Seepage numerical simulation method, device and equipment based on rock three-dimensional grid model

Abstract

The invention relates to the field of three-dimensional simulation, and provides a seepage numerical simulation method, device and equipment based on a rock three-dimensional grid model.The method comprises the steps that a target rock is scanned, component segmentation processing is conducted on a target image obtained through scanning, and a three-dimensional surface model file of rock components is generated; the rock component comprises a rock matrix, pores and fractures; performing grid construction according to the three-dimensional surface model file to generate a uniform rock component grid file; configuring geometric parameters and physical field conditions, and performing rock stress-seepage multi-field coupling simulation according to the rock component grid file and the configured geometric parameters and physical field conditions. According to the method, the problem of seepage-stress coupling simulation distortion caused by insufficient rock three-dimensional modeling precision in the prior art is solved, and pore-fracture accurate characterization and multi-physical field dynamic coupling analysis based on the high-fidelity grid are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of three-dimensional simulation, in particular to a seepage numerical simulation method, device and equipment based on a three-dimensional grid model of rock. BACKGROUND

[0002] In rock mechanics experiments, the threshold value is an important parameter for post-processing structure division. The three-dimensional reconstruction of CT images mainly relies on threshold segmentation. The commonly used threshold division method is the OTSU algorithm, which determines the optimal threshold by maximizing the inter-class variance. The division speed of rock fracture-matrix is fast and the effect is good. However, in rock seepage research, the gray scale distribution of pores and fractures has high similarity, and only relying on the gray scale threshold cannot accurately represent the topological difference between pores and fractures.

[0003] AVIZO software has a simple and operable interface and is an excellent tool for CT scan image processing. However, there are significant technical defects in the data docking of the AVIZO reconstruction results and the mainstream numerical simulation software (FLUENT, COMSOL, ANSYS, etc.): ①Through the built-in MESH module, the concave-convex identification of three-dimensional modeling is not good, and the grid element division is not uniform, which easily causes grid distortion (such as sharp corner element compression), non-uniform distribution (pore domain grid is excessively refined and fracture domain grid is sparse), and other singular phenomena, which directly affects the accuracy of seepage simulation; ②Through the GENERATE SURFACE command, the STL format surface model is saved, but the reconstruction model grid is distorted due to differences in surface fitting algorithms, feature point matching errors, and other problems.

[0004] The above defects make the reconstructed model unable to truly reflect the topological structure of the pores and fractures inside the rock, and further cause the seepage field and stress field coupling simulation results to deviate from the actual physical law. SUMMARY

[0005] The present application provides a seepage numerical simulation method, device and equipment based on a three-dimensional grid model of rock, which solves the problem of seepage-stress coupling simulation distortion caused by the insufficient accuracy of three-dimensional modeling of rock in the prior art, and realizes accurate characterization of pores and fractures and dynamic coupling analysis of multiple physical fields based on high-fidelity grids.

[0006] The present application provides a seepage numerical simulation method based on a three-dimensional grid model of rock, comprising the following steps: Scanning the target rock, and performing component segmentation processing on the target image obtained by scanning to generate a three-dimensional surface model file of rock components; the rock components include rock matrix, pores and fractures; According to the three-dimensional surface model file, a grid is constructed to generate a uniform rock component grid file; The geometry parameters and the physical field conditions are configured, and rock stress-seepage multi-field coupling simulation is performed according to the rock component grid file and the configured geometry parameters and physical field conditions.

[0007] According to the rock three-dimensional grid model-based seepage numerical simulation method provided by the application, the target image obtained by scanning is subjected to component segmentation processing to generate a three-dimensional surface model file of rock components, and specifically includes: performing gray threshold segmentation and noise reduction processing on the target image to extract rock components; performing geometry parameter analysis on the region of the rock components to obtain geometry information of each component region; accurately dividing each structure of the rock components according to the geometry information; and generating a three-dimensional surface model file of rock components after the division.

[0008] According to the rock three-dimensional grid model-based seepage numerical simulation method provided by the application, the target image is subjected to gray threshold segmentation and noise reduction processing to extract rock components, and specifically includes: distinguishing different components in the target image according to a gray threshold; removing image noise points from the target image; and performing region segmentation of different components on the target image after the noise points are removed to extract rock components.

[0009] According to the rock three-dimensional grid model-based seepage numerical simulation method provided by the application, the target image is subjected to gray threshold segmentation and noise reduction processing to extract rock components, and specifically includes: distinguishing different components in the target image according to a gray threshold; removing image noise points from the target image; and performing region segmentation of different components on the target image after the noise points are removed to extract rock components.

[0010] According to the rock three-dimensional grid model-based seepage numerical simulation method provided by the application, the target image is subjected to gray threshold segmentation and noise reduction processing to extract rock components, and specifically includes: distinguishing different components in the target image according to a gray threshold; removing image noise points from the target image; and performing region segmentation of different components on the target image after the noise points are removed to extract rock components.

[0011] According to the rock three-dimensional grid model-based seepage numerical simulation method provided by the application, the target image is subjected to gray threshold segmentation and noise reduction processing to extract rock components, and specifically includes: distinguishing different components in the target image according to a gray threshold; removing image noise points from the target image; and performing region segmentation of different components on the target image after the noise points are removed to extract rock components.

