Hydraulic fracture conductivity evaluation method based on post-fracturing coring fracture reconstruction

Abstract

The invention provides a hydraulic fracture conductivity evaluation method based on post-fracturing coring fracture reconstruction, which comprises the following steps: carrying out a post-fracturing coring or fracturing experiment to obtain a hydraulic fracture, and carrying out CT scanning on the hydraulic fracture; reconstructing a fracture entity model in a normal pressure state; importing the reconstructed fracture entity model into discrete element simulation software, and reconstructing proppant particles in the fracture entity model; simulating a closing process of the support fracture under effective stress on the real support fracture discrete element physical model, setting a wall surface migration velocity in a stress loading process according to a crustal stress parameter, and exporting a fracture parameter and a proppant parameter in the closing process; according to fracture parameters and propping agent parameters in the closing process, a computational fluid mechanics-discrete element coupling model is established, and fracture conductivity changes are simulated and calculated. The evaluation method can quickly, economically and quantitatively evaluate the flow conductivity of the support fracture under different normal effective stresses, and the obtained simulation result is more consistent with the actual situation.

Description

Technical Field

[0001] This invention relates to the field of oil and gas engineering technology, and in particular to a method for evaluating the conductivity of hydraulic fractures based on post-coring fracture reconstruction. Background Technology

[0002] Shale reservoir volumetric fracturing complex fractures are typically classified into three types: main fractures, branch fractures, and self-supporting fractures. In the initial stages of shale gas well production, reservoir pressure drops rapidly, increasing fracture closure pressure. The long-term conductivity of fractures directly impacts the total production of the shale gas well. Currently, shale gas reservoir volumetric fracturing design primarily relies on experiments and numerical simulations of fracture conductivity, with research on the conductivity of branch fractures mainly depending on laboratory experiments under specific conditions. The fracture samples used in conductivity experiments and numerical simulations are mainly regular steel plate fractures and Brazilian split fractures in core samples, with minimal consideration given to the impact of proppant placement on conductivity during experiments. Even when the influence of proppant is considered, its placement is often idealized; numerical simulations use the sparsest or densest arrangement of spherical particles to simulate proppant placement, while experiments often employ manual application and filling methods to simulate proppant placement.

[0003] Therefore, the results obtained from post-compaction coring differ significantly from those from the actual crack morphology, inter-crack coupling state, and proppant placement. This means that the methods described above cannot accurately reflect the crack morphology or inter-crack coupling state, thus failing to accurately determine the impact of proppant placement on the actual crack conductivity. Summary of the Invention

[0004] The main objective of this invention is to provide a method for evaluating the conductivity of hydraulic fractures based on post-coring fracture reconstruction, which aims to quickly, accurately, and quantitatively evaluate the conductivity of supported fractures under different normal effective stresses.

[0005] To achieve the above objectives, this invention provides a method for evaluating the conductivity of hydraulic fractures based on post-coring fracture reconstruction, comprising the following steps: Hydraulic fractures were obtained by coring or true triaxial hydraulic fracturing experiments in adjacent high-angle wells after fracturing, and CT scans were performed on the hydraulic fractures. Based on the CT scan results of the hydraulic fracture, the solid model of the fracture under normal pressure was reconstructed. The reconstructed fracture solid model was imported into the discrete element simulation software, and proppant particles were reconstructed in the fracture solid model based on the CT scan results of the hydraulic fracture to establish a realistic discrete element physical model of the proppant fracture. Based on the servo mechanism, the closure process of the support crack under different normal effective stresses is simulated on the discrete element physical model of the real support crack. The wall migration velocity during the stress loading process is set according to the geostress parameters, and the crack parameters and proppant parameters during the closure process are derived. Based on the crack parameters and proppant parameters during the closure process, a computational fluid dynamics-discrete element coupled model was established. The CFD-DEM method was used to simulate the proppant crack conductivity on the computational fluid dynamics-discrete element coupled model, and the change in crack conductivity was calculated based on the simulation results.

