A numerical simulation method and device for hydraulic fracture propagation in a heterogeneous reservoir

Abstract

The application discloses a numerical simulation method and device for hydraulic fracture propagation in a heterogeneous reservoir. The application uses PFC software to assemble particles to form rocks, which can restore the large deformation and gradual damage characteristics of rock and soil particles. The Fish function of the PFC software is used to write a script file to modify the cementing strength between rock particles in different regions when the reservoir rock is formed into a sample, thereby realizing the simulation of the heterogeneous cementing characteristics of the reservoir. The fluid domain opening of different regions is identified and controlled by using a fluid-structure coupling algorithm, thereby realizing the characteristics of the heterogeneous permeability of the reservoir. Finally, the numerical simulation of the hydraulic fracture propagation process in the heterogeneous reservoir can be realized by using the established heterogeneous hydraulic fracture propagation model. The method of the application can simulate the hydraulic fracture propagation process in the heterogeneous cementing reservoir and the heterogeneous permeability reservoir in the PFC discrete element software, thereby providing reliable simulation results for the hydraulic fracturing operation design.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development and production enhancement in petroleum engineering, and in particular to a numerical simulation method and apparatus for hydraulic fracturing fracture propagation in heterogeneous reservoirs. Background Technology

[0002] Hydraulic fracturing is currently the most important oil and gas production enhancement technology for unconventional oil and gas reservoir development. This technology primarily utilizes surface high-pressure pump units to pump fracturing fluid into the well at a rate exceeding the reservoir's absorption capacity, creating high pressure in the wellbore. When this pressure overcomes the in-situ stress near the wellbore and the tensile strength of the rock, the formation fractures. For fracturing technology, analyzing and summarizing the propagation laws of hydraulic fractures and studying their propagation trajectories are crucial for optimizing the design of hydraulic fracturing operation schemes. However, the strong heterogeneity of unconventional oil and gas reservoirs poses a significant obstacle to the numerical simulation of hydraulic fracture propagation. Traditional numerical simulation methods, including finite element method (FEM), extended finite element method (EBM), and boundary element method (BEM), have significant limitations in handling rock heterogeneity. Therefore, to date, there are few reports on numerical simulation methods for fracture propagation in heterogeneous reservoirs, and how to simulate hydraulic fracture propagation in heterogeneous reservoirs remains one of the challenges that engineering researchers need to overcome. Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention aims to provide a numerical simulation method and apparatus for hydraulic fracturing fracture propagation in heterogeneous reservoirs, thereby providing a reliable numerical tool for simulating and studying how hydraulic fractures propagate in heterogeneous reservoirs.

[0004] The technical solution adopted in this invention is as follows:

[0005] A numerical simulation method for fracture propagation in hydraulic fracturing of heterogeneous reservoirs includes the following steps:

[0006] Establish a numerical rock sample model for hydraulic fracturing: Set the particle size of the numerical rock sample model for hydraulic fracturing using the particle size distribution method of linear functions, calculate the number of particles corresponding to different particle sizes based on the porosity and size of the actual rock sample, and then establish a numerical rock sample model for hydraulic fracturing containing a smooth circular wellbore.

[0007] Sample generation of the numerical rock sample model for hydraulic fracturing: The established numerical rock sample model for hydraulic fracturing was generated using the LinearParallelBond cementation model. The heterogeneous cementation characteristics of the reservoir rock were simulated by writing a Fish function script file.

[0008] Calibration of parameters of hydraulic fracturing numerical rock sample model: The macroscopic mechanical parameters of the hydraulic fracturing numerical rock sample model that has been sampled are measured and calibrated using rock mechanics numerical simulation experiments with PFC software.

[0009] Confining pressure application to the hydraulic fracturing numerical rock sample model: The in-situ stress field, including the maximum and minimum horizontal principal stresses at the application boundary, is applied to the hydraulic fracturing numerical rock sample model that has been parameter-calibrated using the servo mechanism of PFC software.