[0012] According to the rock three-dimensional grid model-based seepage numerical simulation method provided in the application, the corresponding hexahedral grid unit is marked as a fissure grid unit according to the judgment result, and specifically includes: if it is determined that the fissure surface is in the hexahedral grid unit, the corresponding hexahedral grid unit is marked as a fissure grid unit; if it is determined that the fissure surface is not in the hexahedral grid unit, the corresponding hexahedral grid unit is marked as a non-fissure grid unit.

[0013] According to the rock three-dimensional grid model-based seepage numerical simulation method provided in the application, rock stress-seepage multi-field coupling simulation is performed according to the rock component grid file and configured geometric parameters and physical field conditions, and specifically includes: obtaining configured geometric parameters, the geometric parameters including model size, fissure characteristic parameters, grid division parameters and topological optimization parameters; generating a rock test specimen model based on the geometric parameters and the rock component grid file, and performing topological optimization on the rock test specimen model; obtaining configured physical field conditions and solver parameters, the physical field conditions including solid mechanics field parameters, seepage boundary and dynamic coupling equation; based on the topologically optimized rock test specimen model, solving the solid displacement field, seepage pressure field and coupling variable according to the physical field conditions and the solver parameters by using a separate solver, and outputting stress-seepage dynamic response data.

[0014] The application further provides a rock three-dimensional grid model-based seepage numerical simulation device, including the following modules: The rock component segmentation module is used for scanning a target rock, performing component segmentation processing on a target image obtained by scanning, and generating a three-dimensional surface model file of rock components; the rock components include rock matrix, pores and fissures; The component grid construction module is used for constructing a grid according to the three-dimensional surface model file, and generating a uniform rock component grid file; The seepage numerical simulation module is used for configuring geometric parameters and physical field conditions, and performing rock stress-seepage multi-field coupling simulation according to the rock component grid file and the configured geometric parameters and physical field conditions.

[0015] The application further provides an electronic device including a memory, a processor and a computer program stored in the memory and executable on the processor, and the processor implements the rock three-dimensional grid model-based seepage numerical simulation method according to any one of the above when executing the computer program.

[0016] The application further provides a non-transitory computer readable storage medium having a computer program stored thereon, and the computer program is executable on a processor to implement the rock three-dimensional grid model-based seepage numerical simulation method according to any one of the above.

[0017] The application further provides a computer program product comprising a computer program which, when executed by a processor, implements the rock three-dimensional grid model-based seepage numerical simulation method according to any one of the above.

[0018] The application provides a rock three-dimensional grid model-based seepage numerical simulation method, device and equipment, which has the following beneficial effects: the rock scanning image is subjected to component segmentation processing and a three-dimensional surface model file is generated, the key components such as rock matrix, pores and fissures can be accurately distinguished, and therefore a uniform rock component grid file is formed in the grid construction stage, and the fine modeling method based on the real rock structure effectively solves the simulation distortion problem caused by the fuzzy component boundary in the traditional method. Further, the rock structure characteristics are dynamically associated with the stress-seepage coupling mechanism by configuring geometric parameters and physical field conditions, so that the multi-field coupling simulation can reflect the real spatial distribution of the pores and fissures in the rock and accurately depict the seepage law of the fluid in the complex geological structure, and the accuracy and reliability of the seepage simulation are significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the application or prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0020] Figure 1 Fig. 1 is a flowchart of the rock three-dimensional grid model-based seepage numerical simulation method provided by the application.

[0021] Figure 2 Fig. 2 is a principle diagram of the rock three-dimensional grid model-based seepage numerical simulation method provided by the application.

[0022] Figure 3a Fig. 3 is an initial CT scanning image provided by the application.

[0023] Figure 3b Fig. 4 is an OTSU algorithm threshold segmentation processing model diagram provided by the application. Figure 3b

[0024] Fig. 5 is a noise reduction processing model diagram provided by the application. Figure 3c

[0025] Fig. 6 is a component extraction fissure model diagram provided by the application. Figure 3d

[0026] Fig. 7 is a principle diagram of separating pores and fissures by taking volume as a parameter provided by the application. Figure 4

[0027] Figure 5aIt is the regular cylindrical hexahedral model graph provided by the application.

[0028] Figure 5b It is the model graph that the hexahedral grid unit is divided into fissure groups provided by the application.

[0029] Figure 6 It is the coal body seepage velocity graph obtained by the seepage numerical simulation of COMS0L test piece of example 1 provided by the application.

[0030] Figure 7 It is the coal body stress field graph obtained by the seepage numerical simulation of COMS0L test piece of example 1 provided by the application.

[0031] Figure 8 It is the flow velocity average graph obtained by the z-axis section of the coal body of COMS0L test piece of example 1 provided by the application.

[0032] Figure 9 It is the coal body seepage velocity graph obtained by the seepage numerical simulation of COMS0L test piece of example 2 provided by the application.

[0033] Figure 10 It is the coal body stress field graph obtained by the seepage numerical simulation of COMS0L test piece of example 2 provided by the application.

[0034] Figure 11 It is the flow velocity average graph obtained by the z-axis section of the coal body of COMS0L test piece of example 2 provided by the application.

[0035] Figure 12 It is the structural schematic diagram of the seepage numerical simulation device based on the rock three-dimensional grid model provided by the application.

