Method for determining hydrogen and water relative permeability curve of underground hydrogen storage and related equipment

Abstract

The invention discloses a method for determining a hydrogen and water relative permeability curve of an underground hydrogen storage and related equipment, and relates to the field of underground space engineering.The method comprises the steps that a microscopic computed tomography image of a rock sample in the hydrogen flooding process is obtained; performing characterization unit analysis on the pore structure of the microscopic computed tomography image to construct a first pore structured grid model, the first pore structured grid model being used for characterizing the pore structure of the rock sample, and the first pore structured grid model comprising a coordinate system of the pore structure; by taking a coordinate system of the first pore structured grid model as a reference, mapping the wettability distribution data to the first pore structured grid model through the corresponding coordinate position to obtain a second pore structured grid model, the wettability distribution data is calculated along a three-phase contact line of rock, hydrogen and water extracted from the microscopic computed tomography image; and performing water-driven hydrogen two-phase flow simulation operation on the second pore structured grid model to obtain a hydrogen and water relative permeability curve of the hydrogen storage bank.

Description

Technical Field

[0001] This invention relates to the field of underground space engineering, and in particular to a method and related equipment for determining the hydrogen-water phase permeation curve of an underground hydrogen storage facility. Background Technology

[0002] Hydrogen energy, as a clean energy carrier, has shown great potential in energy transition and addressing climate change. However, its large-scale application urgently requires the support of economical and efficient storage technologies. Underground hydrogen storage, utilizing depleted oil and gas reservoirs and aquifers, among other porous underground reservoirs, has become a feasible solution to address energy supply and demand fluctuations due to its wide distribution, large capacity, and good sealing properties. However, the core foundation for accurately predicting the hydrogen storage capacity and recovery efficiency of porous reservoirs and optimizing injection and production schemes lies in accurately obtaining the phase permeability curve of hydrogen and water two-phase flow in rocks. Currently, obtaining this curve mainly relies on two types of methods: traditional indoor core displacement experiments, while direct, have stringent equipment requirements and high experimental costs. The current numerical simulation method suffers from limitations due to its high cost, long cycle time, and inability to broadly cover the complex conditions of real reservoir temperature and pressure. More importantly, the large-scale use of flammable and explosive hydrogen during the experiment poses significant safety hazards. Another alternative method is multiphase flow numerical simulation, which, while saving costs and time and allowing for studies over a wider parameter range, generally simplifies reservoir wettability to a homogeneous condition when simulating hydrogen-water two-phase flow in rocks. This severely contradicts the in-situ heterogeneous wetting conditions caused by the complex mineral distribution in real reservoirs, leading to distorted simulation results. Ultimately, existing numerical simulation methods cannot accurately calculate the phase permeability curves of hydrogen-water two-phase flow in rocks. Therefore, current technologies struggle to obtain highly accurate hydrogen-water phase permeability curves. Summary of the Invention

[0003] In view of the above problems, the present invention provides a method and related equipment for determining the hydrogen-water phase permeation curve of an underground hydrogen storage facility, the main purpose of which is to solve the problem that the existing technology is difficult to obtain a hydrogen-water phase permeation curve with high accuracy.

[0004] To address at least one of the aforementioned technical problems, in a first aspect, the present invention provides a method for determining the hydrogen-water phase permeation curve of an underground hydrogen storage facility, the method comprising: Microscopic computed tomography images of rock samples during the hydrogen-driven water displacement process were obtained, wherein the rock samples were test samples collected from natural hydrogen reservoirs. The pore structure of the micro-computed tomography image is characterized by unit cell analysis to construct a first pore structured mesh model. The first pore structured mesh model is used to characterize the pore structure of the rock sample. The first pore structured mesh model is a geometric structure model and includes a coordinate system for the pore structure. Using the coordinate system of the first pore structured grid model as a reference, the wettability distribution data is mapped to the first pore structured grid model through the corresponding coordinate positions to obtain the second pore structured grid model. The wettability distribution data is calculated along the three-phase contact line of rock, hydrogen and water extracted from the micro-computed tomography image. A two-phase flow simulation of water-driven hydrogen is performed on the second porous structured grid model to obtain the hydrogen and water phase permeation curves of the hydrogen storage tank. The two-phase flow simulation of water-driven hydrogen is a simulation of water phase replacing hydrogen phase in the second porous structured grid model.

[0005] Optionally, acquiring microscopic computed tomography images of rock samples during the hydrogen-driven water displacement process includes: Microscopic computed tomography (CT) images of the rock sample were acquired under a simulated hydrogen-driven water displacement operation, wherein the simulated hydrogen-driven water displacement operation was used to simulate the gas injection operation of a hydrogen storage tank; the microscopic CT images were denoised using median filtering technology. The micro-computed tomography image was segmented using watershed segmentation technology to extract the distribution of hydrogen and water in the pore space of the rock.

[0006] Optionally, the step of characterizing the pore structure of the microscopic computed tomography image to construct a first pore structured mesh model includes: Crop cube sub-images with different side lengths from the center of the microscopic computed tomography image; Calculate the porosity and water saturation of each of the cubic sub-images; Based on the porosity and water saturation of each cube sub-image, the fluctuation trend of porosity and water saturation is determined. When the fluctuation trend of porosity and water saturation is less than a preset amplitude, the corresponding smallest cube sub-image is determined to be the characterizing unit cell model; Each image pixel of the characterization unit model is converted into a hexahedral mesh unit to form the first pore structured mesh model.

[0007] Optionally, the above methods also include: Using the traveling cube algorithm, a multiphase surface mesh model is obtained based on the characterization unit model. The multiphase surface mesh model is used to characterize the distribution of phase interfaces of hydrogen, water and rock solid. Extract each contact point on the three-phase contact line of rock, hydrogen and water from the multiphase surface mesh model; Calculate the in-situ contact angle of each contact point on the three-phase contact line, wherein the in-situ contact angle corresponding to any contact point is obtained by calculating the angle between the unit normal vector of the hydrogen-water phase interface and the unit normal vector of the water-rock solid phase interface at the contact point. Within the space of the characterizing unit model, using the average pore diameter as the moving window size, the local average value of the in-situ contact angle is statistically analyzed to obtain the wettability distribution data.

[0008] Optionally, the step of mapping the wettability distribution data to the first pore structured mesh model through corresponding coordinate positions, using the coordinate system of the first pore structured mesh model as a reference, to obtain the second pore structured mesh model includes: Determine the center point coordinates of each wall grid cell in the first pore structured mesh model, wherein the wall grid cell is the grid cell that contacts the pore under fluid flow conditions; Determine the local average value of the in-situ contact angle in the wettability distribution data corresponding to the coordinates of each of the aforementioned center points; The local average value of the in-situ contact angle is assigned to the wall mesh element corresponding to the coordinate position in the first pore structured mesh model to obtain the second pore structured mesh model.

[0009] Optionally, the above methods also include: Boundary conditions for single-phase flow simulation are set on the first porous structured grid model. The single-phase flow simulation is to simulate water injection into the first porous structured grid model to simulate the flow of water phase in the first porous structured grid model. The boundary conditions include setting the water injection inlet to a fixed pressure and the water injection outlet to a zero pressure value. The walls of the first porous structured grid model other than the inlet and outlet are set as impermeable boundaries. Under the stated boundary conditions, the flow of the water phase in the first porous structured grid model is simulated using the finite volume method. Once the simulation process reaches the convergence criterion, the absolute permeability of the first pore structured mesh model is calculated using Darcy's law.

[0010] Optionally, the step of performing a two-phase flow simulation of water-driven hydrogen on the second pore structured mesh model to obtain the hydrogen-water phase permeation curve of the hydrogen storage reservoir includes: Set reservoir temperature and pressure conditions on the second pore structured grid model; Determine the water phase density, water phase viscosity, hydrogen density, hydrogen viscosity, and hydrogen-water interfacial tension coefficient under the specified reservoir temperature and pressure conditions. The hydrogen and water distribution characterized by the micro-computed tomography image is set as the initial fluid distribution for the two-phase flow simulation of water-driven hydrogen. Boundary conditions for simulating the two-phase flow of water-driven hydrogen are set on the second porous structured grid model. The boundary conditions include setting the inlet of the water injection operation to a constant velocity for injecting the water phase, setting the outlet of the water injection operation to a zero pressure value, and setting the walls of the second porous structured grid model other than the inlet and outlet to impermeable boundaries. Under the boundary conditions, the fluid volume method is used to simulate the two-phase flow of water-driven hydrogen in the second pore structured mesh model, so as to obtain the effective permeability of hydrogen and the effective permeability of water phase under different water saturation during the simulation of the two-phase flow of water-driven hydrogen. Based on the effective hydrogen permeability, effective water phase permeability, and absolute permeability at different water saturations, the relative hydrogen permeability and relative water phase permeability at different water saturations are determined. The hydrogen-water phase permeability curves of the hydrogen storage tank are determined based on the relative permeability of hydrogen and water phase under different water saturation levels.

