Rock fracture closing simulation method, system and equipment and storage medium

Abstract

The invention discloses a rock fracture closing simulation method, system and equipment and a storage medium, firstly, a two-dimensional equivalent model is established based on a fracture sample, a fracture in the two-dimensional equivalent model is equivalent to an ellipse-like section, then a plurality of sampling points are arranged on the upper boundary and the lower boundary of the fracture, a load is loaded, and then the fracture closing simulation model is established based on the displacement of the sampling points on the upper boundary and the lower boundary of the fracture before and after the load is loaded. The length change of the fracture under each load step length is calculated, the fracture area is calculated, finally, the average opening degree of short axes of all the fractures is calculated, and whether all the fractures are completely closed or not is judged; if not, crack equivalent parameters are calculated and updated, and the steps are repeatedly executed after loads are increased; on the basis of a numerical simulation method, the distribution and stress deformation conditions of the fracture in the rock are simulated, the length changes of the long axis and the short axis of the fracture are fully considered, the fracture region area is combined, the stress-strain process of the fracture is more accurately simulated, the fracture closing state is effectively evaluated, and the accuracy of a simulation result is improved.

Description

Technical Field

[0001] The invention relates to a means for simulating the closure of rock fractures, belongs to the field of rock physics, and in particular to a method, system, equipment and storage medium for simulating the closure of rock fractures. Background Art

[0002] Due to the influence of physical diagenesis, weathering and tectonic movement, cracks are widely present in natural rocks and affect the mechanical properties, permeability, and weathering resistance of rocks. At the same time, cracks are also important storage spaces and seepage channels for groundwater resources. For porous rocks, changes in stress state will lead to changes in their internal pore structure, which in turn leads to changes in permeability, elastic modulus, and resistivity. This is because cracks are "soft" pores, and the aspect ratio of the short axis to the long axis of the crack is very small. They are easy to deform or even close under compressive stress, resulting in high sensitivity of rocks to stress changes. In the process of oil and gas exploration and development, a large number of human activities, such as drilling, oil production, water injection, and fracturing, will cause changes in the stress state of underground rocks. This induced stress change can deform the crack structure inside the rock and ultimately change the physical properties of the rock. Therefore, how to accurately evaluate the crack closure phenomenon is of great significance.

[0003] At present, the study of rock crack closure is usually carried out by computer simulation. However, in the process of simulating and describing crack deformation by traditional means, it is often assumed that the deformation of the crack is mainly concentrated in the longitudinal axis, that is, the long axis direction, while ignoring the change of the short axis. That is, the short axis direction of the crack is assumed to remain unchanged. However, under the influence of stress disturbance, the real crack will deform in both the long and short axis directions during the closing process. This leads to the final conclusion being inconsistent with the actual situation and low accuracy. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned defects and problems existing in the prior art and to provide a more accurate rock fracture closure simulation method, system, device and storage medium.

[0005] To achieve the above objectives, the technical solution of the present invention is: a rock fracture closure simulation method, comprising:

[0006] S1. Establishing a two-dimensional equivalent model of rock fractures based on fracture samples; the two-dimensional equivalent model of rock fractures includes a solid matrix and fractures, and the fractures are equivalent to a quasi-elliptical cross-section including a major axis and a minor axis;

[0007] S2, setting a number of sampling points at the upper and lower boundaries of the fracture, and applying a load to the two-dimensional equivalent model of the rock fracture;

[0008] S3, based on the displacement of the upper and lower boundary sampling points of the crack before and after the load is applied, the length change of the major axis and the minor axis of the crack under each load step is calculated, and the area of ​​the corresponding crack region is calculated;

[0009] S4, calculating the average opening of the minor axes of all fractures, and determining whether all fractures are completely closed; if not completely closed, calculating the fracture equivalent parameters in the two-dimensional equivalent model of rock fractures based on the area of ​​the fracture region, updating the two-dimensional equivalent model of rock fractures, and after increasing the load, repeating steps S2 to S4 until all fractures in the two-dimensional equivalent model of rock fractures are completely closed.

[0010] The fracture sample is a rock with fractures. After three-dimensional scanning and numerical simulation of the geometric parameters and material parameters of the fracture sample, the major axis and the minor axis of the fracture are cut off to form a two-dimensional cross-section which is equivalent to an elliptical cross-section, thereby forming a two-dimensional equivalent model of the rock fracture.

