Permeability analysis method, computer equipment and storage medium for rock shear process

Abstract

The present application provides a method for analyzing the permeability of a rock shear process, a computer device, and a storage medium. The method includes: obtaining a fractured rock particle model, the fractured rock particle model includes a first rock particle model and a second rock particle model, and there is a fracture between the first rock particle model and the second rock particle model; simulating the shear process of the fractured rock particle model according to a target confining pressure, obtaining a shear fracture surface between the first rock particle model and the second rock particle model when the shear displacement between the first rock particle model and the second rock particle model reaches a preset shear displacement; obtaining a seepage simulation parameter corresponding to the shear fracture surface, simulating the fracture seepage process of the shear fracture surface according to the seepage simulation parameter, and obtaining a seepage simulation result; determining the fracture permeability of the fractured rock particle model at the preset shear displacement according to the seepage simulation result. The shear seepage process of the rock can be simulated and calculated more accurately.

Description

Technical Field

[0001] The present application relates to the field of rock mechanics engineering technology, and in particular to a permeability analysis method, computer equipment and storage medium for a rock shear process. Background Art

[0002] After a long period of complex geological action, engineering rock mass will form cracks with different numbers and occurrences. These cracks are common in the rock structure, which not only affect the strength of the rock, but also have a great impact on the hydraulic properties of the rock. Due to the compactness of intact rocks, it is not easy for fluids to seep through rocks. Compared with rocks, cracks have a greater water-permeability. The complex fracture network formed by the interaction of fractures is the main channel for fluid flow in dense rock mass. Therefore, the seepage in the rock mass mainly relies on fractures. The existence of complex fracture networks leads to a high degree of complexity in the structural characteristics and mechanical properties of rock mass. Large-scale projects such as deep geothermal energy development, geological storage of carbon dioxide, and geological disposal of high-level radioactive waste will inevitably encounter complex and adverse geological conditions such as fractured rock mass. Exploring the hydraulic properties of complex rock mass containing fractures is of great significance to solving the above major engineering problems.

[0003] The spatial distribution characteristics of cracks largely determine the flow characteristics of underground fluids in the rock mass, further affecting the migration process of solutes. Studies generally believe that the water conductivity of the rock mass is closely related to the degree of development of cracks. In order to explore the degree of agreement between theory and practice, it is of great significance for the laboratory to conduct research on the evolution law of crack permeability. However, due to the difficulty of the experiment and the complex conditions, it is very challenging to reflect the dynamic evolution law of crack permeability under real geological conditions. In addition, due to the great difficulties and technical bottlenecks in observing the microscopic wear and damage of cracks and the evolution of cracks during the experiment, there is no sufficiently reliable experimental means for the dynamic permeability evolution mechanism of cracks during shear. However, it is of great significance to further study the evolution law of the dynamic permeability of cracks and reveal the dynamic evolution mechanism of crack permeability under confining pressure and shear conditions. Therefore, numerical simulation is one of the effective methods to study the permeability evolution law based on the experimental results.

[0004] The relevant technology cannot effectively analyze the fracture permeability during rock shearing process. Summary of the invention

[0005] The main purpose of this application is to provide a permeability analysis method, computer equipment and storage medium for rock shear process, aiming to simulate and calculate the shear seepage process of rock more accurately.

[0006] In a first aspect, the present application provides a method for analyzing the permeability of a rock shear process, which is used in a computer device, and the method comprises:

[0007] Acquire a fractured rock particle model, wherein the fractured rock particle model comprises a first rock particle model and a second rock particle model, wherein a fracture exists between the first rock particle model and the second rock particle model;

[0008] According to the target confining pressure, a shear process simulation is performed on the fractured rock particle model to obtain a shear fracture surface between the first rock particle model and the second rock particle model when the shear displacement between the first rock particle model and the second rock particle model reaches a preset shear displacement;

[0009] Acquire the seepage simulation parameters corresponding to the shear fracture surface, and simulate the fracture seepage process of the shear fracture surface according to the seepage simulation parameters to obtain the seepage simulation results;

[0010] According to the seepage simulation result, the fracture permeability of the fractured rock particle model at the preset shear displacement is determined.

[0011] In a second aspect, the present application also provides a computer device, including a memory and a processor;

[0012] The memory is used to store computer programs;

[0013] The processor is used to execute the computer program and implement the steps of the aforementioned rock shear process permeability analysis method when executing the computer program.

[0014] In a third aspect, the present application also provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the processor implements the steps of the aforementioned permeability analysis method for the rock shear process.

[0015] The present application provides a permeability analysis method, computer equipment and storage medium for a rock shear process, the permeability analysis method comprising: obtaining a fractured rock particle model, the fractured rock particle model comprising a first rock particle model and a second rock particle model, and there being a fracture between the first rock particle model and the second rock particle model; simulating the shear process of the fractured rock particle model according to a target confining pressure, obtaining a shear fracture surface between the first rock particle model and the second rock particle model when the shear displacement between the first rock particle model and the second rock particle model reaches a preset shear displacement; obtaining seepage simulation parameters corresponding to the shear fracture surface, simulating the fracture seepage process of the shear fracture surface according to the seepage simulation parameters, and obtaining a seepage simulation result; determining the fracture permeability of the fractured rock particle model at the preset shear displacement according to the seepage simulation result. The shear seepage process of the rock can be simulated and calculated more accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 It is a schematic flow chart of a method for analyzing the permeability of a rock shear process provided in an embodiment of the present application;

[0018] Figure 2 is a schematic diagram of a fractured rock particle model in one embodiment;

[0019] Figure 3 is a schematic diagram of a crack curve drawn according to axial crack surface information in one implementation;

[0020] Figure 4 is a schematic diagram of a first geometric boundary of a first rock particle model and a second geometric boundary of a second rock particle model in one embodiment;

