A method, system, device and storage medium for simulating fracture closure of a rock

Abstract

A kind of rock fracture closure simulation method, system, equipment and storage medium, first, based on the fracture sample establishes two-dimensional equivalent model, and the fracture in it is equivalent to oval section, then set several sampling points on the upper and lower boundaries of fracture, and load, then based on the displacement of sampling point on the upper and lower boundaries of fracture before and after loading, the length change of each load step under fracture is calculated, and the fracture area is calculated, finally, the average opening of all short axes of fracture is calculated, and whether all fractures are completely closed is judged;If not, the fracture equivalent parameters are calculated to update, and the above steps are repeated after loading;The method based on numerical simulation, simulate the distribution and stress deformation of fracture in rock, and fully consider the length change of long axis and short axis of fracture, combined with fracture area, more accurately simulate the stress-strain process of fracture, effectively evaluate the fracture closure state, improve the accuracy of simulation result.

Description

TECHNICAL FIELD

[0001] The present application relates to a fracture closure simulation method for rock, and belongs to the field of rock physics, in particular to a fracture closure simulation method for rock, a system, a device and a storage medium. BACKGROUND

[0002] Due to the influence of physical diagenesis, weathering and denudation and tectonic movement, fractures are widely present in natural rocks and affect the mechanical properties, permeability, weathering resistance and other abilities of the rocks, and the fractures are also important storage spaces and seepage channels for groundwater resources. For porous rocks, changes in stress state will cause changes in the internal pore structure, and then cause changes in permeability, elastic modulus and resistivity, because the fracture is a "soft" pore, the ratio of the short axis to the long axis of the fracture is very small, and under compression stress, the fracture is easy to deform and even close, resulting in high sensitivity of the rock 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 the underground rock, and such induced stress changes can cause deformation of the fracture structure inside the rock and ultimately change the physical properties of the rock. Therefore, how to accurately evaluate the fracture closure phenomenon is of great significance.

[0003] At present, the research on rock fracture closure is usually carried out by computer simulation, but in the process of simulating and describing the deformation of the fracture by traditional means, it is usually assumed that the deformation of the fracture is mainly concentrated in the longitudinal axis, i.e. the long axis direction, and the change of the short axis is ignored, i.e. it is assumed that the short axis direction of the fracture remains unchanged. However, under the action of stress disturbance, the long and short axis directions of the real fracture will all deform in the closing process, which leads to the fact that the final conclusion does not match the actual situation and the accuracy is not high. SUMMARY

[0004] The purpose of the present application is to overcome the above-mentioned defects and problems 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 purpose, the technical solution of the present application is as follows: a rock fracture closure simulation method, comprising:

[0006] S1, establishing a rock fracture two-dimensional equivalent model based on a fracture sample; the rock fracture two-dimensional equivalent model comprises a solid matrix and a fracture, and the fracture is equivalent to an elliptical cross section comprising a long axis and a short axis;

[0007] S2, setting a plurality of sampling points on the upper and lower boundaries of the fracture, and loading a load on the rock fracture two-dimensional equivalent model;

[0008] S3, based on the displacement of the upper and lower boundary sampling points of the crack before and after loading, calculate the length change of the long axis and short axis of the crack at each load step, and calculate the area of the corresponding crack region;

[0009] S4, calculate the average opening of all crack short axes, and judge whether all cracks are completely closed; if not, calculate the crack equivalent parameters in the rock crack two-dimensional equivalent model based on the area of the crack region, update the rock crack two-dimensional equivalent model, and repeat steps S2-S4 after loading until all cracks in the rock crack two-dimensional equivalent model are completely closed.

[0010] The crack sample is a rock with cracks. After three-dimensional scanning and numerical simulation of the geometric parameters and material parameters of the crack sample, the long axis and short axis of the crack are intercepted to form a two-dimensional cross section and are equivalent to an elliptical cross section, forming the rock crack two-dimensional equivalent model.

