Hydraulic fracture network fracture width calculation method and device, equipment and medium

Abstract

The invention discloses a hydraulic fracture network fracture width calculation method, device and equipment and a medium. The method comprises the steps that a geologic model is established, fracture positions, reservoir material mechanical parameters, boundary conditions and grid parameter setting are input into the geologic model, each grid serves as a unit, and each unit comprises four nodes; the unit containing the crack is divided into an enhancement unit, a common unit and a mixing unit, the enhancement unit is a unit through which the crack completely penetrates, the mixing unit is a unit containing crack tip enhancement nodes, and the crack tip enhancement nodes are all nodes in a preset inter-crack enhancement radius with the crack tip as the circle center; introducing an enhancement function corresponding to each unit to obtain enhancement information of different units; and calculating the width of a single crack and the width of an intersecting crack in the unit according to the enhancement information. According to the method, the additional enhanced degree of freedom is introduced into the displacement difference function, so that grid division and crack expansion are mutually independent, the calculation precision is improved, and the calculation efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas field development, and in particular relates to a method, device, equipment and medium for calculating the width of a hydraulic fracture network. Background Art

[0002] Hydraulic fracturing technology is one of the common means to improve the oil and gas recovery rate of shale oil and gas reservoirs. In essence, it is to fully transform ultra-low permeability reservoirs by injecting high-pressure viscous fluids to create a high-conductivity fracture network system. The long-term production increase effect of fracturing is largely affected by the morphology and permeability of hydraulic fractures. Since it is extremely difficult to observe the distribution characteristics of hydraulic fractures at the fracturing site, numerical simulation is a common method to optimize the fracturing process. In the fluid-solid coupling numerical simulation, the fluid flow boundary is determined by the discontinuous fracture interface (fracture width). Therefore, the evaluation mechanism of the discontinuous field between fractures is an important issue. However, under the influence of reservoir heterogeneity and natural fractures, hydraulic fractures usually interact with natural fractures to form a complex fracture network, which significantly increases the difficulty of fracture width calculation.

[0003] Many scholars have conducted extensive research on this issue based on the finite element method (FEM), boundary element method (BEM) and discrete element method (DEM). However, these methods have their inherent disadvantages: first, the crack interface must be used as the mesh boundary; second, in order to improve the calculation accuracy, the mesh needs to be refined near the crack and at the tip; in addition, as the crack continues to expand, the mesh needs to be continuously updated to adapt to the crack shape. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a method, device, equipment and medium for calculating the width of a hydraulic fracture network. Through an effective algorithm for calculating the discontinuous displacement field of "branch points" and "intersection points", the displacement mutation of the intersection points of the fracture branches in a complex fracture network is taken into account, and a calculation mechanism for the intersection point displacement taking into account different stress conditions around different branches and different branch angles is established, thereby determining the optimal fracture network morphology, providing a basis for fracturing construction design, and can be used to guide the optimization of process parameters during the fracturing process.

[0005] The object of the present invention is achieved through the following technical solutions:

[0006] A method for calculating the width of a hydraulic fracture network, the method comprising:

[0007] Establishing a geological model, inputting fracture locations, reservoir material mechanical parameters, boundary conditions and grid parameter settings into the geological model, wherein each grid is regarded as a unit and each unit contains four nodes;

[0008] The cells containing cracks are divided into enhanced cells, ordinary cells and mixed cells, wherein the enhanced cells are cells completely penetrated by the cracks, and the mixed cells are cells containing crack tip enhanced nodes, and the crack tip enhanced nodes are all nodes within a preset inter-crack enhancement radius with the crack tip as the center;

[0009] Introduce the enhancement function corresponding to each unit to obtain the enhancement information of different units;

[0010] The width of a single crack and the width of intersecting cracks in the unit are calculated according to the enhanced information.

[0011] Furthermore, the enhancement unit that the crack completely passes through is the Heaviside enhancement unit, and the enhancement unit that includes the crack tip is the crack-tip enhancement unit. For the unit that only includes a single crack, the enhancement function includes:

[0012]

[0013] Among them, N represents the number of all nodes, N H * Represents the number of Heaviside enhancement unit nodes, N tip * Represents the number of crack-tip enhancement unit nodes, I * is the set of all enhanced nodes, u i , a j , and b k α is the degree of freedom vector, N i (x), N j (x) and N k (x) is the standard finite element shape function, H(x) represents the Heaviside enhancement function, and F α (x) represents the crack-tip enhancement function, and R(x) is the ramp function of the mixing element, defined as:

[0014]

[0015] For the nodes of the Heaviside enhanced unit, a step function is used as the enhancement function:

[0016]

[0017] Where d(x) is the shortest distance from the x node to the crack surface;

[0018] The enhancement function of the crack-tip enhancement unit is:

[0019]

[0020] where (r, θ) represents the local polar coordinate system at the crack tip.