[0010] Establishment of seepage network for hydraulic fracturing numerical rock sample model: First, the permeability of the hydraulic fracturing numerical rock sample model with applied confining pressure was calibrated using Darcy's flow simulation experiment in PFC software to obtain permeability values ​​of the hydraulic fracturing numerical rock sample model corresponding to different initial openings; then, a fluid domain network was generated in the hydraulic fracturing numerical rock sample model using the fluid-structure interaction algorithm in PFC software. A script file was written using the Fish function to control and identify the initial opening of the fluid domain network in different regions, thereby simulating the heterogeneous permeability characteristics of the reservoir rock;

[0011] Setting the injection conditions in the wellbore of the hydraulic fracturing numerical rock sample model: Using the Fish function file, select the wellbore of the hydraulic fracturing numerical rock sample model with the established seepage network as the injection point, and then inject fracturing fluid. Select the outer boundary of the hydraulic fracturing numerical rock sample model as the free flow boundary and keep the pressure constant at 0 MPa.

[0012] Simulation of hydraulic fracture propagation in numerical rock sample model: By using injection conditions to start pressurizing the wellbore of the hydraulic fracturing numerical rock sample model, and combining the frcature.p2fis function file, the hydraulic fractures of the entire hydraulic fracturing numerical rock sample model are identified and monitored in real time, thereby simulating the hydraulic fracturing fracture propagation process in heterogeneous reservoirs.

[0013] Preferably, let the number of stages of the particle size distribution of the linear function be n, and the particle size of the i-th stage be r. i Then the number of particles that the i-th level particle should generate Using the ballcreate function command, the smallest particles are arranged and assembled into a smooth ring at the center of the rock sample, thus forming a wellbore;

[0014] Where φ is the porosity of the rock in the actual rock sample, L is the length of the actual rock sample, and W is the width of the actual rock sample.

[0015] Preferably, the heterogeneous cementation characteristics of the reservoir rocks include vertical reservoir heterogeneous cementation characteristics and lateral reservoir heterogeneous cementation characteristics.

[0016] The implementation methods for vertical and lateral reservoir heterogeneous cementation characteristics include: grouping particles using the ballgroup command, identifying the groups using the rangegroup command, and assigning grouped cementation properties using the contactproperty command, thereby simulating the vertical and lateral reservoir heterogeneous cementation characteristics.

[0017] Preferably, the process for achieving randomly distributed reservoir heterogeneity includes:

[0018] The contact.list command is used to iterate through the contact bonding of all particles and generate a random number m between 0 and 1. Then, the initial values ​​of the cementation properties tensile strength pb_ten, cohesion pb_coh, and internal friction coefficient pb_fa are multiplied by the random number using the contact.prop function is used to assign random values. Finally, the contact bonding properties of all particles are randomly assigned in a loop, thereby simulating the reservoir heterogeneity of randomly distributed cementation strength.

[0019] Preferably, when measuring and calibrating the macroscopic mechanical parameters of the hydraulic fracturing numerical rock sample model that has been prepared using the rock mechanics numerical simulation experiment of PFC software, the macroscopic mechanical parameters include: Poisson's ratio, Young's modulus and tensile strength.

[0020] Preferably, the process of controlling and identifying the initial opening of the fluid domain network in different regions by writing a script file using the Fish function, thereby simulating the heterogeneous permeability characteristics of reservoir rocks, includes:

[0021] The contact.list command is used to traverse the contact bonds of all particles and identify the coordinates of the contact bonds of the particles corresponding to the pointer cp. Then, the region where the coordinates of the contact bonds of the particles corresponding to the pointer cp are located is divided according to the characteristics of heterogeneous permeability. Finally, the initial aperture value is assigned to each region with different permeability based on the calibration results of the initial aperture, thereby realizing the simulation of the heterogeneous permeability characteristics of reservoir rocks.

[0022] Preferably, the wellbore of the hydraulic fracturing numerical rock sample model with the established seepage network is selected as the injection point using the Fish function file. Then, when injecting fracturing fluid, the fracturing fluid is injected at a constant pressure or a constant flow rate according to the engineering requirements.

[0023] When injecting fracturing fluid at a constant flow rate, the safety threshold P_safe for wellbore pressure is set to be equal to the tensile strength of the casing. Then, the DOM_PRESS function is used to monitor the pressure in real time during the wellbore injection process. The math.min function is used to determine whether the wellbore pressure at each time step exceeds the P_safe value. When the wellbore pressure exceeds the P_safe value, the wellbore pressure will not change further, and the hydraulic fracturing simulation will continue at a constant pressure.

