Fracturing method for reducing stress interference between horizontal well fractures

Abstract

The invention discloses a fracturing method for reducing stress interference between horizontal well fractures, and belongs to the technical field of fracturing transformation in the petroleum and natural gas industry. The method comprises the steps that firstly, a plane of a main fracture with the best extension is selected to be dispersed into a rectangular grid, and the theoretical width and the theoretical radius of the main fracture are solved and obtained by constructing a fracturing plane hydraulic fracturing fracture equation; a simulation experiment is carried out according to the actual expansion condition of the main fracture, and the actual width and the actual radius of the main fracture are obtained by adjusting fracturing parameters; and finally, fitting the actual width and the actual radius of the main crack with the theoretical width and the theoretical radius respectively, and when the actual width and the actual radius of the main crack are matched with the theoretical width and the theoretical radius respectively, obtaining the optimal fracturing parameter for reducing the stress interference between the horizontal well cracks. Finally, the optimal fracturing parameters are used for fracturing, and the purpose of effectively reducing the stress interference between the horizontal well fractures can be achieved.

Description

Technical Field

[0001] This invention belongs to the field of fracturing technology in the oil and gas industry, specifically relating to a fracturing method for reducing stress interference between horizontal well fractures. Background Technology

[0002] Fracturing is an important extraction technology for oil and gas fields. Under complex geological conditions, it involves injecting fracturing fluid and proppant into the formation to further connect oil and gas channels, thereby increasing recovery rates. In areas with poor oil and gas reservoir conditions, fracturing technology can be used to increase oil and natural gas production.

[0003] my country's oil and gas fields are generally characterized by deep burial depths and complex formation environments. Therefore, continuous optimization and innovation of fracturing technology largely determines the development efficiency of challenging oil and gas fields. Currently, most of my country's oil and gas fields are developed using hydraulic fracturing technology. However, many problems exist in practical applications, such as inconsistent fracturing effects, communication between perforation clusters, and some perforation clusters failing to produce effective fracture lengths or even fail to initiate fracturing.

[0004] Domestic research addressing the inconsistent fracturing effects focuses on establishing and optimizing fracturing models. For example, patent document CN117010223A discloses an optimized design method for segmented multi-cluster fracturing in deep shale horizontal wells. This method includes: collecting fracturing parameters; establishing a natural fracture model of the shale reservoir; establishing a fluid-structure interaction model of the stress field and flow field in segmented multi-cluster fracturing of the horizontal well; establishing a flow distribution model between multiple fracture clusters during simultaneous expansion; establishing a model of the interaction between hydraulic fractures and natural fractures; establishing a model of simultaneous expansion of multiple fractures in segmented multi-cluster fracturing; establishing a dynamic mathematical model for the expansion of multiple fractures in segmented multi-cluster fracturing of the horizontal well, considering the effects of natural fractures, inter-fracture stress interference, and complex flow distribution; and optimizing the completion and construction parameters for segmented multi-cluster fracturing of deep shale horizontal wells based on the established mathematical model and the collected parameters. This method optimizes the completion and construction parameters for multi-cluster fracturing in deep shale horizontal wells, overcoming the deficiency of using average values ​​for branch flow rates under fracture bifurcation in existing technologies. It also compensates for the lack of consideration for inter-fracture stress interference in the interaction criterion between hydraulic and natural fractures under multiple fracture influences. However, careful analysis reveals the following technical problems:

[0005] 1. The results simulated by this method cannot be verified by actual experiments, and whether the model can truly reflect the state of formation fracture propagation needs further research.

[0006] 2. The basic models in this method are a fluid model and a stress field model. However, during the coupling process, the disturbance of the reservoir stress field by the change of fracturing fluid flow state is not considered, which still leads to insufficient optimization. Summary of the Invention

[0007] The purpose of this invention is to overcome the aforementioned problems in the prior art and provide a fracturing method to reduce stress interference between horizontal well fractures. This invention first selects the plane of the main fracture with the best extension and discretizes it into a rectangular grid. By constructing the hydraulic fracturing fracture equation for the fracturing plane, the theoretical width and radius of the main fracture are solved and obtained. Then, simulation experiments are conducted based on the actual expansion of the main fracture, and the actual width and radius of the main fracture are obtained by adjusting the fracturing parameters. Finally, the actual width and radius of the main fracture are fitted with the theoretical width and radius, respectively. When the actual width and radius of the main fracture match the theoretical width and radius, the optimal fracturing parameters for reducing stress interference between horizontal well fractures are obtained. Finally, fracturing using the optimal fracturing parameters can effectively reduce stress interference between horizontal well fractures.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A fracturing method for reducing stress interference between horizontal well fractures includes the following steps:

[0010] Step S1: Divide the horizontal section of the horizontal well into several perforation clusters. Each perforation cluster contains several blast holes and produces at least one main fracture.