[0011] Secondly, embodiments of the present invention also provide a device for determining the hydrogen-water phase permeation curve of an underground hydrogen storage facility, comprising: The acquisition unit is used to acquire microscopic computed tomography images of rock samples during the hydrogen-driven water displacement process, wherein the rock samples are test samples collected from natural hydrogen storage reservoirs. A construction unit is used to perform characterization unit volume analysis on the pore structure of the micro-computed tomography image to construct a first pore structured mesh model. The first pore structured mesh model is used to characterize the pore structure of the rock sample. The first pore structured mesh model is a geometric structure model and includes a coordinate system of the pore structure. The mapping unit is used to map the wettability distribution data to the first pore structured grid model through the corresponding coordinate position, with the coordinate system of the first pore structured grid model as a reference, so as to obtain the second pore structured grid model. The wettability distribution data is calculated along the three-phase contact line of rock, hydrogen and water extracted from the micro-computed tomography image. The operation unit is used to perform a two-phase flow simulation operation of water-driven hydrogen on the second porous structured grid model to obtain the hydrogen and water phase permeation curves of the hydrogen storage tank. The two-phase flow simulation operation of water-driven hydrogen is a simulation operation in which the hydrogen phase in the second porous structured grid model is replaced by the water phase.

[0012] To achieve the above objectives, according to a third aspect of the present invention, a computer-readable storage medium is provided, the computer-readable storage medium comprising a stored program, wherein, when the program is executed by a processor, the steps of the method for determining the hydrogen-water phase permeability curve of an underground hydrogen storage reservoir are implemented.

[0013] To achieve the above objectives, according to a fourth aspect of the present invention, an electronic device is provided, comprising at least one processor and at least one memory connected to the processor; wherein the processor is configured to invoke program instructions in the memory to execute the steps of the method for determining the hydrogen-water phase permeation curve of the underground hydrogen storage tank.

[0014] By employing the above technical solution, the present invention provides a method and related equipment for determining the hydrogen-water phase permeation curve of an underground hydrogen storage facility. Addressing the problem that existing technologies struggle to obtain highly accurate hydrogen-water phase permeation curves, this invention acquires microscopic computed tomography (CT) images of rock samples during the hydrogen-water displacement process. The rock samples are collected from natural hydrogen storage facilities. The pore structure of the CT images is characterized by unit cell analysis to construct a first pore structured mesh model. This first pore structured mesh model characterizes the pore structure of the rock sample and is a geometric structure model. The structured mesh model includes a coordinate system for the pore structure. Using the coordinate system of the first pore structured mesh model as a reference, wettability distribution data is mapped to the first pore structured mesh model through corresponding coordinate positions to obtain a second pore structured mesh model. The wettability distribution data is calculated along the three-phase contact line of rock, hydrogen, and water extracted from the microscopic computed tomography image. A two-phase flow simulation of water-driven hydrogen is performed on the second pore structured mesh model to obtain the hydrogen and water phase permeation curves of the hydrogen storage reservoir. The two-phase flow simulation of water-driven hydrogen is a simulation of water displacing the hydrogen phase in the second pore structured mesh model.

[0015] In the above scheme, a first pore structured grid model is first constructed using microscopic computed tomography (CT) images of rock samples. This abandons the high-cost, high-risk indoor water displacement experiments on physical rock cores, and instead employs digital reconstruction technology to replicate the real pore geometry of the rock in virtual space. This transforms complex physical experiments into computer simulations, reducing the reliance on experimental equipment and costs associated with traditional methods. Furthermore, using the wetting properties contained in the same set of microscopic CT images—that is, by extracting the rock-hydrogen-water three-phase contact line—wetness distribution data characterizing the real surface properties of the rock is obtained. Then, using the coordinate system of the first model as a reference, these heterogeneous wettability distribution data are precisely assigned to the geometric walls through coordinate mapping, thereby generating a second pore structured grid model that simultaneously contains accurate pore structure and real heterogeneous wettability properties. This model replaces the distorted assumption of uniform wetting with the real heterogeneous wetting conditions that approximate the complex mineral distribution of underground reservoirs. Finally, numerical simulations were performed on the fully-equipped second-pore structured grid model. By simulating the dynamic migration of hydrogen driven by water in the pores, the fluid distribution under different water saturation levels was obtained, and the relative permeability curves were ultimately calculated. The entire process described above successfully depicted the two-phase flow behavior of hydrogen and water under heterogeneous wetting conditions in a virtual environment. The second-pore structured grid model in this application directly quantifies and reproduces the real wetting characteristics of local areas based on image data, avoiding the systematic biases caused by the assumption of uniform wetting in traditional numerical simulations. This ensures that the boundary conditions for subsequent two-phase flow simulations closely match the actual underground conditions, ultimately improving the fidelity of fluid migration path and phase distribution predictions.

[0016] Correspondingly, the device, equipment, and computer-readable storage medium for determining the hydrogen-water phase permeation curve of an underground hydrogen storage facility provided in this embodiment of the invention also have the above-mentioned technical effects.

[0017] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0018] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 A flowchart illustrating a method for determining the hydrogen-water phase permeation curve in an underground hydrogen storage facility, provided by an embodiment of the present invention, is shown. Figure 2 This diagram illustrates the analysis results of a characterization unit cell for porosity and water saturation provided by an embodiment of the present invention. Figure 3 This illustration shows a schematic diagram of a characterization unit model obtained from a microscopic computed tomography scan of a rock sample, according to an embodiment of the present invention. Figure 4 This diagram illustrates a first pore structured mesh model provided by an embodiment of the present invention. Figure 5 This diagram illustrates the in-situ contact angle distribution of a characterizing unit cell model according to an embodiment of the present invention. Figure 6 This diagram illustrates an in-situ heterogeneous wettability modeling method provided by an embodiment of the present invention. Figure 7 This diagram illustrates the initial fluid distribution for a water-driven hydrogen simulation according to an embodiment of the present invention. Figure 8 A schematic diagram of the boundary conditions for simulating a two-phase flow of water-driven hydrogen gas according to an embodiment of the present invention is shown. Figure 9 This diagram illustrates the fluid distribution in a water-driven hydrogen process according to an embodiment of the present invention. Figure 10 This invention provides a schematic diagram of the streamline distribution in a single-phase flow simulation where hydrogen occupies the pore space, according to an embodiment of the invention. Figure 11 This diagram illustrates a simulated streamline distribution of a single-phase flow where the water phase occupies the pore space, according to an embodiment of the present invention. Figure 12 This diagram illustrates a hydrogen-water phase permeation curve provided by an embodiment of the present invention. Figure 13 This is a schematic block diagram showing the composition of a device for determining the hydrogen-water phase permeation curve of an underground hydrogen storage facility according to an embodiment of the present invention; Figure 14 This diagram illustrates the composition of an electronic device for determining the hydrogen-water phase permeation curve in an underground hydrogen storage facility, as provided in an embodiment of the present invention. Detailed Implementation

[0019] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0020] To address the challenge of obtaining highly accurate hydrogen-water phase permeation curves using existing technologies, this invention provides a method for determining hydrogen-water phase permeation curves in underground hydrogen storage facilities, such as... Figure 1 As shown, the method includes: S101. Obtain microscopic computed tomography images of rock samples during the hydrogen-driven water displacement process, wherein the rock samples are test samples collected from natural hydrogen storage reservoirs. In one embodiment, acquiring microscopic computed tomography images of rock samples during hydrogen-driven water displacement includes: Microscopic computed tomography (CT) images of the rock sample were acquired under a simulated hydrogen-driven water displacement operation, wherein the simulated hydrogen-driven water displacement operation was used to simulate the gas injection operation of a hydrogen storage tank; the microscopic CT images were denoised using median filtering technology. The micro-computed tomography image was segmented using watershed segmentation technology to extract the distribution of hydrogen and water in the pore space of the rock.

[0021] For example, a rock sample refers to a real physical rock core directly collected from a natural hydrogen storage reservoir, serving as the basis for subsequent analysis. A micro-computed tomography (Micro-CT) image is a three-dimensional digital image obtained by imaging the rock sample using computed tomography technology. This image clearly characterizes the distribution of hydrogen and water within the pore space of the rock. Hydrogen-driven water displacement simulation of hydrogen storage reservoir injection refers to the physical experimental process of injecting hydrogen to displace the water phase from a rock sample in a laboratory environment to simulate the hydrogen storage reservoir injection process under reservoir conditions. Median filtering is an image processing method that effectively suppresses random noise introduced during scanning by calculating the median of the pixel neighborhood. The watershed segmentation method treats the image as a topographic surface, simulating the process of floodwater spreading and converging from local minima, ultimately forming a watershed boundary at the confluence to achieve image segmentation.