[0024] The present invention also provides a numerical simulation device for hydraulic fracturing fracture propagation in heterogeneous reservoirs, comprising:

[0025] Numerical simulation module, used for:

[0026] Establish a numerical rock sample model for hydraulic fracturing: Set the particle size of the numerical rock sample model for hydraulic fracturing using the particle size distribution method of linear functions, calculate the number of particles corresponding to different particle sizes based on the porosity and size of the actual rock sample, and then establish a numerical rock sample model for hydraulic fracturing containing a smooth circular wellbore.

[0027] Sample generation of the numerical rock sample model for hydraulic fracturing: The established numerical rock sample model for hydraulic fracturing was generated using the LinearParallelBond cementation model. The heterogeneous cementation characteristics of the reservoir rock were simulated by writing a Fish function script file.

[0028] Calibration of parameters of hydraulic fracturing numerical rock sample model: The macroscopic mechanical parameters of the hydraulic fracturing numerical rock sample model that has been sampled are measured and calibrated using rock mechanics numerical simulation experiments with PFC software.

[0029] Confining pressure application to the hydraulic fracturing numerical rock sample model: The in-situ stress field, including the maximum and minimum horizontal principal stresses at the application boundary, is applied to the hydraulic fracturing numerical rock sample model that has been parameter-calibrated using the servo mechanism of PFC software.

[0030] Establishment of seepage network for hydraulic fracturing numerical rock sample model: First, the permeability of the hydraulic fracturing numerical rock sample model with applied confining pressure was calibrated using Darcy's flow simulation experiment in PFC software to obtain permeability values ​​of the hydraulic fracturing numerical rock sample model corresponding to different initial openings; then, a fluid domain network was generated in the hydraulic fracturing numerical rock sample model using the fluid-structure interaction algorithm in PFC software. A script file was written using the Fish function to control and identify the initial opening of the fluid domain network in different regions, thereby simulating the heterogeneous permeability characteristics of the reservoir rock;

[0031] Setting the injection conditions in the wellbore of the hydraulic fracturing numerical rock sample model: Using the Fish function file, select the wellbore of the hydraulic fracturing numerical rock sample model with the established seepage network as the injection point, and then inject fracturing fluid. Select the outer boundary of the hydraulic fracturing numerical rock sample model as the free flow boundary and keep the pressure constant at 0 MPa.

[0032] Simulation of hydraulic fracture propagation in numerical rock sample model: By using injection conditions to start pressurizing the wellbore of the hydraulic fracturing numerical rock sample model, and combining the frcature.p2fis function file, the hydraulic fractures of the entire hydraulic fracturing numerical rock sample model are identified and monitored in real time, thereby simulating the hydraulic fracturing fracture propagation process in heterogeneous reservoirs.

[0033] The present invention also provides an electronic device, comprising:

[0034] One or more processors;

[0035] A storage device on which one or more programs are stored;

[0036] When the one or more programs are executed by the one or more processors, the one or more processors implement the numerical simulation method for fracture propagation in heterogeneous reservoir hydraulic fracturing as described above.

[0037] The present invention also provides a storage medium on which a computer program is stored, wherein the computer program, when executed by a processor, implements the numerical simulation method for fracture propagation in heterogeneous reservoir hydraulic fracturing as described above.

[0038] The present invention has the following beneficial effects:

[0039] This invention establishes a numerical simulation method for fracture propagation in hydraulic fracturing of heterogeneous reservoirs. This method can simulate the heterogeneous cementation strength and heterogeneous permeability of reservoirs. Based on this method, the propagation law of hydraulic fractures in heterogeneous reservoirs can be studied and analyzed, and the propagation trajectory of hydraulic fractures in heterogeneous reservoirs can be identified, thereby providing guidance for the optimized design of hydraulic fracturing construction schemes in oilfields. Attached Figure Description

[0040] Figure 1 This is a flowchart of the numerical simulation method for fracture propagation in hydraulic fracturing of heterogeneous reservoirs according to the present invention.

