A grid search-based anisotropic shale hydraulic-chemical coupling parameter test inversion method

Abstract

The present application relates to a kind of anisotropic shale hydraulic-chemical coupling parameter test inversion method based on grid search, belong to petroleum drilling engineering, rock mechanics and engineering field.The present application is an anisotropic shale hydraulic-chemical coupling parameter test inversion method based on grid search, including steps S10, carry out the pore pressure transmission test experiment under the anisotropic shale hydraulic-chemical coupling effect;Step S20, establish the pressure transmission finite element model under the anisotropic shale hydraulic-chemical coupling effect;Step S30, in combination with grid search method and pore pressure transmission test experimental data, respectively, to pressure transmission finite element model assignment solution domain basic physical property parameters, exert boundary condition and divide finite element mapping grid, and the best hydraulic-chemical coupling parameter is inverted.The present application overcomes the problem that conventional method cannot quickly and accurately determine the anisotropic shale hydraulic-chemical coupling parameter.

Description

Technical Field

[0001] This invention relates to a grid search-based method for testing and inverting the hydraulic-chemical coupling parameters of anisotropic shale, belonging to the fields of petroleum drilling engineering, rock mechanics and engineering. Background Technology

[0002] As conventional oil and gas resources become increasingly depleted, shale oil and gas is playing an increasingly important role in the global energy landscape. Horizontal well drilling and volumetric fracturing are the only means to commercialize shale oil and gas. However, shale wellbore instability is a serious problem during horizontal drilling. Wellbore instability can lead to complex accidents such as stuck drill bits and burial, severely limiting the safe and efficient development of shale oil and gas resources. Shale is a chemically active porous medium rich in clay. When this medium comes into contact with drilling fluid, a chemical expansion / contraction effect occurs, leading to wellbore instability. This phenomenon is called chemical permeation. Chemical permeation occurs due to a chemical imbalance between the pore fluid in the formation and the drilling fluid entering the formation. This results in a semi-permeable membrane effect within the shale, allowing only a portion of ions to pass through. Under conditions of overbalanced drilling (hydraulic action) and high-solute-concentration drilling fluid (chemical action), the occurrence of hydraulic transmission and chemical permeation increases pore pressure, leading to wellbore instability in shale formations.

[0003] Therefore, to address wellbore instability in shale formations, pressure transfer experiments under hydraulic-chemical coupling are necessary to determine the relationship between hydraulic-chemical coupling parameters between drilling fluid and shale, thereby clarifying the wellbore instability mechanism in shale formations. However, quickly and accurately determining the hydraulic-chemical coupling parameters in the coupling model presents certain challenges. Traditional pressure transfer experiments typically use two core samples, conducting pressure transfer experiments under pure hydraulic and pure chemical effects respectively, and using them to test and invert hydraulic-chemical coupling parameters such as permeability, solute diffusion coefficient, and reflection coefficient. This testing method cannot avoid the influence of sample differences. Furthermore, for anisotropic shale, the hydraulic-chemical coupling parameters parallel to and perpendicular to bedding directions often differ. Traditional pressure transfer experiments not only struggle to avoid the influence of sample differences but also often fail to invert the hydraulic-chemical coupling parameters of anisotropic shale. Summary of the Invention

[0004] To address the aforementioned problems, this invention primarily overcomes the shortcomings of existing technologies by proposing a grid-search-based method for testing and inverting the hydraulic-chemical coupling parameters of anisotropic shale.