[0022] In this application, a microscopic visualization displacement experimental system is first configured in the laboratory. Rock samples are placed in this system to simulate the temperature and pressure conditions of an underground hydrogen storage reservoir. Hydrogen is injected into the rock sample with a saturated aqueous phase at a constant flow rate to simulate the hydrogen injection process of the reservoir. During this physical simulation, a computed tomography (CT) scanner is simultaneously activated to continuously scan the rock sample, capturing the real-time dynamic distribution of hydrogen and water two-phase fluids within the pores, thus obtaining a series of time-series images. Subsequently, a median filtering algorithm is used to process the acquired raw images. This algorithm selects the median of the gray values ​​of all pixels within a predetermined window surrounding each pixel to replace the current pixel value, thereby smoothing out isolated noise points in the image while preserving the sharp information of the pore edges and fluid interface. For example, when the scanned image shows scattered points due to electronic interference from the equipment, median filtering can effectively eliminate these discrete noise points without blurring the pore boundaries. Combined with watershed segmentation technology, the filtered image is segmented into three phases: rock solid, hydrogen, and water, to accurately extract the distribution of hydrogen and water in the rock pore space.

[0023] By employing the aforementioned technical solution, microscopic computed tomography (CT) images are directly acquired during the hydrogen-driven water physics simulation process. This ensures that the acquired images accurately reflect the initial state of the hydrogen and water two-phase distribution in the underground hydrogen storage reservoir after gas injection, providing more realistic input data for subsequent digital modeling. Furthermore, the application of mean-mode filtering for image preprocessing significantly reduces the impact of scanning noise on the accuracy of pore structure extraction and fluid identification. Combined with watershed segmentation technology, the distribution of hydrogen and water in the rock pore space is accurately extracted, thereby improving the reliability of the entire digital reconstruction and simulation process from the data source. This approach transforms high-cost, repetitive physical experiments into one-time, high-quality data acquisition, reducing safety risks and experimental complexity.

[0024] S102. Perform characterization unit volume analysis on the pore structure of the micro-computed tomography image to construct a first pore structured mesh model, wherein the first pore structured mesh model is used to characterize the pore structure of the rock sample, the first pore structured mesh model is a geometric structure model, and the first pore structured mesh model includes a coordinate system of the pore structure. In one embodiment, the step of characterizing the pore structure of the microscopic computed tomography image to construct a first pore-structured mesh model includes: Crop cube sub-images with different side lengths from the center of the microscopic computed tomography image; Calculate the porosity and water saturation of each of the cubic sub-images; Based on the porosity and water saturation of each cube sub-image, the fluctuation trend of porosity and water saturation is determined. When the fluctuation trend of porosity and water saturation is less than a preset amplitude, the corresponding smallest cube sub-image is determined to be the characterizing unit cell model; Each image pixel of the characterization unit model is converted into a hexahedral mesh unit to form the first pore structured mesh model.

[0025] For example, the above scheme utilizes microscopic computed tomography images to study representative features of rock pore structure. Porosity characterizes the proportion of the total volume occupied by pore space in a rock, while water saturation describes the proportion of the pores filled with water. Representative Elementary Volume (REV) analysis aims to select a minimum-sized volume element from large-scale image data that is sufficient to reflect the statistical characteristics of the overall pore and fluid distribution in the rock. The first pore structured mesh model is a three-dimensional mesh structure constructed digitally that accurately reflects the geometry of rock pores. Its coordinate system provides a spatial reference framework for subsequent attribute mapping.

[0026] The results of the above characterization unit analysis are as follows: Figure 2 As shown, the fluctuation range of the calculated porosity and water saturation of the extracted cube image subset gradually decreases with increasing side length. When the side length of the cube image subset exceeds 200 pixels, its corresponding porosity and water saturation values ​​tend to stabilize and no longer change significantly with increasing size. Therefore, based on this stabilizing trend, this application determines the 200-pixel cube image subset extracted from the center of the original segmented image as the REV model for the hydrogen-water distribution image of this rock.

[0027] The above-mentioned characterization unit model is as follows: Figure 3 As shown in the figure, in this three-dimensional digital core model, different colors identify different phases: gray represents the solid particles of the rock, while blue and red represent the water and hydrogen phases distributed in the pore space, respectively. Based on the spatial resolution of the obtained microscopic computed tomography images of 5 μm, the physical size of this characterization unit model is 1 mm × 1 mm × 1 mm. This characterization unit model can effectively represent the statistical characteristics of the hydrogen-water distribution in the pore space of the entire rock sample after undergoing a hydrogen-driven water displacement process. Furthermore, using this representative unit volume for simulation helps to significantly reduce the computational resource consumption of subsequent numerical simulations.

[0028] The first pore structured mesh model constructed based on the characterization unit model is as follows: Figure 4As shown, this model consists of a total of 2.56 million hexahedral mesh elements and 8.24 million quadrilateral mesh elements, laying the geometric foundation for subsequent numerical simulations of hydrogen-water two-phase flow. The computational domain represented by this mesh model precisely corresponds to the pore space jointly occupied by the hydrogen and water phases in the REV model. This provides the necessary guarantee for the computational accuracy and numerical convergence of subsequent two-phase flow simulations.

[0029] This application extracts a series of cubic sub-images with increasing side lengths from the central region of the acquired microscopic computed tomography (CT) images. For each sub-image, the porosity and water saturation values ​​are calculated. By observing the fluctuations of these parameter values ​​as the sub-image size increases, the smallest sub-image corresponding to the point where the fluctuation amplitude significantly decreases and enters a stable plateau is identified and established as the representative unit model. Subsequently, using the technique of equivalent conversion between image pixels and grid cells, each image pixel in the representative unit model is transformed in situ and one-to-one into a regular hexahedral grid cell. All these grid cells are assembled together to form a first pore structured grid model with a geometric shape. For example, when the side length of the sub-image increases to a certain critical value, the calculated porosity and water saturation values ​​no longer fluctuate drastically, but rather fluctuate slightly within a very narrow range. At this point, the sub-image of that size is selected as the optimal representative unit.

[0030] It is understandable that the above fluctuation trend being less than the preset amplitude refers to the stable state that is presented when the changes in porosity and water saturation values ​​calculated by the successively increasing cube sub-images with increasing size decrease to a preset, acceptable threshold range.

[0031] By employing the above technical solutions and scientifically determining the characterization unit model, the constructed digital core model is ensured to fully represent the macroscopic statistical characteristics of rocks while maximizing the optimization of computational scale and avoiding the resource consumption caused by directly processing massive full-size data. Through the equivalent conversion from pixels to grids, the generated pore structured grid model replicates the complex pore channel geometry of real rocks with high quality, laying a reliable geometric foundation for subsequent flow simulation.

[0032] S103. Using the coordinate system of the first pore structured grid model as a reference, the wettability distribution data is mapped to the first pore structured grid model through the corresponding coordinate position to obtain the second pore structured grid model. The wettability distribution data is calculated along the three-phase contact line of rock, hydrogen and water extracted from the micro-computed tomography image. In one embodiment, the above method further includes: Using the traveling cube algorithm, a multiphase surface mesh model is obtained based on the characterization unit model. The multiphase surface mesh model is used to characterize the distribution of phase interfaces of hydrogen, water and rock solid. Extract each contact point on the three-phase contact line of rock, hydrogen and water from the multiphase surface mesh model; Calculate the in-situ contact angle of each contact point on the three-phase contact line, wherein the in-situ contact angle corresponding to any contact point is obtained by calculating the angle between the unit normal vector of the hydrogen-water phase interface and the unit normal vector of the water-rock solid phase interface at the contact point. Within the space of the characterizing unit model, using the average pore diameter as the moving window size, the local average value of the in-situ contact angle is statistically analyzed to obtain the wettability distribution data.

[0033] For example, the above scheme quantifies the physical properties of rock surfaces from the geometric information contained in microscopic computed tomography images. The multiphase surface mesh model is a three-dimensional surface mesh reconstructed using a specific algorithm, capable of accurately depicting the interface between hydrogen, water, and solid rock. The three-phase contact line is the boundary line formed by the spatial convergence of the three phases: hydrogen, water, and rock. The in-situ contact angle is the angle between the hydrogen-water interface and the water-solid rock interface at any point along this contact line, directly reflecting the wetting characteristics of that local point. The local average value is the result of statistically averaging all in-situ contact angle measurements within a given spatial range, used to characterize the average wettability of that local area.