[0041] Figure 2 This is a numerical rock sample model for hydraulic fracturing including a wellbore in an embodiment of the present invention (Ball raius represents the grain size).

[0042] Figure 3 This is a numerical rock sample model of a heterogeneous cementation strength reservoir in this embodiment of the invention (Contact pb_ten represents the cementation strength of the rock).

[0043] Figure 4 This is a schematic diagram of the heterogeneous permeability characteristics of a numerical rock sample model in an embodiment of the present invention.

[0044] Figure 5 Numerical simulation results of hydraulic fracture propagation in heterogeneous cemented reservoirs in this embodiment of the invention (black lines represent fractures). Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0046] The principle of this invention is as follows: The key to numerical simulation of fracture propagation in heterogeneous reservoirs lies in how to realize the heterogeneity of the reservoir using numerical simulation methods. The Discrete Element Method (PFC) is a discontinuous numerical simulation method that uses particles to assemble rocks, realistically reproducing the large deformation and gradual failure characteristics of soil and rock particles. Based on this, this invention uses the Fish function of PFC software to write a script file to simulate the heterogeneous cementation characteristics of the reservoir by modifying the cementation strength between rock particles in different regions during reservoir rock cementation. It also uses a fluid-structure interaction algorithm to identify and control the fluid domain opening in different regions, thereby realizing the characteristics of heterogeneous permeability in the reservoir. Finally, the established heterogeneous hydraulic fracture propagation model can be used to numerically simulate the hydraulic fracture propagation process in heterogeneous reservoirs.

[0047] The specific technical solution of the present invention is as follows:

[0048] See Figure 1 The numerical simulation method for fracture propagation in hydraulic fracturing of heterogeneous reservoirs according to the present invention includes the following steps:

[0049] Step 1: Acquisition of Macroscopic Parameters from Actual Rock Samples for Hydraulic Fracturing: Acquire macroscopic parameters from actual rock samples, including reservoir in-situ stress parameters: maximum horizontal principal stress S. H Minimum horizontal principal stress S h Basic physical properties of the rock: porosity φ; rock sample dimensions: length L, width W;

[0050] Step 2: Establishment of numerical rock sample model for hydraulic fracturing: The particle size of the numerical rock sample model for hydraulic fracturing is set by using the particle size distribution method of linear function. The number of particles corresponding to different particle sizes is calculated by combining the porosity and size of the actual rock sample. Then, a numerical rock sample model for hydraulic fracturing containing a smooth circular wellbore is established based on PFC discrete element software.

[0051] Specifically, in step 2, let n be the number of stages in the linear gradation method, and let r be the particle size of the i-th stage. i Then the number of particles that the i-th level particle should generate The ballcreate function command is used to arrange the smallest particles into a smooth ring at the center of the rock sample, thus forming a wellbore and avoiding unnecessary stress concentration around the wellbore due to the roughness of the well wall.

[0052] Step 3: Sample generation of the hydraulic fracturing numerical rock sample model: The hydraulic fracturing numerical rock sample model is generated using the LinearParallelBond cementation model. The heterogeneous cementation characteristics of the reservoir rock are simulated by writing a Fish function script file. Specifically, the heterogeneous cementation characteristics of the reservoir rock include vertical and lateral reservoir heterogeneous cementation characteristics. The implementation of vertical and lateral reservoir heterogeneous cementation characteristics is as follows: First, the ballgroup command is used to group the particles. Then, the rangegroup command is used to identify the grouping and the contactproperty command is used to assign values ​​to the cementation properties of the particles, thereby simulating the vertical and lateral reservoir heterogeneous cementation.

[0053] The reservoir heterogeneity with randomly distributed cementation strength is realized as follows: First, the contact.list command is used to traverse the contact bonding of all particles and generate a random number m between 0 and 1. Then, the initial values ​​of the cementation properties tensile strength pb_ten, cohesion pb_coh, and internal friction coefficient pb_fa are multiplied by the random number to randomly assign values. Finally, the contact bonding properties of all particles are randomly assigned values ​​through iterative loops, thereby simulating the reservoir heterogeneity with randomly distributed cementation strength.