[0036] Figure 13 It is the structural schematic diagram of the electronic equipment provided by the application. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical scheme and advantages of the application clearer, the technical scheme in the application will be described clearly and completely below in combination with the drawings in the application. Obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the application.

[0038] The English abbreviations involved in the application will be explained below.

[0039] CT (Computed Tomography), a medical and industrial imaging method that uses X-ray or ultrasound technology to obtain cross-sectional images of an object's internal structure.

[0040] AVIZO, a software for scientific and industrial data visualization and analysis, supporting 3D image processing and modeling.

[0041] FLAC (Fast Lagrangian Analysis of Continua), a numerical simulation software based on finite difference method, mainly used for geotechnical engineering and geomechanics analysis.

[0042] COMSOL, a multi-physics simulation software, supporting coupled simulations in fields such as fluid mechanics, structural mechanics, and electromagnetics.

[0043] STL (Stereolithography), a file format for 3D printing and computer-aided design (CAD), describing the geometry of an object's surface.

[0044] TIF (Tagged Image File Format), a commonly used lossless image storage format, supporting multi-channel and high-resolution images.

[0045] OTSU, an image automatic threshold segmentation algorithm based on gray histogram, used to distinguish foreground and background.

[0046] FISH (FISH language), a scripting language built into FLAC software, used for customizing calculation logic and automation.

[0047] DXF (Drawing Exchange Format), a CAD data file format developed by AutoCAD, used for exchanging two-dimensional and three-dimensional graphics.

[0048] ANSYS (Analysis System), a widely used finite element analysis (FEA) software for engineering simulation.

[0049] FLUENT, a computational fluid dynamics (CFD) simulation software, now under the ANSYS umbrella.

[0050] CFD (Computational Fluid Dynamics): A discipline that uses numerical methods to simulate fluid flow, heat transfer, and related phenomena.

[0051] FEA (Finite Element Analysis): A numerical method used to solve engineering and mathematical physics problems.

[0052] Biot Coefficient: A parameter that describes the influence of fluid pressure on solid stress in porous media, used in fluid-structure interaction analysis.

[0053] Darcy's Law: A fundamental law that describes the low-speed flow of fluids in porous media, used in seepage simulation.

[0054] No Jacobian: A numerical calculation operator used to simplify calculations by avoiding the generation of the Jacobian matrix to save memory.

[0055] μm² (Square Micrometer): A common unit of permeability, representing the fluid passing capacity of a porous medium.

[0056] MPa (Megapascal): A unit of pressure, commonly used to represent the compressive strength or stress of rock.

[0057] GPa (Gigapascal): A common unit of elastic modulus, representing the stiffness of a material.

[0058] Pa·s (Pascal-second): A unit of dynamic viscosity of fluid, used to describe the internal friction characteristics of fluid.

[0059] At present, CT scanning image digital reconstruction and numerical simulation have been widely applied in the study of rock mechanics properties of mining engineering, but there are still many problems in the digital three-dimensional reconstruction of the model and the coupling analysis of multiple software: (1) In rock mechanics experiments, the threshold value is an important parameter for the post-processing structure division. The commonly used threshold division method is OTSU algorithm, which can determine the best threshold by maximizing the inter-class variance, and the division speed of rock fracture-matrix is fast and the effect is good. However, in the study of rock seepage, the gray distribution of pores and fractures has high similarity, and the topological difference between pores and fractures cannot be accurately characterized by relying on gray threshold value only; (2) AVIZO software has a simple and operable interface, and is an excellent tool for pre-processing of CT scanning images. At present, there are two methods for connecting the reconstruction results of AVIZO software with the mainstream numerical simulation software (FLUENT, COMSOL, ANSYS, etc.): ① Through the built-in MESH module, FACET SIZE, FACET DISTANCE, CELL SIZE and other parameters are input to divide the grid and export the corresponding file, but there are problems such as poor identification of concave-convex of three-dimensional modeling, uneven grid division, and easy to cause grid distortion (such as sharp corner element compression), non-uniform distribution (pore domain grid is over-refined and fracture domain grid is sparse) and other singular phenomena; ② Through the GENERATE SURFACE command to save the STL format surface model, but the grid of the reconstructed model is easy to distort due to the differences in surface fitting algorithm and feature point matching error.

[0060] Therefore, combined with the current mainstream software, the rock fine modeling technology and seepage simulation method are studied, the rock multi-scale modeling and fluid seepage mechanism are researched, and the time corresponding characteristics of fracture development degree and water permeability under the influence of fluid-structure coupling are revealed.

[0061] In order to solve the problem of mismatching between three-dimensional digital reconstruction of CT scanning image and mainstream numerical simulation software, the present application provides a seepage numerical simulation method based on rock three-dimensional grid model, which takes volume as a parameter, accurately identifies the topological difference between pores and fractures, realizes the digital accurate reconstruction of three-dimensional structure of coal rock, and improves the accuracy of numerical model. The multi-software interface coupling technology is used to weaken the grid distortion and uneven distribution, and realize the dynamic seepage numerical simulation of fluid-structure coupling of porous medium.

