Simulation method for crack propagation of stratified reservoir fracturing

Abstract

The invention provides a stratified reservoir fracturing crack propagation simulation method, which comprises the following steps of: firstly, performing discrete processing on a model corresponding to a stratified reservoir according to a preset polyhedral block to obtain at least one discrete matrix unit, and secondly, determining at least one attribute model corresponding to the at least one discrete matrix unit, according to the at least one attribute model, fluid-solid coupling solution is carried out on the at least one discrete matrix unit, fracture information between adjacent discrete matrix units, fluid pressure distribution between the adjacent discrete matrix units and stress states of the adjacent discrete matrix units are determined, and then the strata characterization parameters of the reservoir stratum are combined to determine the strata characterization parameters of the reservoir stratum. And crack fracture information of stratified reservoir fracturing is determined. According to the technical scheme, on the basis of the stratified reservoir fracturing fracture form and the influence mechanism thereof, the fracture information of stratified reservoir fracturing is determined, and a basis is provided for improving stratified reservoir transformation benefits.

Description

Technical Field

[0001] The present application relates to the field of petroleum engineering technology, and in particular to a method for simulating fracture propagation in laminar reservoirs. Background Art

[0002] Generally, laminar reservoirs have the characteristics of low porosity and ultra-low permeability. The key to the successful development of such reservoirs is to form a large-scale complex fracture network through multi-stage and multi-cluster fracturing of horizontal wells. Unlike conventional reservoirs, laminar reservoirs have significant heterogeneity due to the deposition of layered rocks, and have different mechanical characteristics in different directions, that is, they have inherent anisotropy. The significant anisotropy of laminar reservoirs will have a certain impact on hydraulic fracturing cracks.

[0003] At present, existing technologies have established fracturing models that can simulate the expansion of multiple fractures, including wire-net models, discrete fracture network models, and unconventional fracture models, as well as other numerical models based on finite element method, boundary element method, extended finite element method, discrete element method, and phase field method. These numerical models often simplify the reservoir into isotropic materials and efficiently obtain the fracture state of laminar reservoirs.

[0004] Therefore, how to efficiently obtain the fracture state of laminated reservoirs has become a technical problem that needs to be solved urgently. Summary of the invention

[0005] The present application provides a method for simulating fracture propagation in a laminated reservoir by fracturing, so as to solve the problems of the prior art in efficiently obtaining the fracture state of the laminated reservoir.

[0006] In a first aspect, an embodiment of the present application provides a method for simulating fracture propagation in a laminar reservoir by fracturing, comprising:

[0007] According to the preset polyhedral block, the model corresponding to the laminar reservoir is discretized to obtain at least one discrete matrix unit;

[0008] Determining at least one property model corresponding to the at least one discrete matrix unit;

[0009] According to the at least one property model, performing fluid-solid coupling solution on the at least one discrete matrix unit to determine rupture information between adjacent discrete matrix units, fluid pressure distribution between the adjacent discrete matrix units, and stress states of the adjacent discrete matrix units;

[0010] The fracture information of laminar reservoir fracturing is determined based on the fracture information between all adjacent discrete matrix units, the fluid pressure distribution between all adjacent discrete matrix units, and the stress state of all adjacent discrete matrix units, combined with the laminar characterization parameters of the reservoir.

[0011] In a possible design of the first aspect, determining at least one property model corresponding to the at least one discrete matrix unit includes:

[0012] constructing a model for the at least one discrete matrix unit according to the discretely generated matrix, fluid, perforation and wellbore unit types to obtain the at least one attribute model;

[0013] Wherein, the at least one attribute model includes: a matrix grid unit stress attribute model, and / or a matrix grid unit and laminae strength attribute model.

[0014] In another possible design of the first aspect, each two discrete matrix units include: a first discrete matrix unit and a second discrete matrix unit;

[0015] Accordingly, performing fluid-solid coupling solution on the at least one discrete matrix unit according to the at least one property model to determine the rupture information between adjacent discrete matrix units, the fluid pressure distribution between the adjacent discrete matrix units, and the stress state of the adjacent discrete matrix units includes:

[0016] According to the at least one attribute model, a virtual quadrilateral unit is inserted between the first discrete matrix unit and the second discrete matrix unit, a virtual spring is applied to connect the first discrete matrix unit and the second discrete matrix unit, and a pressure acting between the first discrete matrix unit and the second discrete matrix unit is transmitted, and according to a preset failure criterion, the fracture of the virtual spring is determined to characterize the fracture information of the rock as the fracture information between the adjacent discrete matrix units;

[0017] The fluid pressure distribution between the first discrete matrix unit and the second discrete matrix unit and the stress state between the adjacent discrete matrix units are determined by using the finite element method.

[0018] In yet another possible design of the first aspect, the preset failure criterion is determined based on a maximum tensile stress criterion and a Mohr-Coulomb criterion.

[0019] In yet another possible design of the first aspect, the lamination characterization parameters of the reservoir are equivalent density, equivalent width and mechanical characteristics.