[0011] The step S2 specifically comprises:

[0012] A uniform distributed load is applied to the upper boundary of the rock crack two-dimensional equivalent model; the load step needs to ensure that there are several sampling points in the linear change stage of the crack area with pressure, and the sampling point density needs to be encrypted by more than one times in the nonlinear change stage;

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

[0014] σ·n=F(x,y0);

[0015] Wherein: 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 with respect to the crack boundary curve by Green's formula; the expression of the area of the single crack region is as follows:

[0017]

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

[0019] The step S3 specifically comprises:

[0020] S31, according to the displacement of the upper and lower boundary sampling points [x1, x2...xN ] and the displacement of each sampling point in the loading process, the positions of the upper and lower boundaries of the crack after loading the load are calculated respectively; the calculated position expressions are as follows:

[0021]

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

[0023] S32, based on the positions of the upper and lower boundaries of the crack after loading the load, the interval values of each point in the upper and lower boundaries of the sampling points are calculated; the calculated expression is as follows:

[0024]

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

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

[0027]

[0028] Wherein: is the short 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 loading the load, the long axis length of the crack after loading the load is judged;

[0030] If , it indicates that the crack at the sampling point is closed; then the length of the long axis of the crack isN - x1] is shortened to [x N-1 - x1], at this time, the long axis length of the mth crack becomes

[0031] If , it indicates that the crack at the sampling point is not closed, and the long axis length remains unchanged.

[0032] In the step S3, the step of calculating the area of the corresponding crack region is 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 crack region, x is the x coordinate of the two-dimensional equivalent model of rock crack, n x is the x component of the outward normal vector of the crack contour boundary, and Ω is the crack region.

[0037] The step S4 specifically includes:

[0038] S41, calculate the average value of the short axis length of all cracks, obtain the average opening degree, and judge the closure degree of all cracks;

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

[0040] If the average opening degree of all cracks , it indicates that the mth crack is not completely closed, and step S42 is performed;

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

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

[0043]

[0044] Wherein: is the equivalent long axis radius, is the equivalent short axis radius, is the equivalent porosity, TN is the number of cracks, is the equivalent long axis radius of the mth crack under the i th loading step, is the equivalent short axis radius of the mth crack under the i th loading step, Smod el The area of the two-dimensional equivalent model of the rock fissure.

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

[0046] A two-dimensional equivalent model construction module for establishing a two-dimensional equivalent model of rock fissure based on a fissure sample; the two-dimensional equivalent model of rock fissure comprising a solid matrix and fissures, and the fissures being equivalent to an elliptical cross section comprising a long axis and a short axis;

[0047] A load loading module for setting a plurality of sampling points on the upper and lower boundaries of the fissures and loading the two-dimensional equivalent model of rock fissure with a load;

[0048] An opening degree calculation module for calculating the length changes of the long axis and the short axis of the fissure at each load step based on the displacements of the sampling points on the upper and lower boundaries of the fissure before and after loading the load, and calculating the area of the corresponding fissure region;

[0049] A closure judgment module for calculating the average opening degree of all the short axes of the fissures and judging whether all the fissures are completely closed; if not, calculating the equivalent parameters of the fissures in the two-dimensional equivalent model of rock fissure based on the geometric parameters of the fissure region, updating the two-dimensional model of rock fissure, and repeating the steps of executing the above modules after loading the load until all the fissures in the two-dimensional equivalent model of rock fissure are completely closed.

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

[0051] The memory is used for storing computer program codes and transmitting the computer program codes to the processor;

[0052] The processor is used for executing the rock fissure closure simulation method according to the instructions in the computer program codes.

[0053] A computer readable storage medium, the computer readable storage medium storing computer executable instructions, when the computer executable instructions are executed on a computer, realizing the rock fissure closure simulation method.

[0054] Compared with the prior art, the beneficial effects of the present application are:

[0055] In the rock fracture closure simulation method, system, device and storage medium, firstly, a two-dimensional equivalent model is established based on a fracture sample, and the fracture is equivalent to an elliptical section, then a plurality of sampling points are set on the upper and lower boundaries of the fracture, and a load is loaded, then the length change of the fracture at each load step is calculated based on the displacement of the sampling points on the upper and lower boundaries of the fracture before and after the load is loaded, and the fracture area is calculated, finally, the average opening of all short axes of the fracture is calculated, and whether all fractures are completely closed is judged; if not, the fracture equivalent parameters are calculated for updating, and the load is increased, and the above steps are repeatedly executed; in the application, the distribution and stress deformation of the fracture in the rock are simulated based on the numerical simulation method, the length change of the long axis and the short axis of the fracture is fully considered, the fracture area is combined, the stress and strain process of the fracture is more accurately simulated, the fracture closure state is effectively evaluated, and the accuracy of the simulation result is improved. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 It is the method step flow chart of the application.

[0057] Figure 2 It is the schematic diagram of the fracture equivalent elliptical structure in embodiment 1 of the application.

[0058] Figure 3 It is the schematic diagram of the load in embodiment 1 of the application.

