Numerical simulation method for reproducing whole process of circulating storage and release of hydrogen in horizontal salt cavity

Abstract

The invention discloses a horizontal salt cavity circulating hydrogen storage and release whole process representation numerical simulation method which comprises the following steps: constructing an initial stratum model which comprises a mudstone upper layer, a rock salt interlayer and a mudstone lower layer; an ellipsoid is embedded in the initial stratum model, and a one-fourth stratum model with simplified calculation is obtained; adding a physical field module to the 1 / 4 stratum model to obtain an optimal stratum model; wherein the multi-physics field module comprises a solid mechanics physics field module, a Darcy law physics field module and a porous medium heat transfer physics field module; the optimal stratum model is subjected to grid division, the initial ground stress of the divided optimal stratum model is calculated firstly, then multi-field coupling data after the initial ground stress is added are calculated, and the multi-field coupling data comprise a temperature field, a stress field and a displacement field. The design capacity of the reservoir can be effectively increased, and the stable leakproofness of the reservoir is ensured by improving the structural form of the gas storage.

Description

Technical Field

[0001] The invention belongs to the technical field of salt cavern energy storage, and in particular relates to a numerical simulation method for reproducing the entire process of cyclic storage and release of hydrogen in a horizontal salt cavity. Background Art

[0002] Hydrogen is one of the clean, efficient and widely used secondary energy sources. As an important strategic resource for the economy and society, it plays a very important role in national security and stability and national economic development. As an ideal carrier of clean energy in the future, hydrogen energy has the greatest potential to replace traditional fossil fuels. In order to maximize the contribution of hydrogen energy to net zero emissions and meet the future strategic needs of new energy, it is urgent to carry out large-scale hydrogen energy storage research.

[0003] The low density, low viscosity, strong permeability and high activity of hydrogen pose an important challenge to the sealing of salt caverns and the stability of surrounding rocks during underground injection and production. A lot of relevant research has been done on salt cavern natural gas storage in China, but the research on salt cavern hydrogen storage is still in its infancy. Most of my country's salt rock deposits are layered, with a small thickness and more impurities. If vertical dissolution cavities are still selected as the reservoir design model, a larger reservoir design capacity cannot be obtained under the premise of ensuring the reservoir's tightness. If a larger span horizontal dissolution cavity is used as the design model for domestic salt rock reservoirs, the reservoir design capacity can be effectively increased, and the stable tightness of the reservoir can be ensured by improving the gas storage structure. There is no example of a horizontal salt cavern hydrogen storage built in my country, and the numerical simulation research in this area is also insufficient. The traditional two-dimensional numerical simulation method cannot fully capture the stress concentration phenomenon and its complexity when simulating large-span horizontal caverns due to its dimensional limitations, especially in multi-physics field coupling problems such as hydrogen leakage. In contrast, the three-dimensional simulation method can provide more accurate spatial stress distribution and leakage path analysis, thereby more effectively revealing the mechanical behavior and potential safety risks of large-span horizontal caverns under multi-dimensional stress. Therefore, the present invention uses thermal-fluid-solid coupling to effectively analyze the stability and sealing performance of horizontal three-dimensional salt cavern underground hydrogen storage under real injection and production operation conditions, providing a useful reference for the feasibility and safety of underground hydrogen storage technology. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a numerical simulation method for reproducing the whole process of cyclic storage and release of hydrogen in a horizontal salt cavity, which can better realize the numerical simulation of reproducing the whole process of hydrogen storage and release.

[0005] The present invention provides a method for reproducing a numerical simulation of the entire process of cyclic storage and release of hydrogen in a horizontal salt cavity, comprising:

[0006] Constructing an initial formation model, wherein the initial formation model includes: an upper mudstone layer, a rock salt interlayer and a lower mudstone layer;

[0007] An ellipsoid is embedded in the initial formation model to obtain a quarter formation model for simplified calculation;

[0008] Adding a physical field module to the quarter formation model to obtain an optimal formation model; wherein the physical field module includes: a solid mechanics physical field module, a Darcy's law physical field module and a porous medium heat transfer physical field module;

[0009] The optimal formation model is grid-divided, the initial geostress of the optimal formation model after division is first calculated, and then the multi-field coupling data after adding the initial geostress is calculated, wherein the multi-field coupling data includes: temperature field, stress field and displacement field.

[0010] Optionally, before optimizing the initial formation model, the method further includes: obtaining hydrogen-related parameters and circulation parameters.