[0020] In a second aspect, an embodiment of the present application provides a laminar reservoir fracturing crack propagation simulation device, comprising:

[0021] A processing module, used for discretizing the model corresponding to the laminar reservoir according to the preset polyhedral block to obtain at least one discrete matrix unit;

[0022] A first determining module, used to determine at least one attribute model corresponding to the at least one discrete matrix unit;

[0023] A second determination module is used to perform fluid-solid coupling solution on the at least one discrete matrix unit according to the at least one property model to determine the rupture information between adjacent discrete matrix units, the fluid pressure distribution between the adjacent discrete matrix units, and the stress state of the adjacent discrete matrix units;

[0024] The third determination module is used to determine the fracture rupture information of the laminar reservoir fracturing according to the fracture information between all adjacent discrete matrix units, the fluid pressure distribution between all adjacent discrete matrix units, and the stress state of all adjacent discrete matrix units, combined with the laminar characterization parameters of the reservoir.

[0025] In a possible design of the second aspect, the first determining module determines at least one attribute model corresponding to the at least one discrete matrix unit, specifically for:

[0026] constructing a model for the at least one discrete matrix unit according to the discretely generated matrix, fluid, perforation and wellbore unit types to obtain the at least one attribute model;

[0027] Wherein, the at least one attribute model includes: a matrix grid unit stress attribute model, and / or a matrix grid unit and laminae strength attribute model.

[0028] In another possible design of the second aspect, each two discrete matrix units include: a first discrete matrix unit and a second discrete matrix unit;

[0029] Correspondingly, the second determination module performs fluid-solid coupling solution on the at least one discrete matrix unit according to the at least one property model to determine the rupture information between adjacent discrete matrix units, the fluid pressure distribution between the adjacent discrete matrix units, and the stress state of the adjacent discrete matrix units, specifically for:

[0030] According to the at least one attribute model, a virtual quadrilateral unit is inserted between the first discrete matrix unit and the second discrete matrix unit, a virtual spring is applied to connect the first discrete matrix unit and the second discrete matrix unit, and a pressure acting between the first discrete matrix unit and the second discrete matrix unit is transmitted, and according to a preset failure criterion, the fracture of the virtual spring is determined to characterize the fracture information of the rock as the fracture information between the adjacent discrete matrix units;

[0031] The fluid pressure distribution between the first discrete matrix unit and the second discrete matrix unit and the stress state between the adjacent discrete matrix units are determined by using the finite element method.

[0032] In yet another possible design of the second aspect, the preset failure criterion is determined based on a maximum tensile stress criterion and a Mohr-Coulomb criterion.

[0033] In yet another possible design of the second aspect, the lamination characterization parameters of the reservoir are equivalent density, equivalent width and mechanical characteristics.

[0034] In a third aspect, the present application provides an electronic device, comprising: a processor, and a memory and a transceiver communicatively connected to the processor;

[0035] The memory stores computer-executable instructions; the transceiver is used to send and receive data;

[0036] The processor executes the computer-executable instructions stored in the memory to implement the method as described in the first aspect or any one of the above methods.

[0037] In a fourth aspect, the present application provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions, and when the computer-executable instructions are executed by a processor, they are used to implement the method described in the first aspect or any one of the above methods.

[0038] In a fifth aspect, the present application provides a computer program product, comprising a computer program, wherein the computer program is stored in a computer-readable storage medium, and at least one processor can read the computer program from the computer-readable storage medium. When the at least one processor executes the computer program, the method described in the first aspect or any one of the methods can be implemented.

[0039] The present application provides a method for simulating fracture propagation in laminated reservoirs by fracturing. The method first discretizes the model corresponding to the laminated reservoir according to a preset polyhedral block to obtain at least one discrete matrix unit, then determines at least one attribute model corresponding to the at least one discrete matrix unit, and then performs fluid-solid coupling solution on the at least one discrete matrix unit according to the at least one attribute model to determine the fracture information between adjacent discrete matrix units, the fluid pressure distribution between adjacent discrete matrix units, and the stress state of adjacent discrete matrix units, and then determines the fracture rupture information of laminated reservoir fracturing in combination with the laminae characterization parameters of the reservoir. In this technical solution, based on the fracture morphology of laminated reservoir fracturing and its influencing mechanism, the fracture rupture information of laminated reservoir fracturing is determined, providing a basis for improving the benefits of laminated reservoir transformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0041] Figure 1 Schematic diagram of the process of simulating fracture propagation of laminar reservoir fracturing provided in the embodiment of the present application Figure 1 ;

[0042] Figure 2 A schematic diagram of a model discretization process corresponding to a laminar reservoir provided in an embodiment of the present application;

[0043] Figure 3 A schematic diagram of elastic characteristics of a transversely isotropic material provided in an embodiment of the present application;

[0044] Figure 4 Schematic diagram of the process of simulating fracture propagation of laminar reservoir fracturing provided in the embodiment of the present application Figure 2 ;