[0021] Furthermore, when there are intersecting crack segments in the unit, the intersecting cracks are regarded as a main crack and a branch crack, and the enhancement function expression is:

[0022]

[0023] The Junction enhancement function is used to characterize the branch cracks, which is defined as:

[0024]

[0025] When there are two independent crack segments in the unit, the node is enhanced by the Heaviside functions of the two cracks. The expression of the enhancement function is:

[0026]

[0027] Among them, f I (X) and f II (X) represents the distance function from point X to the two crack segments.

[0028] Furthermore, the calculation of the width of a single crack specifically includes:

[0029] The crack width at any point on the crack surface in the model is w = n·[u(x + )-u(x - )];

[0030] Where n is the unit normal vector of the crack surface;

[0031] For the Heaviside enhanced unit, the crack width calculation formula is:

[0032]

[0033] For the crack-tip enhancement unit, the crack width calculation formula is:

[0034] The inter-crack correction coefficient δ is introduced, which is defined as

[0035]

[0036] For a hybrid unit where all nodes are within the inter-fracture enhancement radius, the crack width calculation formula is:

[0037]

[0038] For hybrid units where some nodes are located within the inter-fracture enhancement radius, the ramp function R(x) is introduced and the fracture width calculation formula is:

[0039]

[0040] Furthermore, the method further includes dividing the intersecting cracks into main cracks and branch cracks, and the calculation of the width of the intersecting cracks specifically includes:

[0041] Introducing a global normal vector and a local normal vector, wherein the global normal vector distinguishes the upper and lower regions of the crack according to the coordinates of the crack segment, and the local normal vector is used to distinguish the direction of the crack tip;

[0042] The intersecting crack width is expressed as:

[0043]

[0044] Where N Hm represents the number of enhanced nodes caused by the main crack, N Hb represents the number of enhanced nodes caused by branch cracks, N b is the number of branch cracks, λ i is the branching crack coefficient, defined as

[0045]

[0046] Γ is the crack direction, and Δ is not zero when the coordinate point is on the overlapping crack segment.

[0047] On the other hand, the present invention also provides a hydraulic fracture network width calculation device, the device comprising:

[0048] A grid division module, wherein the grid division module establishes a geological model, inputs fracture locations, reservoir material mechanical parameters, boundary conditions and grid parameter settings into the geological model, wherein each grid is regarded as a unit and each unit contains four nodes;

[0049] A unit classification module, wherein the unit classification module divides the unit containing cracks into enhanced units, ordinary units and mixed units, wherein the enhanced units are units completely penetrated by the cracks, and the mixed units are units containing crack tip enhanced nodes, wherein the crack tip enhanced nodes are all nodes within a preset inter-crack enhancement radius with the crack tip as the center;

[0050] An enhanced information acquisition module, wherein the enhanced information acquisition module introduces an enhancement function corresponding to each unit to obtain enhanced information of different units;

[0051] A crack width calculation module is used to calculate the width of a single crack and the width of intersecting cracks in the calculation unit according to the enhanced information.

[0052] On the other hand, the present invention also provides a computer device, comprising a processor and a memory, wherein the memory stores a computer program, and the computer program is loaded and executed by the processor to implement any of the above-mentioned methods for calculating the width of a hydraulic fracture network.

[0053] On the other hand, the present invention also provides a computer-readable storage medium, in which a computer program is stored. The computer program is loaded and executed by a processor to implement any of the above-mentioned methods for calculating the width of a hydraulic fracture network.

[0054] The beneficial effects of the present invention are:

[0055] (1) When the formation contains a complex fracture network, the present invention can accurately calculate the displacement mutation of the intersection point of the fracture branches, thereby ensuring the accuracy and reliability of the fracture network width calculation.