[0011] Optionally, the hydrogen-related parameters include: molar mass, dynamic viscosity, thermal conductivity, specific heat capacity and state quantity;

[0012] The cycle parameters include: cycle load and cycle temperature.

[0013] Optionally, adding a physical field module to the quarter formation model to obtain the optimal formation model includes:

[0014] Add the solid mechanics physical field module, and based on the solid mechanics physical field module, set the boundary load to simulate the upper soil layer pressure, the hydrogen injection and production cycle internal pressure, and the constant internal pressure in the salt cavity, and obtain the first parameter for controlling the solution;

[0015] Add the Darcy's law physical field module, improve the fluid properties of hydrogen and the matrix properties of the porous matrix in the porous medium node of the Darcy's law field, set the salt cavity circulation pressure and the edge zero pressure, and obtain the second parameter for controlling the solution;

[0016] Add the porous medium heat transfer physical field module, set the absolute pressure model of hydrogen in the porous medium node in the porous medium heat transfer field, introduce hydrogen heat conduction and fluid type parameters, improve the initial value and thermal insulation boundary conditions, set the temperature of the salt cavity and the boundary surrounding rock, and obtain the third parameter used to control the solution.

[0017] Optionally, set boundary loads to simulate upper soil pressure including:

[0018]

[0019] Where E0 is the soil pressure, n is the number of overlying rock layers, ρ i is the density of the overlying rock layer i, d i Indicates the thickness of the formation.

[0020] Optionally, the first parameters include: thermal expansion, initial stress, strain, external stress, creep and variable-safety.

[0021] Optionally, improving the fluid properties of the hydrogen includes:

[0022]

[0023] Where t is time, ε p is the medium porosity, ρ is the hydrogen density, u is the hydrogen flow rate, k is the porosity, μ is the hydrogen dynamic viscosity, k is the permeability, and p is the pore gas pressure.

[0024] Optionally, the initial geostress of the optimal stratum model after division is calculated first, and then the multi-field coupling data after adding the initial geostress is calculated, including:

[0025] Using COMSOL Multiphysics, steady-state research calculations were performed, and the sparse matrix PARDISO method was used to calculate the initial stress of the divided formation model;

[0026] The multi-field coupling data of the divided formation model are calculated using the MUMPS method in transient research.

[0027] Compared with the prior art, the present invention has the following advantages and technical effects:

[0028] It can fully capture the stress concentration phenomenon and its complexity, provide more accurate spatial stress distribution and leakage path analysis, and thus more effectively reveal the mechanical behavior and potential safety risks of large-span horizontal caverns under multi-dimensional stress, and has good convergence and calculation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0030] Figure 1 This is a flow chart of a numerical simulation method for reproducing the entire process of cyclic storage and release of hydrogen in a horizontal salt cavity according to an embodiment of the present invention;

[0031] Figure 2 It is a three-dimensional model and a grid division schematic diagram of a horizontal salt cavity hydrogen storage and release according to an embodiment of the present invention;

[0032] Figure 3 Schematic diagram of von Mises stress of a solid mechanics module for hydrogen storage and release in a horizontal salt cavity according to an embodiment of the present invention;

[0033] Figure 4Schematic diagram of pressure and Darcy velocity field of the Darcy's law module for storing and releasing hydrogen in a horizontal salt cavity according to an embodiment of the present invention;

[0034] Figure 5 Schematic diagram of the temperature field of the horizontal salt cavity hydrogen storage and release porous medium heat transfer module according to an embodiment of the present invention;

[0035] Figure 6 It is a schematic diagram of the displacement field of the horizontal salt cavity hydrogen storage and release according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0037] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0038] At present, whether it is salt rock gas storage being built or operated at home or abroad, the gas storage cavity is mainly vertical and has a large aspect ratio. However, most salt rock deposits abroad are salt dome deposits with thick salt rock strata, while most salt rock deposits in China are layered and the thickness of the salt rock layer is not large. If the vertical dissolution cavity is still selected as the reservoir design shape, a larger reservoir design capacity cannot be obtained under the premise of ensuring the airtightness of the reservoir. If a horizontal dissolution cavity with a larger span is used as the design shape of domestic salt rock reservoirs, the reservoir design capacity can be effectively increased, and the stable airtightness of the reservoir can be ensured by improving the structural form of the gas storage.