[0034] The in-situ contact angle spatial distribution results obtained based on the characterization unit model are as follows: Figure 5 As shown in the figure, different colors represent the differences in in-situ contact angle values. This distribution indicates that the in-situ contact angle of the rock-hydrogen-water multiphase system exhibits significant spatial heterogeneity along the three-phase contact line. This objective phenomenon confirms that, in order to accurately simulate the two-phase flow behavior of hydrogen and water within rock pores, it is essential to effectively model the in-situ heterogeneous wettability of the rock-hydrogen-water multiphase system.

[0035] In this embodiment, the specific process for obtaining wettability distribution data is as follows: First, based on the determined characterization unit cell model, the traveling cubes algorithm is applied to process the image data to generate a multiphase mesh model that accurately depicts the interface between hydrogen, water, and rock solids. Then, the contact line where the three phases of rock, hydrogen, and water coexist is automatically identified and extracted on this model, and a series of dense contact points on this line are located. For each contact point, the normal vector direction of the hydrogen-water phase interface unit at that point is calculated, and the normal vector direction of the water-rock solid phase interface unit is also calculated. The angle between these two vector directions is then solved, and this angle is the in-situ contact angle of that point. To transform the microscale point measurement data into continuous field data suitable for pore-scale simulation, within the entire characterization unit cell model space, using the average pore diameter obtained through image analysis as the size of the statistical window, a non-overlapping moving window system systematically traverses the entire space, calculating the arithmetic mean of the in-situ contact angle values ​​of all contact points falling within each window, ultimately obtaining a spatially distributed wettability distribution data field.

[0036] For any contact point i on the rock-hydrogen-water three-phase contact line, its in-situ contact angle θ with reference to the aqueous phase is... i Defined by the following formula:

[0037] in, Defined as the in-situ contact angle at contact point i, it directly characterizes the wettability at that local location; Defined as the unit normal vector of the hydrogen-water interface at contact point i; Defined as the unit normal vector of the water-rock solid phase interface at contact point i.

[0038] By employing the aforementioned technical solution, and directly extracting the three-phase contact line from the geometry of real images and calculating the in-situ contact angle point by point, a direct and quantitative characterization of the heterogeneous wettability of rock surfaces is achieved, avoiding the physical distortion caused by the assumption of uniform wettability in traditional numerical simulations. Furthermore, by performing local statistical averaging using a moving window scaled to the pore diameter, the discrete point measurement data is reasonably upscaled into continuously distributed field data. This preserves the spatial variability of rock surface wettability and makes it suitable for subsequent numerical simulations of hydrogen and water two-phase flows at the pore scale. This process ensures that the obtained wettability distribution data accurately reflects the in-situ heterogeneous wetting conditions of the underground reservoir, providing crucial and reliable input parameters for constructing a fully physical digital core model and achieving high-fidelity hydrogen and water two-phase flow simulations.

[0039] In one embodiment, the step of mapping the wettability distribution data to the first pore structured mesh model through corresponding coordinate positions, using the coordinate system of the first pore structured mesh model as a reference, to obtain a second pore structured mesh model includes: Determine the center point coordinates of each wall grid cell in the first pore structured mesh model, wherein the wall grid cell is the grid cell that contacts the pore under fluid flow conditions; Determine the local average value of the in-situ contact angle in the wettability distribution data corresponding to the coordinates of each of the aforementioned center points; The local average value of the in-situ contact angle is assigned to the wall mesh element corresponding to the coordinate position in the first pore structured mesh model to obtain the second pore structured mesh model.

[0040] like Figure 6 As shown, the left side provides a visual representation of the heterogeneous distribution of contact angles. The colors are distributed randomly and erratically across the pore walls, rather than being a single color, confirming the heterogeneity of wettability. The right side shows the corresponding pore structure morphology, representing the exact same physical region as the left image, demonstrating the geometric undulations and topological structure of the rock pore walls. A local window for statistical analysis is defined within the pore space, indicating the same physical region in both images. Operations are performed within this window. Local averaging calculates the average of all contact angle measurements within this window. This average value is used as the wettability attribute of the region represented by the window. By sliding this window across the entire pore space and performing non-repeating statistics, a smoothed wettability data distribution map covering the entire pore wall is obtained.

[0041] This application generates an enhanced second pore structured mesh model by precisely assigning the acquired wettability distribution data to the corresponding positions in the first pore structured mesh model. Here, the wall mesh element specifically refers to those mesh elements in the first pore structured mesh model that directly interact with the rock solid surface during fluid flow; the center point coordinates are the spatial location of the geometric center of each wall mesh element; and the local average value of the in-situ contact angle is statistical data characterizing the average wettability of a local region on the rock surface, calculated based on microscopic computed tomography images.

[0042] In this embodiment, the mapping process is implemented as follows: First, all wall mesh elements in the first porous structured mesh model are traversed, and the center point coordinates of each element are calculated and recorded. These coordinates define the precise position of the model wall in three-dimensional space. Then, based on the first model and the wettability distribution data source, such as the same coordinate system shared by the characterization unit model, for each center point coordinate, the local average value of the in-situ contact angle corresponding to its spatial position is found in the wettability distribution data field. Finally, through one-to-one coordinate matching, each local average value of the queried in-situ contact angle is used as a physical attribute value and directly assigned to the wall mesh element in the first porous structured mesh model whose coordinate position completely corresponds to it.

[0043] For example, for a wall mesh element located at coordinates (x1, y1, z1), the system will find the local average contact angle value also located at (x1, y1, z1) in the wettability distribution data and assign it to the element, thus completing the attribute mapping of a point. By traversing all wall elements, the first model, which originally only contained geometric information, is finally transformed into a second pore structured mesh model that simultaneously contains geometric structure and real heterogeneous wettability attributes.

[0044] By employing the aforementioned technical solution, wettability distribution data is assigned to the wall grid cells through precise coordinate mapping, achieving a high-fidelity fusion of the heterogeneous wettability properties of the rock surface and the pore geometry. This allows the generated second-pore structured grid model to accurately reflect the spatial variations in wettability caused by uneven mineral distribution in the underground reservoir. This process ensures that the boundary conditions for subsequent two-phase flow numerical simulations are highly consistent with the in-situ physical properties of the rock, thereby reducing simulation bias caused by the assumption of uniform wettability, improving the reliability of fluid migration path and phase distribution predictions, and laying a physical foundation for obtaining more accurate phase permeability curves.

[0045] S104. Perform a two-phase flow simulation operation on the second porous structured grid model to obtain the hydrogen and water phase permeation curves of the hydrogen storage tank. The two-phase flow simulation operation is a simulation operation in which the hydrogen phase in the second porous structured grid model is replaced by the water phase.

[0046] In one embodiment, the above method further includes: Boundary conditions for single-phase flow simulation are set on the first porous structured grid model. The single-phase flow simulation is to simulate water injection into the first porous structured grid model to simulate the flow of water phase in the first porous structured grid model. The boundary conditions include setting the water injection inlet to a fixed pressure and the water injection outlet to a zero pressure value. The walls of the first porous structured grid model other than the inlet and outlet are set as impermeable boundaries. Under the stated boundary conditions, the flow of the water phase in the first porous structured grid model is simulated using the finite volume method. Once the simulation process reaches the convergence criterion, the absolute permeability of the first pore structured mesh model is calculated using Darcy's law.

[0047] It can also be understood as: Boundary conditions for simulating single-phase flow of water injection are set on the first pore structured grid model. The single-phase flow simulation is to simulate water injection operation into the first pore structured grid model. The boundary conditions include setting the inlet of the water injection operation to a fixed pressure, setting the outlet of the water injection operation to a zero pressure value, and setting the wall of the first pore structured grid model other than the inlet and outlet to an impermeable boundary. Under the stated boundary conditions, the continuity equation and momentum equation controlling the water phase flow are discretized and solved using the finite volume method to simulate the single-phase flow of water in the first pore structured grid model. The continuity equation is used to define the mass conservation law of water in the first pore structured grid model, and the momentum equation is used to define the momentum conservation law of water in the first pore structured grid model. When the solution process reaches the convergence criterion, Darcy's law is used to calculate the absolute permeability of the first pore structured grid model based on the water phase viscosity, outlet volumetric flow rate, model length, and cross-sectional area. The convergence criterion is a preset flow field solution that satisfies the physical conservation laws.

