method of the present invention for quantitatively evaluating the hydrogen storage capacity of a caprock; Figure 2 This is a schematic diagram of the principle of the non-contact submicron infrared Raman spectroscopy microscope combined device of the present invention; Figure 3 This is a schematic diagram of the submicron analysis device for quantitatively evaluating the hydrogen storage capacity of the cap layer according to the present invention. Figure 4 This is a schematic diagram of the micro thermo-pressure reaction cell structure of the present invention; Figure 5 This is a cross-sectional view of the sapphire window sealing structure of the micro thermobaric reaction cell of the present invention; Figure 6 The results of Raman spectroscopy and infrared spectroscopy detection are shown in Embodiment 1 of the present invention. Figure 7 The results are from the Raman spectroscopy experiment of Embodiment 2 of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0022] Example 1: Evaluation of iron-bearing mudstone caprock under medium temperature and high pressure conditions This embodiment takes the target caprock of an underground hydrogen storage reservoir—hematite-bearing mudstone—as the research object and simulates a reservoir environment with a temperature of 90℃ and a pressure of 30MPa.

[0023] (1) Sample preparation and installation: A rock slice of approximately 15mm × 15mm in area and 2mm in thickness was cut from a representative core of the target caprock section using a diamond wire saw (0.2mm wire diameter). One side of the rock slice (the side to be examined) was sequentially wet-polished using 400-grit, 800-grit, 1200-grit, and 3000-grit SiC abrasive paper, and finally fine-polished using a 0.5μm alumina polishing slurry on a cloth polishing machine. After each step, the surface scratches were examined under an optical microscope. The final polished surface had no obvious scratches, and the surface roughness Ra < 50 nm. The polished rock slice was ultrasonically cleaned in anhydrous ethanol for 5 minutes and dried with nitrogen. Subsequently, the rock slice was fixed using the elastic claws (material: Inconel 718 nickel alloy) integrated into the reaction chamber. Place the fixed sample onto the sample holder of the micro thermobaric reaction cell. Adjust the height fine-tuning knob of the holder to ensure the distance between the polished surface of the sample and the inner surface of the sapphire window is precisely 100±10μm (ensuring this distance is guaranteed by a 100μm thickness precision shim placed on the sample holder). After confirming that everything is correct, close the cell cover and use a torque wrench to alternately tighten the four M3 stainless steel fastening screws diagonally at a torque of 0.5 N·m to ensure a tight seal.

[0024] (2) In-situ hydrogenation simulation treatment: First, charge the reaction tank with helium to 5 MPa, close the valve, and observe the pressure sensor reading. If the decrease is no more than 0.01 MPa within 30 minutes, the tank is considered sealed. Open the outlet valve and introduce high-purity hydrogen at a flow rate of 20 sccm using a mass flow controller, maintaining this for 3 minutes to displace the helium in the tank. Repeat this "charging-venting" operation three times. After each cycle, use a miniature diaphragm pump to reduce the pressure in the tank to below 10 Pa. Close the outlet valve and inject hydrogen into the reaction tank using a high-pressure booster pump at a rate <1 MPa / min until the pressure reaches 30 ± 0.1 MPa. Simultaneously, start the heating jacket surrounding the reaction tank, raising the tank temperature to 90 ± 0.5℃ at a rate of 5℃ / min. During the heating process, the hydrogen pressure increases due to thermal expansion, and the back pressure valve automatically releases pressure to maintain a constant 30 MPa. Maintain constant temperature and pressure at 90℃ and 30 MPa for 48 hours. During the process, the heating power is automatically adjusted by the PID controller to maintain a stable temperature, and the gas replenishment system (connected to a high-pressure hydrogen cylinder and controlled by a solenoid valve) automatically replenishes gas when the pressure drops by more than 0.1 MPa.