[0059] Figure 4 It is the system structure schematic diagram of the application.

[0060] Figure 5 It is the device structure schematic diagram of the application.

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

[0062] The application will be further described in detail in combination with the description and specific implementation of the accompanying drawings.

[0063] Embodiment 1:

[0064] Referring to Figure 1 A rock fracture closure simulation method, characterized in that, comprising:

[0065] S1, a two-dimensional equivalent model of rock fracture is established based on a fracture sample; the two-dimensional equivalent model of rock fracture comprises a solid matrix and a fracture, and the fracture is equivalent to an elliptical section comprising a long axis and a short axis;

[0066] Further, the fissure sample is a rock with fissures, after three-dimensional scanning and numerical simulation of geometric parameters and material parameters of the fissure sample, the long axis and the short axis of the fissure are intercepted, a two-dimensional section is formed and is equivalent to an elliptical section, and the two-dimensional equivalent model of the rock fissure is formed; the geometric parameters include length, width, height, etc. of the rock, and the material parameters include type, elastic modulus, density, etc. of the rock.

[0067] Referring to Figure 2 , the fissure is equivalent to an elliptical structure, the major axis is the long axis of the ellipse, the minor axis is the short axis of the ellipse, and the short half axis is half of the short axis of the ellipse; the maximum grid size of the two-dimensional equivalent model is less than 1 / 10 of the short half axis of the fissure; the three-dimensional fissure is simplified to a two-dimensional one because the cross-sectional geometry perpendicular to the fissure surface is similar, and the displacement of the fissure surface under the normal compression can also be expressed in two dimensions; the fissure closure is simulated as the process of closing the fissure with the increase of the normal compression of the fissure surface. Thus, the actual problem can be modeled and simplified, which is more conducive to calculation.

[0068] S2, a plurality of sampling points are arranged on the upper and lower boundaries of the fissure, and a load is applied to the two-dimensional equivalent model of the rock fissure;

[0069] Further, the step S2 specifically comprises:

[0070] Referring to Figure 3 , a uniformly distributed load is applied to the upper boundary of the two-dimensional equivalent model of the rock fissure; the load step needs to ensure that there are a plurality of sampling points (for example, 4-5) in the linear change stage of the boundary curve of the short axis of the fissure, and the sampling point density needs to be encrypted by more than one time in the nonlinear change stage;

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

[0072] σ·n=F(x, v0);

[0073] Wherein: 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 fissure is converted into an integral with respect to the boundary curve by Green's formula; the expression of the area of the single fissure region is as follows:

[0075]

[0076] Wherein: S is the area of the fissure region, Γ is the contour curve of the fissure region, x is the x coordinate of the two-dimensional equivalent model of the rock fissure, n xΩ is the area of the crack, and x is the x component of the outward normal vector of the crack profile boundary.

[0077] S3, based on the displacement of the sampling points on the upper and lower boundaries of the crack before and after loading, the length changes of the long axis and the short axis of the crack at each load step are calculated, and the area of the corresponding crack region is calculated;

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

[0079] Further, the step S3 specifically comprises:

[0080] S31, according to the positions of the sampling points [x1, x2...x N ] on the upper and lower boundaries of the crack before loading and the displacements of the sampling points during loading, the positions of the sampling points on the upper and lower boundaries of the crack after loading are calculated respectively; the expression of the calculation is as follows:

[0081]

[0082] Wherein: 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 on 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 on 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 each sampling point on the crack, and i is the step index of the loading load.

[0083] S32, based on the positions of the upper and lower boundaries of the crack after loading, the spacing values of the sampling points on the upper and lower boundaries are calculated; the expression of the calculation is as follows:

[0084]

[0085] Wherein: 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, the position of the Nth sampling point of the lower boundary of the crack;

[0086] S33, based on the interval value of the upper and lower boundaries of the sampling point, the short axis length of the mth crack after loading the load step i+1 is obtained; the expression of the calculation is as follows:

[0087]

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

[0089] S34, based on the position of the upper and lower boundaries of the crack after loading the load, the length of the long axis of the crack after loading the load is judged;

[0090] If , it indicates that the crack at the sampling point is closed; then the length of the long axis of the crack is shortened from [x N -x1] to [x N-1 -x1], at this time, the length of the long axis of the mth crack becomes

[0091] If , it indicates that the crack at the sampling point is not closed, and the length of the long axis remains unchanged;