[0006] Preferably, the steps of conducting coring or true triaxial hydraulic fracturing experiments in adjacent high-angle wells after fracturing to obtain hydraulic fractures, and performing CT scans on the hydraulic fractures specifically include: The occurrence of groundwater hydraulic fractures can be obtained by coring the fracturing formation, or the morphology of hydraulic fractures can be obtained by true triaxial experiments. CT scans were performed on hydraulic fractures obtained by post-pressure coring or true triaxial experiments, with a scanning accuracy greater than 50 μm and a scanning size greater than 100 mm × 100 mm.

[0007] Preferably, the step of reconstructing the solid model of the fracture under normal pressure based on the CT scan results of the hydraulic fracture specifically includes: The data obtained from the CT scan of the hydraulic fractures are processed, the fractures and proppant are classified and processed, and after noise reduction and segmentation algorithms, CAD data volume and STL data format are obtained. The STL data format completes the solid reconstruction of the fracture. The CAD data volume is exported as a point cloud data volume. Through this process, the crack surface entity data is exported as three-dimensional coordinate data. Based on the three-dimensional coordinate data, the relative spatial relationship of the coordinates is calculated to obtain the initial crack aperture and crack roughness.

[0008] Preferably, in the step of calculating the relative spatial relationship of coordinates based on three-dimensional coordinate data to obtain the initial crack aperture and crack roughness, the initial crack aperture... Calculate using the following formula: ; in, This represents the maximum height difference of the micro-protrusions on the crack surface; and These are the height values ​​of the micro-protrusions at the measurement points on the upper and lower seam surfaces, respectively, where 1 and 2 represent the upper and lower seam surfaces. These represent the serial numbers of the crack mesh along the x or y axis, respectively; , These represent the placement errors of the upper and lower crack surfaces when measuring the crack surface height data.

[0009] Preferably, in the step of calculating the relative spatial relationship of coordinates based on three-dimensional coordinate data to obtain the initial crack aperture and crack roughness, the crack roughness is based on the root mean square value of the micro-protrusion height. The root mean square value of the micro-convexity height was calculated. It was calculated based on the height of the micro-protrusions in the crack.

[0010] Preferably, the specific process of reconstructing proppant particles in the solid model of the hydraulic fracture based on the CT scan results includes: Determine whether the requirements for reconstruction proppant are met based on the CT scan results of the hydraulic fracture; When the CT scan results do not meet the reconstruction requirements, the proppant placement strength is calculated based on the CT scan results for proppant reconstruction. The proppant particle breakage model is designed as the Tavares breakage model. When the CT scan results meet the reconstruction requirements, the proppant is directly reconstructed inside the reconstructed crack entity model, and the proppant fracture model adopts the liner-bonding model.

[0011] Preferably, the proppant layup strength Calculate using the following formula: ; in, Indicates the volume occupied by the proppant; The radius of the CT scan core column; This represents the initial crack aperture.

[0012] Preferably, in the step of setting the wall migration velocity during the stress loading process based on the geostress parameters, the wall migration velocity... Calculate using the following formula: ; in, The effective stress applied to the proppant particles, The current average stress, For intermediate parameters, Calculate using the following formula: ; in, As a relaxation factor, The effective area of ​​the wall. The average stiffness of the wall contact is... This represents the total number of contacts between the wall and the particles. To calculate the step size; Effective stress Calculate using the following formula: ; in, To determine the minimum principal stress obtained from the well logging curve, This represents the maximum pore pressure value during the simulation process. The value is the ratio of the two factors.

[0013] Preferably, when simulating the conductivity of supported fractures using the CFD-DEM method on a computational fluid dynamics-discrete element coupled model, an inlet and outlet pressure difference is set to simulate the flow of fractured proppant and fluid within the fracture. The fluid is assumed to be reservoir crude oil or natural gas, and then the fracture conductivity is calculated. The governing equations for the motion of the fractured proppant are as follows: ; in, and These are the normal contact force and the tangential contact force, respectively. For gravity, Applying the force of the particle to the fluid surrounding the particle. and These are the particle vector radius and the particle's additional torque, respectively. and They are translational velocity and rotational velocity, respectively. and Particle mass and moment of inertia, respectively; The fluid flow within the crack can be solved using the locally averaged Navier-Stokes equations: ; In the formula, This represents the volume fraction of fluid within the crack. The fluid density inside the crack, The fluid velocity within the crack, The pressure gradient at the crack inlet and outlet. Let be the fluid stress tensor, and t be the time step. This is the momentum exchange source term.