[0011] Step S2: Select the plane with the best-extended main fracture from all the holes in each perforation cluster as the fracturing plane, and discretize the fracturing plane into a rectangular grid;

[0012] Step S3: Simplify the propagation length of the main fracture in each direction into plane stress vector displacement, and characterize the propagation length of the main fracture using plane stress vector displacement within a rectangular grid; then, combine the Caterpillar filtration equation and filtration experiments to establish the plane hydraulic fracturing fracture equation;

[0013] Step S4: Solve the plane hydraulic fracturing fracture equation using the Newton-Raphson iterative method to obtain the theoretical width and theoretical radius of the main fracture;

[0014] Step S5: Conduct a simulation experiment based on the actual propagation of the main fracture, and determine the actual width and radius of the main fracture by adjusting the fracturing parameters;

[0015] Step S6: Fit the actual width and radius of the main fracture to the theoretical width and radius respectively. When the actual width and radius of the main fracture match the theoretical width and radius respectively, determine the optimal fracturing parameters. Then, using the optimal fracturing parameters can reduce stress interference between horizontal well fractures.

[0016] In step S1, the reservoir of the horizontal well meets the following conditions: the reservoir depth is 1500-2500m, the matrix permeability is 0.10-0.15mD, the porosity is 5%-15%, the oil saturation is 70%-75%, the formation pressure distribution range is 15-17MPa, and the pressure coefficient is distributed between 0.77-0.84.

[0017] In step S1, it is assumed that the fluid from the perforation cluster completely enters the fracture. Ignoring the fluid compression, the displacement into each fracture satisfies the following condition:

[0018] ∑Q k =Q c k = 1, 2, 3, ..., Number of perforation clusters (1)

[0019] In equation (1), Qc is the total displacement injected into the wellbore, and Qk is the displacement entering each fracture.

[0020] In step S1, the wellbore pressure at each perforation cluster is set to be equal. Without considering the pressure loss of the fracturing fluid in the fracturing section, the wellbore pressure satisfies the following condition:

[0021] P w =P r,k +P in,k k = 1, 2, 3, ..., Number of perforation clusters (2)

[0022] In equation (2), P in,k This is to prevent flow friction from occurring inside the crack during crack propagation; P r,k This refers to the perforation pressure loss generated when fracturing fluid flows through the perforation cluster.

[0023] In step S2, the fracturing plane satisfies the following settings: rock fracture propagation is elastobrittle fracture, hydraulic fracture propagation is planar propagation, filtration mode follows the Cattell filtration equation, flow pressure loss of fracturing fluid in the wellbore is negligible, the wellbore direction is along the direction of minimum horizontal principal stress, the brittleness index is between 15% and 70%, with an average of 45%, and the horizontal stress difference is between 2 and 7 MPa, with an average of 5 MPa.

[0024] In step S2, the method for discretizing the fracturing plane into a rectangular grid is as follows: taking the center point of the fracturing plane as the origin of the coordinate system, the fracturing plane is evenly divided into vertical and horizontal lines in the X and Y directions, thus completing the discretization of the fracturing plane into a rectangular grid.

[0025] In step S3, the method of characterizing the propagation length of the main fracture using plane stress vector displacement within the rectangular grid is as follows: different colors are used to represent the fracture tip unit, fracture channel unit, and inactive unit within the fracturing plane within the rectangular grid. The fracture channel unit and fracture tip unit corresponding to the main fracture are determined. The propagation length of the main fracture is characterized by plane stress vector displacement based on the coordinate origin and the determined fracture channel unit and fracture tip unit.

[0026] In step S3, when the main crack is a three-dimensional planar crack, the shear displacement of the crack surface is not calculated, and the planar stress vector displacement in each direction of the crack surface is simplified only for the discontinuity of the normal displacement perpendicular to the crack surface.

[0027] In step S3, the established plane hydraulic fracturing fracture equation is as follows:

[0028]

[0029] In equation (3), p(x,y,z) is the fluid pressure within the main fracture, in Pa; σ h (x,y,z) represents the in-situ stress perpendicular to the main fracture, in Pa; w l The opening width of the main crack, in meters; C(x, y, z) is the stress influence coefficient of the main crack on the point (x, y, z), dimensionless; P l * The stress difference, in N / m, acts on the opening width of the main crack.