[0045] Figure 5 A schematic diagram of the matrix unit block gap activation process provided in an embodiment of the present application;

[0046] Figure 6 Transversely homogeneous and inhomogeneous distribution diagrams of laminar strength provided in the embodiments of the present application;

[0047] Figure 7 A schematic diagram of mechanical parameters of lateral heterogeneity of a laminar reservoir provided in an embodiment of the present application;

[0048] Figure 8 The simulated form of crack propagation when the laminar reservoir strength is laterally homogeneous provided in the embodiment of the present application;

[0049] Fig. 9 The simulated form of crack propagation when the laminar reservoir strength is laterally heterogeneous provided in the embodiment of the present application;

[0050] Fig.10 A schematic diagram of the structure of an embodiment of a laminar reservoir fracturing crack extension simulation device provided in an embodiment of the present application;

[0051] Fig.11 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application.

[0052] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0054] Before introducing the embodiments of the present application, the application background of the embodiments of the present application is first explained:

[0055] Generally, laminar reservoirs have the characteristics of low porosity and ultra-low permeability. The key to the successful development of such reservoirs is to form a large-scale complex fracture network through multi-stage and multi-cluster fracturing of horizontal wells. Unlike conventional reservoirs, laminar reservoirs have significant heterogeneity due to the deposition of layered rocks, and have different mechanical characteristics in different directions, that is, they have inherent anisotropy. The significant anisotropy of laminar reservoirs will have a certain impact on hydraulic fracturing cracks.

[0056] Unconventional reservoirs generally have highly dense laminar discontinuities (ranging from a few to thousands per meter). This strong anisotropy poses a huge challenge to fracturing simulation. When fluid is injected into such reservoirs, hydraulic fractures interact strongly with the existing laminar discontinuities, resulting in great uncertainty in the prediction of fracture geometry. The presence of these laminar discontinuities provides a carrier for the expansion of hydraulic fractures, which can increase the complexity of hydraulic fractures, but also limit the extension path of the fractures.

[0057] At present, existing technologies have established fracturing models that can simulate the expansion of multiple fractures, including wire-net models, discrete fracture network models, and unconventional fracture models, as well as other numerical models based on finite element method, boundary element method, extended finite element method, discrete element method, and phase field method. These numerical models often simplify the reservoir into isotropic materials and cannot efficiently obtain the fracture state of laminar reservoirs.

[0058] Therefore, how to efficiently obtain the fracture state of laminated reservoirs has become a technical problem that needs to be solved urgently.

[0059] In view of the technical problems existing in the prior art, the inventors of this application have the following idea: according to the attribute distribution characteristics of the laminar reservoir, a finite element-discrete element hybrid simulation method is used to simulate the expansion of the fracturing cracks in the laminar reservoir. Specifically, the model corresponding to the three-dimensional laminar reservoir is discretized by using unit blocks, different types of units are generated, and attribute models of different units are constructed. Then, the matrix unit is discretized and fluid-solid coupling is solved. The finite element method is used to calculate the fluid pressure distribution, the deformation of the block unit material, and the stress state of the spring. Then, according to the failure criterion, it is evaluated whether the rock is broken, that is, whether hydraulic fractures are generated. The laminar reservoir is simulated in combination with the laminar characterization parameters of the reservoir to obtain the fracture rupture information of the laminar reservoir.

[0060] Wherein, matters not elaborated in detail are disclosed by the following embodiments.

[0061] The technical solution of the present application is described in detail below through specific embodiments. It should be noted that the following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0062] It is worth noting that the application fields of the methods, devices, and equipment involved in this application are not limited.

[0063] Among them, the executor of this application is a device, which can be a server, terminal device, etc.

[0064] Specifically, Figure 1 Schematic diagram of the process of simulating fracture propagation of laminar reservoir fracturing provided in the embodiment of the present application Figure 1 ,like Figure 1 As shown, the method involved in the embodiment of the present application is briefly introduced:

[0065] Step 11: Discretize the model corresponding to the laminar reservoir according to the preset polyhedral block to obtain at least one discrete matrix unit.

[0066] In this step, according to the preset polyhedral block, the matrix part and the laminae structure in the model corresponding to the laminar reservoir are discretized to obtain at least one discrete matrix unit.

[0067] Among them, the preset polyhedron can simplify the discretization process. The preset polyhedron can be a tetrahedron, a pentahedron and a hexahedron; the discretization process can obtain four unit types: matrix, fluid, perforation and wellbore.

[0068] Specifically, the matrix refers to the solid part of the reservoir, usually composed of rock; the fluid refers to the oil, gas or water in the reservoir, which flows through the pores and cracks of the matrix; the wellbore refers to the holes formed during the drilling process, which penetrate the formation and transport oil and gas from underground to the surface; perforation refers to drilling holes in the wellbore by mechanical or chemical methods, the purpose of which is to connect the wellbore to the reservoir rock and allow oil and gas to flow into the wellbore.