[0021] Figure 5 is a schematic diagram of a shear fracture surface corresponding to a preset shear displacement in one embodiment;

[0022] Figure 6 is a schematic diagram of peak shear stress during shear process simulation under different target confining pressures in one embodiment;

[0023] Figure 7 is a schematic diagram of a geometric model of COMSOL seepage numerical simulation in one embodiment;

[0024] Figure 8 is a schematic diagram of a watershed grid of a fracture divided in one embodiment;

[0025] Figure 9a It is the velocity distribution cloud diagram of the seepage field corresponding to the seepage simulation result;

[0026] Figure 9b for Figure 9a A local enlarged cloud diagram of the velocity distribution in the middle seepage field;

[0027] Fig.10a It is the pressure distribution cloud diagram of the seepage field corresponding to the seepage simulation results;

[0028] Fig.10b yes Figure 9a A local magnified cloud diagram of the pressure distribution in the middle seepage field;

[0029] Fig.11a and Fig.11bis a schematic diagram of the evolution curve of fracture permeability with shear displacement;

[0030] Fig.12 is a schematic diagram of shear stress corresponding to a preset shear displacement in one embodiment;

[0031] Fig.13 is a schematic flow chart of a method for analyzing the permeability of a rock shear process in one embodiment;

[0032] Fig.14 It is a schematic block diagram of the structure of a computer device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0034] The flowcharts shown in the accompanying drawings are only examples and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps may also be decomposed, combined or partially merged, so the actual execution order may change according to actual conditions.

[0035] The embodiment of the present application provides a method for analyzing the permeability of a rock shear process, a computer device, and a storage medium. The method for analyzing the permeability of a rock shear process can be applied to a computer device.

[0036] Exemplarily, the computer device may include a terminal device or a server, wherein the terminal device may be an electronic device such as a mobile phone, a tablet computer, a laptop computer, a vehicle-mounted terminal, a desktop computer, a personal digital assistant, and a wearable device; the server may be an independent server or a server cluster.

[0037] The related technology qualitatively explains the evolution law of fracture permeability in the test, but fails to deeply and quantitatively analyze the influence mechanism of fracture aperture and fracture connectivity on fracture permeability during shearing under shear dilation. In addition, there are related technologies that use numerical simulation to analyze the changes in rock microscopic particles and pores during shearing, and analyze the association mechanism between the formation of broken zones and the increase in pore and pore throat volume during shearing. However, this existing technology completely regards the porous area as a fluid flow basin, and does not perform a more accurate numerical simulation of the seepage process, which is somewhat different from the theoretical analysis. Although the related technology can reasonably explain the experimental phenomenon, the numerical simulation method used fails to consider the seepage process more realistically, and needs further improvement.

[0038] The embodiments of the present application can simulate and numerically calculate the shear seepage process of rocks more accurately.

[0039] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0040] See also Figure 1 , Figure 1 It is a flow chart of a permeability analysis method for a rock shear process provided in an embodiment of the present application.

[0041] like Figure 1 As shown, the permeability analysis method of the rock shear process includes steps S110 to S140.

[0042] Step S110: Acquire a fractured rock particle model, wherein the fractured rock particle model comprises a first rock particle model and a second rock particle model, and a fracture is present between the first rock particle model and the second rock particle model.

[0043] The fractured rock particle model may be a two-dimensional fractured rock particle model or a three-dimensional fractured rock particle model. For ease of description, the embodiment of the present application is mainly described by taking a two-dimensional fractured rock particle model as an example.

[0044] like Figure 2 As shown, there is a crack between the first rock particle model and the second rock particle model in the fractured rock particle model. The first rock particle model can be called the hanging wall particle model, and the second rock particle model can be called the foot wall particle model.

[0045] The particles of the first rock particle model and the particles of the second rock particle model can have the same particle parameters, or they can have different particle parameters. The particles of the first rock particle model are associated with each other through a contact model, and the particles of the second rock particle model are associated with each other through a contact model. The particles at the cracks of the first rock particle model and the second rock particle model can also be associated through a contact model; the contact model used by the particles at the cracks is different from the contact model between the particles of the first rock particle model and the contact model between the particles of the second rock particle model, so as to accurately simulate the behavior of the cracks.

[0046] Among them, the contact model is specifically: a method for simulating the mechanical behavior of macroscopic objects by defining physical and mechanical parameters such as elastic modulus, Poisson's ratio, shear strength, cohesion, internal friction angle, etc. between particles. It can be understood that the fractured rock particle model is specifically: the upper and lower plate particle models of the rock separated by the fracture surface, and the particles are associated through the contact model.

[0047] In some embodiments, the axial fracture surface information of the rock is extracted based on the three-dimensional (3D) scanning results of the fracture surface of the rock sample, and the geometric boundary of the model is established accordingly. Based on the geometric boundary and the microscopic parameters of the rock, the fractured rock particle model is created using PFC2D.

[0048] In some embodiments, step S110 obtains a fractured rock particle model, including steps S111 to S113.

[0049] Step S111, obtaining scanning data of the fracture surface of the rock sample and size information of the rock sample.

[0050] Specifically, the 3D scanning result of the fracture surface of the rock sample includes point coordinate information of the fracture surface in three directions of the x-axis, y-axis and z-axis obtained after the 3D scanning of the fracture surface of the rock sample.

[0051] Step S112: determining a first geometric boundary and a second geometric boundary according to the scanning data of the crack surface and the size information.

[0052] For example, based on the scanning data of the fracture surface, the axial fracture surface information of the rock sample is determined, and the axial fracture surface information specifically refers to the two-dimensional fracture data obtained along the axial section of the rock sample from the three-dimensional data of the fracture surface; and the first geometric boundary and the second geometric boundary are determined based on the axial fracture surface information and the size information.