[0005] The technical solution provided by this invention to solve the above-mentioned technical problems is: a method for testing and inverting anisotropic shale hydraulic-chemical coupling parameters based on grid search, comprising the following steps: Step S10: Conduct pore pressure transmission test experiments under the hydraulic-chemical coupling effect of anisotropic shale; Step S20: Establish a finite element model of pressure transmission under the hydraulic-chemical coupling of anisotropic shale; The pressure transmission control equation of the pressure transmission finite element model is:

[0006]

[0007] in,

[0008]

[0009]

[0010]

[0011] In the formula: M Here is the Biot modulus, in GPa; p Pore ​​pressure, MPa; ω is a chemical-stress coupling parameter, and is dimensionless; α Let be the Biot coefficient tensor, which is dimensionless; C Here is the compliance matrix, GPa -1 ; β 1 is the chemical-percolation coupling coefficient, which is dimensionless; k Let m be the permeability tensor. 2 ; η Where is the fluid viscosity, Pa·s; is the reflection coefficient, which is dimensionless; π Chemical osmotic pressure, MPa; S σ Storage coefficient, GPa -1 ; γ These are coefficients related to chemical reactions and are dimensionless. N The chemical coefficient is dimensionless and has no force. R is the molar gas constant, J / (mol·K); x 0 represents the initial reference salt mole fraction, which is dimensionless; c s Molar concentration, mol / L; T 0 represents absolute temperature, in K. ϕ Porosity is dimensionless. v 0 represents the initial molar volume of the solution, in L / mol; the superscript T indicates matrix transpose. Step S30: Combining the mesh search method and the experimental data of pore pressure transmission test, assign values ​​to the basic physical property parameters of the solution domain, apply boundary conditions and divide the finite element mapping mesh for the pressure transmission finite element model, and invert the optimal hydraulic-chemical coupling parameters.

[0012] A further technical solution is that the specific steps for conducting the pressure transmission test experiment under the hydraulic-chemical coupling of anisotropic shale in step S10 are as follows: Step S11, Applying Confining Pressure: After the sample is placed into the triaxial sealed chamber, a confining pressure of 15 MPa is applied to it, denoted as... p c ; Step S12, Shale saturation test stage under pure hydraulic action: Circulate a mass fraction of [missing value] at the upper end of the sample. C A NaCl solution of 0% is simultaneously injected at a pressure of 3 MPa, denoted as . p 0; After the upstream and downstream pressures are balanced, continue to circulate the liquid for at least 4 hours and monitor the downstream discharged liquid. Only after confirming that no air bubbles are discharged can saturation be determined to be complete. Step S13, Shale Pressure Transmission Test Stage under Pure Hydraulic Action: Maintain the upper circulation mass fraction of the sample at [value missing]. C A NaCl solution of 0% is injected simultaneously at an injection pressure of 10 MPa, denoted as . p m When the pressure at the lower end of the sample rises to the injection pressure p m Record the curve of the pressure change at the lower end over time to observe the effect of hydraulic loading on the pressure distribution of the sample. Step S14, Experimental stage of shale pressure transmission test under pure chemical action: A mass fraction of [missing information] is circulated at the upper end of the sample. C m NaCl solution, while maintaining injection pressure p m The pressure remains unchanged; record the curve of the lower end pressure changing over time to observe the effect of chemical loading on the pressure distribution of the sample.

[0013] A further technical solution is that the sample is a cylindrical shale rock sample drilled along or perpendicular to the bedding planes.

[0014] A further technical solution is that the specific process of step S20 is as follows: based on plane strain, sample shape and boundary conditions, the geometric model can be simplified into a two-dimensional rectangle, and then based on the pressure transmission mathematical model under the hydraulic-chemical coupling of anisotropic shale, a finite element model of pressure transmission under the hydraulic-chemical coupling of anisotropic shale is established.