[0014] Preferably, the crack parameters derived during the closure process include the actual crack aperture. Changes in fracture conductivity Calculate using the following formula: , ; in, The permeability of the crack; This represents the actual crack opening. To calculate the obtained export flow; The viscosity of the fluid within the crack; The length of the crack; Let be the cross-sectional area of ​​the crack.

[0015] The hydraulic fracture conductivity evaluation method based on post-coring fracture reconstruction proposed in this invention has the following beneficial effects: 1. The discrete element method was used to simulate the conductivity of the support crack under different normal stresses. This method can quickly, economically, and quantitatively evaluate the conductivity of the support crack under different effective normal stresses, and the simulation results are more consistent with the actual situation. 2. A method for reconstructing real cracks and embedded proppant was established, which can also be applied to proppant breakage simulation and proppant placement simulation. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the method for evaluating the conductivity of hydraulic fractures based on post-coring fracture reconstruction according to the present invention. Figure 2 This is a schematic diagram of the fracture reconstruction process in a specific embodiment of the hydraulic fracture conductivity evaluation method based on post-coring fracture reconstruction according to the present invention; (2a. Characteristics of post-coring fracture; 2b. CT scan of post-coring fracture; 2c. Fracture entity reconstruction based on CT scan; 2d. Point cloud image of fracture surface; 2e. Fracture surface feature analysis; 2f. Importing the fracture entity model into discrete element software); Figure 3 This is a specific embodiment of the proppant reconstruction process of the hydraulic fracture conductivity evaluation method based on post-coring fracture reconstruction according to the present invention (a. characteristics of post-coring proppant; b. CT scan of post-coring proppant; c. proppant filling model in fracture). Figure 4 This is a proppant breakage contact model, a specific embodiment of the method for evaluating the conductivity of hydraulic fractures reconstructed from post-coring fractures according to the present invention. Figure 5 This is a specific embodiment of the method for evaluating the conductivity of hydraulic fractures based on post-coring fracture reconstruction according to the present invention, showing the proppant crushing process under different normal stresses; Figure 6 This is a specific embodiment of the hydraulic fracture conductivity evaluation method based on post-coring fracture reconstruction of the present invention, showing the proppant migration process. Figure 7 This is a simulation of the conductivity of a support fracture under a normal stress of 30 MPa in a specific embodiment of the hydraulic fracture conductivity evaluation method based on post-compression coring fracture reconstruction of the present invention.

[0017] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0018] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0019] It should be noted that in the description of this invention, the terms "lateral," "longitudinal," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used solely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0020] This invention proposes a method for evaluating the conductivity of hydraulic fractures based on post-coring fracture reconstruction.

[0021] This invention proposes a method for evaluating the conductivity of hydraulic fractures based on post-coring fracture reconstruction, comprising the following steps: Step S1: Conduct coring or true triaxial hydraulic fracturing experiments in adjacent high-angle wells after fracturing to obtain hydraulic fractures, and perform CT scans on the hydraulic fractures. Step S2: Based on the CT scan results of the hydraulic fracture, reconstruct the solid model of the fracture under normal pressure. Step S3: Import the reconstructed crack solid model into the discrete element simulation software, and reconstruct the proppant particles in the crack solid model according to the CT scan results of the hydraulic crack, so as to establish a real support crack discrete element physical model. Step S4: Based on the servo mechanism, simulate the closure process of the support crack under different normal effective stresses on the real support crack discrete element physical model. Set the wall migration velocity during the stress loading process according to the geostress parameters, and derive the crack parameters and proppant parameters during the closure process. Step S5: Based on the crack parameters and proppant parameters during the closure process, establish a computational fluid dynamics-discrete element coupled model, and use the CFD-DEM method to simulate the proppant crack conductivity on the computational fluid dynamics-discrete element coupled model. Calculate the change in crack conductivity based on the simulation results.

[0022] Specifically, step S1 includes: Step S11: Obtain the occurrence of groundwater hydraulic fractures by coring the fracturing formation or by obtaining the morphology of hydraulic fractures through true triaxial experiments; Step S12: Perform CT scanning on the hydraulic fractures obtained by post-pressure coring or true triaxial experiments, with a scanning accuracy greater than 50 μm and a scanning size greater than 100 mm × 100 mm.