[0011] The step S2 specifically includes:

[0012] A uniformly distributed load is applied to the upper boundary of the two-dimensional equivalent model of the rock fracture; the load step length needs to ensure that there are a number of sampling points in the linear change stage of the fracture area with pressure, and in the nonlinear change stage, the sampling point density needs to be more than doubled;

[0013] The expression of the load is as follows:

[0014] σ·n=F(x,y0);

[0015] Where: σ is the load, n is the unit normal vector of the loading boundary, F is the force per unit area applied to the loading boundary, x is any point on the loading boundary, and y0 is the position of the loading boundary in the y direction.

[0016] The crack area is converted into an integral about the crack boundary curve by Green's formula; the expression of the area of ​​the single crack area is as follows:

[0017]

[0018] Where: S is the area of ​​the fracture area, Γ is the contour curve of the fracture area, x is the x coordinate of the two-dimensional equivalent model of rock fracture, n x is the x-component of the outward normal vector of the crack contour boundary, and Ω is the crack area.

[0019] The step S3 specifically includes:

[0020] S31, according to the sampling points [x1, x2...xN ] and the displacement of each sampling point during the loading process, and respectively calculate the positions of the upper and lower boundaries of the crack after the load is applied; the calculated position expression is as follows:

[0021]

[0022] in: is the position of the Nth sampling point on the upper boundary of the crack after loading, is the position of the Nth sampling point at the lower boundary of the crack after loading, is the position of the Nth sampling point on the upper boundary of the crack before loading, is the position of the Nth sampling point at the lower boundary of the crack before loading, v i upper (x N ) is the displacement of the Nth sampling point on the upper boundary of the crack during loading, v i lower (x N ) is the displacement of the Nth sampling point on the lower boundary of the crack during loading, N is the sampling point on the crack, and i is the step index of the loading;

[0023] S32, based on the positions of the upper and lower boundaries of the crack after the load is applied, calculate the spacing values ​​of the points in the upper and lower boundaries of the sampling points; the expression for the calculation is as follows:

[0024]

[0025] Where: d i+1 (x N ) is the spacing value of the Nth sampling point after loading, is the position of the Nth sampling point on the upper boundary of the crack after loading, is the position of the Nth sampling point at the lower boundary of the crack after loading;

[0026] S33, based on the spacing values ​​between the upper and lower boundaries of the sampling points, calculate the short axis length of the mth crack after loading step i+1; the calculation expression is as follows:

[0027]

[0028] in: is the minor axis length of the mth crack, and N is the total number of sampling points on the upper surface of the mth crack;

[0029] S34, based on the positions of the upper and lower boundaries of the crack after the load is applied, determining the major axis length of the crack after the load is applied;

[0030] like This indicates that the crack at the sampling point is closed; the length of the long axis of the crack is given by [xN -x1] is shortened to [x N-1 -x1], at this time, the major axis length of the mth crack becomes

[0031] like This indicates that the crack at the sampling point has not closed and the length of the major axis remains unchanged.

[0032] In step S3, the steps of calculating the area of ​​the corresponding crack region are as follows:

[0033] S35. Calculate the area of ​​the mth crack under each loading step index

[0034] The area expression of the crack is as follows:

[0035]

[0036] Where: Γ is the contour curve of the fracture area, x is the x coordinate of the two-dimensional equivalent model of rock fracture, n x is the x-component of the outward normal vector of the crack contour boundary, and Ω is the crack area.

[0037] The step S4 specifically includes:

[0038] S41, calculating the average value of the minor axis lengths of all the cracks, obtaining the average opening, and determining the degree of closure of all the cracks;

[0039] If the average opening of all cracks This indicates that all cracks have been closed;

[0040] If the average opening of all cracks This indicates that the mth crack is not completely closed, and the process proceeds to step S42;

[0041] S42, updating the geometric models of all the cracks according to the geometric parameters of all the cracks in each loading step; and obtaining the two-dimensional equivalent model of the rock crack based on the geometric parameters of different cracks;

[0042] The expression of the equivalent crack parameter is as follows:

[0043]

[0044] in: is the equivalent major axis radius, is the equivalent minor axis radius, is the equivalent porosity, TN is the number of cracks, is the equivalent major axis radius of the mth crack under the i-th loading step, is the equivalent minor axis radius of the mth crack under the i-th loading step, Smod el is the area of ​​the two-dimensional equivalent model of rock fracture.