[0015] A further technical solution is that the specific process of step S30 includes: Step S31: Preprocess the experimental data of pore pressure transmission test; Step S32: Set the permeability parameter set k values Reflection coefficient parameters D svalues and solute diffusion coefficient parameter ; Step S33, Permeability Inversion during Hydraulic Loading Stage: During the hydraulic loading stage, it is assumed that pressure transmission is mainly controlled by the seepage field; the permeability parameter set is traversed sequentially. k values For each k The anisotropic hydraulic-chemical coupled finite element model is invoked, and the Galerkin method is used to approximate the pressure transmission control equations under anisotropic shale hydraulic-chemical coupling to obtain the algebraic equations required for finite element solution. The simulated pore pressure distribution is then calculated. The absolute average error between the simulation results and experimental data is then calculated, and the value that minimizes the absolute average error is recorded. k The value is used as the optimal penetration rate parameter for this stage; Step S34, Solute diffusion and reflection coefficient inversion during chemical loading: In the chemical loading stage, the permeability is set to the optimal value in step S33, and the reflection coefficient parameters are iterated. D svalues and solute diffusion coefficient parameter For each group D s and The combination, combined with the optimal result obtained in step S33 k The finite element model was used to simulate the pressure transmission process during the chemical loading stage; the result that minimized the absolute average error was recorded. D s and The parameter combination serves as the optimal solution for this stage.

[0016] A further technical solution is that, in step S32, the value ranges and step sizes for rock permeability, reflection coefficient, and solute diffusion coefficient are respectively set to form a corresponding permeability parameter set. k values Reflection coefficient parameters D svalues and solute diffusion coefficient parameter .

[0017] A further technical solution is that the formula for calculating the absolute average error is:

[0018] In the formula: To predict pore pressure, MPa; p expThe measured pore pressure is in MPa. n This represents the number of measured pore pressure data points. error This represents the absolute average error.

[0019] The beneficial effects of this invention: This invention utilizes two specific sampling angles ( β Pressure transmission experiments were conducted on samples at 0° and 90°. By combining the grid search method and the anisotropic hydraulic-chemical coupling finite element model, the optimal hydraulic-chemical coupling parameters (anisotropic permeability, solute diffusion coefficient, and reflection coefficient) were inverted, overcoming the difficulty of quickly and accurately determining the hydraulic-chemical coupling parameters of anisotropic shale by conventional methods. Attached Figure Description

[0020] Figure 1 A schematic diagram of a cylindrical rock sample obtained from drilling; Figure 2 for β =0° rock sample test results diagram; Figure 3 for β =90° rock sample test results diagram; Figure 4 Set up a graph for the geometric model, finite mesh generation, and boundary conditions; Figure 5 Determined by grid search method β =0° and β Hydraulic-chemical coupling parameter diagram of the optimal hydraulic loading stage for rock samples at 90°; Figure 6 For the hydraulic loading stage ( β Comparison of experimental and simulation results under the condition of 0°; Figure 7 For the chemical loading stage ( β Comparison of experimental and simulation results under the condition of 0°; Figure 8 For the hydraulic loading stage ( β Comparison of experimental and simulation results under the condition of 90° (=90°); Figure 9 For the chemical loading stage ( β Comparison of experimental and simulation results under the condition of 90° (=90°). Detailed Implementation

[0021] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This invention provides a grid search-based method for testing and inverting the hydraulic-chemical coupling parameters of anisotropic shale, comprising the following steps: Step S10: Conduct pore pressure transmission test experiments under the hydraulic-chemical coupling effect of anisotropic shale; Step S11: Prepare test shale cores; drill cylindrical shale samples along and perpendicular to the bedding planes, with the cylindrical samples measuring Ф50×100mm.

[0023] Step S12, Applying Confining Pressure Stage: After the sample is placed into the triaxial sealed chamber, a confining pressure of 15 MPa is applied to it, denoted as... p c .

[0024] Step S13, Shale saturation test stage under pure hydraulic action: Circulate a mass fraction of [missing value] at the upper end of the sample. C A 5% NaCl solution is prepared, and an injection pressure of 3 MPa is applied simultaneously. This is denoted as 0. p 0; After the upstream and downstream pressures are balanced, the liquid continues to circulate for at least 4 hours, and the downstream discharged liquid is monitored. Saturation is determined to be complete only after confirming that no air bubbles are discharged.

[0025] Step S14, Shale Pressure Transmission Test Stage under Pure Hydraulic Action: Maintain the upper circulation mass fraction of the sample at [value missing]. C A 5% NaCl solution is prepared, and an injection pressure of 10 MPa is applied simultaneously. This is denoted as 0. p m When the pressure at the lower end of the sample rises to the injection pressure p m Record the curve of the lower end pressure changing over time to observe the effect of hydraulic loading on the pressure distribution of the sample.