[0069] Figure 2 Schematic diagram of the discrete process of the model corresponding to the laminar reservoir provided in the embodiment of the present application, combined with Figure 2 The model discrete processing corresponding to the laminar reservoir is introduced:

[0070] First, a three-dimensional model of the reservoir is created based on geological exploration data to identify different laminae. Then, a polyhedral block is used to construct a model corresponding to the laminar reservoir ( Figure 2 (a) in the figure) is discretized to obtain discrete matrix units ( Figure 2 (b) in the .

[0071] Among them, the polyhedral block can be a tetrahedron ( Figure 2 (c) in the figure), the pentahedron ( Figure 2 (d) in the figure) and the hexahedron ( Figure 2 There are 3 types of choices in part (e).

[0072] In a possible implementation, the size of the three-dimensional model of the laminar reservoir is set to 120m×50m×20m, and the matrix unit grid size is a pentahedral unit with a base length of 5m and a height of 2m. The total length of the wellbore is 40m, the unit length is 5m, and the perforation depth is 5m. The three-dimensional model of the laminar reservoir is discretized using pentahedrons to obtain 35,900 discrete matrix units.

[0073] Step 12: Determine at least one attribute model corresponding to at least one discrete matrix unit.

[0074] In this step, different attribute models are constructed based on the matrix, fluid, perforation and wellbore units obtained after discretization of the model corresponding to the laminar reservoir.

[0075] Optionally, before step 12, the method may further include:

[0076] Modeling at least one discrete matrix unit according to the discretely generated matrix, fluid, wellbore and perforation unit types to obtain at least one attribute model;

[0077] In this method, various attribute data points of at least one discrete matrix unit are determined through experimental data and geological models according to the discretely generated matrix, fluid, wellbore and perforation unit types, and then interpolation is performed based on the acquired attribute data points of the discrete matrix unit to generate a continuous attribute distribution, thereby establishing at least one attribute model.

[0078] Wherein, at least one attribute model includes: a matrix grid unit stress attribute model, and / or a matrix grid unit and laminae strength attribute model.

[0079] Specifically, the matrix grid unit stress attribute model includes the minimum horizontal principal stress, the maximum horizontal principal stress, the vertical stress and the pore pressure; the laminae strength attribute model includes Young's modulus, Poisson's ratio, rock density, cohesion, internal friction angle, dilatancy angle, tensile strength and rock permeability.

[0080] Table 1 shows the laminae strength attribute model parameters.

[0081] Table 1

[0082]

[0083] Step 13: According to at least one property model, perform fluid-solid coupling solution on at least one discrete matrix unit to determine the fracture information between adjacent discrete matrix units, the fluid pressure distribution between adjacent discrete matrix units, and the stress state of adjacent discrete matrix units.

[0084] In this step, a fluid-solid coupling analysis method is used to comprehensively analyze the discrete matrix units to determine the rupture information between adjacent discrete matrix units, the fluid pressure distribution between adjacent discrete matrix units, and the stress state of adjacent discrete matrix units.

[0085] In order to represent the deformation of the model corresponding to the laminar reservoir, combined with the attribute model parameters in Table 1, the embodiment of the present application introduces a rock deformation equation to describe the deformation of discrete matrix units in the laminar reservoir under different stress states.

[0086] Specifically, the rock mass deformation equation is:

[0087] Assuming that the motion of the reservoir matrix block unit conforms to Newton's second law, considering that the block unit material is deformable, it satisfies the linear elastic dynamic equation:

[0088] σ ij,j +b i -ρu i,tt -αu i,t =0

[0089] Where: Cauchy tensor σ ij =D ijst ε st, strain ε ij =(u i,j +u j,i ) / 2,D ijst is the elasticity tensor, b i is the body force, ρ is the rock density, α is the damping coefficient, u i is the displacement. For the constitutive model of isotropic (homogeneous) elastic rock, only two parameters are required: Young's modulus (E) and Poisson's ratio (ν). Figure 3 As shown ( Figure 3 Schematic diagram of elastic characteristics of transversely isotropic materials provided in the embodiment of the present application). For reservoirs with developed laminar discontinuities, the laminar planes have obvious transversely isotropic characteristics due to the layered deposition of the rock, that is, the elastic properties within the laminar planes are the same, but the elastic parameters perpendicular to the laminar planes (the longitudinal direction of the formation) are significantly different. At this time, five elastic parameters are needed to characterize the linear elastic characteristics of transversely isotropic rocks, among which Young's modulus (E h 、E v ) and Poisson's ratio (ν h , ν v ) and shear modulus G v (The subscripts h and v represent the directions parallel to and perpendicular to the grain plane, respectively).