[0045] A rock fracture closure simulation system, the system comprising:

[0046] A two-dimensional equivalent model building module is used to establish a two-dimensional equivalent model of rock fractures based on fracture samples; the two-dimensional equivalent model of rock fractures includes a solid matrix and fractures, and the fractures are equivalent to a quasi-elliptical cross-section including a major axis and a minor axis;

[0047] A load loading module, used to set a number of sampling points at the upper and lower boundaries of the fracture, and to load the two-dimensional equivalent model of the rock fracture;

[0048] The opening calculation module is used to calculate the length change of the major axis and the minor axis of the crack under each load step based on the displacement of the upper and lower boundary sampling points of the crack before and after the load is applied, and calculate the area of ​​the corresponding crack region;

[0049] The closure judgment module is used to calculate the average opening of the minor axes of all cracks and judge whether all cracks are completely closed; if not completely closed, the equivalent parameters of the cracks in the two-dimensional equivalent model of rock cracks are calculated based on the geometric parameters of the crack area, and the two-dimensional rock crack model is updated. After increasing the load, the steps corresponding to the above modules are repeated until all cracks in the two-dimensional equivalent model of rock cracks are completely closed.

[0050] A rock fracture closure simulation device, the device comprising a processor and a memory;

[0051] The memory is used to store computer program code and transmit the computer program code to the processor;

[0052] The processor is used to execute the above-mentioned rock fracture closure simulation method according to the instructions in the computer program code.

[0053] A computer-readable storage medium stores computer-executable instructions. When the computer-executable instructions are executed on a computer, the above-mentioned rock fracture closure simulation method is implemented.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] In a rock fracture closure simulation method, system, device and storage medium of the present invention, firstly, a two-dimensional equivalent model is established based on fracture samples, and the fractures therein are equivalent to elliptical cross-sections, then a plurality of sampling points are set at the upper and lower boundaries of the fracture, and loads are applied, then based on the displacements of the upper and lower boundary sampling points of the fracture before and after the loads are applied, the length change of the fracture under each load step is calculated, and the fracture area is calculated, and finally the average opening of all the short axes of the fractures is calculated, and it is judged whether all the fractures are completely closed; if not, the fracture equivalent parameters are calculated and updated, and the above steps are repeated after the load is increased; in application, the design simulates the distribution of fractures in rocks and the stress and deformation conditions based on the numerical simulation method, and fully considers the length changes of the major and minor axes of the fractures, and combines the fracture area to more accurately simulate the stress-strain process of the fracture, effectively evaluate the fracture closure state, and improve the accuracy of the simulation results. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a flow chart of the method steps of the present invention.

[0057] Figure 2 It is a schematic diagram of the crack equivalent ellipse-like structure in Example 1 of the present invention.

[0058] Figure 3 This is a schematic diagram of the loading load in Example 1 of the present invention.

[0059] Figure 4 It is a schematic diagram of the system structure of the present invention.

[0060] Figure 5 It is a schematic diagram of the device structure of the present invention.

[0061] In the figure: two-dimensional equivalent model building module 1, load loading module 2, opening calculation module 3, closing judgment module 4, processor 5, memory 6, computer program code 61. DETAILED DESCRIPTION

[0062] The present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0063] Embodiment 1:

[0064] See also Figure 1 , a rock fracture closure simulation method, characterized by comprising:

[0065] S1. Establishing a two-dimensional equivalent model of rock fractures based on fracture samples; the two-dimensional equivalent model of rock fractures includes a solid matrix and fractures, and the fractures are equivalent to a quasi-elliptical cross-section including a major axis and a minor axis;

[0066] Furthermore, the fracture sample is a rock with fractures. After three-dimensional scanning and numerical simulation of the geometric parameters and material parameters of the fracture sample, the major axis and minor axis of the fracture are cut off to form a two-dimensional cross-section and equivalent to an elliptical cross-section, thereby forming a two-dimensional equivalent model of the rock fracture; the geometric parameters include the length, width, height, etc. of the rock, and the material parameters include the type of rock, elastic modulus, density, etc.