[0039] The present invention proposes a numerical simulation method for reproducing the whole process of cyclic storage and release of hydrogen in a horizontal salt cavity. Figure 1 As shown, the specific steps include:

[0040] Constructing an initial stratigraphic model, wherein the initial stratigraphic model includes: an upper mudstone layer, a rock salt interlayer, and a lower mudstone layer;

[0041] An ellipsoid is embedded in the initial formation model to obtain a quarter formation model for simplified calculation;

[0042] Adding physical field modules to the quarter formation model to obtain the best formation model; wherein the physical field modules include: solid mechanics physical field module, Darcy's law physical field module and porous medium heat transfer physical field module;

[0043] The best formation model is meshed, and the initial geostress of the best formation model after meshing is calculated first, and then the multi-field coupling data after adding the initial geostress is calculated, wherein the multi-field coupling data includes: temperature field, stress field and displacement field.

[0044] Specifically, start COMSOL Multiphysics software (COMSOL Multiphysics software is based on the finite element method and realizes the simulation of real single or multi-physical phenomena by solving partial differential equations or partial differential equations.) Select solid mechanics, Darcy's law, porous media heat transfer physical field modules and add dynamic mesh deformation domains, use steady state to solve initial geostress, and then use transient to solve heat-fluid-solid multi-field coupling;

[0045] Use the geometry module to construct the upper mudstone layer, rock salt interlayer, and lower mudstone layer, then construct an ellipse, adjust the ellipse to the appropriate position, use Boolean operations and the difference function in segmentation, select the upper mudstone layer, salt rock, and lower mudstone layer in the added object, subtract the selected ellipsoid in the object, retain the objects to be added, and retain the internal boundaries, embed the ellipse into the formation model to form a horizontal cavern, and ensure that the model is one-quarter of the actual formation model to simplify the calculation amount.

[0046] Furthermore, before optimizing the initial formation model, the following steps are also included: obtaining hydrogen related parameters and circulation parameters.

[0047] Specifically, the hydrogen molar mass, hydrogen dynamic viscosity, hydrogen state quantity, hydrogen thermal conductivity, and hydrogen specific heat capacity are defined in the global definition. The initial temperature gradient function of the surrounding rock is defined in the component module, and then the interpolation function is added by piecewise cubic interpolation to define the cyclic load and cyclic temperature of 0-3600 days (approximately ten years), and the constants are selected by extrapolation.

[0048] Furthermore, the hydrogen related parameters include: molar mass, dynamic viscosity, thermal conductivity, specific heat capacity and state quantity;

[0049] Cyclic parameters include: cyclic load and cyclic temperature.

[0050] Furthermore, a physical field module is added to the quarter formation model to obtain the optimal formation model including:

[0051] Add a solid mechanics physics module. Based on the solid mechanics physics module, set the boundary load to simulate the upper soil layer pressure, the hydrogen injection and production cycle internal pressure, and the constant internal pressure in the salt cavity to obtain the first parameter for controlling the solution.

[0052] Specifically, add the solid mechanics physical field module, add roller supports, fixed constraints, and symmetry boundaries to the solid mechanics field, constrain the displacement of the model around and at the bottom, and add gravity g to the model. z =-g_const;

[0053] Adding boundary loads to simulate the upper soil pressure is done using the following equation:

[0054]

[0055] In the above formula, p is the soil pressure (unit: Pa); n is the number of overlying rock layers; ρ i is the density of the overlying rock layer i, (i is 1 to n, unit is kg / m 3 );d i Indicates the thickness of the formation (unit: m);

[0056] Then add the internal pressure of hydrogen injection and production cycle and the constant internal pressure and symmetric boundary in the salt cavity. The internal pressure of hydrogen injection and production cycle is defined by the interpolation function in component 1.

[0057] Add linear elastic material to the solid mechanics module, add initial stress and strain, input the initial stress S0 of the 3D model, the diagonal component S z , S y and S z and the off-diagonal components S xy , S yz and S xz .

[0058] Then a thermal expansion node is added, the temperature is imported from the porous media heat transfer, the volume reference temperature is the initial surrounding rock temperature, and the internal thermal strain caused by the temperature change is added using the following formula.

[0059] ε th =α(T)×(TT ref )

[0060] In the above formula, α is the tangent thermal expansion coefficient (unit 1 / K); T is the temperature (unit K); T ref is the volume reference temperature (in K); set the stress input to pore pressure;

[0061] Add a subnode External Stress, with stress input as pore pressure, absolute pressure P A Set to Darcy absolute pressure and calculate the additional stress on the surrounding rock using the following formula.