[0062] The embodiments of the present application will be described below in combination with Figures 1-13 The embodiments of the present application will be described below in combination with

[0063] Figure 1 The present application provides a flowchart of the seepage numerical simulation method based on rock three-dimensional grid model, as shown in Figure 1 The method comprises the following steps: S110, scanning the target rock, performing component segmentation processing on the scanned target image, and generating a three-dimensional surface model file of the rock components. The rock components include rock matrix, pores, and fractures.

[0064] Specifically, as Figure 2 The figure shows the principle of the seepage numerical simulation method based on the rock three-dimensional grid model provided by the application. The CT scan image is processed by AVIZO software to generate STL files of each rock component.

[0065] According to the seepage numerical simulation method based on the rock three-dimensional grid model provided by the application, the scanned target image is subjected to component segmentation processing to generate a three-dimensional surface model file of the rock components, and specifically includes: performing gray threshold segmentation and noise reduction processing on the target image, and extracting the rock components; performing geometric parameter analysis on the rock component region to obtain the geometric information of each component region; according to the geometric information, accurately dividing each structure of the rock component; and generating a three-dimensional surface model file of the rock component after division.

[0066] According to the seepage numerical simulation method based on the rock three-dimensional grid model provided by the application, the target image is subjected to gray threshold segmentation and noise reduction processing, and the rock components are extracted, specifically including: distinguishing different components in the target image according to the gray threshold; removing image noise points from the target image; and performing region segmentation of different components on the target image after removing the noise points to extract the rock components.

[0067] According to the seepage numerical simulation method based on the rock three-dimensional grid model provided by the application, the target image is subjected to gray threshold segmentation and noise reduction processing, and the rock components are extracted, specifically including: distinguishing different components in the target image according to the gray threshold; removing image noise points from the target image; and performing region segmentation of different components on the target image after removing the noise points to extract the rock components.

[0068] Specifically, the CT scan image is processed by AVIZO software to generate STL files of each rock component, specifically including: Step 201: obtaining an initial CT scan image (as shown in Figure 3a The TIF format file generated by CT scanning is imported into AVIZO software.

[0069] Step 202: performing threshold determination and segmentation operation based on the gray value and other information of the scan image by Intensity Auto Classification command, and preliminarily distinguishing different components in the image; as Figure 3b OTSU algorithm threshold segmentation processing model diagram.

[0070] Step 203: Through the Median Filter command, the gray values of the neighborhood pixels of each pixel point in the image are sorted and the median value is taken to replace the gray value of the pixel point, and the image noise points are removed; as shown in Figure 3c is a denoising processing model graph.

[0071] Step 204: Through the Volume Edit command, the internal components of the rock sample are extracted by region segmentation; as shown in Figure 3d is a fracture model graph after component extraction.

[0072] Step 205: Through the Label Analysis command, the geometric parameter analysis of the component extraction region is performed, and the volume, area and other information of each component region are obtained.

[0073] Step 206: Through the Analysis Filter command, the structures of the components are divided, and according to the volume information of each region obtained before, appropriate volume threshold and other parameters are set, and the regions in the image that meet the volume characteristics of pores and cracks are accurately segmented, as shown in Figure 4 .

[0074] Step 207: Exporting the rock component files to STL file format.

[0075] Step 207: Exporting the rock component files to STL file format. In the AVIZO taskbar, select "Edit", select "Preferences", and set the basic content in the Units option, set "Options, Display, unitsWorking units" to decimeter as the default coordinate unit to ensure the export size of the image; export to STL file format through Genertate Surface.

[0076] The present application cooperates with the gray threshold segmentation and the median filter denoising, effectively eliminates the image noise while retaining the topological characteristics of pores and cracks, and provides a high-quality data basis for subsequent analysis; the secondary segmentation based on volume parameters overcomes the defects of traditional gray threshold method that is difficult to distinguish pores and cracks, and through the geometric parameter quantization of Label Analysis and Analysis Filter, accurate component separation according to the volume threshold is realized; through the standardized unit setting and STL format export, the lossless compatibility of the three-dimensional model with the subsequent FLAC and COMSOL software is ensured, and the grid distortion problem caused by the confusion of coordinate units or format conversion is avoided. The fidelity of the rock digital model is significantly improved, and a reliable geometric basis is provided for subsequent seepage-stress coupling simulation.

[0077] S120, according to the three-dimensional surface model file, a uniform rock component grid file is generated.

[0078] Specifically, the STL file is imported into the FLAC software, grid construction is performed, and a uniform rock component grid file is generated.

[0079] According to the seepage numerical simulation method based on the rock three-dimensional grid model, the grid construction is performed according to the three-dimensional surface model file, and the uniform rock component grid file is generated, and the method specifically comprises the following steps: a regular cylindrical hexahedron model is established; the internal space of the cylindrical hexahedron model is discretized into a set of hexahedron grid units; a fracture surface model file is obtained, the corresponding relationship between the fracture surface and the hexahedron grid unit is identified based on the fracture surface model file, and the fracture grid unit is marked; and the non-fracture grid unit is deleted, and a uniform fracture grid file is generated.

[0080] According to the seepage numerical simulation method based on the rock three-dimensional grid model, the corresponding relationship between the fracture surface and the hexahedron grid unit is identified, and the fracture grid unit is marked, and the method specifically comprises the following steps: each key node of the fracture surface and the relative position relationship between the key node and the hexahedron grid unit are detected one by one, and it is judged whether the fracture surface is in the hexahedron grid unit; and the corresponding hexahedron grid unit is marked as a fracture grid unit according to the judgment result.