[0053] According to the axial fracture surface information of the rock sample, the fracture curve can be drawn, such as Figure 3 Shown is a schematic diagram of the crack curve drawn based on the axial crack surface information.

[0054] According to the size information of the rock sample and the fracture curve, a closed two-dimensional closed curve is established to obtain Figure 4 The first geometric boundary and the second geometric boundary are shown. For example, the first geometric boundary and the second geometric boundary can be saved as a "model_border.dxf" file.

[0055] When establishing the first geometric boundary and the second geometric boundary, it can be ensured that the fracture curve corresponding to the fracture surface is located in the middle of the upper and lower plates of the rock, so as to avoid too large a difference between the upper and lower plates of the rock model.

[0056] Step S113: generating the first rock particle model according to the first rock mesoscopic parameter and the first geometric boundary, and generating the second rock particle model according to the second rock mesoscopic parameter and the second geometric boundary.

[0057] The mesoscopic parameters may include physical and mechanical parameters of the rock sample, such as density, porosity, elastic modulus, Poisson's ratio, shear strength, cohesion, internal friction angle, stiffness, etc. The first rock mesoscopic parameter of the first rock particle model and the second rock mesoscopic parameter of the second rock particle model may be the same, or they may be different.

[0058] For example, based on Figure 4 The geometric boundaries and microscopic parameters shown in the figure use PFC2D to create the first rock particle model and the second rock particle model of the fractured rock particle model; the particles of the first rock particle model and the particles of the second rock particle model can be generated separately, and the same particle parameters and contact models are given. The particles located at the fracture use different contact models to simulate the fracture behavior, and the following can be obtained: Figure 2 The fractured rock grain model shown.

[0059] PFC2D particle flow discrete element software is a numerical calculation tool based on discrete medium theory, which has advantages in simulating non-continuous geotechnical engineering problems such as rock failure and fault slip.

[0060] Step S120: simulating a shear process of the fractured rock particle model according to a target confining pressure, and obtaining a shear fracture surface between the first rock particle model and the second rock particle model when the shear displacement between the first rock particle model and the second rock particle model reaches a preset shear displacement.

[0061] For example, the shear process simulation of the fractured rock particle model can be performed based on PFC2D, but it is not limited thereto. The shear deformation of the particle flow discrete element can be accurately simulated based on PFC2D.

[0062] According to the target confining pressure, the servo condition corresponding to the target confining pressure can be set and the shear numerical simulation based on PFC2D can be carried out. By establishing the servo condition, the confining pressure condition of the rock shear process can be simulated. For example, the numerical simulation of the shear process can be started after setting the target confining pressure value for PFC2D.

[0063] In some embodiments, step S120 simulates the shear process of the fractured rock particle model according to the target confining pressure, including steps S121 to S123.

[0064] Step S121: Determine the particles in the first rock particle model and the second rock particle model that are in contact with the servo loading wall, and the stiffness of the contact between the particles and the servo loading wall.

[0065] Stiffness refers to the ability of a material or structure to resist deformation when subjected to force. For example, the number of particles in contact with the servo loading wall is m, and k is iIt represents the stiffness of the contact between the ith particle in contact with the servo loading wall and the servo loading wall, and the unit of stiffness is Pa (Pascal).

[0066] Step S122: determining the loading wall speed when the servo loading wall acts on the first rock particle model and the second rock particle model according to the target confining pressure, the stiffness of the contact between the particle and the servo loading wall, and the contact stress between the servo loading wall and the particle.

[0067] Exemplarily, the loading wall speed is negatively correlated with the target confining pressure, positively correlated with the contact stress between the servo loading wall and the particles, and negatively correlated with the sum of the stiffnesses of the contact between the m particles and the servo loading wall.

[0068] Exemplarily, the loading wall speed of the servo loading wall when acting on the first rock particle model and the second rock particle model can be determined based on a preset speed formula, according to the target confining pressure, the stiffness of the contact between the particles and the servo loading wall, and the contact stress between the servo loading wall and the particles.

[0069] For example, the speed formula is:

[0070]

[0071] Wherein, v is the loading wall velocity (in meters per second), η is the preset servo control velocity factor (in meters per second), σ is the contact stress between the servo loading wall and the particle (in Pa), and σ n is the target confining pressure (in Pa); K is the sum of the stiffness of the particles in the first rock particle model and the second rock particle model that are in contact with the servo loading wall (in Pa); specifically,

[0072]

[0073] K can also be called the total contact stiffness, which specifically refers to the stiffness k between the servo loading wall and the particles at the upper and lower boundaries of the model. i The sum of .

[0074] Step S123: simulating the shear process of the fractured rock particle model according to the loading wall velocity.

[0075] According to the loading wall speed, servo control can be implemented on the upper boundary servo loading wall and the lower boundary servo loading wall of the model in the shear process simulation.

[0076] When simulating the shear process of the fractured rock particle model, the current shear displacement between the first rock particle model and the second rock particle model can be obtained in real time; when the current shear displacement is equal to the preset shear displacement, the model fracture surface data of PFC2D can be exported (the exported data can be saved as a "fracture.dxf" file) to obtain the shear fracture surface corresponding to the preset shear displacement.

[0077] The preset shear displacement is the shear displacement that needs to derive the fracture surface. In some embodiments, the number of the preset shear displacements is multiple, and in step S120, the shear process of the fractured rock particle model is simulated to obtain the shear fracture surface between the first rock particle model and the second rock particle model when the shear displacement between the first rock particle model and the second rock particle model reaches the preset shear displacement, including: when the shear process of the fractured rock particle model is simulated, the current shear displacement between the first rock particle model and the second rock particle model is obtained; when the current shear displacement is equal to any of the preset shear displacements, the shear fracture surface corresponding to the preset shear displacement is stored, and the shear fracture surface is the fracture between the first rock particle model and the second rock particle model of the fractured rock particle model at the preset shear displacement.