[0030] In step S4, the specific process of solving the hydraulic fracturing fracture equation in the plane is as follows:

[0031] (1) On the discrete grid, the plane stress vector displacement on the fracturing plane is represented by the difference in displacement of the lower surface, denoted by -, and the plane stress vector displacement on the fracturing plane is represented by the difference in displacement of the upper surface, denoted by +; then, the plane stress vector displacement in the three-dimensional x, y, z axis directions is:

[0032]

[0033] (2) Let I x Let x be the partial derivative of function I with respect to x, then:

[0034]

[0035] (3) When the integration domain is a rectangular grid, then:

[0036]

[0037] (4) Without considering filtration loss on the fracturing plane, the analytical solutions for the theoretical width and theoretical radius of the main fracture as a function of fracturing time are:

[0038]

[0039] In equations (7) and (8), W0 is the theoretical width of the main fracture, R is the theoretical radius of the main fracture, and Q0 is the initial flow rate entering the main fracture, m 3 / s; t is the time for the main crack to open, s; v is Poisson's ratio, dimensionless; E is the shear modulus, MPa; μ is the viscosity, mPa·s.

[0040] The advantages of using this invention are:

[0041] 1) All the basic data required for this invention can be obtained using laboratory instruments, making the data acquisition widely applicable and the process relatively simple and convenient.

[0042] 2) This invention utilizes a rectangular grid structure to quantitatively study the plane of the best-extended main fracture, achieving a high degree of mathematical quantification compared to traditional methods. The abstract concept of inter-fracture stress interference, which is difficult to express, is quantified as the area of ​​the rectangular grid activated and filled on the dominant hydraulic fracture propagation surface. By continuously optimizing various fracturing parameters and iteratively solving the problem, the optimal fracturing parameters for reducing inter-fracture stress interference in horizontal wells can be obtained. Furthermore, by characterizing the stress change on the fracturing surface through the fracture vector displacement caused by fracturing fluid entering the fracture, mutual disturbance is avoided. In summary, the results of this invention have higher accuracy and stronger theoretical support in practical applications.

[0043] 3) This invention completes the modeling and solution of fracturing methods to reduce stress interference between horizontal well fractures. This method can be similarly applied to fracturing operations in oil and gas fields with similar geological conditions. Furthermore, it allows for targeted modeling and analysis based on the methods presented in this invention, combined with practical considerations, to explore fracturing methods for reducing stress interference between horizontal well fractures in different oil and gas reservoirs. This demonstrates broad applicability and provides a reference for future fracturing stress interference control. Attached Figure Description

[0044] Figure 1 This is a flowchart of the present invention;

[0045] Figure 2 A schematic diagram of selecting the plane of the main fracture with the best extension in step S2 as the fracturing plane;

[0046] Figure 3 This is a schematic diagram of discretizing the fracturing plane into a rectangular grid in step S2;

[0047] Figure 4 This is a schematic diagram illustrating the propagation length of the main crack within a rectangular grid using planar stress vector displacement in step S3.

[0048] Figure 5 This is a fitting graph of the actual radius and the theoretical radius in step S6;

[0049] Figure 6 This is a fitting graph of the actual width and the theoretical width in step S6;

[0050] Figure 7 A schematic diagram before applying the optimal fracturing parameters of this invention to a horizontal well;

[0051] Figure 8 A schematic diagram showing the application of the optimal fracturing parameters of this invention to a horizontal well. Detailed Implementation

[0052] Example 1

[0053] This embodiment provides a fracturing method to reduce stress interference between horizontal well fractures, such as... Figure 1 As shown, it includes the following steps:

[0054] Step S1: Select horizontal well reservoirs. Based on the actual situation, select reservoirs with large differences in geomechanical parameters, strong heterogeneity, and relatively undeveloped natural fractures as standard reservoirs. The reservoirs of horizontal wells should meet the following conditions: reservoir depth of 1500-2500m, matrix permeability of 0.10-0.15mD, porosity of 5%-15%, oil saturation of 70%-75%; formation pressure distribution range of 15-17MPa, and pressure coefficient distribution between 0.77-0.84.

[0055] After determining the standard reservoir, the horizontal section of the horizontal well is divided into several perforation clusters. Each perforation cluster contains several boreholes and produces at least one main fracture.