[0048] For example, this step involves obtaining basic seepage characteristic parameters of a rock sample through numerical simulation. Single-phase flow simulation specifically refers to a simulation process that considers only the water phase flow in a porous model. In the boundary conditions, the fixed pressure set at the inlet and the zero pressure set at the outlet of the water injection operation together form the driving force for the water phase flow, while the impermeable boundary ensures that the fluid flows only between the preset inlet and outlet. The finite volume method is a numerical method that discretizes the computational domain and integrates the governing equations. The continuity equation describes the law of mass conservation in the fluid flow process, and the momentum equation defines the motion law of the fluid under the action of driving force and viscous force. The convergence criterion is the basis for judging whether the numerical solution satisfies the physical conservation laws. Darcy's law reveals the relationship between the seepage velocity and pressure gradient of a fluid in a porous medium. Absolute permeability is an inherent property parameter characterizing the rock's ability to conduct single-phase fluids.

[0049] The specific implementation process of this step is as follows: First, a fixed pressure is set at the inlet boundary of the first pore structured grid model, a zero pressure value is set at the outlet boundary, and the remaining walls are set as impermeable boundaries to establish stable flow driving conditions. Then, the computational domain is discretized into grid cells using the finite volume method. The continuity and momentum equations controlling the water phase flow are spatially and temporally discretized. The pressure and velocity distribution on each grid cell are obtained through iterative solutions, achieving an accurate simulation of water flow in the pore model. When the solution results meet the preset convergence criterion, i.e., the flow field parameters tend to stabilize, the absolute permeability value of the rock model is calculated based on Darcy's law, combined with the known water phase viscosity, the simulated outlet volumetric flow rate, and the geometric length and cross-sectional area parameters of the model.

[0050] In the process of calculating absolute permeability based on Darcy's law, the absolute permeability of the first pore structured mesh model is defined by the following formula:

[0051] in, This represents the absolute permeability of the first pore structured mesh model. Indicates the viscosity of the aqueous phase. This represents the outlet volumetric flow rate of the first pore structured mesh model. This represents the length of the first pore structured mesh model along the flow direction. This represents the cross-sectional area of ​​the first pore structured mesh model perpendicular to the flow direction. Indicates inlet pressure, This indicates export pressure.

[0052] By employing the aforementioned technical solution, and through setting reasonable boundary conditions and applying the finite volume method to solve the fluid motion equations, the aqueous phase seepage process can be reproduced with high fidelity in a digital core model, providing a reliable numerical experimental environment for obtaining absolute permeability. This method transforms complex physical measurements into controllable computer simulations, avoiding dependence on experimental equipment. The calculated absolute permeability serves as a benchmark parameter, providing a standardized basis for subsequent relative permeability calculations, ensuring the accuracy and comparability of the relative permeability curve determination results, and providing crucial data support for evaluating reservoir seepage characteristics.

[0053] In one embodiment, the step of performing a two-phase flow simulation of water-driven hydrogen on the second pore structured mesh model to obtain the hydrogen-water phase permeation curve of the hydrogen storage reservoir includes: Set reservoir temperature and pressure conditions on the second pore structured grid model; Determine the water phase density, water phase viscosity, hydrogen density, hydrogen viscosity, and hydrogen-water interfacial tension coefficient under the specified reservoir temperature and pressure conditions. The hydrogen and water distribution characterized by the micro-computed tomography image is set as the initial fluid distribution for the two-phase flow simulation of water-driven hydrogen. Boundary conditions for simulating the two-phase flow of water-driven hydrogen are set on the second porous structured grid model. The boundary conditions include setting the inlet of the water injection operation to a constant velocity for injecting the water phase, setting the outlet of the water injection operation to a zero pressure value, and setting the walls of the second porous structured grid model other than the inlet and outlet to impermeable boundaries. Under the boundary conditions, the fluid volume method is used to simulate the two-phase flow of water-driven hydrogen in the second pore structured mesh model, so as to obtain the effective permeability of hydrogen and the effective permeability of water phase under different water saturation during the simulation of the two-phase flow of water-driven hydrogen. Based on the effective hydrogen permeability, effective water phase permeability, and absolute permeability at different water saturations, the relative hydrogen permeability and relative water phase permeability at different water saturations are determined. The hydrogen-water phase permeability curves of the hydrogen storage tank are determined based on the relative permeability of hydrogen and water phase under different water saturation levels.

[0054] It can also be understood as: Set reservoir temperature and pressure conditions on the second pore structured grid model; Determine the water phase density, water phase viscosity, hydrogen density, hydrogen viscosity, and hydrogen-water interfacial tension coefficient under the specified reservoir temperature and pressure conditions. The hydrogen and water distribution characterized by the micro-computed tomography image is set as the initial fluid distribution for the two-phase flow simulation of water-driven hydrogen. Boundary conditions for simulating the two-phase flow of water-driven hydrogen are set on the second porous structured grid model. The boundary conditions include setting the inlet of the water injection operation to a constant velocity for injecting the water phase, setting the outlet of the water injection operation to a zero pressure value, and setting the walls of the second porous structured grid model other than the inlet and outlet to impermeable boundaries. Under the boundary conditions, the fluid volume method is used to discretize and solve the equations controlling the fluid motion to simulate the two-phase flow of water-driven hydrogen in the second pore structured grid model. The fluid motion equations are used to calculate the motion law of the hydrogen-water interface affected by the heterogeneous wettability in the second pore structured grid model. If the solution process reaches the convergence criterion, the fluid distribution data of each grid cell of the second pore structured mesh model under different water saturation levels are extracted. Based on the fluid distribution data, a three-dimensional digital image of the distribution of the water phase and the hydrogen phase is generated; Connectivity analysis was performed on the three-dimensional digital image to screen out connected hydrogen and water phase regions; Using the method of equivalent conversion between image pixels and grid cells, a single-phase flow grid model is constructed for each of the connected hydrogen phase and water phase regions; Determine the effective permeability of hydrogen and the effective permeability of water in the structured grid model constructed by connecting the hydrogen and water phases; The hydrogen effective permeability and the aqueous phase effective permeability at each water saturation level are divided by the absolute permeability to obtain the hydrogen relative permeability and the aqueous phase relative permeability. The hydrogen-water phase permeability curves are generated based on the relative permeability of hydrogen and the relative permeability of water phase at different water saturation levels.

[0055] For example, the above scheme simulates the two-phase flow process of water displacing hydrogen under real reservoir conditions on a second-pore structured grid model with heterogeneous wetting properties to obtain phase permeability curves characterizing reservoir seepage characteristics. Reservoir temperature and pressure conditions refer to the temperature and pressure parameters simulating the actual environment of the underground hydrogen storage tank. Water phase density, water phase viscosity, hydrogen density, hydrogen viscosity, and the hydrogen-water interfacial tension coefficient are physical property parameters exhibited by the fluid under the above reservoir conditions, which collectively affect the interaction and transport behavior of the two-phase fluids. The hydrogen and water distribution characterized by microscopic computed tomography images reflects the initial spatial configuration of the hydrogen and water phases in the rock pores after gas injection into the hydrogen storage tank. In the boundary conditions of the water-driven hydrogen two-phase flow simulation operation, the water injection inlet is set to inject water phase at a constant velocity to provide driving force, the outlet is set to zero pressure, and the model walls other than the inlet and outlet are set as impermeable boundaries to constrain the flow path. The fluid volume method is a numerical simulation method used to trace phase interfaces. Water saturation represents the volume fraction of water in the pore space. Effective hydrogen permeability and effective aqueous permeability represent the effective conductivity of hydrogen and water phases through rock pores at a specific water saturation level, respectively. Absolute permeability is an inherent property parameter of the rock itself for conducting single-phase fluids. Relative hydrogen permeability and relative aqueous permeability are the ratios of the effective permeability to the absolute permeability of each phase, used to quantify the flow capacity when two phases coexist. Hydrogen and aqueous phase permeability curves are graphs characterizing the relationship between relative permeability and water saturation.

[0056] The initial fluid distribution settings for the water-driven hydrogen two-phase flow simulation are as follows: Figure 7 As shown, red and blue indicate the hydrogen and water phases occupying the pore space, respectively. To improve simulation convergence, a reservoir saturated with water and hydrogen phases was added to the left and right ends of the second pore structured mesh model during the actual simulation. This was used to supply water at the left end of the pore model and recover produced fluid at the right end. During the simulation, a V1 was applied at the inlet boundary. i=7.5×10 - 4 A constant velocity of m / s is injected into the water phase to displace the hydrogen phase, and the outlet boundary is set as follows: Under the pressure condition of 0 Pa, all other wall surfaces in the model are set as impermeable boundaries. Based on this injection rate V... i and the determined aqueous phase viscosity μ w The capillary number Ca = μ is calculated from the hydrogen-water interfacial tension coefficient σ. w V i / σ=6×10 -6 The capillary values ​​are within the common range of hydrogen-water two-phase flow dynamics in typical underground hydrogen storage reservoirs, indicating that the set simulation conditions can effectively reflect the flow characteristics of actual reservoirs.