[0078] Exemplarily, the multiple preset shear displacements are arranged from small to large, and when the current shear displacement is equal to the first preset shear displacement, the shear crack surface corresponding to the first preset shear displacement is stored; then the PFC2D shear process numerical simulation is continued, and when the current shear displacement is equal to the second preset shear displacement, the shear crack surface corresponding to the second preset shear displacement is stored, and so on, until the shear crack surface corresponding to the last preset shear displacement is obtained.

[0079] Exemplarily, the difference between adjacent preset shear displacements is equal, and the multiple preset shear displacements are all less than or equal to the target shear displacement. For example, the target shear displacement is 2.00 millimeters (mm), and the difference between adjacent preset shear displacements is 0.5 mm, then the multiple preset shear displacements are 0.00 mm, 0.50 mm, 1.00 mm, 1.50 mm, and 2.00 mm respectively; Figure 5 It is shown as a schematic diagram of the shear fracture surface corresponding to each of the plurality of preset shear displacements. It should be noted that the value of the difference between the aforementioned target shear displacement and the preset shear displacement is only an example, and it can be understood that the difference between adjacent preset shear displacements can also be other values, such as 0.025mm, that is, the fracture surface can also be derived at every 0.025mm shear displacement.

[0080] By using PFC2D to create a rock model based on the model boundary and mesoscopic parameters, setting the target confining pressure servo conditions and conducting PFC2D shear numerical simulation, the advantages of PFC2D granular flow discrete element software in simulating rock failure problems can be fully utilized.

[0081] like Figure 6 The figure shows the peak shear stress under different target confining pressures when simulating the shear process of the fractured rock particle model, and a schematic diagram of the comparison results of the peak shear stress under different target confining pressures under actual test conditions. It can be determined that the numerical simulation results of the shear process when simulating the shear process in the embodiment of the present application are consistent with the experiment.

[0082] It should be noted that when PFC2D simulates fluid-solid coupling, the simulation method based on the pore-pipeline network model relies on the relative position and contact state of the particles. However, during the rock shear process, the upper and lower sliders of the fracture will produce a large relative displacement, and the relative position and contact state of the particles will change. If the fracture seepage simulation is based on this simulation method, the fluid network needs to be updated in real time, resulting in low computational efficiency and difficulty in completing the fracture seepage simulation study. Moreover, the change in permeability during the shear process is a dynamic process. Therefore, PFC2D has great limitations in simulating fracture seepage and cannot meet the calculation requirements of the dynamic evolution of permeability.

[0083] Some implementations of the embodiments of the present application can realize the numerical analysis of the dynamic evolution of permeability in the rock shear process based on the coupling of PFC2D and COMSOL, and solve the defects of PFC2D in the numerical calculation of seepage.

[0084] COMSOL is a multi-physics coupling analysis and calculation program based on the finite element method, which is suitable for solving multi-field coupling problems in geotechnical engineering. COMSOL achieves coupling of multiple physical fields by solving partial differential equations, and can simulate fluid-solid coupling problems well. In terms of seepage, COMSOL provides a fluid flow module including multiple interfaces such as single-phase flow, porous media flow, groundwater flow, and fluid-solid coupling, which can solve a variety of complex seepage problems. In COMSOL, fluid flow and other problems are handled by solving the corresponding partial differential equations (such as Forchheimer equations, Navier-Stokes equations, etc.). Compared with the fluid-solid coupling implementation in PFC2D, COMSOL has a more reliable theoretical basis.

[0085] However, COMSOL is a numerical simulation software based on the finite element method, and its basic assumption requires that the continuity assumption must be satisfied. This also leads to many difficulties in the simulation of the shear process with large deformation using the finite element method, and it is difficult to complete the numerical simulation of the shear process. Some implementation methods of the present application can combine the respective advantages of PFC2D and COMSOL, decompose and solve the shear seepage process, realize the coupling of the PFC2D rock fracture model shear numerical simulation and the COMSOL rock fracture seepage numerical simulation, solve the defects of PFC2D in the numerical calculation of seepage, and make up for the shortcomings of COMSOL in the numerical calculation of shear deformation.

[0086] Specifically, some implementation methods of the embodiments of the present application can establish a connection between the two computing softwares, PFC2D and COMSOL, through the shear fracture surface of the shear process, that is, the fracture surface data, to complete the coupled simulation of the shear deformation of the PFC2D particle flow discrete element and the COMSOL finite element seepage, and fully utilize the advantages of the two simulation computing software to solve the shortcomings of the single simulation computing software in the HM (hydraulic) coupled numerical calculation of shear and seepage, which can more reasonably reflect the phenomena and laws in the experiment and can more accurately simulate the shear seepage process of the rock.

[0087] Step S130: obtaining seepage simulation parameters corresponding to the shear fracture surface, and simulating the fracture seepage process of the shear fracture surface according to the seepage simulation parameters to obtain a seepage simulation result.

[0088] In some embodiments, based on COMSOL, according to the seepage simulation parameters, the fracture seepage process of the shear fracture surface is simulated to obtain a seepage simulation result.

[0089] Exemplarily, COMSOL is used to import the model fracture surface data file "fracture.dxf" of PFC2D during shear process simulation, and to construct a geometric model for COMSOL seepage numerical simulation.

[0090] For details, please refer to Figure 5 , the shear fracture surface obtained by simulating the shear process of the fractured rock particle model includes a plurality of fracture line segments. Optionally, before step S130, the method further includes: determining non-target line segments among the plurality of fracture line segments, and deleting the non-target line segments among the plurality of fracture line segments. Non-target line segments specifically refer to redundant line segments that are irrelevant to the COMSOL seepage numerical simulation process, and may also be referred to as invalid line segments. For example, the method may automatically identify non-target line segments among the plurality of fracture line segments, or may determine the non-target line segments according to user operations. By deleting the non-target line segments among the plurality of fracture line segments, the accuracy and efficiency of the analysis may be improved.