[0025] (3) In-situ transfer and optical focusing: Turn off the heating power and allow the reaction cell to cool naturally to below 40°C (approximately 2 hours). Keep the back pressure valve fully open, allowing the pressure inside the cell to decrease synchronously with the temperature. When the temperature drops to 40°C and the pressure drops to approximately 28.5 MPa, manually adjust the back pressure valve to slowly release the pressure (< 0.5 MPa / min) to 2.0 ± 0.1 MPa. Close the inlet and outlet valves of the reaction cell itself, making it an independent, sealed miniature container filled with high-pressure hydrogen. Remove it from the heating jacket and gas piping system, and wipe the outer surface of the sapphire window with a lint-free cloth dampened with anhydrous ethanol. Place the entire reaction cell on the motorized XYZ shift stage of the non-contact submicron resolution infrared Raman microscopy system (O-PTIR system, model: mIRage, Photothermal Spectroscopy Corp.) and secure it with a special clamp. Using the system software, switch the 5× objective lens to the optical path and manually coarsely adjust the objective lens height so that its tip is approximately 5 mm from the upper surface of the sapphire window. Turn on the system's bright-field illumination LED (wavelength 590nm) and observe in the real-time video window. Slowly lower the objective lens (in 1μm steps) while adjusting the Z-axis focusing knob until a clear sample surface morphology appears in the video image. Then switch to the 50× objective lens (NA=0.8, working distance 1mm) and finely focus again to ensure the spot is precisely located on the polished sample surface.

[0026] (4) Multimodal micro-region chemical data acquisition: At a 5× objective lens field of view, capture a stitched overview image of the entire sample area (approximately 2mm × 2mm). Select the target micro-area on the overview image: Micro-region A: A microcrack approximately 2 μm wide, its color changing from reddish-brown to dark gray.

[0027] Micro-region B: Inside a siderite (FeCO3) particle with a diameter of approximately 10 μm.

[0028] Micro-region C: The contact boundary between clay minerals and quartz particles. The clay is rich in montmorillonite, as determined by energy dispersive spectroscopy (EDAX, OctanePlus).

[0029] Micro-region D: The original mudstone matrix region with a distance >50μm from the micro-crack, serving as a blank control.

[0030] (5) Raman spectroscopy detection Switch to Raman spectroscopy mode, select an excitation wavelength of 532 nm (power 10 mW), a grating of 1200 lines / mm, a slit width of 50 μm, and set the spectral center wavenumber to 4000 cm⁻¹. -1 Coverage range 100-7000cm -1 The integration time is 2 seconds, and the increment is 3 times. The displacement stage is moved sequentially to the center of micro-regions A, B, C, and D to collect spectra. Results: Refer to... Figure 6 Micro-region A is at 4156 cm. -1 A sharp, characteristic peak with a signal-to-noise ratio >10 and a peak width of approximately 10 cm appears. -1 The peak intensity in microregions B and C is 1 / 5 to 1 / 3 of that in microregion A, while the peak was not detected in microregion D.

[0031] (6) Infrared spectroscopy detection Maintain the same field of view and switch to O-PTIR infrared mode. Set the laser pump wavelength tuning range to cover 800-1800cm. -1 and 2800-3800cm -1 Spectral resolution 4cm -1 A dual-beam differential detection mode was employed. Infrared absorption spectra were acquired for micro-regions A, B, C, and D respectively. Result interpretation: Refer to... Figure 6 540cm in the micro-area D spectrum -1 A broad and strong absorption peak exists at 540 cm⁻¹ (Fe-O vibration of hematite α-Fe₂O₃), as shown in the micro-area A spectrum. -1 Peak intensity decreased by about 70%, while at 570cm -1 A new absorption peak appears at (Fe3O4 in magnetite). 2+ -O vibration), 330cm -1 Shoulder peaks appear (Fe3O4 Fe) 3+ -O vibration). 3625 cm⁻¹ in micro-region C. -1 The intensity of the (Al-Al-OH) peak decreased by about 20%, while the peak width increased to 3670 cm⁻¹. -1 A new peak appears (Fe-OH bond). Submicron infrared imaging: 540 cm⁻¹ -1 and 570cm -1 Using the characteristic wavenumber, a surface scan was performed on the region (20 μm × 20 μm) containing micro-region A and its two sides, with a pixel size of 0.2 μm and a scan rate of 0.5 seconds per point, completing the scan in approximately 10 minutes. A pseudo-color intensity map (red 540 cm⁻¹) was then generated. -1 Green, 570cm -1 An intensity profile was drawn perpendicular to the fracture direction, and the half-width at half-maximum (FWHM) of magnetite was defined as the thickness of the alteration zone. The thickness of the alteration zone on the left side of the fracture was measured to be 2.6 μm, on the right side 2.3 μm, with an average of 2.45 μm.