[0062] P ext =-α B (P A -P ref )

[0063] In the above formula, α B is the Biot-Willis coefficient (unit 1); P A is the absolute pressure (unit: Pa); P refis the reference pressure level (unit: Pa);

[0064] Add a creep node, the material model is Norton, and the equivalent stress σ e The vonmises stress is used, and the thermal effect g(T) is Arrhenius. The constitutive equation is as follows.

[0065] ε c =f1(σ)·f2(T)·f3(t)

[0066] In the above formula, f1(σ), f2(T), and f3(t) are creep strains ε c Functional relationship with time t, temperature T and stress σ. Where f1(σ)=Aσ n , A is a constant related to temperature and material properties; n is the stress exponent.

[0067] Then the Mohr-Coulomb failure criterion and Drucker-Prager failure criterion are selected to evaluate the stability of the salt cavity. The failure formulas for the cavern stress state and mechanical strength evaluation are as follows.

[0068]

[0069] In the above formula, c and φ are the Mohr-Coulomb cohesion and internal friction angle, respectively; k and α are the Drucker-Prager coefficients related to the mechanical strength of rock salt; and m is the Mohr-Coulomb parameter determined by the internal friction angle and the Lode angle θ.

[0070] Add the Darcy's law physics field module, improve the fluid properties of hydrogen and the matrix properties of the porous matrix in the porous medium node of the Darcy's law field, set the salt cavity circulation pressure and edge zero pressure, and obtain the second parameter used to control the solution;

[0071] Specifically, add the physical field module of Darcy's law, set the operating environment and boundary conditions, improve the fluid properties of hydrogen and the matrix properties of the porous matrix in the porous medium node of Darcy's law field, set the salt cavity circulation pressure and the edge zero pressure, and then set the material parameters required by Darcy's law. The numerical simulation of hydrogen flow in salt rock layers and interlayers is calculated using the following formula.

[0072]

[0073] In the above formula, t is time (unit, s); ε p is the porosity of the medium (unit, %); ρ is the hydrogen density (unit, kg / m 3 ); u is the hydrogen flow rate (unit, m / s); k is the porosity (unit, m 3 ); μ is hydrogen dynamic viscosity (unit, Pa·s); k is permeability (unit, m 2); p is stress (unit, Pa).

[0074] Add the porous media heat transfer physical field module, set the absolute pressure model of hydrogen in the porous media node in the porous media heat transfer field, introduce hydrogen heat conduction and fluid type parameters, improve the initial value and thermal insulation boundary conditions, set the temperature of the salt cavity and boundary surrounding rock, and obtain the third parameter used to control the solution.

[0075] Specifically, add a physical field module for porous media heat transfer, set the operating environment and boundary conditions, and set the absolute pressure model input of hydrogen to Darcy pressure in the porous media node in the porous media heat transfer field;

[0076] Introduce hydrogen heat conduction and fluid type parameters in the global definition, improve the initial value and thermal insulation boundary conditions, set the temperature of the salt cavity and boundary surrounding rock, add symmetric boundaries, and finally set the material parameters required for porous medium heat transfer.

[0077] Furthermore, meshing the formation model includes: first checking the mesh quality to ensure that the mesh accuracy is within the preset accuracy and no negative volume mesh appears, otherwise meshing is performed again to improve the meshing precision, thereby better ensuring that subsequent calculations are accurate and reliable.

[0078] Furthermore, the initial geostress of the optimal stratum model after division is calculated first, and then the multi-field coupling data after adding the initial geostress is calculated, including:

[0079] Using COMSOL Multiphysics, steady-state research calculations were performed, and the sparse matrix PARDISO method was used to calculate the initial stress of the divided formation model;

[0080] The multi-field coupling data of the divided formation model are calculated using the MUMPS method in transient studies. Specifically, the direct solver PARDISO selects automatic scheduling, Bunch-Kaufman selects the principal element, the maximum number of mesh refinements is 20, and the direct solver MUMPS; the steady-state and transient nonlinear methods use automatic high nonlinearity (Newton), the termination technique uses tolerance, and the maximum number of iterations is set to 25. The implicit backward difference formula is used for transient solution of differential algebraic equations. The scaling factors of the displacement field, temperature field, and pressure field are input as the expected peak intensity of the field over the entire simulation time span.