[0054] Step 4: Calibration of parameters for the hydraulic fracturing numerical rock sample model: The macroscopic mechanical parameters of the prepared hydraulic fracturing numerical rock sample model are measured and calibrated using rock mechanics numerical simulation experiments with PFC software. These macroscopic mechanical parameters include Poisson's ratio ν, Young's modulus E, and tensile strength σ. t ;

[0055] Step 5: Applying confining pressure to the hydraulic fracturing numerical rock sample model: Using the servo mechanism of PFC software, apply the in-situ stress field to the hydraulic fracturing numerical rock sample model, including the maximum horizontal principal stress S at the boundary. H and minimum horizontal principal stress S h ;

[0056] Step 6: Establishment of the seepage network for the hydraulic fracturing numerical rock sample model: First, the permeability of the hydraulic fracturing numerical rock sample model is calibrated using Darcy's flow simulation experiments in PFC software, thereby obtaining different initial apertures w. o The permeability value K of the corresponding hydraulic fracturing numerical rock sample model oThen, the fluid-structure interaction algorithm of PFC software is used to generate a fluid domain network in the hydraulic fracturing numerical rock sample model. A script file is written using the Fish function to control and identify the initial opening degree of the fluid domain network in different regions, thereby simulating the heterogeneous permeability characteristics of the reservoir rock. The implementation method of the reservoir heterogeneous permeability characteristics is as follows: First, the contact.list command is used to traverse the contact bonds of all particles, identifying the coordinates (x, y) of the contact bond corresponding to the particle at pointer cp; then, the region at coordinates (x, y) is divided according to the characteristics of heterogeneous permeability; finally, the initial opening degree w is used... o The calibration results are used to assign initial aperture values ​​to regions with different permeability, thereby ultimately simulating the heterogeneous permeability characteristics of the reservoir.

[0057] Step 7: Setting the injection conditions for the hydraulic fracturing numerical rock sample model wellbore: Use the Fish function file to select the wellbore of the hydraulic fracturing numerical rock sample model as the injection point. Then, inject fracturing fluid at a constant pressure or constant flow rate according to engineering needs. Select the outer boundary of the hydraulic fracturing numerical rock sample model as the free flow boundary with a constant pressure of 0 MPa. If a constant flow rate is used to inject fracturing fluid, the safety threshold P_safe of the wellbore pressure needs to be set to the tensile strength value of the casing. Then, use the DOM_PRESS function to monitor the pressure in real time during the wellbore injection process. Use the math.min function to determine whether the wellbore pressure at each time step exceeds the P_safe value. When the wellbore pressure exceeds the P_safe value, the wellbore pressure will no longer change, and the hydraulic fracturing simulation will continue at a constant pressure.

[0058] Step 8: Simulation of hydraulic fracture propagation in the hydraulic fracturing numerical rock sample model: Using the injection conditions set in Step 7, pressure is initially built up in the wellbore of the hydraulic fracturing numerical rock sample model. The hydraulic fractures in the entire hydraulic fracturing numerical rock sample model are identified and monitored in real time using the frcature.p2fis function file, thereby simulating the hydraulic fracture propagation process.

[0059] The method of this invention can be used to simulate the hydraulic fracture propagation process in heterogeneous cemented reservoirs and heterogeneous permeable reservoirs in PFC discrete element software, thereby providing reliable simulation results for hydraulic fracturing construction design.

[0060] Example:

[0061] The numerical simulation method for fracture propagation in heterogeneous reservoir hydraulic fracturing in this embodiment includes the following steps:

[0062] Step (1): Establish a hydraulic fracturing numerical rock sample model with a length and width of 0.25m to conduct numerical simulation of reservoir fracture propagation based on heterogeneous cementation strength. Collect the macroscopic parameters of the actual rock samples required, including reservoir in-situ stress parameters: maximum horizontal principal stress S0. H =20MPa, minimum horizontal principal stress S h =10MPa; Basic physical properties of rock: Porosity φ = 0.15.