[0056] When implementing this embodiment, the following prerequisites must be met:

[0057] 1. A horizontal section is divided into several perforation clusters, each containing several boreholes. Assuming that the fluid in the perforation clusters completely enters the fracture, and neglecting the fluid compression, the displacement entering each fracture satisfies the following condition:

[0058] ∑Q k =Q c k = 1, 2, 3, ..., Number of perforation clusters (1)

[0059] In equation (1), Qc is the total displacement injected into the wellbore, and Qk is the displacement entering each fracture.

[0060] 2. A horizontal section is divided into several perforation clusters, each containing several boreholes. Assuming equal wellbore pressure at each perforation cluster, and neglecting the pressure loss of fracturing fluid flow in the fracturing section, the wellbore pressure satisfies the following condition:

[0061] P w =P r,k +P in,k k = 1, 2, 3, ..., Number of perforation clusters (2)

[0062] In equation (2), P in,k This is to prevent flow friction from occurring inside the crack during crack propagation; P r,k This refers to the perforation pressure loss generated when fracturing fluid flows through the perforation cluster.

[0063] Step S2: First, select the plane with the best-extended main fracture from all boreholes in each perforation cluster as the fracturing plane, and then discretize each fracturing plane into a rectangular grid. Wherein,

[0064] The fracturing plane satisfies the following settings: rock fracture propagation is elastobrittle fracture, hydraulic fracture propagation is planar propagation, filtration mode follows Caterpillar filtration equation, flow pressure loss of fracturing fluid in wellbore is negligible, wellbore direction is along the direction of minimum horizontal principal stress; brittleness index is between 15% and 70%, with an average of 45%; horizontal stress difference is between 2 and 7 MPa, with an average of 5 MPa.

[0065] The method for discretizing the fracturing plane into a rectangular grid is as follows: taking the center point of the fracturing plane as the origin of the coordinate system, the fracturing plane is evenly divided into vertical and horizontal lines in the X and Y directions, thus completing the discretization of the fracturing plane into a rectangular grid.

[0066] Step S3: During the hydraulic fracturing process within the rectangular grid, the main controlling factors of the force field on the fracture surface and the surrounding rock are the internal pressure and the external field stress. The extension length of the main fracture in each direction is simplified to the plane stress vector displacement, and the extension length of the main fracture is characterized by the plane stress vector displacement within the rectangular grid.

[0067] The method for simplifying the propagation length of the main fracture in each direction into a plane stress vector displacement, and representing the propagation length of the main fracture using the plane stress vector displacement within a rectangular grid, is as follows: Different colors are used within the rectangular grid to represent the fracture tip unit, fracture channel unit, and inactive unit within the fracturing plane. As the hydraulic fracture continuously expands dynamically, the rectangular grid is continuously activated and filled. All activated and filled grids collectively represent the fracturing plane. Then, the fracture channel unit and fracture tip unit corresponding to the main fracture are determined. Based on the coordinate origin and the determined fracture channel unit and fracture tip unit, the plane stress vector displacement is determined. This plane stress vector displacement is the distance from the center point of the fracturing plane to the fracture tip unit. Therefore, the propagation length of the main fracture can be represented by the plane stress vector displacement.

[0068] Combining the Caterpillar filtration equation and filtration experiments, the hydraulic fracturing fracture equation for the plane is established as follows:

[0069]

[0070] In equation (3), p(x,y,z) is the fluid pressure within the main fracture, in Pa; σ h (x,y,z) represents the in-situ stress perpendicular to the main fracture, in Pa; w l The opening width of the main crack, in meters; C(x, y, z) is the stress influence coefficient of the main crack on the point (x, y, z), dimensionless; P l * The stress difference, in N / m, acts on the opening width of the main crack.

[0071] Step S4: Solve the plane hydraulic fracturing fracture equation using the Newton-Raphson iterative method to obtain the theoretical width and radius of the main fracture. The specific process of solving the plane hydraulic fracturing fracture equation is as follows:

[0072] (1) On the discrete grid, the plane stress vector displacement on the fracturing plane is represented by the difference in displacement of the lower surface, denoted by -, and the plane stress vector displacement on the fracturing plane is represented by the difference in displacement of the upper surface, denoted by +; then, the plane stress vector displacement in the three-dimensional x, y, z axis directions is:

[0073]

[0074] In equation (4), each of the sub-equations is a displacement representation. The left side of the equation is the sum of the plane stress vector displacement, and the right side is the displacement difference between the initial point and the final point.