[0026] Step S15, Experimental stage of shale pressure transmission test under pure chemical action: A mass fraction of [value missing] is circulated at the upper end of the sample. C m A 20% NaCl solution was used, while maintaining the injection pressure. p m The pressure remains unchanged; record the curve of the lower end pressure changing over time to observe the effect of chemical loading on the pressure distribution of the sample.

[0027] Step S30: Establish a finite element model of pressure transmission under the hydraulic-chemical coupling of anisotropic shale; Based on plane strain, specimen shape, and boundary conditions, the geometric model can be simplified to a two-dimensional rectangle. Then, based on the mathematical model of pressure transmission under the hydraulic-chemical coupling of anisotropic shale, a finite element model of pressure transmission under the hydraulic-chemical coupling of anisotropic shale is established.

[0028] Specific boundary condition settings: (1) Hydraulic loading stage: upstream pressure and solution mass fraction are respectively p m and C 0, the initial value of the entire field. p 0 and C 0. (2) Chemical loading stage: upstream pressure and solution mass fraction are respectively p m and C m The initial value of the entire domain is p m and C 0.

[0029] Among them, a mathematical model of pressure transmission under the hydraulic-chemical coupling of anisotropic shale was established; The specific steps are as follows: Step 1: Establish the pressure transmission control equations under the hydraulic-chemical coupling of anisotropic shale: (1) (2) in, (3) (4) (5) (6) In the formula: M Here is the Biot modulus, in GPa; p Pore ​​pressure, MPa; ω is a chemical-stress coupling parameter, and is dimensionless; α Let be the Biot coefficient tensor, which is dimensionless; C Here is the compliance matrix, GPa -1 ; β 1 is the chemical-percolation coupling coefficient, which is dimensionless; k Let m be the permeability tensor. 2 ; η Where is the fluid viscosity, Pa·s; is the reflection coefficient, which is dimensionless; π Chemical osmotic pressure, MPa; S σ Storage coefficient, GPa -1 ; γ These are coefficients related to chemical reactions and are dimensionless. N The chemical coefficient is dimensionless and has no force. R is the molar gas constant, J / (mol·K); x0 represents the initial reference salt mole fraction, which is dimensionless; c s Molar concentration, mol / L; T 0 represents absolute temperature, in K. ϕ Porosity is dimensionless. v 0 represents the initial molar volume of the solution, in L / mol; the superscript T indicates matrix transpose.

[0030] Step S2: Use the Galerkin method to approximate the pressure transmission control equation under the hydraulic-chemical coupling of anisotropic shale, where the finite element solution scheme of the pressure transmission control equation is as follows: (7) in, (8) (9) (10) (11) (12) (13) (14) (15) Where: N P N is a shape function of pore pressure and is dimensionless. π B is a shape function of chemiostopressure and has no dimension. p B is the pore pressure gradient matrix, dimensionless; π This is the chemiostostatic gradient matrix, which is dimensionless. p and π Unknown variables p and π ; p t and π t Unknown variables p and π Time derivative; F p F π These are the fluid source / sink vector and the solute source / sink vector, respectively.

[0031] Step S40: Combining the grid search method and the pressure transmission finite element model under the hydraulic-chemical coupling of anisotropic shale, the basic physical property parameters of the solution domain are assigned, boundary conditions are applied, and the finite element mapping mesh is divided for the pressure transmission finite element model. Finally, the pore pressure distribution is calculated, and the optimal hydraulic-chemical coupling parameters are inverted using the pressure transmission experimental data. The specific inversion process is as follows: (1) Experimental data preparation: Obtain the experimental data of pressure transmission under hydraulic-chemical coupling, and preprocess the experimental data, including noise reduction, time alignment and other operations, so as to facilitate subsequent comparison.