[0090] The elastic tensor D connects the relationship between stress and strain and can represent the deformation behavior of the laminar reservoir under external forces. Assume that the laminar surface is horizontal, that is, the laminar surface is perpendicular to the vertical stress (σ v ) is vertical, and the elastic tensor D is:

[0091]

[0092] Where, the shear modulus Gv is:

[0093] Among them, fluid-solid coupling refers to discretizing the laminar numerical model. When the fluid is injected into the fracture, it acts on the adjacent blocks. After the matrix block is deformed, the width of the fracture changes, and the flow rate in the fracture also changes accordingly, which in turn affects the size of the fluid pressure in the fracture. That is, the fluid unit pressure in the fracture and the fracture width affect each other. Fluid-solid coupling can accurately describe and predict the complex interaction between fluid and discrete matrix units.

[0094] The embodiment of the present application adopts a weak coupling method to realize the iterative process of fluid flow and solid deformation in the fracture, and discretizes the flow equation and the rock deformation equation by applying the Galerkin finite element method and the minimum potential energy principle, and solves them in a sequential cycle. Before the matrix block unit is fractured, since the permeability of the initial fluid unit is equal to the permeability of the matrix block, the permeability of the matrix block is equivalent to the initial width of the fracture, which is the original fracture width designed for the initial flow of the fluid, that is, Then, within the current time step m, it is necessary to select a suitable experimental solution p m and w m , solve the pressure p of the next iteration step m+1 , and then find w m+1 .

[0095] Usually, when 0<α≤0.5, the time step is small enough to facilitate the iterative convergence of the equation.

[0096]

[0097] Step 14: determine the fracture information of the laminar reservoir fracturing according to the fracture information between all adjacent discrete matrix units, the fluid pressure distribution between all adjacent discrete matrix units, and the stress state of all adjacent discrete matrix units, combined with the laminar characterization parameters of the reservoir.

[0098] In this step, according to the fracture information between all adjacent discrete matrix units, the fluid pressure distribution between all adjacent discrete matrix units, and the stress state of all adjacent discrete matrix units, the characterization parameters of the lamination of the reservoir are input into the model, the fracture rupture mode in the lamination is analyzed, and the influence of the lamination on the fracture propagation is considered, so as to determine the fracture rupture information of the laminar reservoir fracturing.

[0099] The embodiment of the present application provides a method for simulating the expansion of fractures in a laminated reservoir by fracturing. First, according to a preset polyhedral block, the model corresponding to the laminated reservoir is discretized to obtain at least one discrete matrix unit. Then, at least one attribute model corresponding to the at least one discrete matrix unit is determined. Then, according to the at least one attribute model, the at least one discrete matrix unit is fluid-solid coupling solved to determine the fracture information between adjacent discrete matrix units, the fluid pressure distribution between adjacent discrete matrix units, and the stress state of adjacent discrete matrix units. According to the fracture information between all adjacent discrete matrix units, the fluid pressure distribution between all adjacent discrete matrix units, and the stress state of all adjacent discrete matrix units, combined with the laminae characterization parameters of the reservoir, the fracture rupture information of the laminated reservoir is determined. In this technical solution, based on the fracture morphology of the laminated reservoir fracture and its influencing mechanism, the fracture rupture information of the laminated reservoir fracture is determined, providing a basis for improving the benefits of the laminated reservoir transformation.

[0100] Based on the above embodiment, every two discrete matrix units include: a first discrete matrix unit and a second discrete matrix unit, then Figure 4 Schematic diagram of the process of simulating fracture propagation of laminar reservoir fracturing provided in the embodiment of the present application Figure 2 ,like Figure 4 As shown, the above step 13 may include the following steps:

[0101] Step 41: insert a virtual quadrilateral unit between a first discrete matrix unit and a second discrete matrix unit according to at least one attribute model, apply a virtual spring to connect the first discrete matrix unit and the second discrete matrix unit, and transfer the pressure acting between the first discrete matrix unit and the second discrete matrix unit, and determine the fracture of the virtual spring according to a preset failure criterion to characterize the fracture information of the rock as the fracture information between adjacent discrete matrix units.

[0102] In this step, a virtual quadrilateral unit is inserted between two discrete matrix units. The two discrete matrix units are connected by virtual springs. According to the failure criterion, it is judged whether the virtual spring is broken, thereby determining the fracture information of the two discrete matrix units.

[0103] In one possible implementation, Figure 5 Schematic diagram of the activation process of the matrix unit block gap provided in the embodiment of the present application, combined with Figure 5 This step is described in detail.

[0104] Figure 5 Part (a) is a fracturing numerical model corresponding to a laminar reservoir, part (b) is a discrete matrix based on the fluid injection point, part (c) is the gap between two discrete matrix units as a fluid channel, part (d) is the state of different fracture units, and part (e) is a virtual quadrilateral unit inserted between two discrete matrix units.