[0081] According to the seepage numerical simulation method based on the rock three-dimensional grid model, the corresponding hexahedron grid unit is marked as a fracture grid unit according to the judgment result, and the method specifically comprises the following steps: if it is determined that the fracture surface is in the hexahedron grid unit, the corresponding hexahedron grid unit is marked as a fracture grid unit; and if it is determined that the fracture surface is not in the hexahedron grid unit, the corresponding hexahedron grid unit is marked as a non-fracture grid unit.

[0082] Specifically, the STL file is imported into the FLAC software, grid construction is performed, and a uniform rock component grid file is generated, and the method specifically comprises the following steps: Step 208: in the FLAC software, a regular cylindrical hexahedron model is established, as shown in the drawing. Figure 5a The internal space of the cylindrical hexahedron model is discretized into a set of hexahedron grid units.

[0083] Step 209: a FISH language is written to realize the detection and judgment of each key node of the fracture surface and the relative position relationship between the key node and the hexahedron grid one by one, to determine whether the fracture surface is in the grid unit, and to obtain a corresponding judgment result. If the judgment result is yes, it indicates that the fracture surface is in the corresponding grid unit, and then the hexahedron grid unit is divided into a “fracture” group, as shown in the drawing. Figure 5b If the judgment result is no, it indicates that the hexahedron grid unit has no intersection with the fracture surface, and then the hexahedron grid unit is divided into an “other” group.

[0084] Step 210: after completing the grouping operation of the grid unit, further performing all selected operations inside the closed fracture grid.

[0085] Step 211: deleting other group units, obtaining a complete rule fracture file, and exporting a DXF file.

[0086] The application provides a uniform discretization calculation framework for subsequent analysis by establishing a rule cylindrical hexahedral basic grid, and fundamentally avoids the grid distortion problem caused by traditional STL direct import; the node detection algorithm written in FISH language accurately identifies the topological relationship between the fracture and the grid unit, ensures the grid integrity of the fracture area through the "fracture group" mark, and solves the non-uniform distribution problem of the over-refined pore domain and the sparse fracture domain; through selective retention of the fracture grid unit and deletion of the redundant unit, the generated DXF file not only retains the geometric characteristics of the original fracture, but also optimizes the calculation efficiency, and provides a grid basis with both accuracy and stability for subsequent COMSOL multi-field coupling simulation. Through the combination of regular grid reconstruction and intelligent grouping technology, the accuracy of the fracture representation is significantly improved, and a reliable numerical experiment platform is provided for fluid-solid coupling analysis.

[0087] S130, configuring geometric parameters and physical field conditions, and performing rock stress-seepage multi-field coupling simulation according to the rock component grid file and the configured geometric parameters and physical field conditions.

[0088] According to the rock seepage numerical simulation method based on the rock three-dimensional grid model, the rock stress-seepage multi-field coupling simulation is performed according to the rock component grid file and the configured geometric parameters and physical field conditions, and specifically includes: obtaining the configured geometric parameters, the geometric parameters including model size, fracture characteristic parameters, grid division parameters and topological optimization parameters; generating a rock sample model based on the geometric parameters and the rock component grid file, and performing topological optimization on the rock sample model; obtaining the configured physical field conditions and solver parameters, the physical field conditions including solid mechanics field parameters, seepage boundary and dynamic coupling equation; based on the topologically optimized rock sample model, according to the physical field conditions and the solver parameters, using a separate solver to solve the solid displacement field, the seepage pressure field and the coupling variable, and outputting stress-seepage dynamic response data.

[0089] Specifically, the rock component grid file is imported into the COMSOL software, and the rock stress-seepage multi-field coupling simulation is performed, specifically including: Step 212: COMSOL geometry modeling and preprocessing work: select the "geometry" toolbar in the software interface, adjust the length reference unit from the default meter to decimeter, complete the coordinate system calibration; establish a cylinder, input the radius value 0.25 m in the parameter panel, and the height is 0.1 m; specify the coordinate origin (0, 0, 0) as the bottom center point. Through the "import" toolbar: select the DXF file format import; select "for face objects" setting not to join; select "remove details" "processed entity" select all geometry, topological optimization is carried out on the model, and the rock specimen with surface streamline and natural fracture network is generated.

[0090] Step 213: Physical field setting and multi-physical field coupling: determine the parameters such as boundary conditions, initial conditions, etc., including fluid inlet and outlet positions, initial fluid pressure setting, porous medium permeability setting, solid model mechanical parameter setting, solid constraint boundary setting, and external stress setting. Use the "porous elasticity" multi-physical field node, which contains the pressure time rate of change in the "Darcy's law" interface and the strain time rate of change in the "solid mechanics" interface, add fluid pressure gradient as stress contribution in the "solid mechanics" interface, and increase strain as permeability change index in fluid mechanics, to solve the micro flow characteristics of fluid in porous media.

[0091] The solid mechanics field sets the elastic mechanics model, and the control equation is: In the formula, ρ is the solid density; u is the deformation; t is the time; σ is the stress level; f v is the external force; ∇· is the divergence operator.