[0032] (7) Cross-scale quantitative evaluation Initial permeability K0: Helium permeability was measured using a pressure-controlled permeability meter (CoreLab, PoroPDP-200) on standard core columns (25mm in diameter and 25mm in length) drilled from adjacent locations within the same core sample, under a net confining pressure of 35MPa (pulse decay method, upstream pressure pulse 1MPa). The average of three measurements was K0 = 8.5 × 10⁻⁶.-20 m 2 Permeability K1 after reaction: The sample that has undergone the above analysis was carefully removed (using acetone to dissolve the epoxy resin) and measured under the same pressure-controlled permeameter and the same net confining pressure of 35 MPa. The average value of three measurements was K1 = 3.2 × 10⁻⁶. -19 m 2 The rate of change in permeability ΔK = (K1 - K0) / K0 = (3.2 × 10⁻¹⁰) -19 -8.5×10 -20 ) / 8.5×10 -20 ≈2.76 (+276%). The average thickness of the micro-alteration zone (2.45 μm) and the macro-permeability change rate (+276%) in this embodiment are used as a data point. The operation is repeated, changing the saturated immersion time (12 hours, 24 hours, 72 hours, 96 hours), to obtain another four sets of data points (alteration zone thicknesses of 0.8 μm, 1.5 μm, 3.2 μm, and 4.1 μm, corresponding to ΔK values ​​of +45%, +120%, +410%, and +580%, respectively). A nonlinear fitting is performed with the alteration zone thickness as the x-axis and ΔK as the y-axis to obtain an exponential function equation (Rk). 2 =0.97): ΔK=0.12×exp(thickness / 1.15)-0.1.

[0033] Example 2: Evaluation of gypsum-bearing salt rock caprock under high temperature and high pressure conditions This embodiment takes the gypsum-salt rock caprock overlying a hydrogen storage reservoir as the research object. The main mineral is anhydrite (CaSO4), with a small amount of clay minerals, and simulates a reservoir environment with a temperature of 120℃ and a pressure of 50MPa.

[0034] Sample preparation and mounting: The sample cutting and polishing methods are the same as in Example 1, but the polishing medium is changed to anhydrous ethanol, and the cold mounting resin is hydrophobic to avoid hydration.

[0035] In-situ hydrogenation simulation treatment: The operation process is the same as in Example 1, but the pressurization rate is reduced to 0.2 MPa / min and the soaking time is extended to 72 hours.

[0036] In-situ transfer and spectral acquisition: Same as in Example 1.

[0037] Key Results: Reference Figure 7 Raman spectroscopy detected a 4156 cm⁻¹ region in the microcrack area. -1 Hydrogen peak. Infrared spectrum: Unreacted region at 1100 cm⁻¹. -1 1150cm -1 A strong absorption double peak of SO expansion and contraction vibration was observed at the site of anhydrite; the intensity of the double peak decreased by about 50% in the reaction zone (microcrack wall), while at 990 cm⁻¹... -1 A new peak appears (calcium sulfite CaSO3), 400 cm⁻¹ -1A weak, broad peak appears nearby (possibly ferrous sulfide FeS). At 1100 cm⁻¹ -1 (Hard plaster) and 990cm -1 (Calcium sulfite) was used as the characteristic wavenumber for imaging, and the average thickness of the alteration zone was measured to be 1.8 μm.

[0038] Permeability change: Initial permeability K0 = 2.1 × 10 -21 m 2 After the reaction, the permeability K1 = 8.5 × 10⁻⁶ -21 m 2 ΔK = +305%.

[0039] Example 3: Method repeatability and blank control experiment Blank control: A mudstone sample identical to that in Example 1 was treated with high-purity argon gas without the introduction of hydrogen gas for 48 hours under the same temperature and pressure conditions (90℃ / 30MPa). Subsequently, the same O-PTIR analysis was performed. Results: The 4156 cm⁻¹ region was not detected in the Raman spectrum. -1 Hydrogen peak; 540 cm⁻¹ in infrared spectrum -1 The peak did not weaken, 570cm -1 No peaks appeared; no alteration bands were formed in infrared imaging.