[0081] Furthermore, the calculation results are displayed and output to obtain parameters including temperature field, pressure field and displacement field. Volume measurement is performed in the derived value and the following formula is imported.

[0082] V 收缩率 =(V 后 -V 前 ) / V后 ×100%

[0083] In the above formula, V 前 is the initial volume (unit, m 3 );V 后 is the volume after contraction (unit: m 3 ).

[0084] The present embodiment is described in detail below with reference to the accompanying drawings:

[0085] like Figure 2-6 As shown in the figure, the formation model is a cube of 800m×800m, which is composed of the upper and lower layers of mudstone with a height of 300m and the interlayer of rock salt with a height of 200m. The lengths of the major semi-axis, the middle semi-axis and the minor semi-axis of the structural ellipsoid are 200m, 60m and 45m respectively. The working surface of the ellipsoid is the xy plane, and the positions of the center x, y and z are 0m, 0m and -800m respectively. The rotation angle is 180deg, and it is embedded in the formation. The difference in Boolean operation is used to make it a quarter of the salt cavity.

[0086] The method is used to perform three-dimensional water flow numerical simulation in the above-mentioned formation model, which specifically includes the following steps:

[0087] 1. Using the geometry module of COMSOL Multiphysics 6.2 software, the formation model is a 800m×800m cube, which consists of an upper and lower mudstone layer with a height of 300m and a 200m rock salt interlayer. The lengths of the major, middle and minor axes of the constructed ellipsoid are 200m, 60m and 45m respectively. The working surface of the ellipsoid is the xy plane, and the central x, y and z positions are 0m, 0m and -800m respectively. The rotation angle is 180deg and it is embedded in the formation. The difference in Boolean operation is used to make it a quarter of the salt cavity.

[0088] 2. In the global definition, the molar mass of hydrogen is defined as 0.002016 kg / mol, the dynamic viscosity is 8.915E-6 Pa·s, the thermal conductivity is 0.1805 W / (m·K), the specific heat capacity is 14300 J / (kg·K), and the state quantity is 4124 J / (kg·K). In comp1, the cyclic load and cyclic temperature are defined as piecewise cubic interpolation functions, and the constants are selected by extrapolation. The cyclic load is Pa(t), the maximum internal pressure is 1.5×107 Pa, the minimum internal pressure is 7×106 Pa, and the cyclic temperature T(t) has a maximum temperature of 60degC and a minimum temperature of 45degC.

[0089] 3. Add physical fields in sequence: dynamic mesh, solid mechanics, Darcy's law, porous media heat transfer, and set the operating environment and boundary conditions, adjust the parameters used to control the solution, and assign parameters to the required materials

[0090] 4. First, customize the free tetrahedron mesh of the upper and lower layers of mudstone, with a maximum unit size of 125m, a minimum unit size of 22m, a maximum growth rate of 1.4, a curvature factor of 0.4, and a resolution of 0.4 in narrow areas; then customize the free tetrahedron mesh around the salt rock cavity, with a maximum unit size of 100m, a minimum unit size of 4m, a maximum growth rate of 1.2, a curvature factor of 0.4, and a resolution of 0.8 in narrow areas; then customize the free tetrahedron mesh inside the salt cavity, with a maximum unit size of 44m, a minimum unit size of 3.2m, a maximum growth rate of 1.4, a curvature factor of 0.4, and a resolution of 0.7 in narrow areas, and control the maximum unit size of 2m and the minimum unit size of 0.16m at the horizontal boundary line of the salt cavity. Check the mesh quality to ensure that the mesh accuracy is within the preset accuracy and that no negative volume mesh appears, otherwise meshing is performed again to improve the fineness of meshing. This can better ensure that subsequent calculations are accurate and reliable.

[0091] This embodiment can conveniently and quickly realize the three-dimensional grid division of horizontal salt cavities, generate a three-dimensional grid assembly of mudstone and salt rock, so as to meet the numerical simulation requirements of cyclic hydrogen storage and release in horizontal salt cavities, improve the accuracy, reliability and stability of subsequent three-dimensional horizontal salt cavity numerical simulations and simplify calculations. At the same time, the method utilizes the existing simple model three-dimensional division software to realize the three-dimensional division of complex spaces. This embodiment itself has the advantages of simple steps, strong operability, and high degree of automation.