[0092] The calculation domain excludes the pre-defined fracture area from the complete rock domain, and only the matrix part is retained for elastic mechanics calculation. The boundary condition parameters are set as: the bottom boundary is fixed with full degree of freedom constraint, and the top boundary and the surrounding lateral boundary are free and unconstrained; Darcy's law sets the porous medium model.

[0093] In the formula, ρ is the fluid density; ε p is the porosity; ρ is the solid density; p is the fluid pressure; t is the time; ∇· is the divergence operator; ∇ is the gradient operator; k is the permeability; μ is the fluid dynamic viscosity; Q m is the seepage quantity.

[0094] The domain selects the matrix except the fracture, and the permeability is set as: In the formula: K f is the permeability of fractured rock; K f0σ is the initial permeability of rock; σ z σ is the initial permeability of rock; σ z0 σ is the vertical stress.

[0095] Top boundary: constant gas pressure boundary condition is applied; Bottom boundary: constant pressure outlet condition is set; Lateral boundary: zero flux boundary is applied to simulate the lateral closed geological characteristics in actual engineering; Domain Ordinary Differential and Differential Algebraic Equation Set Distributed Ordinary Differential Equation, Control Equation is: In the formula, e a is the mass coefficient; d a is the damping coefficient; f is the source term; m is the variable to be solved; t is the time variable.

[0096] Wherein, the mass coefficient and the damping coefficient are 0, and f is (m-nojac(if(t>0.5[s],exp(solid.sz-solid.sz0),1))), which is used to store the stress solution in the previous time step, wherein the nojac operator is used to reduce the memory requirement and avoid filling the Jacobian matrix.

[0097] “Porous Elasticity” Multi-Physics Field Coupling Model, Control Equation is: In the formula, ρ is the solid density; ε p is the solid porosity; ρ f is the fluid density; u is the deformation; t is the time; ∇· is the divergence operator; σ is the stress level; α B is the Biot coefficient; p f is the fluid pressure; p ref is the standard atmospheric pressure; f v is the external force, and I is the unit matrix.

[0098] In the formula, ε p is the solid porosity; ρ f is the fluid density; χ f is the fluid compressibility coefficient; α B is the Biot coefficient; χ s is the solid phase compression coefficient; p f is the fluid pressure; t is the time; ∇· is the divergence operator; ε vol is the volumetric strain; v d is the fluid velocity; Q m is the permeation.

[0099] The matrix is selected except for the fracture, and the change law of the permeability and stress field under the influence of the rock fluid-solid coupling is simulated.

[0100] Step 214: solver configuration and result output: in the parameter configuration of the solver, the selected pressure field p', displacement field u' and differential equation m' are variable, the automatic scaling algorithm is used to realize the normalization processing of the physical dimension; the time-dependent solver is selected based on the transient dynamic characteristics, the consistent initialization option is closed in the algebraic equation iteration strategy to improve the nonlinear convergence stability; the separate solver is selected, the linear convergence is improved through multi-step separation: separation step one is to solve the time-varying response of the displacement field through the solid mechanics interface, separation step two is to solve the pressure field redistribution through the Darcy's law interface, and separation step three is to couple the auxiliary variable and the main physical field through the differential equation. The numerical simulation results can obtain the seepage field pressure, permeability, mechanical field stress and strain data of the rock in the time-varying process.

[0101] Embodiment 1 The basic parameters of the coal sample are obtained according to the triaxial experiment, wherein the radius is 25 mm, the height is 100 mm, the compressive strength is 15 MPa, the elastic modulus is 7.5 GPa, the porosity is 0.03%, and the initial permeability is 1e-10 cm·s -1 The fracture inclination angle is 50°-90°, the fracture aperture is 0.1-0.2 mm, and the gas dynamic viscosity is 1e-3 pa·s.

[0102] Figure 6 、 Figure 7 、 Figure 8 The coal sample permeation result display diagram simulated and calculated by the present application is shown in the figure. As shown in the figure, the fractures in the coal sample are mainly concentrated in the upper part of the sample, the fracture influence increasing speed area is small, the high stress affected area affected by fluid flow is small, the peak value of the sample permeation speed is 0.07 m / s, which appears at the position of 0.8 dm height of the sample, the volume flow rate of the coal sample is 0.02 kg·s -1 , and the permeability value is about 1.0 μm 2 .

[0103] Embodiment 2 The basic parameters of the sandstone sample are obtained according to the triaxial experiment, wherein the radius is 25 mm, the height is 100 mm, the compressive strength is 49 MPa, the elastic modulus is 12.0 GPa, the porosity is 0.04%, and the initial permeability is 1e-8 cm·s -1 The fracture inclination angle is 80°-90°, the fracture aperture is 0.1-0.2 mm, and the gas dynamic viscosity is 1e-3 pa·s.

[0104] Figure 9 、 Figure 10 、 Figure 11The sandstone sample permeation result display diagram simulated by the present application is shown in the figure. As shown in the figure, the sandstone sample crack network is complex, since the cracks pass through the sample, the upper and lower surfaces are connected, a large range of speed increasing area is formed near the cracks, the flow rate peak value reaches 10 m / s, the sandstone sample flow rate presents an overall increasing trend on the whole cross section. The sample permeation speed peak value is 0.12 m / s, the volume flow of the coal sample is 0.06 kg·s -1 , and the permeability value is about 3.5 μm 2 .