[0056] (2) The present invention does not need to re-divide the computing grid as time changes, thereby improving computing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is a flowchart of a method for calculating the width of a hydraulic fracture network according to an embodiment of the present invention;

[0058] Figure 2 is a schematic diagram of a local normal vector according to an embodiment of the present invention;

[0059] Figure 3 is a schematic diagram of an intersecting seam unit according to an embodiment of the present invention;

[0060] Figure 4 Schematic diagram of a T-shaped intersecting seam model according to an embodiment of the present invention;

[0061] Figure 5 Schematic diagram of a cross-intersecting seam model according to an embodiment of the present invention;

[0062] Figure 6 1 is a diagram showing calculation results of different branches of the T-shaped intersecting seam model according to an embodiment of the present invention;

[0063] Figure 7 1 is a diagram showing calculation results of different branches of the cross-intersecting seam model according to an embodiment of the present invention;

[0064] Figure 8 It is a structural block diagram of a hydraulic fracture network width calculation device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0065] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0066] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0067] Existing technologies based on finite element method (FEM), boundary element method (BEM) and discrete element method (DEM) have studied the problem that hydraulic fractures usually interact with natural fractures to form complex fracture networks, but these methods have their inherent disadvantages: first, the fracture interface must be used as the mesh boundary; second, in order to improve the calculation accuracy, the mesh needs to be refined near and at the tip of the fracture; in addition, as the fracture continues to expand, the mesh needs to be continuously updated to adapt to the fracture morphology.

[0068] In order to solve the above technical problems, the following embodiments of the method, device, equipment and medium for calculating the width of a hydraulic fracture network of the present invention are proposed.

[0069] Example 1

[0070] This embodiment establishes a method for calculating the width of a complex fracture network based on the extended finite element method and the modified branch enhancement function, and proposes an effective algorithm for calculating the discontinuous displacement field of "branch points" and "intersection points", which provides the necessary basis for further numerical simulation research, provides theoretical support for the optimization of fracturing technology, and promotes the efficient development of shale gas resources.

[0071] Reference Figure 1 ,like Figure 1 The figure is a flowchart of the method for calculating the width of a hydraulic fracture network in this embodiment, and the method specifically includes the following steps:

[0072] Step 1: Establish a geological model and input fracture locations, reservoir material mechanical parameters, boundary conditions and grid parameter settings into the geological model.

[0073] It should be noted that each grid is regarded as a unit, and each unit contains four nodes.

[0074] Specifically, the model first needs to input the locations of hydraulic fractures and natural fractures, mechanical parameters of reservoir materials, boundary conditions, and grid parameter settings.

[0075] Step 2: Divide the cells containing cracks into enhanced cells, ordinary cells and mixed cells. Enhanced cells are cells that are completely penetrated by cracks. Mixed cells are cells that contain crack tip enhanced nodes. Crack tip enhanced nodes are all nodes within a preset inter-crack enhancement radius with the crack tip as the center.

[0076] Specifically, based on the level set method, this embodiment divides all units (nodes) of the single crack model into enhanced units (nodes), ordinary units (nodes) and mixed units. Among them, the unit that the crack completely passes through is the Heaviside enhanced unit; in order to improve the calculation accuracy of the crack tip area, r is defined. tip The crack tip enhancement radius is used to increase the crack tip enhancement range. With the crack tip as the center, r tip All nodes within the radius are defined as crack tip enhancement nodes; the element in which only some nodes are crack tip enhancement nodes is a mixed element.

[0077] For a unit with multiple crack segments, assume that the unit contains crack segments a, b, and c. At this time, the unit nodes are superimposed with enhanced nodes corresponding to the three crack segments. Crack segments a and b are represented by 4 Heaviside enhanced nodes respectively; crack segment c is represented by 16 crack tip enhanced nodes. At this time, the unit has a total of 4 ordinary nodes and 24 enhanced nodes.

[0078] Step 3: Introduce the enhancement function corresponding to each unit to obtain the enhancement information of different units.