[0092] S35, the area of the mth crack under each loading step index is calculated

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

[0094]

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

[0096] S4, the average opening of all crack short axes is calculated, and whether all cracks are completely closed is judged; if not, based on the geometric parameters of the crack area, the equivalent parameters of the crack in the two-dimensional equivalent model of the rock crack are calculated, the two-dimensional equivalent model of the rock crack is updated, and the load is increased, and the steps S2-S4 are repeatedly executed until all cracks in the two-dimensional equivalent model of the rock crack are completely closed;

[0097] Further, the step S4 specifically comprises:

[0098] S41, the average value of the short axis length of all cracks is calculated to obtain the average opening, and the closure degree of all cracks is judged;

[0099] if the average opening of all the cracks then it indicates that all the cracks have been closed;

[0100] if the average opening of all the cracks then it indicates that the mth crack is not completely closed, and step S42 is performed;

[0101] S42, calculate the equivalent crack parameters of all the cracks under each loading step, and update the two-dimensional equivalent model of the rock cracks based on the equivalent crack parameters;

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

[0103]

[0104] wherein: is the equivalent long axis radius, is the equivalent short axis radius, is the equivalent porosity, TN is the number of cracks, is the equivalent long axis radius of the mth crack under the ith loading step, is the equivalent short axis radius of the mth crack under the ith loading step, S model is the area of the two-dimensional equivalent model of the rock cracks.

[0105] Example 2:

[0106] Referring to Figure 4 , a crack closure simulation system of a rock, comprising:

[0107] a two-dimensional equivalent model construction module 1 for establishing a two-dimensional equivalent model of rock cracks based on a crack sample; the two-dimensional equivalent model of rock cracks comprises a solid matrix and cracks, and the cracks are equivalent to an elliptical cross section comprising a long axis and a short axis;

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

[0109] The crack sample is a rock with cracks. After three-dimensional scanning and numerical simulation of the geometric parameters and material parameters of the crack sample, the long axis and the short axis of the cracks are intercepted, formed into a two-dimensional cross section, and equivalent to an elliptical cross section, thereby forming the two-dimensional equivalent model of rock cracks.

[0110] a load loading module 2 for setting a plurality of sampling points on the upper and lower boundaries of the cracks, and loading a load on the two-dimensional equivalent model of rock cracks;

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

[0112] A uniform distributed load is applied on the upper boundary of the rock fracture two-dimensional equivalent model; the load step should ensure that there are several sampling points (for example, 4-5) in the linear change stage of the pressure dependence of the fracture area, and the sampling point density should be doubled in the nonlinear change stage;

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

[0114] σ·n=F(x,y0);

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

[0116] The boundary curve of the minor axis is converted into an integral with respect to the boundary curve by Green's formula, and the area of the single fracture area is converted into an integral with respect to the boundary curve by Green's formula. The expression of the area of the single fracture area is as follows:

[0117]

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

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

[0120] Further, the opening degree calculation module 3 calculates according to the following method:

[0121] S31, according to the positions of the sampling points [x1, x2...x N ] on the upper and lower boundaries of the fracture before loading and the displacement of each sampling point during loading, the positions of the upper and lower boundaries of the fracture after loading are calculated respectively; the expression of the calculation is as follows:

[0122]

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

[0124] S32, based on the positions of the upper and lower boundaries of the crack after the load is loaded, the spacing values of the upper and lower boundaries of the sampling points are calculated; the expression of the calculation is as follows:

[0125]

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

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

[0128]

[0129] Wherein: is the short 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 loaded, the long axis length of the crack after the load is loaded is judged;

[0131] If , it indicates that the crack at the sampling point is closed; then the length of the long axis of the crack is shortened from [x N -x1] to [x N-1 -x1], at this time, the long axis length of the mth crack becomes

[0132] If , it indicates that the crack at the sampling point is not closed, and the long axis length remains unchanged;

[0133] S35, the area of the mth crack at each loading step index is calculated

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

[0135]

[0136] wherein: Γ is the contour curve of the fracture region, 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 fracture contour boundary, and Ω is the fracture region.

[0137] The closure judging module 4 is configured to calculate the average opening degree of all short axes of the fractures, and judge whether all the fractures are completely closed; if not, calculate the equivalent parameters of the fractures in the two-dimensional equivalent model of rock fracture based on the geometric parameters of the fracture region, update the two-dimensional equivalent model of rock fracture, and repeat the steps corresponding to the above modules after loading until all the fractures in the two-dimensional equivalent model of rock fracture are completely closed.