[0105] The present application eliminates the tiny geometric defects while preserving the natural crack network characteristics through standardized geometric preprocessing and topological optimization, provides a high-quality geometric basis for multi-field coupling; the innovative multi-physical field setting dynamically associates Darcy seepage and solid mechanics through the "porous elastic" coupling node, wherein the exponential relationship between permeability and stress accurately depicts the influence mechanism of crack opening and closing on seepage, and the boundary condition truly restores the engineering geological environment; the optimized solver configuration adopts a separate solver and an automatic scaling algorithm, which not only solves the ill-conditioned problem of the stiffness matrix in fluid-structure coupling calculation, but also significantly improves the calculation efficiency and stability through the nojac operator and dynamic time step, and solves the problem of non-convergent calculation results. Finally, the stable convergence and reliable prediction of the seepage-stress field of the coal and sandstone sample are realized, and an effective numerical experiment platform is provided for engineering practice.

[0106] In summary, the seepage numerical simulation method based on the rock three-dimensional grid model provided by the present application solves the problems of grid distortion and non-uniform distribution caused by the import of traditional STL format files and poor multi-field numerical model coupling, improves the digital representation accuracy of the coal rock porous medium structure, and realizes the rock fluid-structure coupling time response simulation. The method shows high reliability in the experimental scale.

[0107] The seepage numerical simulation device based on the rock three-dimensional grid model provided by the present application is described below, and the seepage numerical simulation device based on the rock three-dimensional grid model described below can be correspondingly referred to the seepage numerical simulation method based on the rock three-dimensional grid model described above.

[0108] As Figure 12 shown is a seepage numerical simulation device based on a rock three-dimensional grid model provided by the present application, comprising: A rock component segmentation module 1210 is configured to scan a target rock, perform component segmentation processing on a target image obtained by scanning, and generate a three-dimensional surface model file of rock components; the rock components include a rock matrix, pores and cracks; A component grid construction module 1220 is configured to construct a grid according to the three-dimensional surface model file, and generate a uniform rock component grid file. The seepage numerical simulation module 1230 is configured to configure geometric parameters and physical field conditions, and perform rock stress-seepage multi-field coupling simulation according to the rock component grid file and the configured geometric parameters and physical field conditions.

[0109] Figure 13 An example of an entity structure diagram of an electronic device is shown in Figure 13 As shown, the electronic device can include a processor 1310, a communications interface 1320, a memory 1330, and a communications bus 1340, wherein the processor 1310, the communications interface 1320, and the memory 1330 complete mutual communication through the communications bus 1340. The processor 1310 can invoke a logical instruction in the memory 1330 to execute a seepage numerical simulation method based on a rock three-dimensional grid model, the method including: scanning a target rock, performing component segmentation processing on a target image obtained by scanning to generate a three-dimensional surface model file of rock components; the rock components including rock matrix, pores, and fractures; performing grid construction according to the three-dimensional surface model file to generate a uniform rock component grid file; configuring geometric parameters and physical field conditions, and performing rock stress-seepage multi-field coupling simulation according to the rock component grid file and the configured geometric parameters and physical field conditions.

[0110] In addition, the logical instruction in the memory 1330 described above can be implemented in the form of a software function unit and sold or used as an independent product, and can be stored in a computer-readable storage medium. Based on this understanding, the technical solutions of the present application essentially or the part that contributes to the prior art or part of the technical solutions can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a plurality of instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) execute all or part of the steps of the embodiments of the present application. The foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and various program code storage media.

[0111] In another aspect, the present application also provides a computer program product, which comprises a computer program, the computer program being stored in a non-transitory computer readable storage medium, and the computer program being executable by a processor to enable a computer to perform the numerical simulation method of seepage based on a three-dimensional grid model of rock, the method comprising: scanning a target rock, performing component segmentation processing on a target image obtained by scanning to generate a three-dimensional surface model file of rock components; the rock components comprising rock matrix, pores and fractures; performing grid construction according to the three-dimensional surface model file to generate a uniform rock component grid file; configuring geometric parameters and physical field conditions, and performing rock stress-seepage multi-field coupling simulation according to the rock component grid file and the configured geometric parameters and physical field conditions.

[0112] In another aspect, the present application also provides a non-transitory computer readable storage medium, which stores a computer program, the computer program being executable by a processor to implement the numerical simulation method of seepage based on a three-dimensional grid model of rock, the method comprising: scanning a target rock, performing component segmentation processing on a target image obtained by scanning to generate a three-dimensional surface model file of rock components; the rock components comprising rock matrix, pores and fractures; performing grid construction according to the three-dimensional surface model file to generate a uniform rock component grid file; configuring geometric parameters and physical field conditions, and performing rock stress-seepage multi-field coupling simulation according to the rock component grid file and the configured geometric parameters and physical field conditions.

[0113] The device embodiments described above are merely illustrative, wherein the units illustrated as separate components can or can not be physically separated, and the components illustrated as units can or can not be physical units, i.e., can be located in one place or distributed on multiple network units. Part or all of the modules can be selected to achieve the purpose of the embodiment scheme according to actual needs. Those skilled in the art can understand and implement without creative labor.