[0079] Specifically, in the modified XFEM framework, the solution of the displacement exists in a discrete finite-dimensional space represented by nodal degrees of freedom. All global degrees of freedom include two parts, namely the normal degrees of freedom of the continuous part and the enriched degrees of freedom of the discontinuous region. For the single slit case, the displacement interpolation function of any point in the model can be expressed as:

[0080]

[0081] Among them, N represents the number of all nodes, N H * Represents the number of Heaviside enhancement unit nodes, N tip * Represents the number of crack-tip enhancement unit nodes, and defines I * is the set of all enhanced nodes. In addition, u i , a j , and b k α are the corresponding ordinary and enhanced degree of freedom vectors, N i (x), N j (x) and N k (x) is the standard finite element shape function, H(x) represents the Heaviside enhancement function, and Fα (x) represents the crack-tip enhancement function. R(x) is the ramp function of the mixing element, defined as:

[0082]

[0083] For the nodes of the Heaviside enhanced unit, a step function is used as the enhancement function:

[0084]

[0085] Where d(x) is the shortest distance from the x node to the crack surface. To explain how to determine the positive or negative of the distance, the unit normal vector of the crack surface is defined as n. If x is on the same side of the direction pointed by n, the distance is positive; if x is on the other side of n, the distance is negative.

[0086] The crack-tip enhancement function is actually extracted from the crack tip displacement field to characterize all possible displacement states of the crack tip. The expression is:

[0087]

[0088] Among them, (r, θ) represents the local polar coordinate system of the crack tip. In the crack-tip enhancement function of isotropic media, only the first term is discontinuous across the crack surface, and the other terms have no contribution to the crack width calculation.

[0089] When there is a crack intersection problem in the region, the enhancement scheme is different from the single crack problem. There are mainly two cases: the unit contains two independent crack segments and the unit contains cross-intersecting cracks. In the unit with intersecting crack segments, the intersecting crack can be regarded as a main crack and a branch crack, and an additional junction enhancement function is used to represent it. The expression of the enhancement scheme is:

[0090]

[0091] Among them, the Junction enhancement function term is used to characterize branch cracks, which is defined as:

[0092]

[0093] In the unit with two independent crack segments, the nodes are enhanced with the degrees of freedom added by the Heaviside functions of the two cracks. The expression of the enhancement scheme is:

[0094]

[0095] f I (X) and f II (X) represents the distance function from point X to the two crack segments.

[0096] Step 4: Calculate the width of a single crack and the width of intersecting cracks within the unit based on the enhanced information.

[0097] Specifically, the steps for calculating the width of a single crack in a cell are as follows:

[0098] After obtaining the information of the enhanced unit in the fractured area, the calculation of the fracture width involves the inter-fracture enhanced unit, Heaviside enhanced unit and mixed unit. The fracture width at any point on the fracture surface in the model can be expressed as:

[0099] w=n·[u(x + )-u(x - )] (8)

[0100] Where n is the unit normal vector of the crack surface.

[0101] From the displacement difference functions of different types of enhanced units, it can be seen that x in formula (8) + The Heaviside enhancement degrees of freedom are the same as the standard degrees of freedom at x-, but the positive and negative values ​​are opposite. For the crack tip region, only the first term of the four intercrack enhancement functions is discontinuous across the crack surface

[22] . Therefore, the crack width is mainly related to the Heaviside enhancement degrees of freedom and the first term of the intercrack enhancement degrees of freedom.

[0102] For a simple Heaviside unit, only the Heaviside degree of freedom contributes to the crack width, and the crack width formula can be expressed as:

[0103]

[0104] For the unit in the crack tip enhancement area, based on the first term of the crack enhancement function, the crack width formula can be expressed as:

[0105]

[0106] There may be two inter-fractures in a crack. Since the directions of the two inter-fracture coordinate systems are different, the inter-fracture correction coefficient δ is introduced in formula (10), which is defined as

[0107]

[0108] For a hybrid unit where all nodes are within the inter-crack enhancement radius, based on the first term of the inter-crack enhancement function of the crack surface, the crack width formula can be expressed as:

[0109]

[0110] For hybrid elements whose nodes are located within the inter-crack enhancement radius, the ramp function R(x) is introduced to correct the normalization of the element displacement interpolation function, and the crack width formula can be expressed as:

[0111]

[0112] The calculation of the intersecting crack width is as follows:

[0113] When considering a unit with multiple cracks, refer to Figure 2 ,like Figure 2 The figure shows a schematic diagram of the local normal vector of this embodiment. First, the global normal vector and the local normal vector need to be introduced. Among them, the role of the global normal vector is to distinguish the upper and lower areas of the crack according to the coordinates of the crack segment; the local normal vector defined based on the local coordinate system (ξ, η) of the crack tip is used to define the local polar coordinates (r, θ) of the region, and its role is to distinguish the direction of the crack tip. The two normal vectors are in opposite directions at the left crack tip and in the same direction at the right crack tip. Figure 3 ,like Figure 3 The figure shows a schematic diagram of the intersecting crack unit in this embodiment. An intersecting crack is defined as two equivalent cracks with its intersection point as the boundary, which are represented by AOB and BOC respectively, and their directions are represented by red arrows. Crack AOB represents the main crack, and crack BOC represents the branch crack. Among them, OB is the overlapping crack segment. At this time, the e1 unit is enhanced by two cracks at the same time, and the width of the intersecting crack can be expressed as:

[0114]

[0115] Where N Hm and N Hb Represents the number of enhanced nodes caused by the main crack and branch crack respectively. N b is the number of branch cracks. i is the branching crack coefficient, which can be defined as

[0116]

[0117] Where Γ is the crack direction, Δ is when the coordinate point is on the overlapping crack segment, Δ is not zero. When Δ is not zero and the main crack direction is the same as the branch crack direction and Γm=Γi, λ i The value of is 1. For example, Figure 3 In the figure, the crack points P1, P2, P8, and P9 are located on independent single crack segments AO and OC, so Δ is zero and λ i = 0. That is, for the crack point P belonging to an independent single crack segment i , only one displacement discontinuity needs to be considered. The crack points P3~P7 belong to the overlapping crack segment BO, and the two cracks have different directions, so Δ is not zero, λ i =-1.

[0118] The intersection point O is the common point of the AO, BO, and CO fracture segments. The calculation of the fracture width at this point is more complicated and requires additional discussion. When the intersecting fractures are opened, the points corresponding to the original O point positions of the three branch fractures are marked as O1, O2, and O3, respectively. Figure 2 . In order to satisfy the discontinuous displacement of different branches, this method assumes that the intersection belongs to different branch segments and discusses the situation separately. If the intersection point O belongs to the AO crack segment, after the crack is opened, its corresponding points on the upper and lower crack surfaces are O1 and O2 respectively. If the intersection point O belongs to the BO crack segment, after the crack is opened, its corresponding points on the upper and lower crack surfaces are O1 and O3 respectively. Similarly, if the intersection point O belongs to the CO crack segment, after the crack is opened, its corresponding points on the upper and lower crack surfaces are O3 and O2 respectively. The positive and negative values ​​of the Heaviside enhancement function values ​​at the upper and lower points of the crack are opposite, so the value of the cross-crack surface enhancement function H(x) is different in different cases, see Table 2.

[0119] Table 2 Signs of enhancement function H(x) in different cases

[0120]

[0121] In Table 2, “upper” and “lower” represent the corresponding points on the upper and lower sides of the crack, respectively, and “+” and “-” represent the signs of the enhancement function.

[0122] When the intersection point belongs to AO, only the enhanced degrees of freedom of the main fracture AOB contributes to the fracture width at the intersection, because the OC segment H(x) is continuous across the fracture surface; when the intersection point belongs to BO, the enhanced degrees of freedom of both the main fracture AOB and the branch fracture BOC contribute to the fracture width at the intersection.

[0123] This embodiment can accurately calculate the displacement mutation of the intersection point of the fracture branches when considering the formation containing complex fracture networks, and ensure the accuracy and reliability of the fracture network width calculation. This embodiment does not need to re-divide the calculation grid as time changes, thereby improving the calculation efficiency.

[0124] Example 2

[0125] In this embodiment, the complex fracture network is divided into a number of T-shaped fractures and cross fractures, and a block model with a size of 100m×100m is established, wherein the center contains a T-shaped fracture and a cross fracture respectively.

[0126] Reference Figure 4 and Figure 5 ,like Figure 4 FIG. 1 is a schematic diagram of a T-shaped intersecting seam model of this embodiment. Figure 5Schematic diagram of the cross-intersecting seam model of this embodiment. The right boundary of the region is a fixed boundary, and the upper and lower boundaries are respectively subjected to a normal load of 10 MPa. The Young's modulus of the model is set to 6089 MPa, and the Poisson's ratio is set to 0.30. The length of each initial crack branch is 20 m.