[0057] The boundary conditions for the two-phase flow simulation of water-driven hydrogen are as follows: Figure 8 As shown, a constant velocity injection is performed on the left side of the aqueous reservoir, while the extracted fluid is recovered at a zero-pressure boundary on the right side of the hydrogen reservoir. The initial hydrogen-water distribution in the central porous media region is derived from the hydrogen-water distribution described in a micro-computed tomography image. This setup simulates the initial spatial separation of the hydrogen and water phases at a moment after hydrogen injection into an underground hydrogen storage reservoir, before hydrogen extraction begins (i.e., before water recirculation). The velocity inlet on the left (blue side) is located on the aqueous reservoir side, with a constant velocity injection boundary condition. Water is continuously injected at this location at a fixed velocity during the simulation. This is the active driving force for the simulated water drive process. The velocity inlet is chosen to precisely control the injection rate, ensuring that the simulated capillary number falls within the common range of real reservoirs. Similarly, another pressure inlet could be considered for this application. The pressure outlet on the right (gray side) is located on the hydrogen reservoir side. The boundary condition is set to fixed pressure, typically... =0 Pa, serving as the reference pressure point. The displaced hydrogen and subsequent water will exit from here. The boundary condition type of the wall is impermeable boundary, no-slip wall, meaning that no fluid will pass through these surfaces; the fluid can only flow from the inlet to the outlet within the model. This simulates the real situation where rock is surrounded by impermeable strata, ensuring that the flow is a displacement process from inlet to outlet. The arrow in the figure clearly indicates the physical process in this simulation: water is injected from the left, displacing the hydrogen in the pores to the right, and finally exiting from the outlet on the right.

[0058] It should be noted that, according to V i =7.5×10 -4 The capillary number, calculated from the injection velocity of m / s, is Ca = μ. w V i / σ=6×10 -6This number of capillary tubes falls within the common range for hydrogen-water two-phase flow in underground hydrogen storage facilities.

[0059] Understandably, in numerical simulations, the inlet boundary conditions can be set using either a constant injection rate or a fixed injection pressure, depending on the specific research requirements. Both methods share the same physical essence and objective in simulating water-driven hydrogen flow: by controlling the driving conditions at the inlet, a stable driving force is formed within the pore space, thereby achieving continuous displacement of the hydrogen phase. Choosing a constant injection rate directly controls the capillary number to fall within the typical range of the actual reservoir, ensuring the realism of the flow dynamics. Conversely, if a fixed pressure injection is used, as long as the average driving force formed is consistent with the gradient corresponding to the constant rate condition, an equivalent displacement effect and the same simulation objective can be achieved—effectively reproducing the two-phase flow behavior of water displacing hydrogen under reservoir conditions. Therefore, both methods, under reasonable parameters, can be considered different technical paths to achieve the same simulation objective.

[0060] Two-phase flow simulation of water-driven hydrogen was performed under set boundary conditions, and the fluid distribution results at different times were obtained. Figure 9 This shows the water saturation of the system at simulation time t=12ms. The figure shows the distribution of hydrogen and water phases in the pore space at a concentration of 0.62. In the figure, the red area represents the pore space occupied by the hydrogen phase, and the blue area represents the pore space occupied by the water phase. This transient distribution result intuitively reflects the microscopic configuration of the hydrogen and water phases in a heterogeneous wetted pore network at a specific water saturation level.

[0061] Specifically, under the simulated conditions of an in-situ reservoir temperature of 50℃ and a pressure of 10MPa, and by consulting standard databases, the corresponding fluid properties were determined: the density of the aqueous phase ρw = 992.31 kg / m³, and the viscosity of the aqueous phase μw = 5.49 × 10⁻⁶. -4 Pa·s; the density of hydrogen gas ρh = 7.10 kg / m³, and the viscosity of hydrogen gas μh = 9.51 × 10⁻⁶ Pa·s; -6 Pa·s; the interfacial tension coefficient between the aqueous phase and hydrogen gas σ = 6.83 × 10⁻⁶. - ²N / m.

[0062] For example, to obtain a specific water saturation The effective permeability of each phase fluid under the given conditions was calculated using the same single-phase flow simulation method as for calculating absolute permeability. The pore space formed by the connected hydrogen phase region and the connected water phase region at this saturation level was simulated separately. Water saturation was used as the metric. Taking a value of 0.62 as an example, the streamline distribution shown in the single-phase flow simulation results of the connected hydrogen phase region is as follows: Figure 10As shown, this result characterizes the permeability of hydrogen in its connected pathway. The streamline distribution shown in the single-phase flow simulation results of the connected aqueous region is as follows. Figure 11 As shown, the results characterize the seepage capacity of water in its connected pathways.

[0063] Based on the above-mentioned specific water saturation Under the given conditions, single-phase flow simulations were performed on the connected pore water phase region and the connected pore hydrogen phase region, respectively. Based on Darcy's law, the effective permeability of each phase fluid at this saturation level was calculated. Effective permeability of the water phase. Effective permeability with hydrogen phase Calculated using the following formulas respectively:

[0064]

[0065] in, To achieve water saturation Under the given conditions, the effective permeability of the aqueous phase; To achieve the same water saturation Under the given conditions, the effective permeability of the hydrogen phase; The volumetric flow rate of the water phase at the outlet boundary when performing single-phase flow simulation on a connected water phase region; The hydrogen phase volumetric flow rate obtained at the outlet boundary when performing single-phase flow simulation on a connected hydrogen phase region; The length of the pore model along the flow direction; This represents the cross-sectional area of ​​the pore model perpendicular to the flow direction. and These are the inlet and outlet pressures set in the simulation, respectively.

[0066] To obtain a specific water saturation The relative permeability under the given conditions will be the effective permeability of the aqueous phase at that saturation level, obtained based on single-phase flow simulation. Effective permeability with hydrogen phase The absolute permeability of the original pore model is respectively compared with that of the original pore model. Normalization was performed. The relative permeability of the aqueous phase was then calculated. Relative permeability with hydrogen phase Defined by the following formula:

[0067]

[0068] in, Defined as at water saturation Under certain conditions, the relative permeability of the aqueous phase; Defined as at the same water saturation Under certain conditions, the relative permeability of the hydrogen phase; To achieve water saturation The effective permeability of the aqueous phase obtained through single-phase flow simulation under the given conditions; To achieve water saturation Effective hydrogen phase permeability obtained through single-phase flow simulation under the given conditions; This represents the absolute penetration rate.

[0069] By iteratively executing the steps described above—from extracting fluid distribution data at a specific saturation level, to simulating the effective permeability of each phase, and finally determining the relative permeability—a series of data with different water saturation levels can be obtained. Relative permeability of water phase under the corresponding conditions relative permeability with hydrogen Based on the obtained discrete data points, a hydrogen-water two-phase flow phase permeation curve characterizing the relationship between relative permeability and water saturation is finally generated. The complete hydrogen-water two-phase flow phase permeation curve is shown below. Figure 12 As shown, the results intuitively reveal the dynamic variation law of hydrogen and water two-phase permeation capacity in the underground hydrogen storage reservoir under the aforementioned heterogeneous wettability conditions.

[0070] In this embodiment, the specific method for implementing this process is as follows: First, temperature and pressure conditions consistent with the actual reservoir are set on the second pore structured grid model, and the density, viscosity, and interfacial tension coefficient between the water phase and hydrogen are queried or calculated under these conditions. The hydrogen-water distribution state captured in the micro-computed tomography image is set as the initial condition for the simulation, realistically reproducing the fluid distribution of the reservoir at a certain moment after gas injection into the underground hydrogen storage tank. Boundary conditions are set on the model: the inlet continuously injects the water phase at a constant rate, the outlet maintains the reference pressure, and the remaining walls are impermeable boundaries to simulate the hydrogen extraction process driven by water. The fluid volume method is used to discretize and solve the equations controlling the motion of the two-phase fluids, accurately simulating the dynamic process of how the water phase displaces the hydrogen phase, how the two-phase interface evolves, and how heterogeneous wettability affects the micro-distribution of hydrogen-water. When the simulation calculation reaches the convergence criterion, that is, when the flow field solution satisfies the physical conservation law, the fluid volume fraction data of each grid cell in each state is extracted for a series of different water saturation states reached during the simulation. Based on this data, a three-dimensional digital image of the pore space occupied by the aqueous and hydrogen phases is generated through coordinate inversion. Connectivity analysis is performed on this image to identify interconnected hydrogen and aqueous phase regions, and independent single-phase flow mesh models are constructed for each of these connected regions. Flow simulation is performed on the single-phase flow mesh model of each connected region to calculate the effective permeability of the hydrogen and aqueous phases at that saturation level. The effective permeability at each saturation level is divided by the pre-obtained absolute permeability to obtain the corresponding relative permeability value. Finally, the relative permeability data points at different saturations are connected to form a complete hydrogen-water phase permeability curve.