[0067] See also Figure 2 , the crack is equivalent to an ellipse-like structure, the major axis is the major axis of the ellipse-like structure, the minor axis is the minor axis of the ellipse-like structure, and the minor semi-axis is half of the minor axis of the ellipse-like structure; the maximum grid size of the two-dimensional equivalent model is less than 1 / 10 of the minor semi-axis of the crack; this scheme simplifies the three-dimensional crack into two-dimensional because the cross-sectional geometry perpendicular to the crack surface is similar, and the displacement of the crack surface under normal compression can also be expressed in two dimensions. The crack closure simulates the process of closing the crack as the normal compression of the crack surface increases. In this way, the actual problem can be modeled and simplified, which is more conducive to calculation.

[0068] S2, setting a number of sampling points at the upper and lower boundaries of the fracture, and applying a load to the two-dimensional equivalent model of the rock fracture;

[0069] Furthermore, the step S2 specifically includes:

[0070] See also Figure 3 , a uniformly distributed load is applied to the upper boundary of the two-dimensional equivalent model of the rock fracture; the load step length needs to ensure that there are a number of sampling points (e.g., 4-5) in the linear change stage of the boundary curve of the short axis of the fracture, and the sampling point density needs to be more than doubled in the nonlinear change stage;

[0071] The expression of the load is as follows:

[0072] σ·n=F(x,v0);

[0073] Where: σ is the load, n is the unit normal vector of the loading boundary, F is the force per unit area applied to the loading boundary, x is any point on the loading boundary, and y0 is the position of the loading boundary in the y direction;

[0074] The area of ​​the single crack is converted into an integral about the boundary curve by Green's formula; the expression of the area of ​​the single crack is as follows:

[0075]

[0076] Where: S is the area of ​​the fracture area, Γ is the contour curve of the fracture area, x is the x coordinate of the two-dimensional equivalent model of rock fracture, n xis the x-component of the outward normal vector of the crack contour boundary, and Ω is the crack area.

[0077] S3, based on the displacement of the upper and lower boundary sampling points of the crack before and after the load is applied, the length change of the major axis and the minor axis of the crack under each load step is calculated, and the area of ​​the corresponding crack region is calculated;

[0078] Each iteration update is each load step, and the deformation is the deformation of the major and minor axes. The opening of the crack will decrease under uniform normal pressure. For a specific crack, the stress on the model surface is not uniformly distributed due to the interaction of the cracks. Therefore, several sampling points need to be set for calculation.

[0079] Furthermore, the step S3 specifically includes:

[0080] S31, according to the sampling points [x1, x2...x N ] and the displacement of each sampling point during the loading process, and respectively calculate the positions of the upper and lower boundaries of the crack after the load is applied; the calculation expression is as follows:

[0081]

[0082] in: is the position of the Nth sampling point on the upper boundary of the crack after loading, is the position of the Nth sampling point at the lower boundary of the crack after loading, is the position of the Nth sampling point on the upper boundary of the crack before loading, is the position of the Nth sampling point at the lower boundary of the crack before loading, v i upper (x N ) is the displacement of the Nth sampling point on the upper boundary of the crack during loading, v i lower (x N ) is the displacement of the Nth sampling point on the lower boundary of the crack during loading, N is the sampling point on the crack, and i is the step index of the loading;

[0083] S32, based on the positions of the upper and lower boundaries of the crack after the load is applied, calculate the spacing value of the upper and lower boundaries of the sampling points; the expression for the calculation is as follows:

[0084]

[0085] Where: d i+1 (x N ) is the spacing value of the Nth sampling point, is the position of the Nth sampling point on the upper boundary of the crack, is the position of the Nth sampling point at the lower boundary of the crack;

[0086] S33, based on the spacing values ​​between the upper and lower boundaries of the sampling points, calculate the short axis length of the mth crack after loading step i+1; the calculation expression is as follows:

[0087]

[0088] in: is the minor axis length of the mth crack, and N is the total number of sampling points on the upper surface of the mth crack;

[0089] S34, based on the positions of the upper and lower boundaries of the crack after the load is applied, determining the major axis length of the crack after the load is applied;

[0090] like This indicates that the crack at the sampling point is closed; the length of the long axis of the crack is given by [x N -x1] is shortened to [x N-1 -x1], at this time, the major axis length of the mth crack becomes

[0091] like This indicates that the crack at the sampling point has not closed and the length of the major axis remains unchanged;

[0092] S35. Calculate the area of ​​the mth crack under each loading step index

[0093] The area expression of the crack is as follows:

[0094]

[0095] Where: Γ is the contour curve of the fracture area, x is the x coordinate of the two-dimensional equivalent model of rock fracture, n x is the x-component of the outward normal vector of the crack contour boundary, and Ω is the crack area.