[0127] Formulas (1) to (4) in the above embodiments are used to assign enhanced degrees of freedom to the Heaviside enhanced unit, the unit within the crack tip enhanced radius, and the hybrid unit. Based on formulas (5) to (8), the node displacement interpolation function containing enhanced degrees of freedom is introduced, and the control equation is discretized based on the principle of virtual work to solve the vectors of each enhanced degree of freedom and the model stress and displacement fields.

[0128] The intersecting cracks are divided into main cracks and branch cracks, and the values ​​of the enhancement functions of the upper and lower surfaces are solved based on the coordinates of the points. Then, the displacement vector at that location is calculated by using the enhanced degree of freedom vector interpolation. For any input point p(x,y), if p is not on any crack, the crack width is zero, and the calculation is stopped. If p is on the crack surface, the enhancement information of the unit containing point p will be obtained first.

[0129] Determine whether the point is a crack branch intersection. If point p is an intersection, it is necessary to determine the subordinate relationship between the point and the crack segment. Then, all displacement discontinuities will be calculated by equation (14). If the point is located on the crack surface and is not an intersection, the crack width is calculated according to equations (9)-(13).

[0130] Reference Figure 6 and Figure 7 ,like Figure 6 The figure shows the calculation results of different branches of the T-shaped intersecting seam model in this embodiment. Figure 7 The figure shows the calculation results of different branches of the cross-intersecting seam model in this embodiment. The calculation results of the intersection point displacement (seam width) are shown in Table 1:

[0131] Table 1 Intersection point displacement calculation results

[0132]

[0133]

[0134] Example 3

[0135] Reference Figure 8 ,like Figure 8 The figure is a structural block diagram of the hydraulic fracture network width calculation device of this embodiment, and the device specifically includes the following structures:

[0136] The meshing module establishes the geological model, inputs the fracture location, reservoir material mechanical parameters, boundary conditions and mesh parameter settings into the geological model, and each mesh is regarded as a unit, and each unit contains four nodes;

[0137] Unit classification module, the unit classification module divides the units containing cracks into enhanced units, ordinary units and mixed units. Enhanced units are units that are completely penetrated by cracks. Mixed units are units that contain crack tip enhanced nodes. Crack tip enhanced nodes are all nodes within a preset inter-crack enhancement radius with the crack tip as the center.

[0138] Enhanced information acquisition module, the enhanced information acquisition module introduces the enhancement function corresponding to each unit to obtain enhanced information of different units;

[0139] The crack width calculation module calculates the width of a single crack and the width of intersecting cracks in the unit according to the enhanced information.

[0140] Example 4

[0141] This preferred embodiment provides a computer device, which can implement the steps in any embodiment of the method for calculating the width of a hydraulic fracture network provided in the embodiments of the present application. Therefore, the beneficial effects of the method for calculating the width of a hydraulic fracture network provided in the embodiments of the present application can be achieved. Please refer to the previous embodiments for details and will not be repeated here.

[0142] Example 5

[0143] Those skilled in the art can understand that all or part of the steps in the various methods of the above embodiments can be completed by instructions, or by controlling related hardware through instructions, and the instructions can be stored in a computer-readable storage medium and loaded and executed by a processor. To this end, an embodiment of the present invention provides a storage medium, which stores a plurality of instructions, and the instructions can be loaded by a processor to execute the steps of any embodiment of the method for calculating the width of a hydraulic fracture network provided in an embodiment of the present invention.

[0144] The storage medium may include: a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, etc.

[0145] Since the instructions stored in the storage medium can execute the steps in any embodiment of the method for calculating the width of a hydraulic fracture network provided in the embodiments of the present invention, the beneficial effects that can be achieved by any method for calculating the width of a hydraulic fracture network provided in the embodiments of the present invention can be achieved. For details, please refer to the previous embodiments and will not be repeated here.

[0146] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for calculating the width of a hydraulic fracture network, characterized in that: The method comprises: Establishing a geological model, inputting fracture locations, reservoir material mechanical parameters, boundary conditions and grid parameter settings into the geological model, wherein each grid is regarded as a unit and each unit contains four nodes; The cells containing cracks are divided into enhanced cells, ordinary cells and mixed cells, wherein the enhanced cells are cells completely penetrated by the cracks, and the mixed cells are cells containing crack tip enhanced nodes, and the crack tip enhanced nodes are all nodes within a preset inter-crack enhancement radius with the crack tip as the center; Introduce the enhancement function corresponding to each unit to obtain the enhancement information of different units; The width of a single crack and the width of intersecting cracks in the unit are calculated according to the enhanced information.