[0063] Step (2) uses the particle size distribution method of a linear function to assemble a numerical rock sample model for hydraulic fracturing containing a circular wellbore, such as... Figure 2 As shown, the macroscopic mechanical parameters of the hydraulic fracturing numerical rock sample model were measured and calibrated using PFC software-based rock mechanics numerical simulation experiments. The results are as follows: Young's modulus E = 42.72 GPa; Poisson's ratio ν = 0.20; and the tensile strength σ of the rock is... t 8.76 MPa

[0064] Step (3) establishes a heterogeneous cemented strength reservoir model based on the hydraulic fracturing numerical rock sample model by using the fish function to control the cementation strength, such as... Figure 3 As shown, the upper half of the heterogeneous cementation strength reservoir model is strongly cemented (Contactpb_ten = 12MPa), the lower half is weakly cemented (Contactpb_ten = 9MPa), and the cementation strength around the wellbore is set to the maximum (Contactpb_ten = 15MPa) due to the compaction zone.

[0065] Step (4): Using a servo mechanism, confining pressure is applied to the established numerical rock samples according to the collected macroscopic geostress parameters, and minimum horizontal principal stress S is applied to the surfaces of the upper and lower numerical rock samples. h =10MPa; Approximately the maximum horizontal principal stress S applied to the surface of the rock sample. H =20MPa.

[0066] Step (5): The permeability of the hydraulic fracturing numerical rock sample model was calibrated using Darcy flow simulation experiments in PFC software. The calibration result is the fluid domain channel opening w corresponding to 220mD in the high-permeability reservoir. o The fluid domain channel opening w1 for a low-permeability reservoir with a permeability of 10 mD is 0.00022; the permeability of the compacted zone around the wellbore is 2 mD, and the corresponding fluid domain channel opening w2 is 0.0001.

[0067] A fluid domain network was generated in a hydraulic fracturing numerical rock sample model using the fluid-structure interaction algorithm in PFC software. Then, using the calibration results of the fluid domain channel opening, the initial opening w of the fluid domain network in different cemented regions was assigned through the Fish function. oFor strongly cemented reservoirs, w1 corresponds to weakly cemented reservoirs; w2 corresponds to the wellbore compaction zone. Then, the heterogeneous permeability characteristics of the reservoir rocks are simulated, such as... Figure 4 As shown, the upper side of the numerical rock sample is a low-permeability region, and the lower side is a high-permeability region.

[0068] Step (6): Select the wellbore as the injection point and inject fracturing fluid at a constant pressure of 32 MPa. Select the outer boundary of the hydraulic fracturing numerical rock sample model as the free flow boundary and keep the pressure constant at 0 MPa.

[0069] Step (7) involves using the frcature.p2fis function file to perform real-time identification and monitoring of hydraulic fractures in the entire hydraulic fracturing numerical rock sample model, simulating the hydraulic fracture propagation process in heterogeneous cemented reservoirs. The simulation results are as follows: Figure 5 As shown. Figure 5 As shown, the hydraulic fractures extend along the direction of the maximum horizontal principal stress after they originate from the wellbore. During the extension process, the fractures on the left and right sides are deflected due to the heterogeneity of the rock sample.