[0105] The fracturing numerical model corresponding to the laminar reservoir in part (a) is discretized into multiple discrete matrices (polyhedral units) as shown in part (b), and then virtual quadrilateral units (i.e., fracturing fluid units) are inserted, and virtual springs are used to connect adjacent blocks (i.e., Figure 5 The fluid in the fluid channel in part (c) transmits the interaction force on the matrix block unit, which also acts on the virtual spring. The break of the spring represents the fracture of the rock (that is, the fracture unit is activated). There is a fracture unit (that is, Figure 5 Part (d) in the figure is used to calculate the flow of the fracturing fluid and the distribution of the fluid pressure in the fracture. The fluid pressure acts on the fracture surface as an external load.

[0106] Optionally, the preset failure criterion can be determined based on the maximum tensile stress criterion and the Mohr-Coulomb criterion.

[0107] In this implementation, there are fractures between adjacent blocks after discretization, which is manifested as the fracture of the corresponding deformable block virtual spring in the discrete element method calculation. At this time, the spring will produce two types of fractures: stretching and shear slip fracture, corresponding to tensile failure or shear failure. Its fracture criteria include the maximum tensile stress criterion and the Mohr-Coulomb criterion. When the normal stress F at the nth step is n(n) Less than the maximum load profit F n,max When there is no damage between adjacent contact points, the normal stress and shear stress of the nth step are solved according to the following formula:

[0108]

[0109] For the maximum tensile stress criterion, if the maximum tensile stress σ1 reaches the rock tensile strength σT, the spring begins to break (generating tensile cracks), that is, F n (n) ≥F n,max =AT0, T0 is the tensile strength, adjacent blocks separate (Δu n >0), the interaction force disappears, the spring cannot transmit the node stress, and the crack unit is formed. Since the crack trajectory extends along the fluid unit, when the number of grids is large enough, the grid topology along the direction of the maximum principal stress can generate any crack shape, that is:

[0110]

[0111] The Mohr-Coulomb criterion is a criterion used to describe the failure of materials under shear stress, which is specifically expressed as:

[0112]

[0113] Where τ is the shear stress, σ is the normal stress, and φ is the internal friction angle.

[0114] According to the Mohr-Coulomb criterion, when S 0 is the cohesion. When the shear strength peak of the rock is reached, the fracture unit begins to fail in shear, and a normal displacement Δu is generated between adjacent blocks. n , tangential displacement Δu s , and Δu n >0,Δu s >0, the spring is sheared and there is pressure and friction between the blocks, that is:

[0115]

[0116] According to the above failure criteria, it can be judged whether the virtual spring is broken, that is, whether the rock is cracked.

[0117] Step 42: using the finite element method, determine the fluid pressure distribution between the first discrete matrix unit and the second discrete matrix unit and the stress state between adjacent discrete matrix units.

[0118] Specifically, for a rock mass with developed laminar discontinuities, its rock mass medium is closer to a discrete body of a discontinuous medium, and the fluid in the rock mass is a continuous medium that is continuous and does not leave any free gaps. The discrete processing in step 11 can inherit the advantages of discrete matrix units in dealing with discontinuous deformation problems such as rock and soil cracks, and the finite element method in this step can inherit the advantages of finite elements in describing continuous deformation of elastic media.

[0119] In this step, when using the finite element method to analyze the fluid pressure distribution, it is necessary to use the fluid flow equation to represent the movement of the fluid and the pressure it is subjected to. The specific method is as follows:

[0120] The fluid between adjacent block units is regarded as the laminar flow of incompressible Newtonian fluid in a flat plate, ignoring the influence of gravity, and is characterized by the cubic law, local continuity equation and global mass conservation continuity equation:

[0121]

[0122] ∫ Ωf wds=tQ

[0123] Where: p is the fluid unit pressure, unit MPa; ω is the block unit gap, i.e., the dynamic crack width; t is the time; q is the volume flow rate, unit m 3 / s; s is the coordinate of any point in the fluid unit; q l is the fluid loss, unit is m 3 / s, since the laminar reservoir matrix has extremely low permeability, the fluid loss can be ignored, that is, q l =0, Q is the sum of the flow rates entering each fracture unit, unit: m 3 / s; μ is the fluid viscosity, unit: mPa·s.

[0124] The embodiment of the present application provides a method for simulating fracture propagation in a laminar reservoir by fracturing. According to at least one attribute model, a virtual quadrilateral unit is inserted between a first discrete matrix unit and a second discrete matrix unit, a virtual spring is used to connect the first discrete matrix unit and the second discrete matrix unit, and the pressure acting between the first discrete matrix unit and the second discrete matrix unit is transmitted. According to a preset failure criterion, the fracture of the virtual spring is determined to characterize the fracture information of the rock as the fracture information between adjacent discrete matrix units, and then the finite element method is used to determine the fluid pressure distribution and the stress state between the first discrete matrix unit and the second discrete matrix unit. In this technical solution, virtual springs are used to connect adjacent discrete matrix units, and then the fracture of the springs can accurately characterize the fracture information of the rock.

[0125] On the basis of the above-mentioned embodiment, the laminae characterization parameters of the reservoir are equivalent density, equivalent width and mechanical characteristics.