[0092] 5. The direct solver PARDISO selects automatic scheduling, Bunch-Kaufman selects the principal element, the maximum number of mesh refinements is 20, and the direct solver MUMPS; the steady-state nonlinear method uses automatic (Newton), the termination technique uses tolerance, and the maximum number of iterations is set to 25. The transient solution of differential algebraic equations uses implicit backward difference formulas, and the scaling factors of the displacement field, temperature field, and pressure field are input as the expected peak intensity of the field over the entire simulation time span. In the steady-state study, the Mohr-Coulomb and Drucker-Prager failure criteria of linear elastic materials in the starting grid and solid mechanics, as well as freedom, initial values, roll supports, fixed constraints, upper soil loads, initial internal pressure, and gravity are turned on to calculate the initial ground stress before excavation of the cavern. In the transient study, the Mohr-Coulomb and Drucker-Prager failure criteria of linear elastic materials in the starting grid and solid mechanics, creep, thermal expansion, initial stress and strain, external stress, and porous media in freedom, initial values, roll supports, fixed constraints, upper soil loads, initial internal pressure, gravity and Darcy's law, no flow, initial values, pressure 1, pressure 2 and porous media 1, initial values, thermal insulation, temperature 1, temperature 2 in heat transfer in porous media are turned on. The automatic highly nonlinear Newton's fully coupled solution method is selected for transient solution of thermal-fluid-solid multi-field coupling.

[0093] In this way, this method can effectively improve convergence and increase the accuracy and success rate of calculations.

[0094] 6. Display and output the calculation results, and obtain parameters including temperature field, pressure field, and displacement field. Perform volume measurement in the derived values.

[0095] The implementation of the third step above specifically includes the following small steps:

[0096] a Click Physics Field - Add Physics Field - Structural Mechanics - Solid Mechanics, click Solid Mechanics (solid), click Material Model - Linear Elastic Material, Boundary Load, Fixed Constraint, Roll Support, More Constraints - Symmetry, Gravity; click Linear Elastic Material, click Thermal Expansion, Initial Stress and Strain, External Stress, Creep, Variables - Safety;

[0097] b Click Physics Field - Add Physics Field - Fluid Flow - Porous Media and Groundwater Flow - Darcy's Law (DL), click Darcy's Law (DL), click No Flow, Initial Value, and Pressure;

[0098] c Click Physics Field - Add Physics Field - Heat Transfer - Porous Media - Porous Media Heat Transfer (ht), then click Porous Media Heat Transfer (ht), Temperature, and Symmetry.

[0099] In step a, two boundary loads are added as internal pressure and cyclic internal pressure. In the solid mechanics physical field, roller supports are added to the back of the model along the y-axis and x-axis directions, and fixed constraints are added to the bottom to constrain the boundary displacement of the model. The upper boundary load is the deadweight of the surrounding rock, and gravity g is added to the entire model. z , add an internal pressure of P = 10 × 106Pa and a cyclic internal pressure Pa(t) to the inner wall of the salt chamber. Add a linear elastic material to the solid mechanics module, add initial stress and strain, input the initial stress S0 of the three-dimensional model, and the diagonal component S z , S y and S z and the off-diagonal components S xy , S yz and S xz Add a subnode Thermal Expansion, where the temperature is imported from the porous media heat transfer, and the volume reference temperature is the initial surrounding rock temperature. Add a subnode External Stress, where the stress input is the pore pressure, absolute pressure P A Set to Darcy absolute pressure. Add a Creep node, set the material model to Norton, and the equivalent stress σ eThe von Mises stress was used, the thermal effect g(T) was Arrhenius, the reference temperature Tref = Inf (unit, K), the creep activation energy Q = 12000 J / mol, and a symmetric boundary was added. Then the Mohr-Coulomb failure criterion and the Drucker-Prager failure criterion were selected to evaluate the stability of the salt cavity, where the material parameters of the Drucker-Prager failure criterion were the Mohr-Coulomb parameters (matching the la meridian).

[0100] Among them, in step b, the fluid properties of hydrogen and the matrix properties of the porous matrix are improved in the porous medium node of the Darcy's law field, and the circulating pressure and the zero pressure at the edge of the model are set inside the salt cavity. Then, the hydrogen density, dynamic viscosity, and the porosity and permeability of mudstone and salt rock are set, and symmetric boundaries are added.