[0091] For example, after deleting the non-target line segments in the shear fracture surface, the following can be obtained based on the seepage simulation parameters corresponding to the shear fracture surface: Figure 7 The geometric model shown can be used for COMSOL seepage numerical simulation.

[0092] In some embodiments, the seepage simulation parameters corresponding to the shear fracture surface include at least: seepage flow domain inlet, inlet fluid pressure, seepage flow domain outlet, no flow boundary, fluid material properties, and flow domain grid. Figure 7 , according to the geometric model of the shear fracture surface, the seepage flow domain inlet, the inlet fluid pressure, the seepage flow domain outlet, the no-flow boundary and the fluid material properties are set; and Figure 8 The flow domain grid that divides the fracture is shown, that is, the fluid model and boundary conditions are set to carry out the numerical simulation of the fracture seepage process in COMSOL. Figure 8 Shows Figure 7 Region A in the middle corresponds to the flow grid of the fracture.

[0093] Among them, the seepage domain specifically refers to the fluid flow area when conducting COMSOL seepage numerical simulation, the no-flow boundary specifically refers to the boundary with no fluid inflow and outflow and a flux of 0; the fluid material properties specifically refer to the physical and mechanical parameters of the fluid such as density and dynamic viscosity.

[0094] Figures 9a to 10b Shown Figure 7 The image obtained by visualizing the seepage simulation results of the fracture corresponding to area A in the middle. Figure 9a is the velocity distribution cloud diagram of the seepage field, Figure 9b It is a local enlarged cloud map of the flow velocity distribution of the seepage field. The corresponding flow velocity can be determined according to the color of each position of the seepage field in the cloud map; Fig.10a is the pressure distribution cloud diagram of the seepage field, Fig.10b This is a locally enlarged cloud map of the pressure distribution in the seepage field. The corresponding pressure can be determined based on the color of each position in the seepage field in the cloud map.

[0095] In some embodiments, the seepage simulation result of the shear fracture surface corresponding to the preset shear displacement includes at least one of the following items of the shear fracture surface: fracture normal stiffness, maximum normal closure amount, and the target confining pressure σ. n The deformation, crack roughness coefficient, average crack opening, volume flow rate of the crack section, and crack width.

[0096] Step S140: determining the fracture permeability of the fractured rock particle model at the preset shear displacement according to the seepage simulation result.

[0097] In some embodiments, step S140 determines the fracture permeability of the fractured rock particle model at the preset shear displacement according to the seepage simulation result, including: determining the fracture permeability of the fractured rock particle model at the preset shear displacement according to the target confining pressure, the fracture roughness coefficient corresponding to the shear fracture surface, and the seepage simulation result.

[0098] Roughness is an indicator to measure the roughness of rock fracture walls, and is generally characterized by the difference in fracture wall undulation. Roughness is one of the factors that affect fracture permeability. By adding the fracture roughness coefficient to characterize the roughness of the fracture wall when determining the fracture permeability, the accuracy of fracture permeability analysis can be improved.

[0099] Exemplarily, the rougher the wall surface of the crack between the first rock particle model and the second rock particle model, the greater the corresponding crack roughness coefficient. The crack permeability is negatively correlated with the crack roughness coefficient.

[0100] Exemplarily, the fracture permeability is negatively correlated with the target confining pressure. By adding the target confining pressure to make a correction when determining the fracture permeability, the accuracy of fracture permeability analysis can be improved.

[0101] Exemplarily, based on a preset fracture permeability formula, the fracture permeability of the fractured rock particle model at the preset shear displacement is determined according to the target confining pressure, the fracture roughness coefficient corresponding to the shear fracture surface, and the seepage simulation result. In the fracture permeability formula, the fracture permeability is negatively correlated with the target confining pressure, and the fracture permeability is negatively correlated with the fracture roughness coefficient.

[0102] For example, the fracture permeability formula can be expressed as:

[0103]

[0104] Wherein, κ is the fracture permeability (in Darcy), C is the preset cubic law correction coefficient, and d is the initial fracture opening of the shear fracture surface (in meter).

[0105] Optionally, an equivalent initial fracture opening may be determined based on the actual flow rate passing through the fracture as the initial fracture opening d. Compared with using the average fracture opening as the fracture opening d, using the equivalent initial fracture opening may improve the accuracy of the fracture permeability.

[0106] For example, the equivalent initial fracture opening d can be determined based on the actual flow rate through the fracture according to the following formula: h0 , the equivalent initial crack opening d h0 It can also be called the initial equivalent crack opening:

[0107]

[0108] Among them, d h0 is the initial equivalent crack opening of the shear crack surface corresponding to the preset shear displacement (in meters), μ is the dynamic viscosity of the fluid (in Pa·s), Q is the volume flow rate of the crack section of the shear crack surface (in cubic meters / second), w is the crack width of the shear crack surface (in meters), is the fluid pressure gradient (in Pa / m); for example, the fluid pressure gradient can be calculated by taking the quotient of the difference between the inlet fluid pressure p1 and the outlet fluid pressure p2 and the height difference H between the seepage basin inlet and the seepage basin outlet, for example, expressed as (p1-p2) / H.