[0071] Understandably, the inlet boundary conditions mentioned in the above scheme can be set as either constant velocity inlet boundary conditions or fixed pressure inlet boundary conditions. The key is to provide continuous driving conditions for the water phase to displace the hydrogen phase. Considering that water is an incompressible fluid, it can provide more stable pressure boundary conditions in pore-scale flow simulations; the physical properties of water are more stable under conventional reservoir conditions, which is beneficial to improving the repeatability of simulation results.

[0072] By employing the aforementioned technical solution, the two-phase displacement process under real reservoir conditions can be simulated on a digital core model with complete physical properties. This allows for the accurate reproduction of the hydrogen-water phase interface migration behavior on the surface of heterogeneous wetted pores, thereby obtaining effective permeability data that reflects actual geological conditions. By correlating effective permeability with absolute permeability to calculate relative permeability, data standardization and comparability are ensured. This method significantly reduces the high cost and safety risks of traditional laboratory experiments and avoids the distortion problems caused by the assumption of uniform wettability in traditional numerical simulations. The resulting phase permeability curve more accurately reflects reservoir dynamics, providing a reliable basis for optimizing hydrogen storage injection and production schemes and predicting performance.

[0073] In summary, the method for determining the hydrogen and water phase permeability curves of underground hydrogen storage reservoirs involved in this application achieves a high-fidelity characterization of the two-phase flow behavior of hydrogen and water in rock pores by comprehensively utilizing microscopic computed tomography (CT) technology, digital core modeling, and pore-scale numerical simulation. Rock samples were collected from natural hydrogen storage reservoirs, and their microscopic CT scans were obtained. This process was conducted under laboratory hydrogen-driven water-fluidized simulated hydrogen storage reservoir injection operations. Median filtering was used to reduce image noise and improve data quality. Simultaneously, watershed segmentation was used to segment the filtered images, accurately extracting the distribution of hydrogen and water in the rock pore space. Subsequently, the pore structure of the images was analyzed using characterization unit cell analysis. By extracting cubic sub-images of different sizes and calculating porosity and water saturation, the smallest representative sub-image with a stable fluctuation trend was identified as the characterization unit cell model. This model was then converted into a hexahedral mesh to form the first pore structured mesh model. This model accurately replicates the geometric structure of the rock and includes a coordinate system. Based on segmented microscopic computed tomography images, a multiphase surface mesh model was generated using the traveling cubes algorithm. Points on the rock-hydrogen-water three-phase contact line were extracted, and the angle between the normal vectors of the hydrogen-water interface and the water-rock interface at each point was calculated as the in-situ contact angle. The local average value of the in-situ contact angle was statistically calculated using the average pore diameter as a window to obtain wettability distribution data. Based on this, the wettability distribution data was assigned to the wall mesh elements of the first pore structured mesh model through coordinate mapping, generating a second pore structured mesh model that simultaneously includes geometric and wettability properties. Then, a single-phase flow simulation of water was performed on the first pore structured mesh model, setting boundary conditions of fixed inlet pressure and zero outlet pressure. The flow equations were solved using the finite volume method, and the absolute permeability was calculated using Darcy's law after convergence. Finally, the water-driven hydrogen process under real reservoir temperature and pressure conditions was simulated on the second model. The physical properties of hydrogen and water and the initial fluid distribution were set. The fluid volume method was applied to simulate two-phase flow, and the effective permeability under different water saturation was obtained. The relative permeability was derived by combining the absolute permeability, and finally the relative permeability curve was generated.

[0074] By employing the aforementioned technical solution, the high-cost indoor core displacement experiment is transformed into a digital modeling process based on microscopic computed tomography images, reducing reliance on specialized experimental equipment and hazardous hydrogen handling, thus lowering experimental costs and safety risks. Secondly, the heterogeneous wettability of the rock-hydrogen-water multiphase system is calculated using the three-phase contact relationship of rock, hydrogen, and water extracted from real images. This data is then precisely mapped to the digital core model via coordinate mapping, enabling the constructed second-pore structured grid model to accurately reflect the spatial variation of wettability in underground reservoirs due to uneven mineral distribution, thus mitigating the distortion caused by the uniform wettability assumption in traditional numerical simulations. In the specific implementation process, representative volumetric units are determined through characterization unit analysis, ensuring both model representativeness and optimized computational efficiency. The absolute permeability obtained through single-phase flow simulation provides a reliable benchmark for subsequent relative permeability calculations. Finally, in the two-phase flow simulation, by considering the actual reservoir temperature and pressure conditions and fluid properties, and combining them with heterogeneous wettability attributes, the simulated hydrogen-water two-phase permeation behavior more closely resembles actual reservoir conditions. This series of operations collectively resulted in higher accuracy and reliability of the final hydrogen-water phase permeability curves, providing a more precise theoretical basis for assessing the storage capacity of hydrogen reservoirs and optimizing injection and production schemes. Furthermore, the digital workflow established in this application is highly repeatable and can adapt to the reservoir evaluation needs under different geological conditions.

[0075] It is understood that the aforementioned description of the hydrogen-water phase permeation curve can also be interpreted technically as a hydrogen-water two-phase flow phase permeation curve, a hydrogen-water relative permeability curve, or an H2-water system phase permeation curve, among other industry-standard terms. All these different expressions refer to the functional relationship curve of the relative permeability of each phase as a function of saturation under the condition of coexistence of hydrogen and water in a porous medium. This application does not limit the specific naming of the curves; any equivalent name that can be reasonably inferred by a person skilled in the art based on the same technical essence falls within the protection scope of the technical solution described in this application.

[0076] Furthermore, as a response to the above Figure 1 In addition to the method shown, this embodiment of the invention also provides a device for determining the hydrogen-water phase permeation curve of an underground hydrogen storage facility, used for the above-mentioned... Figure 1 The method shown is implemented accordingly. This device embodiment corresponds to the foregoing method embodiment. For ease of reading, this device embodiment will not repeat the details of the foregoing method embodiment, but it should be clear that the device in this embodiment can implement all the contents of the foregoing method embodiment. Figure 13 As shown, the device includes: an acquisition unit 21, a construction unit 22, a mapping unit 23, and an operation unit 24, wherein: The acquisition unit 21 is used to acquire microscopic computed tomography images of rock samples during the hydrogen-driven water displacement process, wherein the rock samples are test samples collected from natural hydrogen storage reservoirs. Construction unit 22 is used to perform characterization unit volume analysis on the pore structure of the micro-computed tomography image to construct a first pore structured mesh model, wherein the first pore structured mesh model is used to characterize the pore structure of the rock sample, the first pore structured mesh model is a geometric structure model, and the first pore structured mesh model includes a coordinate system of the pore structure; The mapping unit 23 is used to map the wettability distribution data to the first pore structured grid model through the corresponding coordinate position, with the coordinate system of the first pore structured grid model as a reference, so as to obtain the second pore structured grid model. The wettability distribution data is calculated along the three-phase contact line of rock, hydrogen and water extracted from the micro-computed tomography image. Operation unit 24 is used to perform a two-phase flow simulation operation of water-driven hydrogen on the second pore structured grid model to obtain the hydrogen and water phase permeation curves of the hydrogen storage tank. The two-phase flow simulation operation of water-driven hydrogen is a simulation operation in which the hydrogen phase in the second pore structured grid model is replaced by the water phase.

[0077] The processor contains a kernel, which retrieves the corresponding program units from memory. One or more kernels can be configured, and by adjusting kernel parameters, a method for determining the hydrogen-water phase permeation curve in underground hydrogen storage facilities can be implemented. This method addresses the problem of existing technologies struggling to obtain highly accurate hydrogen-water phase permeation curves.

[0078] This invention provides a computer-readable storage medium including a stored program that, when executed by a processor, implements a method for determining the hydrogen-water phase permeation curve of an underground hydrogen storage reservoir.

[0079] This invention provides a processor for running a program, wherein the program executes a method for determining the hydrogen-water phase permeation curve of the underground hydrogen storage tank.

[0080] This invention provides an electronic device, which includes at least one processor and at least one memory connected to the processor; wherein the processor is used to call program instructions in the memory to execute the method for determining the hydrogen-water phase permeation curve of an underground hydrogen storage tank as described above. This invention provides an electronic device 30, such as... Figure 14As shown, the electronic device includes at least one processor 301, and at least one memory 302 and bus 303 connected to the processor; wherein, the processor 301 and the memory 302 communicate with each other through the bus 303; the processor 301 is used to call program instructions in the memory to execute the above-mentioned method for determining the hydrogen-water phase permeation curve of the underground hydrogen storage tank.