[0138] Further, the closure judging module 4 judges the closure according to the following method:

[0139] S41, calculate the average value of the short axis length of all fractures to obtain the average opening degree, and judge the closure degree of all fractures;

[0140] If the average opening degree of all fractures is less than the preset threshold value, it indicates that all the fractures have been closed. If the average opening degree of all fractures is greater than the preset threshold value, it indicates that the mth fracture is not completely closed, and step S42 is performed.

[0141]

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

[0143] The expression of the equivalent fracture parameters is as follows:

[0144]

[0145] wherein: is the equivalent long axis radius, is the equivalent short axis radius, is the equivalent porosity, TN is the number of fractures, is the equivalent long axis radius of the mth fracture at the i th loading step, is the equivalent short axis radius of the mth fracture at the i th loading step, S mod el is the area of the two-dimensional equivalent model of rock fracture.

[0146] Embodiment 3:

[0147] Referring to Figure 5 , a fracture closure simulation device of rock, the device comprising a processor 5 and a memory 6;

[0148] ​​The memory 6 is configured to store computer program code 61 and transmit the computer program code 61 to the processor 5.

[0149] The processor 5 is configured to execute the method of fracture closure simulation of rock according to the instructions in the computer program code 61.

[0150] In this embodiment, a computer readable storage medium is also included, and the computer readable storage medium stores computer executable instructions. When the computer executable instructions are executed on a computer, the method of fracture closure simulation of rock in embodiment 1 is implemented.

[0151] Generally, the computer instructions used to implement the method of the present application can be carried by any combination of one or more computer readable storage media. The non-transitory computer readable storage medium can include any computer readable medium except a transitory signal per se.

[0152] The computer readable storage medium may, for example, be, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, device or apparatus, or any combination of the above. More specific examples (a non-exhaustive list) of the computer readable storage medium include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In this application, the computer readable storage medium can be any tangible medium that contains or stores a program that can be used by or in connection with an instruction execution system, apparatus or device.

[0153] Computer program code for carrying out operations of the present application can be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like, and conventional procedural programming languages, such as the "C" programming language or similar programming languages, particularly Python language and platform frameworks based on TensorFlow, PyTorch, etc. suitable for neural network computing. The program code can execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer can be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection can be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0154] The above apparatus and non-transitory computer readable storage medium can refer to the specific description of the method and advantages of the fracture closure simulation of a rock, which will not be repeated here.

[0155] Although the embodiments of the present application have been shown and described above, it should be understood by those skilled in the art that the above embodiments are exemplary and cannot be interpreted as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A method for simulating fracture closure in rock, characterized in that, include: S1. Establish a two-dimensional equivalent model of rock fractures based on fractured samples; the two-dimensional equivalent model of rock fractures includes a solid matrix and fractures, and the fractures are equivalent to an elliptical cross section including a major axis and a minor axis; S2. Set several sampling points at the upper and lower boundaries of the fracture, and apply load to the two-dimensional equivalent model of the rock fracture. S3. Based on the displacement of the sampling points at the upper and lower boundaries of the crack before and after the loading load, calculate the change in the length of the major axis and minor axis of the crack under each load step, and calculate the area of ​​the corresponding crack region. S4. Calculate the average opening of the minor axis of all cracks and determine whether all cracks are completely closed. If the fracture is not completely closed, the equivalent parameters of the fracture in the two-dimensional equivalent model of the rock fracture are calculated based on the area of ​​the fracture region. The two-dimensional equivalent model of the rock fracture is then updated, and after adding a load, steps S2-S4 are repeated until all fractures in the two-dimensional equivalent model of the rock fracture are completely closed.

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

3. The method for simulating rock fracture closure according to claim 1, characterized in that: 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 size must ensure that there are several sampling points in the linear change stage of the fracture area with pressure, while in the nonlinear change stage, the sampling point density must be increased by more than double. The expression for the load is as follows: ； in: For load, The unit normal vector of the loaded boundary. The force per unit area applied on the loading boundary. For any point on the loading boundary, To load the boundary at Position in the direction.

4. The method for simulating rock fracture closure according to claim 3, characterized in that: The area of ​​the fracture is converted into an integral about the fracture boundary curve using Green's formula; the expression for the area of ​​a single fracture region is as follows: ； in: The area of ​​the fractured region. This is the contour curve of the fractured region. Two-dimensional equivalent model of rock fracture coordinate, The outward normal vector of the crack profile boundary Quantity, This is a fractured region.