[0032] (2) Parameter space setting: Set the value range and step size of rock permeability, reflection coefficient and solute diffusion coefficient respectively to form the corresponding discrete parameter set; (3) Permeability Inversion During Hydraulic Loading: During the hydraulic loading stage, it is assumed that pressure transmission is mainly controlled by the seepage field. The permeability parameter set is then iterated sequentially. k values For each k The anisotropic hydraulic-chemical coupled finite element model is invoked to simulate the pressure transmission process during the hydraulic loading stage; the error between the simulation results and experimental data is calculated; and the value that minimizes the absolute average error is recorded. k The value is used as the optimal penetration rate parameter for this stage.

[0033] (16) In the formula: To predict pore pressure, MPa; p exp The measured pore pressure is in MPa. n This represents the number of measured pore pressure data points. error The absolute average error; (4) Solute diffusion and reflection coefficient inversion during the chemical loading stage: In the chemical loading stage, assuming the permeability is the optimal value in step (2), the process is iterated through... D svalues and For each group D s and The combination of these factors, combined with the optimal result obtained in step (2), k The finite element model was used to simulate the pressure transmission process during the chemical loading stage; the result that minimized the error was recorded. D s and The parameter combination serves as the optimal solution for this stage.

[0034] (5) Output the optimal parameters: The obtained optimal parameter combination (permeability, solute diffusion coefficient, reflection coefficient) is used as the inversion result corresponding to the experimental data for subsequent analysis and verification.

[0035] Example Step S10: Prepare test shale cores. Drill cylindrical shale samples along and perpendicular to the bedding planes. The dimensions of the cylindrical samples are Ф50×100mm. The obtained cylindrical samples are shown below. Figure 1 As shown.

[0036] Step S20: Conduct a pressure transmission test experiment on anisotropic hydraulic-chemical coupling. The experimental results are as follows: Figure 2 , 3 As shown.

[0037] from Figure 2 , 3 It can be seen that during the saturated sample stage and the hydraulic loading stage, the pressure at the lower end of the sample increases with time, but the rate of increase gradually decreases, eventually synchronizing with the pressure at the upper end. During the chemical loading stage, the pressure at the lower end of the sample decreases with time, but the rate of decrease gradually decreases, eventually stabilizing. (Comparison) Figure 2 and Figure 3 It can be seen that the pressure evolution rates differ significantly depending on the angle of the hydraulic-chemical coupling experiment. This indicates that shale exhibits strong anisotropy; Step S30: Establish a finite element model of pressure transmission under the hydraulic-chemical coupling of anisotropic shale. The basic physical properties of the solution domain, boundary conditions, and finite element mapping mesh are respectively assigned to the pressure transmission finite element model. Figure 4 a) Boundary conditions for the upper fluid pressure and mass fraction, and initial values ​​over the entire domain, such as... Figure 4 As shown in b to 4d; Step S40: Combining the grid search method and the pressure transmission finite element model under the hydraulic-chemical coupling of anisotropic shale, the optimal hydraulic-chemical coupling parameters are inverted using the pressure transmission experimental data; (1) Experimental data preparation: Obtain the raw data of the hydraulic-chemical coupling pressure transmission experiment and preprocess the experimental data, including noise reduction and time alignment, for subsequent comparison.

[0038] (2) Parameter space setting: Set the value range and step size of rock permeability, reflection coefficient and solute diffusion coefficient respectively to form the corresponding discrete parameter set; (3) Permeability Inversion During Hydraulic Loading: During the hydraulic loading stage, it is assumed that pressure transmission is mainly controlled by the seepage field. The permeability parameter set is iterated sequentially. k values For each k The anisotropic hydraulic-chemical coupled finite element model is invoked to simulate the pressure transmission process during the hydraulic loading stage; the absolute average error between the simulation results and experimental data is calculated; and the value that minimizes the absolute average error is recorded. k The value is used as the optimal penetration rate parameter for this stage.