[0109] Optionally, considering that the existence of the target confining pressure during the shearing process will affect the distribution of the seepage field, when calculating the fracture permeability, the influence of the target confining pressure may be increased to improve the accuracy of the fracture permeability:

[0110]

[0111] d 0 =d max

[0112] Wherein, Δd is the shear fracture surface corresponding to the preset shear displacement at the target confining pressure σ n Deformation under (in meters), d max is the maximum normal closure of the shear fracture surface (in meters), K n is the normal stiffness of the crack, d 0 is the initial crack opening of the shear crack surface (for example, the average crack opening or the initial equivalent crack opening d h0 ). Thus, the initial mechanical crack opening d of the shear crack surface can be calculated according to the following formula: m (Unit is meter):

[0113]

[0114] The initial fracture opening is taken as the initial equivalent fracture opening d h0 For example, according to the preset fitting relationship equation between the equivalent crack opening and the mechanical crack opening, the final corrected initial equivalent crack opening d can be calculated. h0 (Unit is meter):

[0115]

[0116] Wherein, J is the crack roughness coefficient.

[0117] Optionally, considering that the above fitting relationship equation is applicable to a variety of fracture types, ranging from very smooth artificial fractures to very rough in-situ rock fractures, when the above fitting relationship equation is applied to a specific fracture sample to calculate the equivalent fracture aperture, some obvious deviations will appear in the calculation results, and the left and right dimensions of the formula are inconsistent. The fitting relationship equation can be modified as follows to improve the accuracy of the initial equivalent fracture aperture:

[0118]

[0119] Among them, D is the preset fracture connectivity correction coefficient, which corrects the dimensional problem existing in the original fitting formula itself and the numerical deviation existing in this study, and better solves the original dimensional problem.

[0120] The initial fracture opening is taken as the initial equivalent fracture opening d h0 Taking 2 as an example, combining the above formulas, the preset fracture permeability formula can be obtained:

[0121]

[0122] Wherein, κ is the fracture permeability, C is the preset cubic law correction coefficient, D is the preset fracture connectivity correction coefficient, K n is the crack normal stiffness of the shear crack surface, d h0 is the initial equivalent crack opening of the shear crack surface, σ n is the target confining pressure, and J is the crack roughness coefficient corresponding to the shear crack surface.

[0123] In some embodiments, after determining the fracture permeability of the fractured rock particle model at the preset shear displacement in step S140, the method further includes: determining the permeability evolution result of the fractured rock particle model under the target confining pressure according to the fracture permeabilities corresponding to the plurality of preset shear displacements. The analysis of the dynamic evolution of fracture permeability during rock shearing is realized, which provides a new and effective way to study the dynamic evolution law of rock permeability during shearing, and provides a reasonable numerical analysis method for revealing the dynamic evolution mechanism of fracture shear permeability.

[0124] Fig.11a and Fig.11b The graphs show the evolution curve of fracture permeability with shear displacement obtained in the embodiment of the present application, and the evolution curve of fracture permeability with shear displacement under the test conditions; Fig.11a and Fig.11bThe corresponding confining pressure conditions (target confining pressure) are different. It can be determined that the evolution of the fracture permeability with shear displacement determined in the embodiment of the present application can be well consistent with the evolution of the fracture permeability with shear displacement under the test conditions. The method of the embodiment of the present application can more reasonably reflect the phenomena and laws in the test, and can more accurately simulate and calculate the shear seepage process of the rock.

[0125] In some embodiments, see Fig.12 The numerical simulation results of shear and seepage are shown, and the method also includes: drawing a shear stress curve according to the shear stress corresponding to each preset shear displacement, and the shear stress curve and the evolution curve of the fracture permeability with shear displacement can be displayed at the same time, so that the user can analyze the dynamic evolution process of the fracture permeability and shear stress during the shear process.

[0126] In some embodiments, see Fig.13 ,The permeability analysis methods of rock shear process include shear process simulation (shear simulation) based on PFC2D and fracture seepage process simulation (seepage simulation) based on COMSOL.

[0127] The shear simulation includes the following steps:

[0128] Obtaining a fractured rock particle model, including generating model particles, setting a contact model, and generating a servo loading wall and setting a servo condition corresponding to a target confining pressure;

[0129] Initialize the current shear displacement x to 0 and the number of cycles t to 0;

[0130] The shear process of the fractured rock particle model is simulated, and the servo loading wall can act on the fractured rock particle model according to the servo condition to achieve servo shearing;

[0131] When the current shear displacement x reaches the preset shear displacement corresponding to the current number of cycles t, the shear crack surface corresponding to the preset shear displacement is obtained and derived;

[0132] If the current shear displacement x is less than the target shear displacement and / or the current cycle number t is less than the target cycle number, the current cycle number t is increased by 1, and the preset shear displacement corresponding to the current cycle number t is updated (e.g., increased by 0.025 mm);

[0133] If the current shear displacement reaches the target shear displacement, the shear simulation ends.

[0134] Seepage simulation includes the following steps:

[0135] Input the shear crack surface corresponding to the preset shear displacement into COMSOL;

[0136] Construct a geometric model for COMSOL seepage numerical simulation based on the shear fracture surface corresponding to the preset shear displacement;

[0137] Set the boundary conditions, inlet fluid pressure, and outlet fluid pressure of the seepage simulation;

[0138] Set up the fluid model, seepage basin inlet, and seepage basin outlet;

[0139] The seepage flow domain of the shear fracture surface is meshed to obtain the flow domain mesh;

[0140] Simulating the fracture seepage process on the shear fracture surface to obtain a seepage simulation result;

[0141] The seepage simulation results of the shear fracture surface corresponding to each preset shear displacement are analyzed, including determining the fracture permeability of the fracture rock particle model at the preset shear displacement according to the seepage simulation results.