[0096] S4, calculating the average opening of the minor axes of all the cracks, and judging whether all the cracks are completely closed; if not completely closed, calculating the crack equivalent parameters in the two-dimensional equivalent model of rock cracks based on the geometric parameters of the crack area, updating the two-dimensional equivalent model of rock cracks, and after increasing the load, repeating steps S2 to S4 until all the cracks in the two-dimensional equivalent model of rock cracks are completely closed;

[0097] Furthermore, the step S4 specifically includes:

[0098] S41, calculating the average value of the minor axis lengths of all the cracks, obtaining the average opening, and determining the degree of closure of all the cracks;

[0099] If the average opening of all cracks This indicates that all cracks have been closed;

[0100] If the average opening of all cracks This indicates that the mth crack is not completely closed, and the process proceeds to step S42;

[0101] S42, calculating equivalent fracture parameters of all fractures in each loading step, and updating the two-dimensional equivalent model of rock fractures based on the equivalent fracture parameters;

[0102] The expression of the equivalent crack parameter is as follows:

[0103]

[0104] in: is the equivalent major axis radius, is the equivalent minor axis radius, is the equivalent porosity, TN is the number of cracks, is the equivalent major axis radius of the mth crack under the i-th loading step, is the equivalent minor axis radius of the mth crack under the i-th loading step, S model is the area of ​​the two-dimensional equivalent model of rock fracture.

[0105] Embodiment 2:

[0106] See also Figure 4 , a rock fracture closure simulation system, comprising:

[0107] A two-dimensional equivalent model building module 1 is used to establish a two-dimensional equivalent model of rock fractures based on fracture samples; the two-dimensional equivalent model of rock fractures includes a solid matrix and fractures, and the fractures are equivalent to a quasi-elliptical cross-section including a major axis and a minor axis;

[0108] Furthermore, the two-dimensional equivalent model construction module 1 constructs a two-dimensional equivalent model of rock fractures according to the following method:

[0109] The fracture sample is a rock with fractures. After three-dimensional scanning and numerical simulation of the geometric parameters and material parameters of the fracture sample, the major axis and the minor axis of the fracture are cut off to form a two-dimensional cross-section which is equivalent to an elliptical cross-section, thereby forming a two-dimensional equivalent model of the rock fracture.

[0110] A load loading module 2 is used to set a number of sampling points at the upper and lower boundaries of the fracture and to load the two-dimensional equivalent model of the rock fracture;

[0111] Furthermore, the load loading module 2 loads the load according to the following method:

[0112] A uniformly distributed load is applied to the upper boundary of the two-dimensional equivalent model of the rock fracture; the load step length needs to ensure that there are a number of sampling points (e.g., 4-5) in the linear change stage of the pressure dependence of the fracture area, and the sampling point density needs to be more than doubled in the nonlinear change stage;

[0113] The expression of the load is as follows:

[0114] σ·n=F(x,y0);

[0115] Where: Γ is the load, n is the unit normal vector of the loading boundary, F is the force per unit area applied to the loading boundary, x is any point on the loading boundary, and y0 is the position of the loading boundary in the y direction;

[0116] The boundary curve of the short axis is converted into an integral of the area of ​​a single crack region with respect to the boundary curve by Green's formula; the expression of the area of ​​the single crack region is as follows:

[0117]

[0118] Where: S is the area of ​​the fracture area, Γ is the contour curve of the fracture area, x is the x coordinate of the two-dimensional equivalent model of rock fracture, n x is the x-component of the outward normal vector of the crack contour boundary, and Ω is the crack area.