[0101] In step c, add two temperatures as boundary conditions for heat transfer, set the operating environment and boundary conditions, and set the absolute pressure model input of hydrogen to Darcy pressure in the porous medium node in the porous medium heat transfer field. Introduce hydrogen heat conduction and fluid type parameters in the global definition, improve the initial value and thermal insulation boundary conditions, set the temperature of the salt cavity and the boundary surrounding rock, add symmetric boundaries, and finally set the material parameters required for porous medium heat transfer.

[0102] This embodiment can conveniently and quickly set the physical field boundary conditions of the horizontal salt chamber to meet the numerical simulation requirements of cyclic hydrogen storage and release in the horizontal salt chamber under various working conditions, laying a foundation for subsequent post-processing.

[0103] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A numerical simulation method for reproducing the whole process of cyclic storage and release of hydrogen in a horizontal salt cavity, characterized in that: include: Constructing an initial formation model, wherein the initial formation model includes: an upper mudstone layer, a rock salt interlayer and a lower mudstone layer; An ellipsoid is embedded in the initial formation model to obtain a quarter formation model for simplified calculation; Adding a physical field module to the quarter formation model to obtain an optimal formation model; wherein the physical field module includes: a solid mechanics physical field module, a Darcy's law physical field module and a porous medium heat transfer physical field module; The optimal formation model is grid-divided, the initial geostress of the optimal formation model after division is first calculated, and then the multi-field coupling data after adding the initial geostress is calculated, wherein the multi-field coupling data includes: temperature field, stress field and displacement field.

2. According to claim 1, a numerical simulation method for reproducing the whole process of cyclic storage and release of hydrogen in a horizontal salt cavity is characterized in that: Before optimizing the initial formation model, the method further includes: obtaining hydrogen related parameters and circulation parameters.

3. According to claim 2, a method for reproducing the whole process of cyclic storage and release of hydrogen in a horizontal salt chamber is characterized in that: The hydrogen related parameters include: molar mass, dynamic viscosity, thermal conductivity, specific heat capacity and state quantity; The cycle parameters include: cycle load and cycle temperature.

4. The method for reproducing the whole process of cyclic storage and release of hydrogen in a horizontal salt chamber according to claim 3 is characterized in that: Adding a physical field module to the quarter formation model to obtain the optimal formation model includes: Add the solid mechanics physical field module, and based on the solid mechanics physical field module, set the boundary load to simulate the upper soil layer pressure, the hydrogen injection and production cycle internal pressure, and the constant internal pressure in the salt cavity, and obtain the first parameter for controlling the solution; Add the Darcy's law physical field module, improve the fluid properties of hydrogen and the matrix properties of the porous matrix in the porous medium node of the Darcy's law field, set the salt cavity circulation pressure and the edge zero pressure, and obtain the second parameter for controlling the solution; Add the porous medium heat transfer physical field module, set the absolute pressure model of hydrogen in the porous medium node in the porous medium heat transfer field, introduce hydrogen heat conduction and fluid type parameters, improve the initial value and thermal insulation boundary conditions, set the temperature of the salt cavity and the boundary surrounding rock, and obtain the third parameter used to control the solution.

5. The method for reproducing the whole process of cyclic storage and release of hydrogen in a horizontal salt chamber according to claim 4 is characterized in that: Setting boundary loads to simulate upper soil pressure includes: Where E0 is the soil pressure, n is the number of overlying rock layers, ρ i is the density of the overlying rock layer i, d i Indicates the thickness of the formation.

6. The method for reproducing the whole process of cyclic storage and release of hydrogen in a horizontal salt chamber according to claim 4 is characterized in that: The first parameters include: thermal expansion, initial stress, strain, external stress, creep and variable-safety.

7. The method for reproducing the whole process of cyclic storage and release of hydrogen in a horizontal salt chamber according to claim 4 is characterized in that: Completing the fluid properties of the hydrogen include: Where t is time, ε p is the medium porosity, ρ is the hydrogen density, u is the hydrogen flow rate, k is the porosity, μ is the hydrogen dynamic viscosity, k is the permeability, and p is the pore gas pressure.

8. The method for reproducing the whole process of cyclic storage and release of hydrogen in a horizontal salt chamber according to claim 1 is characterized in that: First, calculate the initial geostress of the optimal stratum model after division, and then calculate the multi-field coupling data after adding the initial geostress, including: COMSOL Multiphysics was used to perform steady-state research calculations, and the sparse matrix PARDISO method was used to calculate the initial stress of the divided formation model; The multi-field coupling data of the divided formation model are calculated using the MUMPS method in transient research.

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