[0039] (4) Inversion of solute diffusion coefficient and reflection coefficient during the chemical loading stage: In the chemical loading stage, assuming the permeability is the optimal value in step (2), traversing... Dsvalues and For each group D s and The combination of these factors, combined with the optimal result obtained in step (2), k The finite element model was used to simulate the pressure transmission process during the chemical loading stage; the result that minimized the absolute average error was recorded. D s and The parameter combination serves as the optimal solution for this stage.

[0040] (5) Output Optimal Parameters: The obtained optimal parameter combination (permeability, solute diffusion coefficient, reflection coefficient) is used as the inversion result corresponding to the experimental data for subsequent analysis and verification. The optimal parameter combination result is shown below. Figure 5 As shown. From Figure 5 It can be seen that, for β The shale sample with a permeability of 1.3e-20m at 0° has a permeability of 1. 2 The reflectance coefficient is 0.17 and the solute diffusion coefficient is 2e-9m. 2 / s. For β A shale sample with a permeability of 6e-20m at 90°. 2 The reflectance coefficient is 0.25 and the solute diffusion coefficient is 6e-9m. 2 / s.

[0041] Step S50: Verify the accuracy of the inverted anisotropic hydraulic-chemical coupling parameters; To verify the correctness and accuracy of the inverted hydraulic-chemical coupling parameters using the mesh search method combined with the finite element model, this paper substitutes the optimal hydraulic-chemical coupling parameters into the anisotropic hydraulic-chemical coupling finite element model, simulates the pressure at different stages and times, and compares the simulation results (solid line) with the measured pressure transmission data (solid points). The solid point-solid line represents the relative error, such as... Figure 6-9 As shown in the figure, it is easy to see that the simulated pressure under the optimal combination of hydraulic-chemical coupling parameters is basically consistent with the actual pressure transmission experimental data.

[0042] The above description is not intended to limit the present invention in any way. Although the present invention has been disclosed through the above embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall fall within the scope of the present invention.

Claims

1. A grid-search-based method for testing and inverting hydraulic-chemical coupling parameters of anisotropic shale, characterized in that, Includes the following steps: Step S10: Conduct pore pressure transmission test experiments under the hydraulic-chemical coupling effect of anisotropic shale; Step S20: Establish a finite element model of pressure transmission under the hydraulic-chemical coupling of anisotropic shale; The pressure transmission control equation of the pressure transmission finite element model is: in, In the formula: M Here is the Biot modulus, in GPa; p Pore ​​pressure, MPa; ω is a chemical-stress coupling parameter, and is dimensionless; α Let be the Biot coefficient tensor, which is dimensionless; C Here is the compliance matrix, GPa -1 ; β 1 is the chemical-percolation coupling coefficient, which is dimensionless; k Let m be the permeability tensor. 2 ; η Where is the fluid viscosity, Pa·s; is the reflection coefficient, which is dimensionless; π Chemical osmotic pressure, MPa; S σ Storage coefficient, GPa -1 ; γ These are coefficients related to chemical reactions and are dimensionless. N The chemical coefficient is dimensionless and has no force. R is the molar gas constant, J / (mol·K); x 0 represents the initial reference salt mole fraction, which is dimensionless; c s Molar concentration, mol / L; T 0 represents absolute temperature, in K. Porosity is dimensionless. v 0 represents the initial molar volume of the solution, in L / mol; the superscript T indicates matrix transpose. Step S30: Combining the mesh search method and the pore pressure transmission test data, assign values ​​to the basic physical property parameters of the solution domain, apply boundary conditions and divide the finite element mapping mesh for the pressure transmission finite element model, and invert the optimal hydraulic-chemical coupling parameters. Step S31: Preprocess the experimental data of pore pressure transmission test; Step S32: Set the permeability parameter set k values Reflection coefficient parameters D svalues and solute diffusion coefficient parameter ; Step S33, Permeability Inversion during Hydraulic Loading Stage: During the hydraulic loading stage, it is assumed that pressure transmission is mainly controlled by the seepage field; the permeability parameter set is traversed sequentially. k values For each k The anisotropic hydraulic-chemical coupled finite element model is invoked, and the Galerkin method is used to approximate the pressure transmission control equations under anisotropic shale hydraulic-chemical coupling to obtain the algebraic equations required for finite element solution. The simulated pore pressure distribution is then calculated. The absolute average error between the simulation results and experimental data is then calculated, and the value that minimizes the absolute average error is recorded. k The value is used as the optimal penetration rate parameter for this stage; Step S34, Solute diffusion and reflection coefficient inversion during chemical loading: In the chemical loading stage, the permeability is set to the optimal value in step S33, and the reflection coefficient parameters are iterated. D svalues and solute diffusion coefficient parameter For each group D s and The combination, combined with the optimal result obtained in step S33 k The finite element model was used to simulate the pressure transmission process during the chemical loading stage; the result that minimized the absolute average error was recorded. D s and The parameter combination serves as the optimal solution for this stage.