[0119] The opening calculation module 3 is used to calculate the length change of the major axis and the minor axis of the crack under each load step based on the displacement of the upper and lower boundary sampling points of the crack before and after the load is applied, and calculate the area of ​​the corresponding crack region;

[0120] Furthermore, the opening calculation module 3 performs calculation according to the following method:

[0121] S31, according to the sampling points [x1, x2...x N ] and the displacement of each sampling point during the loading process, and respectively calculate the positions of the upper and lower boundaries of the crack after the load is applied; the calculation expression is as follows:

[0122]

[0123] in: is the position of the Nth sampling point on the upper boundary of the crack after loading, is the position of the Nth sampling point at the lower boundary of the crack after loading, is the position of the Nth sampling point on the upper boundary of the crack before loading, is the position of the Nth sampling point at the lower boundary of the crack before loading, v i upper (xN ) is the displacement of the Nth sampling point on the upper boundary of the crack during loading, v i lower (x N ) is the displacement of the Nth sampling point on the lower boundary of the crack during loading, N is the sampling point on the crack, and i is the step index of the loading;

[0124] S32, based on the positions of the upper and lower boundaries of the crack after the load is applied, calculate the spacing value of the upper and lower boundaries of the sampling points; the expression for the calculation is as follows:

[0125]

[0126] Where: d i+1 (x N ) is the spacing value of the Nth sampling point, is the position of the Nth sampling point on the upper boundary of the crack, is the position of the Nth sampling point at the lower boundary of the crack;

[0127] S33, based on the spacing values ​​between the upper and lower boundaries of the sampling points, calculate the short axis length of the mth crack after loading step i+1; the calculation expression is as follows:

[0128]

[0129] in: is the minor axis length of the mth crack, and N is the total number of sampling points on the upper surface of the mth crack;

[0130] S34, based on the positions of the upper and lower boundaries of the crack after the load is applied, determining the major axis length of the crack after the load is applied;

[0131] like This indicates that the crack at the sampling point is closed; the length of the long axis of the crack is given by [x N -x1] is shortened to [x N-1 -x1], at this time, the major axis length of the mth crack becomes

[0132] like This indicates that the crack at the sampling point has not closed and the length of the major axis remains unchanged;

[0133] S35. Calculate the area of ​​the mth crack under each loading step index

[0134] The area expression of the crack is as follows:

[0135]

[0136] Where: Γ is the contour curve of the fracture area, x is the x coordinate of the two-dimensional equivalent model of rock fracture, n x is the x-component of the outward normal vector of the crack contour boundary, and Ω is the crack area.

[0137] The closure judgment module 4 is used to calculate the average opening of the short axes of all cracks and judge whether all cracks are completely closed; if not completely closed, the equivalent parameters of the cracks in the two-dimensional equivalent model of rock cracks are calculated based on the geometric parameters of the crack area, the two-dimensional equivalent model of rock cracks is updated, and after increasing the load, the steps corresponding to the above modules are repeated until all cracks in the two-dimensional equivalent model of rock cracks are completely closed.

[0138] Furthermore, the closure determination module 4 determines closure according to the following method:

[0139] S41, calculating the average value of the minor axis lengths of all the cracks, obtaining the average opening, and determining the degree of closure of all the cracks;

[0140] If the average opening of all cracks This indicates that all cracks have been closed;

[0141] If the average opening of all cracks This indicates that the mth crack is not completely closed, and the process proceeds to step S42;

[0142] S42, calculating equivalent fracture parameters of all fractures in each loading step, and updating the two-dimensional equivalent model of rock fractures based on the equivalent fracture parameters;

[0143] The expression of the equivalent crack parameter is as follows:

[0144]

[0145] in: is the equivalent major axis radius, is the equivalent minor axis radius, is the equivalent porosity, TN is the number of cracks, is the equivalent major axis radius of the mth crack under the i-th loading step, is the equivalent minor axis radius of the mth crack under the i-th loading step, S mod el is the area of ​​the two-dimensional equivalent model of rock fracture.

[0146] Embodiment 3:

[0147] See also Figure 5 , a rock fracture closure simulation device, the device comprising a processor 5 and a memory 6;

[0148] The memory 6 is used to store the computer program code 61 and transmit the computer program code 61 to the processor 5;

[0149] The processor 5 is used to execute the rock fracture closure simulation method described in Example 1 according to the instructions in the computer program code 61.

[0150] This embodiment also includes a computer-readable storage medium, in which computer-executable instructions are stored. When the computer-executable instructions are executed on a computer, the rock fracture closure simulation method described in Example 1 is implemented.