[0126] In this method, the model corresponding to the laminar reservoir established in the embodiment of the present application is characterized by equivalent density, equivalent width and mechanical characteristics.

[0127] Equivalent density ρ B : The number of layers per unit thickness in the vertical direction (can also be expressed as 1 / m). Limited by the model calculation efficiency of cross-scale problems, the model mainly considers the equivalent seepage effect in the direction parallel to the laminae, that is, the equivalent laminae permeability k B '=ρ B / ρ B '×k B , ρ B ' is the equivalent lamination density, the equivalent lamination spacing d B =1 / ρ B '.

[0128] Equivalent width: Equivalent lamination width under ground stress conditions

[0129] Mechanical parameters: strength (Young's modulus, Poisson's ratio, tensile strength, cohesion, friction coefficient or internal friction angle) anisotropic parameters. Figure 6 As shown ( Figure 6 The horizontal homogeneous and inhomogeneous distribution diagram of laminae strength provided in the embodiment of the present application) is for the horizontal inhomogeneous distribution of laminae in actual strata, so the model can consider the horizontal homogeneous (a) and inhomogeneous (b) distribution of laminae strength. The normal distribution is used to characterize the horizontal inhomogeneity of laminae strength:

[0130]

[0131] In the formula, μ is the mean value and σ is the standard deviation.

[0132] Table 2 Basic parameters for reservoir lamination characterization.

[0133] Table 2

[0134]

[0135] In one possible implementation, Figure 7 A schematic diagram of mechanical parameters of lateral heterogeneity of a laminar reservoir provided in an embodiment of the present application is shown in FIG. Figure 7 As shown, Young's modulus, Poisson's ratio, permeability, tensile strength, cohesion and friction are used to characterize the lamination of the reservoir.

[0136] The embodiment of the present application provides a method for simulating fracture propagation in a laminar reservoir, wherein the laminar characterization parameters of the reservoir are equivalent density, equivalent width and mechanical characteristics. This technical solution can fully consider the homogeneous and heterogeneous distribution characteristics of laminar attributes in the vertical and horizontal directions when characterizing the laminae, and can quickly determine the fracture rupture information in the laminar reservoir.

[0137] In one possible implementation, Figure 8 The simulated form of crack expansion when the laminar reservoir strength is laterally homogeneous provided in the embodiment of the present application is as follows: Figure 8 As shown, the wellbore is the fluid injection point of the embodiment of the present application. After the liquid is injected into the model corresponding to the laminar reservoir, a fracture unit (i.e., a virtual quadrilateral unit between two discrete matrix units) will be generated, wherein part (a) is a top view of the simulated morphology of fracture extension when the laminar reservoir strength is transversely homogeneous, and part (b) is a front view of the simulated morphology of fracture extension when the laminar reservoir strength is transversely homogeneous. The different color depths in the figure represent different fluid pressures, and the darker the color, the greater the fluid pressure. The part covered with color represents that the fractures in the laminar reservoir are broken, and the fluid can pass smoothly. The part without color coverage represents that the fractures in the laminar reservoir are not broken, and the fluid cannot pass.

[0138] Among them, the wellbore injection method is used to simulate the fluid injection of on-site construction, and the basic parameters are shown in Table 3.

[0139] Table 3 Basic parameters of wellbore injection for simulation of fracture propagation when the strength of laminated reservoir is laterally homogeneous.

[0140] Table 3

[0141] Parameter (symbol) unit Numeric <![CDATA[Number of fracturing stages, N stage > Integer 1 <![CDATA[Number of perforation clusters, N cluster > Integer 1 <![CDATA[Displacement, Q t > <![CDATA[m 3 / s]]> 0.05 Fracturing fluid viscosity, μ mPa·s 50

[0142] In one possible implementation, Fig. 9 The simulated form of crack propagation when the laminar reservoir strength is laterally heterogeneous provided in the embodiment of the present application is: Fig. 9 Part (a) is a top view of the simulated morphology of crack propagation when the strength of the laminar reservoir is laterally heterogeneous, and part (b) is a front view of the simulated morphology of crack propagation when the strength of the laminar reservoir is laterally heterogeneous.

[0143] The following are device embodiments of the present application, which can be used to execute the method embodiments of the present application. For details not disclosed in the device embodiments of the present application, please refer to the method embodiments of the present application.

[0144] Fig.10 This is a schematic diagram of the structure of an embodiment of a laminar reservoir fracturing crack expansion simulation device provided in the present application. Fig.10 As shown, the device comprises:

[0145] A processing module 101 is used to discretize the model corresponding to the laminar reservoir according to a preset polyhedral block to obtain at least one discrete matrix unit;

[0146] A first determination module 102 is used to determine at least one attribute model corresponding to at least one discrete matrix unit;

[0147] The second determination module 103 is used to perform fluid-solid coupling solution on at least one discrete matrix unit according to at least one property model to determine the fracture information between adjacent discrete matrix units, the fluid pressure distribution between adjacent discrete matrix units, and the stress state of adjacent discrete matrix units;

[0148] The third determination module 104 is used to determine the fracture rupture information of the laminar reservoir fracturing according to the fracture information between all adjacent discrete matrix units, the fluid pressure distribution between all adjacent discrete matrix units, and the stress state of all adjacent discrete matrix units, combined with the laminar characterization parameters of the reservoir.