[0023] Specifically, step S2 includes: Step S21: The data obtained from the CT scan of the hydraulic fracture is processed, the fracture and proppant are classified and processed, and after noise reduction and segmentation algorithms, CAD data volume and STL data format are obtained. The STL data format completes the solid reconstruction of the fracture. Step S22: Export the CAD data volume as a point cloud data volume. Through this process, export the crack surface entity data as three-dimensional coordinate data. Calculate the coordinate relative spatial relationship based on the three-dimensional coordinate data to obtain the initial crack opening and crack roughness in order to calculate the initial crack width. In step S22, the initial crack aperture and crack roughness are obtained by calculating the relative spatial relationship of coordinates based on the three-dimensional coordinate data. Calculate using the following formula: , in, This represents the maximum height difference of the micro-protrusions on the crack surface; and These are the height values ​​of the micro-protrusions at the measurement points on the upper and lower seam surfaces, respectively, where 1 and 2 represent the upper and lower seam surfaces. These represent the serial numbers of the crack mesh along the x or y axis, respectively; , These represent the placement errors of the upper and lower crack surfaces when measuring the crack surface height data.

[0024] Specifically, in the step of calculating the relative spatial relationship of coordinates based on three-dimensional coordinate data to obtain the initial crack aperture and crack roughness, the crack roughness is based on the root mean square value of the micro-protrusion height. The root mean square value of the micro-convexity height was calculated. It was calculated based on the height of the micro-protrusions in the crack.

[0025] Root mean square value of the height of the micro-convexity of the seam surface Calculate using the following formula: ; In the formula, The height of the mesh micro-protrusion numbered i; This represents the number of crack meshes along the x or y axis. Let be the projected side length of the mesh on the reference plane, in mm.

[0026] Based on Tse and Cruden's study of the roughness coefficient of the Barton standard two-dimensional curve, the roughness coefficient JRC of the seam surface is related to the root mean square of the micro-convexity height coordinate. The following fitting relationship exists [22,23]: .

[0027] In step S3, the specific process of reconstructing proppant particles in the solid model of the hydraulic fracture based on the CT scan results includes: Determine whether the requirements for reconstruction proppant are met based on the CT scan results of the hydraulic fracture; When the CT scan results do not meet the reconstruction requirements, the proppant placement strength is calculated based on the CT scan results to be used for proppant reconstruction. The proppant particle breakage model is designed as the Tavares breakage model (the proppant particles are assumed to be spherical particles with a filling volume of A1). When the CT scan results meet the reconstruction requirements, the proppant is directly reconstructed inside the reconstructed crack entity model, and the proppant fracture model adopts the liner-bonding model.

[0028] If the CT scan accuracy is insufficient to reconstruct the fine-grained proppant, the proppant is assumed to be spherical, and the particle size is obtained based on the particle size distribution curve of 40-70 mesh quartz sand; if the CT scan accuracy is sufficient to identify the proppant, the proppant aggregate STL file can be directly exported.

[0029] When CT scan results do not meet reconstruction requirements, it is necessary to calculate the proppant placement strength. Calculate using the following formula: ; in, Indicates the volume occupied by the proppant; The radius of the CT scan core column; This represents the initial crack aperture.

[0030] Furthermore, in the calculation process of step S4, the contact model calculation requires the use of contact stiffness and stress conditions, which affect the analysis of fracture closure and proppant breakage rate. Therefore, in step S4, based on rock mechanics experiments and well logging parameter inversion, the mechanical parameters to be obtained include the Young's modulus and Poisson's ratio of the fractured rock mass. The Young's modulus and Poisson's ratio of the proppant are set according to the properties of quartz minerals. Then, based on a servo mechanism, the closure process of the propped fracture under different normal effective stresses is simulated on a real propped fracture discrete element physical model. Since the friction coefficients between proppants and between proppant and rock mass are difficult to obtain, the friction coefficient between quartz minerals is used instead. In simulating the closure process of a support crack on a realistic discrete element physical model, the servo mechanism works as follows: In one loading cycle step, the numerical servo continuously adjusts the position of the wall surface (baffle, crack surface) to achieve the combined stress of the particle forces and confining pressure on the servo sidewall. Discrete element method (DEM) software cannot directly apply forces to the wall; it can only set the wall's velocity. Therefore, it is necessary to determine the appropriate force based on the wall's velocity. and The difference is used to adjust the wall movement speed.