[0151] Generally speaking, the computer instructions for implementing the method of the present invention may be carried by any combination of one or more computer-readable storage media. Non-transitory computer-readable storage media may include any computer-readable media, except for the signal itself that is temporarily propagating.

[0152] The computer-readable storage medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device or device, or any combination thereof. More specific examples of computer-readable storage media (a non-exhaustive list) include: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EKROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof. In the present invention, a computer-readable storage medium may be any tangible medium containing or storing a program that may be used by or in conjunction with an instruction execution system, device, or device.

[0153] Computer program code for performing the operation of the present invention can be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, SMalltalk, C++, and conventional procedural programming languages ​​such as "C" or similar programming languages, in particular, Python suitable for neural network computing and platform frameworks based on TensorFlow, PyTorch, etc. can be used. The program code can be executed entirely on the user's computer, partially on the user's computer, as an independent software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer can be connected to the user's computer or to an external computer (for example, using an Internet service provider to connect via the Internet) through any type of network, including a local area network (LAN) or a wide area network (WAN).

[0154] The above-mentioned device and non-temporary computer-readable storage medium can be found in the detailed description of a rock fracture closure simulation method and its beneficial effects, which will not be repeated here.

[0155] Although the embodiments of the present invention have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A rock fracture closure simulation method, characterized in that: include: S1. Establishing a two-dimensional equivalent model of rock fractures based on fracture samples; the two-dimensional equivalent model of rock fractures includes a solid matrix and fractures, and the fractures are equivalent to a quasi-elliptical cross-section including a major axis and a minor axis; S2, setting a number of sampling points at the upper and lower boundaries of the fracture, and applying a load to the two-dimensional equivalent model of the rock fracture; S3, based on the displacement of the upper and lower boundary sampling points of the crack before and after the load is applied, the length change of the major axis and the minor axis of the crack under each load step is calculated, and the area of ​​the corresponding crack region is calculated; S4, calculating the average opening of the short axes of all cracks, and determining whether all cracks are completely closed; If it is not completely closed, the equivalent parameters of the cracks in the two-dimensional equivalent model of rock cracks are calculated based on the area of ​​the crack region, the two-dimensional rock crack model is updated, and after increasing the load, steps S2 to S4 are repeated until all cracks in the two-dimensional equivalent model of rock cracks are completely closed.

2. The rock fracture closure simulation method according to claim 1, characterized in that: The fracture sample is a rock with fractures. After three-dimensional scanning and numerical simulation of the geometric parameters and material parameters of the fracture sample, the major axis and the minor axis of the fracture are cut off to form a two-dimensional cross-section which is equivalent to an elliptical cross-section, thereby forming a two-dimensional equivalent model of the rock fracture.

3. The rock fracture closure simulation method according to claim 1, characterized in that: The step S2 specifically includes: A uniformly distributed load is applied to the upper boundary of the two-dimensional equivalent model of the rock fracture; the load step length needs to ensure that there are a number of sampling points in the linear change stage of the fracture area with pressure, and the sampling point density needs to be more than doubled in the nonlinear change stage; The expression of the load is as follows: σ·n=F(x,y0); Where: σ is the load, n is the unit normal vector of the loading boundary, F is the force per unit area applied to the loading boundary, x is any point on the loading boundary, and y0 is the position of the loading boundary in the y direction.

4. The rock fracture closure simulation method according to claim 3, characterized in that: The crack area is converted into an integral about the crack boundary curve by Green's formula. The expression of the area of ​​the single crack area is as follows: Where: S is the area of ​​the fracture area, Γ is the contour curve of the fracture area, x is the x coordinate of the two-dimensional equivalent model of rock fracture, n x is the x-component of the outward normal vector of the crack contour boundary, and Ω is the crack area.