[0075] (2) Let I x Let x be the partial derivative of function I with respect to x, then:

[0076]

[0077] Equation (5) is a process equation. The Newton-Raphson iteration method is used to continuously calculate the partial derivatives of the discontinuous displacement.

[0078] (3) When the integration domain is a rectangular grid, then:

[0079]

[0080] Equation (5) is a process formula, which is used to bring in the discrete grid.

[0081] (4) Without considering filtration loss on the fracturing plane, the analytical solutions for the theoretical width and theoretical radius of the main fracture as a function of fracturing time are:

[0082]

[0083] In equations (7) and (8), W0 is the theoretical width of the main fracture, R is the theoretical radius of the main fracture, and Q0 is the initial flow rate entering the main fracture, m 3 / s; t is the time for the main crack to open, s; v is Poisson's ratio, dimensionless; E is the shear modulus, MPa; μ is the viscosity, mPa·s.

[0084] Step S5: Conduct a simulation experiment based on the actual propagation of the main fracture, and determine the actual width and radius of the main fracture by adjusting the fracturing parameters.

[0085] It should be noted that fracturing parameters include the injection time, viscosity, and flow rate of the fracturing fluid. By adjusting different fracturing parameters, multiple different actual widths and actual radii can be obtained.

[0086] Step S6: Fit the actual width and actual radius of the main fracture to the theoretical width and theoretical radius, respectively. When the actual width and actual radius of the main fracture match the theoretical width and theoretical radius, determine that the fracturing parameters corresponding to the actual width and actual radius of the main fracture are optimal. Then, using the optimal fracturing parameters can reduce stress interference between horizontal well fractures.

[0087] In practical applications, by continuously optimizing the injection time, viscosity, and flow rate of the fracturing fluid, it is possible to improve the uniformity of fracturing initiation and propagation of each cluster, and to make the radius of each hydraulic fracture cluster continuously approach the center width, thereby reducing stress interference between horizontal well fractures.

[0088] Example 2

[0089] This embodiment experimentally verifies the method described in Embodiment 1, as follows:

[0090] 1. For example Figure 2 As shown, in this experiment, the horizontal section of the horizontal well was divided into several perforation clusters, and the plane with the best extension of the main fracture was selected from all the blast holes of each perforation cluster as the fracturing plane.

[0091] 2. For example Figure 3 , 4 As shown, in this experiment, the fracturing plane is discretized into a rectangular grid, and the propagation length of the main fracture is characterized by the plane stress vector displacement within the rectangular grid.

[0092] 3. After solving the plane hydraulic fracturing fracture equation and obtaining the theoretical width and radius of the main fracture, as follows: Figure 5 , 6 As shown, the actual width and radius of the main fracture are fitted with the theoretical width and radius, respectively, and the optimal fracturing parameters are determined when the actual width and radius of the main fracture match the theoretical width and radius.

[0093] 4. Figure 7 The diagram shows a horizontal well before using the optimal fracturing parameters of this invention. As can be seen from the diagram, the stress interference between the fractures is relatively large. Figure 8 A schematic diagram is shown of a horizontal well after using the optimal fracturing parameters of this invention, which shows that the stress interference between fractures is significantly reduced.

[0094] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All features or steps in the disclosed methods or processes may be combined in any way, except for mutually exclusive features and / or steps.

Claims

1. A method of fracturing to reduce interfracture stress interference in a horizontal well, characterized by The method comprises the following steps: Step S1: divide the horizontal section of the horizontal well into several perforation clusters, each perforation cluster containing several perforation holes and generating at least one main fracture; Step S2: select the plane of the best developed main fracture from all perforation holes of each perforation cluster as a fracturing plane, and discretize the fracturing plane into a rectangular grid; Step S3: simplify the development length of the main fracture in each direction into a plane stress vector displacement, and represent the development length of the main fracture in the rectangular grid by the plane stress vector displacement; then combine the Carter filtration equation and the filtration experiment to establish a fracturing plane hydraulic fracturing fracture equation; Step S4: solve the fracturing plane hydraulic fracturing fracture equation by using the Newton-Raphson iteration method to obtain the theoretical width and theoretical radius of the main fracture; Step S5: perform a simulation experiment according to the actual expansion of the main fracture, and obtain the actual width and actual radius of the main fracture by adjusting the fracturing parameters; Step S6: fit the actual width and actual radius of the main fracture with the theoretical width and theoretical radius respectively, and determine that the corresponding fracturing parameters are optimal when the actual width and actual radius of the main fracture are consistent with the theoretical width and theoretical radius respectively, so that the optimal fracturing parameters can be used to reduce the inter-fracture stress interference of the horizontal well.