[0031] In the step of setting the wall migration velocity during stress loading based on the geostress parameters, the wall migration velocity... Calculate using the following formula: ; in, The effective stress applied to the proppant particles, The current average stress, For intermediate parameters, Calculate using the following formula: ; in, As a relaxation factor, The effective area of ​​the wall. The average stiffness of the wall contact is... This represents the total number of contacts between the wall and the particles. To calculate the step size; Effective stress Calculate using the following formula: ; in, To determine the minimum principal stress obtained from the well logging curve, This represents the maximum pore pressure value during the simulation process. The value is the ratio of the two factors.

[0032] In step S4, the closure process of the support crack under different normal effective stresses is simulated on the real support crack discrete element physical model based on the servo mechanism. As the effective stress gradually increases, the crack closes and the proppant gradually breaks. The crack parameters and proppant parameters during the closure process are recorded and exported, laying the physical model foundation for the next step of flow conduction capacity simulation.

[0033] In step S5, when simulating the conductivity of the propped fracture using the CFD-DEM method on a computational fluid dynamics-discrete element coupled model, firstly, based on the fracture parameters obtained in step S4 under different effective stresses, a computational fluid dynamics mesh is established. The mesh size is required to be 3-10 times the proppant particle size. Then, the computational fluid dynamics-discrete element coupled model is re-established using CFDEM software, and the inlet and outlet pressure differences are set to simulate the flow of broken proppant and fluid within the fracture. The fluid is assumed to be reservoir crude oil or natural gas, and then the fracture conductivity is calculated. The governing equations for the motion of the fractured proppant are as follows: ; in, and These are the normal contact force and the tangential contact force, respectively. For gravity, Applying the force of the particle to the fluid surrounding the particle. and These are the particle vector radius and the particle's additional torque, respectively. and They are translational velocity and rotational velocity, respectively. and Particle mass and moment of inertia, respectively; The fluid flow within the crack can be solved using the locally averaged Navier-Stokes equations: ; In the formula, This represents the volume fraction of fluid within the crack. The fluid density inside the crack, The fluid velocity within the crack, The pressure gradient at the crack inlet and outlet. Let be the fluid stress tensor, and t be the time step. This is the momentum exchange source term.

[0034] Exporting crack parameters during the closure process includes the actual crack aperture. Changes in fracture conductivity Calculate using the following formula: , ; in, The permeability of the crack; This represents the actual crack opening. To calculate the obtained export flow; The viscosity of the fluid within the crack; The length of the crack; Let be the cross-sectional area of ​​the crack.

[0035] Reference Figures 2 to 7 The following example illustrates the specific process of this hydraulic fracture conductivity evaluation method based on post-coring fracture reconstruction: 1. Based on the CT scan results of post-compression coring fractures from the Fuling shale gas field, the fracture characteristics were reconstructed. The reconstruction process and results are as follows: Figure 2 As shown, the reconstruction result is as follows Figure 2 As shown in f, the parameters of the reconstructed crack surface and crack width are analyzed. Figure 2 The seam JRC coefficient is 12.19, the fractal dimension calculated by the triangular prism method is 2.11, and the average seam width is 0.26 mm.

[0036] 2. At the same time, based on the proppant scanning results ( Figure 3 a) Reconstructing proppant morphology ( Figure 3(b) The proppant particles are connected using the Bonding model and then filled into the cracks, but this method can simulate a limited number of proppant particles. Alternatively, based on the proppant particle size analysis results, spherical particles combined with the Tavares fragmentation model can be used to simulate the proppant fragmentation process (e.g., Figure 4 ).

[0037] 3. Based on the identification results of the number of proppant layers and proppant strength in the fractures obtained from post-compression coring, proppant is generated in the simulated fractures. This invention provides an example result of one of the Tabares fracture models (e.g., Figure 5 The basic mechanics of the particles and the contact parameters between particles and between particles and cracks are shown in Table 1.