[0081] The smart electronic devices mentioned in this article can be PCs, tablets, mobile phones, etc.

[0082] This application also provides a computer program product that, when executed on a process management electronic device, is suitable for executing the program that initializes the steps of the method for determining the hydrogen-water phase permeation curve of the aforementioned underground hydrogen storage tank.

[0083] It should be noted that the descriptions of each embodiment in the above embodiments have different focuses. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0084] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0085] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create a machine for implementing the flowchart illustrations. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0086] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0087] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0088] This application also provides a computer program product, which includes computer software instructions that, when executed on a processing device, cause the processing device to perform actions such as... Figure 1 The control flow of the memory in the corresponding embodiment.

[0089] A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium may be any available medium that a computer can store or a data storage device such as a server or data center that integrates one or more available media. The available medium may be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid-state disk (SSD)).

[0090] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0091] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, or indirect coupling or communication connection between apparatuses or units, and may be electrical, mechanical, or other forms.

[0092] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0093] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0094] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0095] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for determining the hydrogen-water phase permeation curve of an underground hydrogen storage facility, characterized in that, include: Microscopic computed tomography images of rock samples during the hydrogen-driven water displacement process were obtained, wherein the rock samples were test samples collected from natural hydrogen reservoirs. The pore structure of the micro-computed tomography image is characterized by unit cell analysis to construct a first pore structured mesh model. The first pore structured mesh model is used to characterize the pore structure of the rock sample. The first pore structured mesh model is a geometric structure model and includes a coordinate system for the pore structure. Using the coordinate system of the first pore structured grid model as a reference, the wettability distribution data is mapped to the first pore structured grid model through the corresponding coordinate positions to obtain the second pore structured grid model. The wettability distribution data is calculated along the three-phase contact line of rock, hydrogen and water extracted from the micro-computed tomography image. A two-phase flow simulation of water-driven hydrogen is performed on the second porous structured grid model to obtain the hydrogen and water phase permeation curves of the hydrogen storage tank. The two-phase flow simulation of water-driven hydrogen is a simulation of water phase replacing hydrogen phase in the second porous structured grid model.

2. The method according to claim 1, characterized in that, The acquisition of microscopic computed tomography images of rock samples during the hydrogen-driven water displacement process includes: Obtain microscopic computed tomography images of the rock sample under a simulated hydrogen-driven water displacement operation, wherein the simulated hydrogen-driven water displacement operation is used to simulate the hydrogen storage tank injection operation. The microscopic computed tomography images are denoised using median filtering techniques. The micro-computed tomography image was segmented using watershed segmentation technology to extract the distribution of hydrogen and water in the pore space of the rock.

3. The method according to claim 1, characterized in that, The step of characterizing the pore structure of the microscopic computed tomography image to construct a first pore-structured mesh model includes: Crop cube sub-images with different side lengths from the center of the microscopic computed tomography image; Calculate the porosity and water saturation of each of the cubic sub-images; Based on the porosity and water saturation of each cube sub-image, the fluctuation trend of porosity and water saturation is determined. When the fluctuation trend of porosity and water saturation is less than a preset amplitude, the corresponding smallest cube sub-image is determined to be the characterizing unit cell model; Each image pixel of the characterization unit model is converted into a hexahedral mesh unit to form the first pore structured mesh model.

4. The method according to claim 3, characterized in that, Also includes: Using the traveling cube algorithm, a multiphase surface mesh model is obtained based on the characterization unit model. The multiphase surface mesh model is used to characterize the distribution of phase interfaces of hydrogen, water and rock solid. Extract each contact point on the three-phase contact line of rock, hydrogen and water from the multiphase surface mesh model; Calculate the in-situ contact angle of each contact point on the three-phase contact line, wherein the in-situ contact angle corresponding to any contact point is obtained by calculating the angle between the unit normal vector of the hydrogen-water phase interface and the unit normal vector of the water-rock solid phase interface at the contact point. Within the space of the characterizing unit model, using the average pore diameter as the moving window size, the local average value of the in-situ contact angle is statistically analyzed to obtain the wettability distribution data.

5. The method according to claim 1, characterized in that, The step of mapping the wettability distribution data to the first pore structured mesh model through corresponding coordinate positions, using the coordinate system of the first pore structured mesh model as a reference, to obtain the second pore structured mesh model includes: Determine the center point coordinates of each wall grid cell in the first pore structured mesh model, wherein the wall grid cell is the grid cell that contacts the pore under fluid flow conditions; Determine the local average value of the in-situ contact angle in the wettability distribution data corresponding to the coordinates of each of the aforementioned center points; The local average value of the in-situ contact angle is assigned to the wall mesh element corresponding to the coordinate position in the first pore structured mesh model to obtain the second pore structured mesh model.

6. The method according to claim 1, characterized in that, Also includes: Boundary conditions for single-phase flow simulation are set on the first porous structured grid model. The single-phase flow simulation is to simulate water injection into the first porous structured grid model to simulate the flow of water phase in the first porous structured grid model. The boundary conditions include setting the water injection inlet to a fixed pressure and the water injection outlet to a zero pressure value. The walls of the first porous structured grid model other than the inlet and outlet are set as impermeable boundaries. Under the stated boundary conditions, the flow of the water phase in the first porous structured grid model is simulated using the finite volume method. Once the simulation process reaches the convergence criterion, the absolute permeability of the first pore structured mesh model is calculated using Darcy's law.

7. The method according to claim 6, characterized in that, The step of performing a two-phase flow simulation of water-driven hydrogen on the second pore structured mesh model to obtain the hydrogen-water phase permeation curve of the hydrogen storage reservoir includes: Set reservoir temperature and pressure conditions on the second pore structured grid model; Determine the water phase density, water phase viscosity, hydrogen density, hydrogen viscosity, and hydrogen-water interfacial tension coefficient under the specified reservoir temperature and pressure conditions. The hydrogen and water distribution characterized by the micro-computed tomography image is set as the initial fluid distribution for the two-phase flow simulation of water-driven hydrogen. Boundary conditions for simulating the two-phase flow of water-driven hydrogen are set on the second porous structured grid model. The boundary conditions include setting the inlet of the water injection operation to a constant velocity for injecting the water phase, setting the outlet of the water injection operation to a zero pressure value, and setting the walls of the second porous structured grid model other than the inlet and outlet to impermeable boundaries. Under the boundary conditions, the fluid volume method is used to simulate the two-phase flow of water-driven hydrogen in the second pore structured mesh model, so as to obtain the effective permeability of hydrogen and the effective permeability of water phase under different water saturation during the simulation of the two-phase flow of water-driven hydrogen. Based on the effective hydrogen permeability, effective water phase permeability, and absolute permeability at different water saturations, the relative hydrogen permeability and relative water phase permeability at different water saturations are determined. The hydrogen-water phase permeability curves of the hydrogen storage tank are determined based on the relative permeability of hydrogen and water phase under different water saturation levels.

8. A device for determining the hydrogen-water phase permeation curve of an underground hydrogen storage facility, characterized in that, Also includes: The acquisition unit is used to acquire microscopic computed tomography images of rock samples during the hydrogen-driven water displacement process, wherein the rock samples are test samples collected from natural hydrogen storage reservoirs. A construction unit is used to perform characterization unit volume analysis on the pore structure of the micro-computed tomography image to construct a first pore structured mesh model. The first pore structured mesh model is used to characterize the pore structure of the rock sample. The first pore structured mesh model is a geometric structure model and includes a coordinate system of the pore structure. The mapping unit is used to map the wettability distribution data to the first pore structured grid model through the corresponding coordinate position, with the coordinate system of the first pore structured grid model as a reference, so as to obtain the second pore structured grid model. The wettability distribution data is calculated along the three-phase contact line of rock, hydrogen and water extracted from the micro-computed tomography image. The operation unit is used to perform a two-phase flow simulation operation of water-driven hydrogen on the second porous structured grid model to obtain the hydrogen and water phase permeation curves of the hydrogen storage tank. The two-phase flow simulation operation of water-driven hydrogen is a simulation operation in which the hydrogen phase in the second porous structured grid model is replaced by the water phase.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored program, wherein, when the program is executed by a processor, it implements the steps of the method for determining the hydrogen-water phase permeability curve of an underground hydrogen storage facility as described in any one of claims 1 to 7.

10. An electronic device, characterized in that, The electronic device includes at least one processor and at least one memory connected to the processor; wherein the processor is used to call program instructions in the memory to execute the steps of the method for determining the hydrogen-water phase permeation curve of an underground hydrogen storage tank as described in any one of claims 1 to 7.

Images