[0142] The permeability analysis method of the rock shear process provided by the above embodiment includes: obtaining a fractured rock particle model, wherein the fractured rock particle model includes a first rock particle model and a second rock particle model, and there is a fracture between the first rock particle model and the second rock particle model; simulating the shear process of the fractured rock particle model according to the target confining pressure, and obtaining the shear fracture surface between the first rock particle model and the second rock particle model when the shear displacement between the first rock particle model and the second rock particle model reaches a preset shear displacement; obtaining the seepage simulation parameters corresponding to the shear fracture surface, and simulating the fracture seepage process of the shear fracture surface according to the seepage simulation parameters to obtain the seepage simulation results; and determining the fracture permeability of the fractured rock particle model at the preset shear displacement according to the seepage simulation results. It can be used to carry out numerical calculations of the shear seepage process, providing a new and effective way to study the permeability of rocks in the shear process, and can simulate and calculate the shear seepage process of rocks more accurately.

[0143] In some embodiments, the coupling of the PFC2D rock fracture model shear numerical simulation and the COMSOL rock fracture seepage numerical simulation can be achieved, and the advantages of the PFC2D particle flow discrete element software and the COMSOL finite element software in simulating rock failure and fluid seepage respectively can be used to more reasonably reflect the phenomena and laws in the experiment, and the shear seepage process of the rock can be simulated and calculated more accurately.

[0144] In some embodiments, the target confining pressure and the influence of fracture roughness are taken into account when calculating the permeability by numerical simulation of seepage, and the target confining pressure and the fracture roughness coefficient are introduced into the fracture permeability formula. The fracture permeability formula finally obtained contains correction terms for the confining pressure and the fracture roughness coefficient, which can reflect the influence of the confining pressure and the fracture roughness on the permeability, and provides a permeability calculation formula containing the confining pressure and the fracture roughness coefficient correction with a clear physical meaning.

[0145] In some embodiments, when the equivalent opening and the mechanical opening are used for the calculation of the seepage numerical simulation, the equivalent opening calculation formula is corrected, and the correction coefficient solves the original dimension problem well.

[0146] The method of the present application can be used in many general or special computer system environments or configurations. For example: personal computers, server computers, handheld devices or portable devices, tablet devices, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable consumer electronic devices, network PCs, minicomputers, mainframe computers, distributed computing environments including any of the above systems or devices, etc. The present application can be described in the general context of computer-executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types. The present application can also be practiced in distributed computing environments, in which tasks are performed by remote processing devices connected through a communication network. In a distributed computing environment, program modules can be located in local and remote computer storage media including storage devices.

[0147] Exemplarily, the above method may be implemented in the form of a computer program, and the computer program may be run on a computer device.

[0148] Please refer to the above examples. Fig.14 , Fig.14 It is a schematic block diagram of the structure of a computer device provided in an embodiment of the present application.

[0149] like Fig.14 As shown, the computer device includes a memory and a processor. The memory and the processor may be connected via a system bus, and the memory may include a storage medium and an internal memory.

[0150] The storage medium can store an operating system and a computer program. When the computer program is executed, the processor can execute any permeability analysis method of a rock shear process.

[0151] The processor is used to provide computing and control capabilities and support the operation of the entire computer equipment.

[0152] The internal memory provides an environment for the operation of the computer program in the storage medium. When the computer program is executed by the processor, the processor can execute any permeability analysis method of the rock shear process.

[0153] Computer devices may include terminal devices or servers, wherein the terminal devices may be electronic devices such as mobile phones, tablet computers, laptop computers, vehicle-mounted terminals, desktop computers, personal digital assistants and wearable devices; the servers may be independent servers or server clusters.

[0154] Those skilled in the art will understand that Fig.14 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0155] It should be understood that the processor may be a central processing unit (CPU), and the processor may also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. Among them, the general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0156] In one embodiment, the processor is used to execute a computer program and implement the following steps when executing the computer program:

[0157] Acquire a fractured rock particle model, wherein the fractured rock particle model comprises a first rock particle model and a second rock particle model, wherein a fracture exists between the first rock particle model and the second rock particle model;

[0158] According to the target confining pressure, a shear process simulation is performed on the fractured rock particle model to obtain a shear fracture surface between the first rock particle model and the second rock particle model when the shear displacement between the first rock particle model and the second rock particle model reaches a preset shear displacement;

[0159] Acquire the seepage simulation parameters corresponding to the shear fracture surface, and simulate the fracture seepage process of the shear fracture surface according to the seepage simulation parameters to obtain the seepage simulation results;

[0160] According to the seepage simulation result, the fracture permeability of the fractured rock particle model at the preset shear displacement is determined.

[0161] The specific principles and implementation methods of the computer device provided in the embodiments of the present application are similar to the methods in the aforementioned embodiments and will not be repeated here.

[0162] It should be noted that those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the computer device described above can refer to the corresponding process in the aforementioned permeability analysis method embodiment of the rock shear process, and will not be repeated here.

[0163] An embodiment of the present application also provides a computer-readable storage medium, on which a computer program is stored. The method implemented when the computer program is executed by a processor can refer to the various embodiments of the permeability analysis method of the rock shear process of the present application.

[0164] The computer-readable storage medium may be an internal storage unit of the computer device described in the above embodiment, such as a hard disk or memory of the computer device. The computer-readable storage medium may also be an external storage device of the computer device, such as a plug-in hard disk, a smart memory card (SmartMedia Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), etc. equipped on the computer device.

[0165] It should be understood that the terms used in this application specification are only for the purpose of describing specific embodiments and are not intended to limit the application. As used in this application specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0166] It should also be understood that the term "and / or" used in the specification of this application and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, including these combinations. It should be noted that, in this article, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or system. In the absence of further restrictions, an element defined by the sentence "including a..." does not exclude the presence of other identical elements in the process, method, article or system including the element.