[0038] Table 1. Particle mechanical parameters of proppant characteristic settings in a certain gas field

[0039] 4. The fracture aperture and proppant under effective stress of 15MPa were derived, and the flow region inside the fracture was meshed. Based on the basic parameters of the fracturing fluid and the production pressure of the Fuling shale gas field, a seepage field was added and corresponding flow parameters were assigned (Table 2). The computational fluid dynamics (CFD)-discrete element (DEM) coupled method was used to simulate the backflow process and flow capacity of the fractured proppant. Table 2 Fluid domain parameters set according to the production dynamic characteristics of a certain gas field.

[0040] 5. Calculation examples show that, under low proppant coverage, the breakage of the proppant exhibits a phenomenon similar to "sand production or particle migration" in tight sandstone reservoirs, which may further reduce conductivity. Figure 6 After the simulation, the pressure gradient distribution within the support crack is as follows: Figure 7 As shown.

[0041] The hydraulic fracture conductivity evaluation method based on post-coring fracture reconstruction proposed in this invention has the following beneficial effects: 1. The discrete element method was used to simulate the conductivity of the support crack under different normal stresses. This method can quickly, economically, and quantitatively evaluate the conductivity of the support crack under different effective normal stresses, and the simulation results are more consistent with the actual situation. 2. A method for reconstructing real cracks and embedded proppant was established, which can also be applied to proppant breakage simulation and proppant placement simulation.

[0042] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for evaluating the conductivity of hydraulic fractures based on post-coring fracture reconstruction, characterized in that, Includes the following steps: Hydraulic fractures were obtained by coring or true triaxial hydraulic fracturing experiments in adjacent high-angle wells after fracturing, and CT scans were performed on the hydraulic fractures. Based on the CT scan results of the hydraulic fracture, the solid model of the fracture under normal pressure was reconstructed. The reconstructed fracture solid model was imported into the discrete element simulation software, and proppant particles were reconstructed in the fracture solid model based on the CT scan results of the hydraulic fracture to establish a realistic discrete element physical model of the proppant fracture. Based on the servo mechanism, the closure process of the support crack under different normal effective stresses is simulated on the discrete element physical model of the real support crack. The wall migration velocity during the stress loading process is set according to the geostress parameters, and the crack parameters and proppant parameters during the closure process are derived. Based on the crack parameters and proppant parameters during the closure process, a computational fluid dynamics-discrete element coupled model was established. The CFD-DEM method was used to simulate the proppant crack conductivity on the computational fluid dynamics-discrete element coupled model, and the change in crack conductivity was calculated based on the simulation results.

2. The method for evaluating the conductivity of hydraulic fractures based on post-coring fracture reconstruction as described in claim 1, characterized in that, The steps of conducting post-fracturing coring or true triaxial hydraulic fracturing experiments in adjacent high-angle wells to obtain hydraulic fractures, and then performing CT scans on the hydraulic fractures, specifically include: The occurrence of groundwater hydraulic fractures can be obtained by coring the fracturing formation, or the morphology of hydraulic fractures can be obtained by true triaxial experiments. CT scans were performed on hydraulic fractures obtained by post-pressure coring or true triaxial experiments, with a scanning accuracy greater than 50 μm and a scanning size greater than 100 mm × 100 mm.

3. The method for evaluating the conductivity of hydraulic fractures based on post-coring fracture reconstruction as described in claim 1, characterized in that, The step of reconstructing the solid model of the hydraulic fracture under normal pressure based on the CT scan results specifically includes: The data obtained from the CT scan of the hydraulic fractures are processed, the fractures and proppant are classified and processed, and after noise reduction and segmentation algorithms, CAD data volume and STL data format are obtained. The STL data format completes the solid reconstruction of the fracture. The CAD data volume is exported as a point cloud data volume. Through this process, the crack surface entity data is exported as three-dimensional coordinate data. Based on the three-dimensional coordinate data, the relative spatial relationship of the coordinates is calculated to obtain the initial crack aperture and crack roughness.