2. The method for testing and inverting anisotropic shale hydraulic-chemical coupling parameters based on grid search according to claim 1, characterized in that, The specific steps for conducting the pressure transmission test experiment under the anisotropic hydraulic-chemical coupling of shale in step S10 are as follows: Step S11, Applying Confining Pressure: After the sample is placed into the triaxial sealed chamber, a confining pressure of 15 MPa is applied to it, denoted as... p c ; Step S12, Shale saturation test stage under pure hydraulic action: Circulate a mass fraction of [missing value] at the upper end of the sample. C A NaCl solution of 0% is simultaneously injected at a pressure of 3 MPa, denoted as . p 0; After the upstream and downstream pressures are balanced, continue to circulate the liquid for at least 4 hours and monitor the downstream discharged liquid. Only after confirming that no air bubbles are discharged can saturation be determined to be complete. Step S13, Shale Pressure Transmission Test Stage under Pure Hydraulic Action: Maintain the upper circulation mass fraction of the sample at [value missing]. C A NaCl solution of 0% is injected simultaneously at an injection pressure of 10 MPa, denoted as . p m When the pressure at the lower end of the sample rises to the injection pressure p m Record the curve of the pressure change at the lower end over time to observe the effect of hydraulic loading on the pressure distribution of the sample. Step S14, Experimental stage of shale pressure transmission test under pure chemical action: A mass fraction of [missing information] is circulated at the upper end of the sample. C m NaCl solution, while maintaining injection pressure p m The pressure remains unchanged; record the curve of the lower end pressure changing over time to observe the effect of chemical loading on the pressure distribution of the sample.

3. The method for testing and inverting anisotropic shale hydraulic-chemical coupling parameters based on grid search according to claim 2, characterized in that, The sample is a cylindrical shale rock sample drilled along or perpendicular to the bedding planes.

4. The method for testing and inverting anisotropic shale hydraulic-chemical coupling parameters based on grid search according to claim 1, characterized in that, The specific process of step S20 is as follows: Based on plane strain, sample shape and boundary conditions, the geometric model can be simplified into a two-dimensional rectangle. Then, based on the pressure transmission mathematical model under the hydraulic-chemical coupling of anisotropic shale, a finite element model of pressure transmission under the hydraulic-chemical coupling of anisotropic shale is established.

5. The method for testing and inverting anisotropic shale hydraulic-chemical coupling parameters based on grid search according to claim 1, characterized in that, In step S32, the value ranges and step sizes for rock permeability, reflection coefficient, and solute diffusion coefficient are set respectively to form a corresponding permeability parameter set. k values Reflection coefficient parameters D svalues and solute diffusion coefficient parameter .

6. The method for testing and inverting anisotropic shale hydraulic-chemical coupling parameters based on grid search according to claim 1, characterized in that, The formula for calculating the absolute average error is: In the formula: To predict pore pressure, MPa; p exp The measured pore pressure is in MPa. n This represents the number of measured pore pressure data points. error This represents the absolute average error.

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