5. The method for simulating rock fracture closure according to claim 1, characterized in that: Step S3 specifically includes: S31. Based on the sampling points at the upper and lower boundaries of the crack before the load is applied... Based on the location of the sampling points and their displacements during the loading process, the positions of the upper and lower boundaries of the crack after the load is applied are calculated; the calculation expressions are as follows: ； in: For the upper boundary of the crack after loading The location of each sampling point For the lower boundary of the crack after loading The location of each sampling point For the first crack boundary before loading The location of each sampling point For the lower boundary of the crack before loading The location of each sampling point For the upper boundary of the crack during loading process The displacement of each sampling point For the lower boundary of the crack during loading process The displacement of each sampling point For each sampling point on the crack, Index of the steps for loading the load; S32. Based on the positions of the upper and lower boundaries of the crack after the load is applied, calculate the spacing between the upper and lower boundaries of the sampling points; the calculation expression is as follows: ； in: For the first The interval value of each sampling point; S33. Based on the spacing values ​​of the upper and lower boundaries of the sampling points, calculate the first... The crack during the loading process The length of the minor axis after calculation; the expression for the calculation is as follows: ； in: For the first The length of the minor axis of the crack, For the first The total number of sampling points on the upper surface of each crack; S34. Based on the positions of the upper and lower boundaries of the crack after the load is applied, determine the length of the major axis of the crack after the load is applied; like This indicates that the crack at the sampling point is closed; therefore, the length of the crack's major axis is determined by... shortened to At this time, the first The length of the major axis of the crack becomes ; like This indicates that the crack at the sampling point is not closed and the length of the major axis remains unchanged.

6. The method for simulating rock fracture closure according to claim 5, characterized in that: In step S3, the steps for calculating the area of ​​the corresponding fracture region are as follows: S35. Calculate the index of each loading step. Area of ​​each crack ; The area expression for the crack is as follows: ； in: This is the contour curve of the fractured region. Two-dimensional equivalent model of rock fracture coordinate, The outward normal vector of the crack profile boundary Quantity, This is a fractured region.

7. The method for simulating rock fracture closure according to claim 6, characterized in that: Step S4 specifically includes: S41. Calculate the average value of the minor axis length of all cracks to obtain the average aperture, and determine the degree of closure of all cracks. If the average aperture of all cracks This indicates that all cracks have been closed; If the average aperture of all cracks , then it indicates the first The crack was not completely closed, proceed to step S42; S42. Update the geometric model of all fractures according to the geometric parameters of all fractures under each loading step; and obtain the two-dimensional equivalent model of the rock fractures based on the geometric parameters of different fractures. The expression for the equivalent fracture parameter is as follows: ； in: For the equivalent major axis radius, For the equivalent minor axis radius, For equivalent porosity, The number of cracks, For the first The first crack in the... Equivalent major axis radius under each loading step For the first The first crack in the... Equivalent minor axis radius under each loading step This represents the area of ​​the two-dimensional equivalent model of rock fractures.

8. A rock fracture closure simulation system, characterized in that, The system includes: Two-dimensional equivalent model construction module (1) is used to establish a two-dimensional equivalent model of rock fracture based on fracture samples; the two-dimensional equivalent model of rock fracture includes a solid matrix and fractures, and the fractures are equivalent to an elliptical cross section including a major axis and a minor axis; The load loading module (2) is used to set several sampling points at the upper and lower boundaries of the fracture and to load the two-dimensional equivalent model of the rock fracture. The opening calculation module (3) is used to calculate the length changes of the major axis and minor axis of the crack under each load step based on the displacement of the sampling points of the upper and lower boundaries of the crack before and after the loading load, and to calculate the area of ​​the corresponding crack region. The closure judgment module (4) is used to calculate the average opening of the minor axis of all cracks and determine whether all cracks are completely closed. If they are not completely closed, the equivalent parameters of the cracks in the two-dimensional equivalent model of the rock cracks are calculated based on the geometric parameters of the crack region, and the two-dimensional model of the rock cracks is updated. After adding the load, the steps corresponding to the above module are repeated until all cracks in the two-dimensional equivalent model of the rock cracks are completely closed.

9. A rock fracture closure simulation device, characterized in that: The device includes a processor (5) and a memory (6); The memory (6) is used to store computer program code (61) and to 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 1-7 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, which, when executed on a computer, implement the rock fracture closure simulation method according to any one of claims 1-7.

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