4. The method for evaluating the conductivity of hydraulic fractures based on post-coring fracture reconstruction as described in claim 3, characterized in that, In the step of calculating the relative spatial relationship of coordinates based on three-dimensional coordinate data to obtain the initial crack aperture and crack roughness, the initial crack aperture... Calculate using the following formula: ； in, This represents the maximum height difference of the micro-protrusions on the crack surface; and These are the height values ​​of the micro-protrusions at the measurement points on the upper and lower seam surfaces, respectively, where 1 and 2 represent the upper and lower seam surfaces. These represent the serial numbers of the crack mesh along the x or y axis, respectively; , These represent the placement errors of the upper and lower crack surfaces when measuring the crack surface height data.

5. The method for evaluating the conductivity of hydraulic fractures based on post-coring fracture reconstruction as described in claim 3, characterized in that, In the step of calculating the relative spatial relationship of coordinates based on three-dimensional coordinate data to obtain the initial crack aperture and crack roughness, the crack roughness is based on the root mean square value of the micro-protrusion height. The root mean square value of the micro-convexity height was calculated. It was calculated based on the height of the micro-protrusions in the crack.

6. The method for evaluating the conductivity of hydraulic fractures based on post-coring fracture reconstruction as described in claim 4, characterized in that, The specific process of reconstructing proppant particles in the solid model of the hydraulic fracture based on the CT scan results includes: Determine whether the requirements for reconstruction proppant are met based on the CT scan results of the hydraulic fracture; When the CT scan results do not meet the reconstruction requirements, the proppant placement strength is calculated based on the CT scan results for proppant reconstruction. The proppant particle breakage model is designed as the Tavares breakage model. When the CT scan results meet the reconstruction requirements, the proppant is directly reconstructed inside the reconstructed crack entity model, and the proppant fracture model adopts the liner-bonding model.

7. The method for evaluating the conductivity of hydraulic fractures based on post-coring fracture reconstruction as described in claim 6, characterized in that, The proppant layup strength Calculate using the following formula: ； in, Indicates the volume occupied by the proppant; The radius of the CT scan core column; This represents the initial crack aperture.

8. The method for evaluating the conductivity of hydraulic fractures based on post-coring fracture reconstruction as described in any one of claims 1 to 7, characterized in that, In the step of setting the wall migration velocity during stress loading based on the ground stress parameters, the wall migration velocity... Calculate using the following formula: ； in, The effective stress applied to the proppant particles, The current average stress, Here, i is the intermediate parameter, and i is the simulation step size. Calculate using the following formula: ； in, As a relaxation factor, The effective area of ​​the wall. The average stiffness of the wall contact is... This represents the total number of contacts between the wall and the particles. To calculate the step size; Effective stress Calculate using the following formula: ； in, To determine the minimum principal stress obtained from the well logging curve, This represents the maximum pore pressure value during the simulation process. The value is the ratio of the two factors.

9. The method for evaluating the conductivity of hydraulic fractures based on post-coring fracture reconstruction as described in claim 4, characterized in that, When simulating the conductivity of supported fractures using the CFD-DEM method on a computational fluid dynamics-discrete element coupled model, an inlet and outlet pressure difference is set to simulate the flow of fractured proppant and fluid within the fracture. The fluid is assumed to be reservoir crude oil or natural gas, and then the fracture conductivity is calculated. The governing equations for the motion of the fractured proppant are as follows: ； in, and These are the normal contact force and the tangential contact force, respectively. For gravity, Applying the force of the particle to the fluid surrounding the particle. and These are the particle vector radius and the particle's additional torque, respectively. and They are translational velocity and rotational velocity, respectively. and Particle mass and moment of inertia, respectively; The fluid flow within the crack can be solved using the locally averaged Navier-Stokes equations: ； In the formula, This represents the volume fraction of fluid within the crack. The fluid density inside the crack, The fluid velocity within the crack, The pressure gradient at the crack inlet and outlet. Let be the fluid stress tensor, and t be the time step. This is the momentum exchange source term.

10. The method for evaluating the conductivity of hydraulic fractures based on post-coring fracture reconstruction as described in claim 9, characterized in that, Exporting crack parameters during the closure process includes the actual crack aperture. Changes in fracture conductivity Calculate using the following formula: ， ； in, The permeability of the crack; This represents the actual crack opening. To calculate the obtained export flow; The viscosity of the fluid within the crack; The length of the crack; Let be the cross-sectional area of ​​the crack.

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