[0040] Repeatability test: Two additional parallel samples from the same core were tested independently using all parameters from Example 1. Results: The alteration zone thicknesses of the two samples were 2.5 μm and 2.4 μm, respectively, with ΔK values ​​of +268% and +282%. Compared with the results of Example 1 (2.45 μm, +276%), the relative deviation was <5%.

[0041] Analysis of the data from the above embodiments: A series of examples demonstrate that, under conditions of 90°C and 30 MPa, as the saturated immersion time increased from 12 hours to 96 hours, the alteration zone thickness monotonically increased from 0.8 μm to 4.1 μm, and the rate of change in permeability increased from +45% to +580% in iron-bearing mudstone. This indicates that the reduction reaction between hydrogen and hematite is a cumulative process over time, and the range of reaction influence (alteration zone thickness) is exponentially positively correlated with the degree of permeability degradation (fitted R²). 2 =0.97). Among them, 48 hours of treatment was enough to increase the permeability by nearly 3 times, indicating that even under moderate temperature and pressure conditions, hydrogen poses a significant threat to the storage capacity of ferrous caprocks.

[0042] The results of Example 2 show that, for the gypsum-salt caprock, under more stringent conditions (120℃, 50MPa), hydrogen can undergo a reduction reaction with anhydrite to generate calcium sulfite and sulfides, resulting in an alteration zone thickness of 1.8μm and a permeability increase of +305%. Compared with Example 1, although the alteration zone thickness of the gypsum-salt rock is thinner (1.8μm vs 2.45μm), its initial permeability is extremely low (10... -21 m 2 Even slight mineral reduction (accompanied by the release of water of crystallization) can multiply permeability and significantly damage storage capacity.

[0043] The blank control in Example 3, under argon atmosphere, did not exhibit hydrogen peaks, mineral peak changes, or alteration bands, confirming that temperature and pressure themselves do not induce mineral phase transitions; hydrogen is the sole driving force. The relative deviations of the alteration band thickness and ΔK results of the two parallel samples in the repeatability experiment from those in Example 1 were both less than 5%, demonstrating the good repeatability and data reliability of this method.

[0044] It should be understood that the above embodiments are merely exemplary. Those skilled in the art can make various non-substantial improvements and substitutions based on the technical concept of this invention, and all such improvements and substitutions should be considered to fall within the protection scope of this application.

Claims

1. A submicron analytical device for quantitatively evaluating the hydrogen storage capacity of a caprock, characterized in that, This includes a first component and a second component that work together. The first component is a micro thermo-pressure reaction cell, used to saturate rock samples with hydrogen under temperature and pressure conditions simulating a hydrogen storage environment. It includes a cell body, a sapphire optical window fixed to the top of the cell body, a sample holder set inside the cell body for fixing rock slices, and a temperature and pressure control system that covers the periphery of the cell body and is connected to an external gas pipeline. The second component is a non-contact submicron resolution infrared Raman microscope combined with an infrared laser source, a visible light probe laser, a lock-in amplifier, and a spectrometer, used to perform in-situ analysis of the hydrogen-saturated rock sample through the sapphire optical window using infrared absorption and Raman scattering spectra.

2. The submicron analytical apparatus for quantitatively evaluating the hydrogen storage capacity of a caprock according to claim 1, characterized in that, The temperature and pressure control system includes a heating element and a temperature controller located around the periphery of the pool body, an air inlet and an air outlet located on the side wall of the pool body, a booster pump and a mass flow meter connected to the air inlet, and a back pressure valve and a pressure sensor connected to the air outlet.

3. The submicron analytical apparatus for quantitatively evaluating the hydrogen storage capacity of a caprock according to claim 1, characterized in that, The second component also includes an objective lens with a numerical aperture greater than or equal to 0.78; the visible light probe laser has a wavelength of 532 nm or 785 nm; and the infrared laser source has a tuning range covering 800 cm. -1 Up to 1800cm -1 and / or 2800cm -1 Up to 3600cm -1 .