2. The method for calculating the width of a hydraulic fracture network according to claim 1, characterized in that: The enhancement unit that the crack completely passes through is the Heaviside enhancement unit, and the enhancement unit that contains the crack tip is the crack-tip enhancement unit. For the unit that contains only a single crack, the enhancement function includes: Among them, N represents the number of all nodes, N H * Represents the number of Heaviside enhancement unit nodes, N tip * Represents the number of crack-tip enhancement unit nodes, I * is the set of all enhanced nodes, u i , a j , and b k α is the degree of freedom vector, N i (x), N j (x) and N k (x) is the standard finite element shape function, H(x) represents the Heaviside enhancement function, and F α (x) represents the crack-tip enhancement function, and R(x) is the ramp function of the mixing element, defined as: For the nodes of the Heaviside enhanced unit, a step function is used as the enhancement function: Where d(x) is the shortest distance from the x node to the crack surface; The enhancement function of the crack-tip enhancement unit is: where (r,θ) represents the local polar coordinate system at the crack tip.

3. The method for calculating the width of a hydraulic fracture network according to claim 2, characterized in that: When there are intersecting crack segments in a cell, the intersecting cracks are regarded as a main crack and a branch crack, and the enhancement function expression is: The Junction enhancement function is used to characterize the branch cracks, which is defined as: When there are two independent crack segments in the unit, the node is enhanced with the Heaviside functions of the two cracks. The expression of the enhancement function is: Among them, f I (X) and f II (X) represents the distance function from point X to the two crack segments.

4. The method for calculating the width of a hydraulic fracture network according to claim 3, characterized in that: The calculation of the width of a single crack specifically includes: The crack width at any point on the crack surface in the model is w = n·[u(x + )-u(x - )]; Where n is the unit normal vector of the crack surface; For the Heaviside enhanced unit, the crack width calculation formula is: For the crack-tip enhancement unit, the crack width calculation formula is: And introduce the inter-crack correction coefficient δ, which is defined as For a hybrid unit where all nodes are within the inter-crack enhancement radius, the crack width calculation formula is: For hybrid units where some nodes are located within the inter-crack enhancement radius, the ramp function R(x) is introduced and the crack width calculation formula is:

5. The method for calculating the width of a hydraulic fracture network according to claim 3, characterized in that: The method further includes dividing the intersecting cracks into main cracks and branch cracks, and the calculation of the width of the intersecting cracks specifically includes: Introducing a global normal vector and a local normal vector, wherein the global normal vector distinguishes the upper and lower regions of the crack according to the coordinates of the crack segment, and the local normal vector is used to distinguish the direction of the crack tip; The intersecting crack width is expressed as: Where N Hm represents the number of enhanced nodes caused by the main crack, N Hb represents the number of enhanced nodes caused by branch cracks, N b is the number of branch cracks, λ i is the branching crack coefficient, defined as Γ is the crack direction, and Δ is not zero when the coordinate point is on the overlapping crack segment.

6. A hydraulic fracture network width calculation device, characterized in that: The device comprises: A grid division module, wherein the grid division module establishes a geological model, inputs fracture locations, reservoir material mechanical parameters, boundary conditions and grid parameter settings into the geological model, wherein each grid is regarded as a unit and each unit contains four nodes; A unit classification module, wherein the unit classification module divides the unit containing cracks into enhanced units, ordinary units and mixed units, wherein the enhanced units are units completely penetrated by the cracks, and the mixed units are units containing crack tip enhanced nodes, wherein the crack tip enhanced nodes are all nodes within a preset inter-crack enhancement radius with the crack tip as the center; An enhanced information acquisition module, wherein the enhanced information acquisition module introduces an enhancement function corresponding to each unit to obtain enhanced information of different units; A crack width calculation module is used to calculate the width of a single crack and the width of intersecting cracks in the calculation unit according to the enhanced information.

7. A computer device, characterized in that: The computer device includes a processor and a memory, wherein a computer program is stored in the memory, and the computer program is loaded and executed by the processor to implement the method for calculating the width of a hydraulic fracture network according to any one of claims 1 to 5.

8. A computer-readable storage medium, characterized in that: The storage medium stores a computer program, which is loaded and executed by a processor to implement the method for calculating the width of a hydraulic fracture network according to any one of claims 1 to 5.

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