5. The rock fracture closure simulation method according to claim 1, characterized in that: The step S3 specifically includes: S31, according to the sampling points [x1, x2...x N ] and the displacement of each sampling point during the loading process, and respectively calculate the positions of the upper and lower boundaries of the crack after loading the load; the calculation expression is as follows: in: is the position of the Nth sampling point on the upper boundary of the crack after loading, is the position of the Nth sampling point at the lower boundary of the crack after loading, is the position of the Nth sampling point on the upper boundary of the crack before loading, is the position of the Nth sampling point at the lower boundary of the crack before loading, is the displacement of the Nth sampling point on the upper boundary of the crack during loading, is the displacement of the Nth sampling point on the lower boundary of the crack during loading, N is the sampling point on the crack, and i is the step index of the loading; S32, based on the positions of the upper and lower boundaries of the crack after the load is applied, calculate the spacing value of the upper and lower boundaries of the sampling points; the expression for the calculation is as follows: Where: d i+1 (x N ) is the spacing value of the Nth sampling point, is the position of the Nth sampling point on the upper boundary of the crack, is the position of the Nth sampling point at the lower boundary of the crack; S33, based on the spacing values ​​between the upper and lower boundaries of the sampling points, calculate the short axis length of the mth crack after loading step i+1; the calculation expression is as follows: in: is the minor axis length of the mth crack, and N is the total number of sampling points on the upper surface of the mth crack; S34, based on the positions of the upper and lower boundaries of the crack after the load is applied, determining the major axis length of the crack after the load is applied; like This indicates that the crack at the sampling point is closed; the length of the long axis of the crack is given by [x N -x1] is shortened to [x N-1 -x1], at this time, the major axis length of the mth crack becomes like This indicates that the crack at the sampling point has not closed and the length of the major axis remains unchanged.

6. The rock fracture closure simulation method according to claim 5, characterized in that: In step S3, the steps of calculating the area of ​​the corresponding crack region are as follows: S35. Calculate the area of ​​the mth crack under each loading step index The area expression of the crack is as follows: Where: Γ is the contour curve of the fracture area, x is the x coordinate of the two-dimensional equivalent model of rock fracture, n x is the x-component of the outward normal vector of the crack contour boundary, and Ω is the crack area.

7. The rock fracture closure simulation method according to claim 6, characterized in that: The step S4 specifically includes: S41, calculating the average value of the minor axis lengths of all the cracks, obtaining the average opening, and determining the degree of closure of all the cracks; If the average opening of all cracks This indicates that all cracks have been closed; If the average opening of all cracks This indicates that the mth crack is not completely closed, and the process proceeds to step S42; S42, updating the geometric models of all the cracks according to the geometric parameters of all the cracks in each loading step; and obtaining the two-dimensional equivalent model of the rock crack based on the geometric parameters of different cracks; The expression of the equivalent crack parameter is as follows: in: is the equivalent major axis radius, is the equivalent minor axis radius, is the equivalent porosity, TN is the number of cracks, is the equivalent major axis radius of the mth crack under the i-th loading step, is the equivalent minor axis radius of the mth crack under the i-th loading step, S model is the area of ​​the two-dimensional equivalent model of rock fracture.

8. A rock fracture closure simulation system, characterized in that: The system comprises: A two-dimensional equivalent model building module (1) is used to establish a two-dimensional equivalent model of rock fractures based on fracture samples; the two-dimensional equivalent model of rock fractures includes a solid matrix and fractures, and the fractures are equivalent to a quasi-elliptical cross-section including a major axis and a minor axis; A load loading module (2) is used to set a plurality of sampling points at the upper and lower boundaries of the crack and to load the two-dimensional equivalent model of the rock crack; The opening calculation module (3) is used to calculate the length change of the major axis and the minor axis of the crack under each load step based on the displacement of the upper and lower boundary sampling points of the crack before and after the load is applied, and calculate the area of ​​the corresponding crack region; A closure judgment module (4) is used to calculate the average opening of the minor axes of all cracks and judge whether all cracks are completely closed; if not completely closed, then based on the geometric parameters of the crack area, the crack equivalent parameters in the two-dimensional equivalent model of rock cracks are calculated, and the two-dimensional model of rock cracks is updated. After the load is increased, the steps corresponding to the above modules are repeatedly executed until all cracks in the two-dimensional equivalent model of rock cracks are completely closed.

9. A rock fracture closure simulation device, characterized in that: The device comprises a processor (5) and a memory (6); The memory (6) is used to store computer program code (61) and transmit the computer program code (61) to the processor (5); The processor (5) is used to execute the rock fracture closure simulation method according to any one of claims 1 to 7 according to the instructions in the computer program code (61).

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, and when the computer-executable instructions are executed on a computer, the rock fracture closure simulation method according to any one of claims 1 to 7 is implemented.

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