4. The submicron analytical apparatus for quantitatively evaluating the hydrogen storage capacity of a caprock according to claim 1, characterized in that, The thickness of the sapphire optical window is 1.0 mm to 2.0 mm; the height of the sample holder is configured such that the distance between the polished surface of the rock sheet and the inner surface of the sapphire optical window is set to 50 μm to 200 μm.

5. A submicron analytical method for quantitatively evaluating the hydrogen storage capacity of a caprock using the analytical apparatus according to any one of claims 1-4, characterized in that, Includes the following steps: Step S1: Prepare the target caprock sample into a thin slice, install it on the sample holder in the micro thermo-pressure reaction cell, and adjust the sample holder so that the polished surface of the thin slice faces the sapphire optical window. Step S2: Hydrogen gas is introduced into the micro temperature and pressure reaction tank through the temperature and pressure control system, and the target reservoir temperature and target reservoir pressure are set and stabilized to perform hydrogen saturation treatment on the sheet. Step S3: While keeping the micro thermo-pressure reaction cell sealed and its interior under the pressure of carrying the hydrogen gas, transfer the entire micro thermo-pressure reaction cell to the sample stage of the non-contact submicron resolution infrared Raman microscope. Step S4: Activate the non-contact submicron resolution infrared Raman microscope combined device, and simultaneously acquire infrared absorption spectrum and Raman scattering spectrum with spatial resolution better than 500 nm on one or more target micro-regions on the thin film after the processing in step S2 through the sapphire optical window. Step S5: Analyze the spectral data obtained in step S4, find the characteristic peak of hydrogen in the Raman scattering spectrum, analyze the changes of mineral characteristic peaks related to hydrogen reduction in the infrared spectrum at the same location, and spatially correlate the micro-region location of detected hydrogen with the micro-region location of detected mineral chemical changes to form a microscopic evidence chain of hydrogen entering and causing reduction reaction of caprock minerals.

6. The submicron analysis method for quantitatively evaluating the hydrogen storage capacity of a caprock according to claim 5, characterized in that, In step S2, the target reservoir temperature is from room temperature to 150°C, the target reservoir pressure is from 0.1 MPa to 30 MPa, and the hydrogen saturation treatment time is from 24 hours to 7 days.

7. The submicron analysis method for quantitatively evaluating the hydrogen storage capacity of a caprock according to claim 5, characterized in that, Step S2 further includes: before performing the hydrogen saturation treatment, introducing inert gas into the micro thermo-pressure reaction tank to check for air tightness, and then using hydrogen to purge and exchange the air inside the micro thermo-pressure reaction tank multiple times to replace the air in the tank.

8. The submicron analysis method for quantitatively evaluating the hydrogen storage capacity of a caprock according to claim 5, characterized in that, Step S4 further includes: selecting a specific infrared absorption wavenumber to perform point-by-point scanning on at least one of the one or more target micro-regions to generate a pseudo-color image showing the spatial distribution of specific chemical components, wherein the pixel size of the point-by-point scanning is less than 500nm.

9. The submicron analysis method for quantitatively evaluating the hydrogen storage capacity of a caprock according to claim 5, characterized in that, In step S5, the evidence for the mineral chemical change is selected from one or more of the following: changes in the intensity ratio of the Fe-O vibration peak of iron oxides, peak position shift or intensity decay of the hydroxyl stretching vibration peak of clay minerals, and weakening of the SO stretching vibration peak of sulfate minerals or the appearance of new characteristic peaks of sulfides.

10. The submicron analysis method for quantitatively evaluating the hydrogen storage capacity of a caprock according to claim 5, characterized in that, The method also includes step S6: statistically quantifying the degree of mineral chemical changes in multiple different micro-regions obtained in step S5 to obtain microscopic reaction characteristic parameters, and coupling the microscopic reaction characteristic parameters with the macroscopic permeability change data of the rock sample measured by independent core displacement experiments to establish a quantitative evaluation model with the microscopic reaction characteristic parameters as independent variables and the macroscopic permeability change rate as dependent variable.

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