Claims

1. A numerical simulation method for fracture propagation in hydraulic fracturing of heterogeneous reservoirs, characterized in that, The process includes the following: Establish a numerical rock sample model for hydraulic fracturing: Set the particle size of the numerical rock sample model for hydraulic fracturing using the particle size distribution method of linear functions, calculate the number of particles corresponding to different particle sizes based on the porosity and size of the actual rock sample, and then establish a numerical rock sample model for hydraulic fracturing containing a smooth circular wellbore. Sample generation of the numerical rock sample model for hydraulic fracturing: The established numerical rock sample model for hydraulic fracturing was generated using the LinearParallelBond cementation model. The heterogeneous cementation characteristics of the reservoir rock were simulated by writing a Fish function script file. Calibration of parameters of hydraulic fracturing numerical rock sample model: The macroscopic mechanical parameters of the hydraulic fracturing numerical rock sample model that has been sampled are measured and calibrated using rock mechanics numerical simulation experiments with PFC software. Confining pressure application to the hydraulic fracturing numerical rock sample model: The in-situ stress field, including the maximum and minimum horizontal principal stresses at the application boundary, is applied to the hydraulic fracturing numerical rock sample model that has been parameter-calibrated using the servo mechanism of PFC software. Establishment of seepage network for hydraulic fracturing numerical rock sample model: First, the permeability of the hydraulic fracturing numerical rock sample model with applied confining pressure was calibrated using Darcy's flow simulation experiment in PFC software to obtain permeability values ​​of the hydraulic fracturing numerical rock sample model corresponding to different initial openings; then, a fluid domain network was generated in the hydraulic fracturing numerical rock sample model using the fluid-structure interaction algorithm in PFC software. A script file was written using the Fish function to control and identify the initial opening of the fluid domain network in different regions, thereby simulating the heterogeneous permeability characteristics of the reservoir rock; Setting the injection conditions in the wellbore of the hydraulic fracturing numerical rock sample model: Using the Fish function file, select the wellbore of the hydraulic fracturing numerical rock sample model with the established seepage network as the injection point, and then inject fracturing fluid. Select the outer boundary of the hydraulic fracturing numerical rock sample model as the free flow boundary and keep the pressure constant at 0 MPa. Simulation of hydraulic fracture propagation in numerical rock sample model: By using injection conditions to start pressurizing the wellbore of the hydraulic fracturing numerical rock sample model, and combining the frcature.p2fis function file, the hydraulic fractures of the entire hydraulic fracturing numerical rock sample model are identified and monitored in real time, thereby simulating the hydraulic fracturing fracture propagation process in heterogeneous reservoirs.

2. The numerical simulation method for fracture propagation in hydraulic fracturing of heterogeneous reservoirs according to claim 1, characterized in that, Let the number of stages of the particle size distribution of the linear function be n, and the particle size of the i-th stage be r. i Then the number of particles that the i-th level particle should generate Using the ballcreate function command, the smallest particles are arranged and assembled into a smooth ring at the center of the rock sample, thus forming a wellbore; Where φ is the porosity of the rock in the actual rock sample, L is the length of the actual rock sample, and W is the width of the actual rock sample.

3. The numerical simulation method for fracture propagation in hydraulic fracturing of heterogeneous reservoirs according to claim 1, characterized in that, The heterogeneous cementation characteristics of reservoir rocks include vertical reservoir heterogeneous cementation characteristics and lateral reservoir heterogeneous cementation characteristics. The implementation methods for vertical and lateral reservoir heterogeneous cementation characteristics include: grouping particles using the ballgroup command, identifying the groups using the rangegroup command, and assigning grouped cementation properties using the contactproperty command, thereby simulating the vertical and lateral reservoir heterogeneous cementation characteristics.

4. The numerical simulation method for fracture propagation in hydraulic fracturing of heterogeneous reservoirs according to claim 1, characterized in that, The process of achieving randomly distributed reservoir heterogeneity includes: The contact.list command is used to iterate through the contact bonding of all particles and generate a random number m between 0 and 1. Then, the initial values ​​of the cementation properties tensile strength pb_ten, cohesion pb_coh, and internal friction coefficient pb_fa are multiplied by the random number using the contact.prop function is used to assign random values. Finally, the contact bonding properties of all particles are randomly assigned in a loop, thereby simulating the reservoir heterogeneity of randomly distributed cementation strength.

5. The numerical simulation method for fracture propagation in hydraulic fracturing of heterogeneous reservoirs according to claim 1, characterized in that, When measuring and calibrating the macroscopic mechanical parameters of the hydraulic fracturing numerical rock sample model that has been prepared using PFC software, the macroscopic mechanical parameters include: Poisson's ratio, Young's modulus, and tensile strength.

6. The numerical simulation method for fracture propagation in hydraulic fracturing of heterogeneous reservoirs according to claim 1, characterized in that, The process of controlling and identifying the initial opening of the fluid domain network in different regions by writing script files using the Fish function, thereby simulating the heterogeneous permeability characteristics of reservoir rocks, includes: The contact.list command is used to traverse the contact bonds of all particles and identify the coordinates of the contact bonds of the particles corresponding to the pointer cp. Then, the region where the coordinates of the contact bonds of the particles corresponding to the pointer cp are located is divided according to the characteristics of heterogeneous permeability. Finally, the initial aperture value is assigned to each region with different permeability based on the calibration results of the initial aperture, thereby realizing the simulation of the heterogeneous permeability characteristics of reservoir rocks.