[0114] From the above description of the embodiments, those skilled in the art can clearly understand that the embodiments can be implemented by means of software plus necessary general hardware platforms, and of course can also be implemented by hardware. Based on such understanding, the above technical solutions can be embodied in the form of a software product, which can be stored in a computer readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes a plurality of instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) execute the methods of the embodiments or some parts of the embodiments.

[0115] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit the same; and although the present application has been described in detail with reference to the foregoing embodiments, it should be appreciated by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features thereof can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A numerical simulation method for seepage based on a three-dimensional rock mesh model, characterized in that, include: The target rock is scanned, and the scanned target image is segmented into its components to generate a three-dimensional surface model file of the rock components; the rock components include the rock matrix, pores, and fractures. Based on the three-dimensional surface model file, a mesh is constructed to generate a uniform rock composition mesh file; Configure geometric parameters and physical field conditions, and perform rock stress-seepage multi-field coupling simulation based on the rock component mesh file and the configured geometric parameters and physical field conditions.

2. The seepage numerical simulation method based on a three-dimensional rock mesh model according to claim 1, characterized in that, The step of performing component segmentation processing on the scanned target image to generate a three-dimensional surface model file of the rock components specifically includes: The target image is subjected to grayscale thresholding and noise reduction processing to extract rock components; Geometric parameter analysis is performed on the regions of the rock components to obtain geometric information for each component region; Based on the geometric information, the structures of the rock components are precisely divided; After partitioning, a three-dimensional surface model file of the rock components is generated.

3. The seepage numerical simulation method based on a three-dimensional rock mesh model according to claim 2, characterized in that, The target image is subjected to grayscale thresholding and noise reduction processing to extract rock components, specifically including: Different components in the target image are distinguished based on grayscale thresholds; Remove image noise points from the target image; The target image after noise removal is segmented into regions of different components, and rock components are extracted.

4. The seepage numerical simulation method based on a three-dimensional rock mesh model according to claim 3, characterized in that, The removal of image noise points from the target image specifically includes: The grayscale values ​​of the neighboring pixels of each current pixel in the target image are sorted, and the median value is used to replace the grayscale value of the current pixel.

5. The seepage numerical simulation method based on a three-dimensional rock mesh model according to claim 1, characterized in that, The step of constructing a mesh based on the three-dimensional surface model file to generate a uniform rock composition mesh file specifically includes: A regular cylindrical hexahedron model is established; the internal space of the cylindrical hexahedron model is discretized into a set of hexahedral mesh elements; Obtain the fracture surface model file, identify the correspondence between the fracture surface and the hexahedral mesh element based on the fracture surface model file, and mark the fracture mesh element; Delete non-cracked mesh elements to generate a uniform cracked mesh file.

6. The seepage numerical simulation method based on a three-dimensional rock mesh model according to claim 5, characterized in that, The process of identifying the correspondence between the fracture surface and the hexahedral mesh element, and marking the fracture mesh element, specifically includes: Each key node on the crack surface and its relative position to the hexahedral mesh element are checked one by one to determine whether the crack surface is within the hexahedral mesh element. Based on the judgment results, the corresponding hexahedral mesh elements are marked as crack mesh elements.

7. The seepage numerical simulation method based on a three-dimensional rock mesh model according to claim 6, characterized in that, The step of marking the corresponding hexahedral mesh elements as fracture mesh elements based on the judgment result specifically includes: If it is determined that the crack surface is within a hexahedral mesh element, then the corresponding hexahedral mesh element is marked as a crack mesh element. If it is determined that the crack surface is not within a hexahedral mesh element, then the corresponding hexahedral mesh element is treated as a non-crack mesh element.

8. The seepage numerical simulation method based on a three-dimensional rock mesh model according to claim 1, characterized in that, Based on the rock composition mesh file and configured geometric parameters and physical field conditions, a multi-field coupled simulation of rock stress-seepage is performed, specifically including: Obtain the configured geometric parameters, including model size, crack feature parameters, mesh generation parameters, and topology optimization parameters; A rock specimen model is generated based on the geometric parameters and the rock composition mesh file, and topology optimization is performed on the rock specimen model. Obtain the configured physical field conditions and solver parameters, wherein the physical field conditions include solid mechanical field parameters, seepage boundary and dynamic coupling equations; Based on the topology-optimized rock specimen model, according to the physical field conditions and the solver parameters, a separate solver is used to solve the solid displacement field, seepage pressure field and coupling variables, and output stress-seepage dynamic response data.

9. A seepage numerical simulation device based on a three-dimensional rock mesh model, characterized in that, include: The rock component segmentation module is used to scan the target rock, perform component segmentation processing on the scanned target image, and generate a three-dimensional surface model file of the rock components; the rock components include rock matrix, pores, and fractures; The component mesh construction module is used to construct a mesh based on the three-dimensional surface model file and generate a uniform rock component mesh file. The seepage numerical simulation module is used to configure geometric parameters and physical field conditions, and to perform rock stress-seepage multi-field coupled simulation based on the rock component mesh file and the configured geometric parameters and physical field conditions.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the seepage numerical simulation method based on a three-dimensional rock mesh model as described in any one of claims 1 to 8.

11. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the seepage numerical simulation method based on a three-dimensional rock mesh model as described in any one of claims 1 to 8.

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