[0167] The serial numbers of the embodiments of the present application are for description only and do not represent the advantages and disadvantages of the embodiments. The above description is only a specific implementation mode of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for analyzing the permeability of rock during shearing, characterized in that: For use in a computer device, the method comprises: Acquire a fractured rock particle model, wherein the fractured rock particle model comprises a first rock particle model and a second rock particle model, wherein a fracture exists between the first rock particle model and the second rock particle model; According to the target confining pressure, a shear process simulation is performed on the fractured rock particle model to obtain a shear fracture surface between the first rock particle model and the second rock particle model when the shear displacement between the first rock particle model and the second rock particle model reaches a preset shear displacement; Acquire the seepage simulation parameters corresponding to the shear fracture surface, and simulate the fracture seepage process of the shear fracture surface according to the seepage simulation parameters to obtain the seepage simulation results; Determining the fracture permeability of the fractured rock particle model at the preset shear displacement according to the seepage simulation result; The step of simulating the shear process of the fractured rock particle model according to the target confining pressure includes: simulating the shear process of the fractured rock particle model according to the loading wall speed corresponding to the target confining pressure, wherein the loading wall speed is the loading wall speed when the servo loading wall acts on the first rock particle model and the second rock particle model, and the loading wall speed is negatively correlated with the target confining pressure; The method of determining the fracture permeability of the fractured rock particle model at the preset shear displacement according to the seepage simulation result includes: determining the fracture permeability of the fractured rock particle model at the preset shear displacement according to the target confining pressure, the fracture roughness coefficient corresponding to the shear fracture surface, and the seepage simulation result, wherein the fracture permeability is negatively correlated with the target confining pressure, negatively correlated with the fracture roughness coefficient, and positively correlated with the initial equivalent fracture opening, and the initial equivalent fracture opening is an equivalent initial fracture opening determined according to the actual flow rate passing through the fracture.

2. The permeability analysis method according to claim 1, characterized in that: The method of obtaining a fractured rock particle model comprises: Obtaining scanning data of a fracture surface of a rock sample and size information of the rock sample; Determining a first geometric boundary and a second geometric boundary according to the scan data of the crack surface and the size information; The first rock particle model is generated according to the first rock mesoscopic parameter and the first geometric boundary, and the second rock particle model is generated according to the second rock mesoscopic parameter and the second geometric boundary.

3. The permeability analysis method according to claim 1, characterized in that: The step of simulating the shear process of the fractured rock particle model according to the target confining pressure includes: Determining particles in the first rock particle model and the second rock particle model that are in contact with the servo loading wall, and the stiffness of the contact between the particles and the servo loading wall; Determining a loading wall velocity when the servo loading wall acts on the first rock particle model and the second rock particle model according to a target confining pressure, a stiffness of contact between the particle and the servo loading wall, and a contact stress between the servo loading wall and the particle; The shear process of the fractured rock particle model is simulated according to the loading wall velocity.

4. The permeability analysis method according to claim 3, characterized in that: Based on a preset speed formula, according to the target confining pressure, the stiffness of the contact between the particles and the servo loading wall, and the contact stress between the servo loading wall and the particles, the loading wall speed when the servo loading wall acts on the first rock particle model and the second rock particle model is determined; the speed formula is: in, is the loading wall speed, η is the preset servo control speed factor, σ is the contact stress between the servo loading wall and the particle, σ n is the target confining pressure, and K is the sum of the stiffnesses of the particles in the first rock particle model and the second rock particle model that are in contact with the servo loading wall.

5. The permeability analysis method according to any one of claims 1 to 4, characterized in that: The number of the preset shear displacements is multiple, and the multiple preset shear displacements are arranged from small to large; The simulating the shear process of the fractured rock particle model to obtain a shear fracture surface between the first rock particle model and the second rock particle model when the shear displacement between the first rock particle model and the second rock particle model reaches a preset shear displacement includes: When simulating a shear process on the fractured rock particle model, obtaining a current shear displacement between the first rock particle model and the second rock particle model; When the current shear displacement is equal to any of the preset shear displacements, storing the shear crack surface corresponding to the preset shear displacement; After determining the fracture permeability of the fractured rock particle model at the preset shear displacement, the method further includes: According to the fracture permeabilities corresponding to the plurality of preset shear displacements, the permeability evolution result of the fractured rock particle model under the target confining pressure is determined.

6. The permeability analysis method according to any one of claims 1 to 4, characterized in that: The shear fracture surface obtained by simulating the shear process of the fractured rock particle model includes a plurality of fracture line segments; before obtaining the seepage simulation parameters corresponding to the shear fracture surface, simulating the fracture seepage process of the shear fracture surface according to the seepage simulation parameters, and obtaining the seepage simulation results, the method further includes: The method further includes: determining non-target line segments among the plurality of fracture line segments, and deleting the non-target line segments among the plurality of fracture line segments.

7. The permeability analysis method according to any one of claims 1 to 4, characterized in that: The seepage simulation parameters corresponding to the shear fracture surface include: seepage flow domain inlet, inlet fluid pressure, seepage flow domain outlet, no-flow boundary, fluid material properties, and flow domain grid.

8. The permeability analysis method according to any one of claims 1 to 4, characterized in that: Based on a preset fracture permeability formula, the fracture permeability of the fracture rock particle model at the preset shear displacement is determined according to the target confining pressure, the fracture roughness coefficient corresponding to the shear fracture surface, and the seepage simulation result; the fracture permeability formula is: in, is the fracture permeability, C is the preset cubic law correction coefficient, D is the preset fracture connectivity correction coefficient, is the crack normal stiffness of the shear crack surface, is the initial equivalent crack opening of the shear crack surface, is the target confining pressure, is the crack roughness coefficient corresponding to the shear crack surface.

9. A computer device, characterized in that: including memory and processor; The memory is used to store computer programs; The processor is used to execute the computer program and implement the steps of the permeability analysis method of rock shear process according to any one of claims 1 to 8 when executing the computer program.

10. A computer-readable storage medium, characterized in that: The computer readable storage medium stores a computer program, and when the computer program is executed by a processor, the processor is enabled to implement: The steps of the method for permeability analysis of rock shear process as described in any one of claims 1-8.

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