7. The numerical simulation method for fracture propagation in hydraulic fracturing of heterogeneous reservoirs according to claim 1, characterized in that, Using the Fish function file, select the wellbore of the hydraulic fracturing numerical rock sample model with the established seepage network as the injection point. Then, when injecting fracturing fluid, inject the fracturing fluid at a constant pressure or a constant flow rate according to the engineering requirements. When injecting fracturing fluid at a constant flow rate, the safety threshold P_safe for wellbore pressure is set to be equal to the tensile strength of the casing. Then, the DOM_PRESS function is used to monitor the pressure in real time during the wellbore injection process. The math.min function is used to determine whether the wellbore pressure at each time step exceeds the P_safe value. When the wellbore pressure exceeds the P_safe value, the wellbore pressure will not change further, and the hydraulic fracturing simulation will continue at a constant pressure.

8. A numerical simulation device for hydraulic fracturing fracture propagation in heterogeneous reservoirs, characterized in that, include: Numerical simulation module, used for: Establish a numerical rock sample model for hydraulic fracturing: Set the particle size of the numerical rock sample model for hydraulic fracturing using the particle size distribution method of linear functions, calculate the number of particles corresponding to different particle sizes based on the porosity and size of the actual rock sample, and then establish a numerical rock sample model for hydraulic fracturing containing a smooth circular wellbore. Sample generation of the numerical rock sample model for hydraulic fracturing: The established numerical rock sample model for hydraulic fracturing was generated using the LinearParallelBond cementation model. The heterogeneous cementation characteristics of the reservoir rock were simulated by writing a Fish function script file. Calibration of parameters of hydraulic fracturing numerical rock sample model: The macroscopic mechanical parameters of the hydraulic fracturing numerical rock sample model that has been sampled are measured and calibrated using rock mechanics numerical simulation experiments with PFC software. Confining pressure application to the hydraulic fracturing numerical rock sample model: The in-situ stress field, including the maximum and minimum horizontal principal stresses at the application boundary, is applied to the hydraulic fracturing numerical rock sample model that has been parameter-calibrated using the servo mechanism of PFC software. Establishment of seepage network for hydraulic fracturing numerical rock sample model: First, the permeability of the hydraulic fracturing numerical rock sample model with applied confining pressure was calibrated using Darcy's flow simulation experiment in PFC software to obtain permeability values ​​of the hydraulic fracturing numerical rock sample model corresponding to different initial openings; then, a fluid domain network was generated in the hydraulic fracturing numerical rock sample model using the fluid-structure interaction algorithm in PFC software. A script file was written using the Fish function to control and identify the initial opening of the fluid domain network in different regions, thereby simulating the heterogeneous permeability characteristics of the reservoir rock; Setting the injection conditions in the wellbore of the hydraulic fracturing numerical rock sample model: Using the Fish function file, select the wellbore of the hydraulic fracturing numerical rock sample model with the established seepage network as the injection point, and then inject fracturing fluid. Select the outer boundary of the hydraulic fracturing numerical rock sample model as the free flow boundary and keep the pressure constant at 0 MPa. Simulation of hydraulic fracture propagation in numerical rock sample model: By using injection conditions to start pressurizing the wellbore of the hydraulic fracturing numerical rock sample model, and combining the frcature.p2fis function file, the hydraulic fractures of the entire hydraulic fracturing numerical rock sample model are identified and monitored in real time, thereby simulating the hydraulic fracturing fracture propagation process in heterogeneous reservoirs.

9. An electronic device, characterized in that, include: One or more processors; A storage device on which one or more programs are stored; When the one or more programs are executed by the one or more processors, the one or more processors implement the numerical simulation method for hydraulic fracturing fracture propagation in heterogeneous reservoirs as described in any one of claims 1 to 7.

10. A storage medium, characterized in that, It stores a computer program, wherein the computer program, when executed by a processor, implements the numerical simulation method for hydraulic fracturing fracture propagation in heterogeneous reservoirs as described in any one of claims 1 to 7.

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