2. The method of claim 1, wherein: In step S1, the reservoir of the horizontal well satisfies the following conditions: the reservoir burial depth is 1500-2500m, the matrix permeability is 0.10-0.15mD, the porosity is 5%-15%, and the oil saturation is 70%-75%; the formation pressure distribution range is 15-17MPa, and the pressure coefficient is distributed between 0.77 and 0.

84.

3. The method of claim 1 wherein: In step S1, it is assumed that the perforation cluster liquid completely enters the fracture, and under the condition of ignoring the liquid compression amount, the discharge amount entering each fracture satisfies the following condition: ∑Q k = Q c k = 1, 2, 3,..., number of perforation clusters (1) In formula (1), Qc is the total discharge amount injected into the wellbore, and Qk is the discharge amount entering each fracture.

4. The method of claim 3 wherein: In step S1, it is assumed that the wellbore pressure at each perforation cluster is equal, and under the condition of not considering the flow pressure loss of the fracturing fluid in the fracturing well section, the wellbore pressure satisfies the following condition: P w = P r,k + P in,k k = 1, 2, 3,..., number of perforation clusters (2) In formula (2), P in,k is the flow friction generated inside the fracture when the fracture propagates; P r,k is the perforation pressure loss generated when the fracturing fluid flows through the perforation cluster.

5. The method of claim 1 wherein: In step S2, the fracturing plane satisfies the following conditions: the rock fracture expansion is elastic-brittle fracture, the hydraulic fracture development mode is plane development, the filtration mode obeys the Carter filtration equation, the flow pressure loss of the fracturing fluid in the wellbore is not considered, and the wellbore direction is along the direction of the minimum horizontal principal stress; the brittleness index is between 15% and 70%, and the average value is 45%; the horizontal stress difference is between 2MPa and 7MPa, and the average value is 5MPa.

6. The method of claim 1 wherein: In step S2, the method for discretizing the fracturing plane into a rectangular grid is as follows: taking the center point of the fracturing plane as the coordinate origin, the fracturing plane is equally divided in the X-axis and Y-axis directions by using longitudinal and transverse lines, so that the fracturing plane is discretized into a rectangular grid.

7. The method of claim 1 wherein: In step S3, the method for representing the development length of the main fracture in the rectangular grid by the plane stress vector displacement is as follows: in the rectangular grid, different colors are used to represent the crack tip element, crack passage element and unactivated element existing in the fracturing plane, the crack passage element and crack tip element corresponding to the main fracture are determined, and the development length of the main fracture is represented by the plane stress vector displacement according to the coordinate origin and the determined crack passage element and crack tip element.

8. The method of claim 1 wherein: In step S3, when the main crack is a three-dimensional planar crack, the shear displacement of the crack surface is not calculated, and only the normal displacement discontinuity of the crack surface is simplified to the planar stress vector displacement in each direction of the crack surface.

9. A method of fracturing to reduce interfracture stress interference in a horizontal well according to any of claims 1-8, characterized in that: In step S3, the established hydraulic fracturing crack equation of the fracturing plane is: In formula (3), p(x, y, z) is the fluid pressure in the main fracture, Pa; σ h (x, y, z) is the ground stress perpendicular to the main fracture, Pa; w l is the opening width of the main fracture, m; C(x, y, z) is the stress influence coefficient of the main fracture on point (x, y, z), dimensionless; P l * is the stress difference acting on the opening width of the main fracture, N / m.

10. The method of claim 9, wherein: In step S4, the specific process of solving the hydraulic fracturing crack equation of the fracturing plane is: (1) On the discrete grid, the planar stress vector displacement on the fracturing plane is the difference between the displacements of the lower surface, denoted by -, and the planar stress vector displacement on the fracturing plane is the difference between the displacements of the upper surface, denoted by +; then, the planar stress vector displacement in the three-dimensional x, y, z axis directions is: (2) Let I x The partial derivative of I with respect to x is then: (3) When the integral domain is a rectangular grid, then: (4) Without considering the filtration on the fracturing plane, the analytical solution of the theoretical width and the theoretical radius of the main crack changing with the fracturing time is: In formula (7), (8), W0 is the theoretical width of the main crack, R is the theoretical radius of the main crack; Q0 is the initial flow rate into the main crack, m 3 / s; t is the time of opening of the main crack, s; v is the Poisson's ratio, dimensionless; E is the shear modulus, MPa; and μ is the viscosity, mPa-s.

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