[0149] In a possible implementation, the first determining module 102 determines at least one attribute model corresponding to at least one discrete matrix unit, specifically for:

[0150] Modeling at least one discrete matrix unit according to the discretely generated matrix, fluid, perforation and wellbore unit types to obtain at least one attribute model;

[0151] Wherein, at least one attribute model includes: a matrix grid unit stress attribute model, and / or a matrix grid unit and laminae strength attribute model.

[0152] In a possible implementation, every two discrete matrix units include: a first discrete matrix unit and a second discrete matrix unit.

[0153] Correspondingly, the second determination module performs fluid-solid coupling solution on at least one discrete matrix unit according to at least one property model to determine the rupture information between adjacent discrete matrix units, the fluid pressure distribution between adjacent discrete matrix units, and the stress state of adjacent discrete matrix units, specifically for:

[0154] According to at least one attribute model, a virtual quadrilateral unit is inserted between a first discrete matrix unit and a second discrete matrix unit, a virtual spring is applied to connect the first discrete matrix unit and the second discrete matrix unit, and a pressure acting between the first discrete matrix unit and the second discrete matrix unit is transmitted, and according to a preset failure criterion, the fracture of the virtual spring is determined to characterize the fracture information of the rock as the fracture information between adjacent discrete matrix units;

[0155] The finite element method is used to determine the fluid pressure distribution between the first discrete matrix unit and the second discrete matrix unit and the stress state between adjacent discrete matrix units.

[0156] In a possible implementation manner, the preset failure criterion is determined based on a maximum tensile stress criterion and a Mohr-Coulomb criterion.

[0157] In a possible implementation, the lamination characterization parameters of the reservoir are equivalent density, equivalent width and mechanical characteristics.

[0158] A laminar reservoir fracturing crack expansion simulation device provided in an embodiment of the present application can be used to execute the determination method in any of the above embodiments. Its implementation principle and technical effects are similar and will not be repeated here.

[0159] It should be noted that it should be understood that the division of the various modules of the above device is only a division of logical functions. In actual implementation, they can be fully or partially integrated into one physical entity, or they can be physically separated. And these modules can all be implemented in the form of software calling through processing elements; they can also be all implemented in the form of hardware; some modules can also be implemented in the form of software calling through processing elements, and some modules can be implemented in the form of hardware. In addition, all or part of these modules can be integrated together, or they can be implemented independently. The processing element described here can be an integrated circuit with signal processing capabilities. In the implementation process, each step of the above method or each module above can be completed by an integrated logic circuit of hardware in the processor element or instructions in the form of software.

[0160] Fig.11 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application, such as Fig.11 As shown, the electronic device may include: a processor 111, a memory 112, and computer program instructions stored in the memory 112 and executable on the processor 111, and the processor 111 implements the method provided in any of the foregoing embodiments when executing the computer program instructions.

[0161] Optionally, the above-mentioned components of the electronic device may be connected via a system bus.

[0162] The memory 112 may be a separate storage unit or a storage unit integrated in the processor 111. The number of the processor 111 is one or more.

[0163] It should be understood that the processor 111 may be a central processing unit (CPU), or other general-purpose processors 111, digital signal processors 111 (DSP), application-specific integrated circuits (ASIC), etc. The general-purpose processor 111 may be a microprocessor 111 or the processor 111 may be any conventional processor 111, etc. The steps of the method disclosed in the present application may be directly embodied as being executed by the hardware processor 111, or may be executed by a combination of hardware and software modules in the processor 111.

[0164] The system bus may be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. The system bus may be divided into an address bus, a data bus, a control bus, etc. For ease of representation, only one thick line is used in the figure, but it does not mean that there is only one bus or one type of bus. The memory 112 may include a random access memory 112 (Random Access Memory, RAM), and may also include a non-volatile memory 112 (Non-Volatile Memory, NVM), such as at least one disk memory 112.

[0165] All or part of the steps of the above-mentioned method embodiments can be completed by hardware related to program instructions. The aforementioned program can be stored in a readable memory 112. When the program is executed, the steps of the above-mentioned method embodiments are executed; and the aforementioned memory 112 (storage medium) includes: read-only memory 112 (Read-Only Memory, ROM), RAM, flash memory 112, hard disk, solid state hard disk, magnetic tape (English: Magnetic Tape), floppy disk (English: FloppyDisk), optical disc (English: Optical Disc) and any combination thereof.

[0166] The electronic device provided in the embodiment of the present application can be used to execute the method provided in any of the above method embodiments. Its implementation principles and technical effects are similar and will not be repeated here.

[0167] An embodiment of the present application provides a computer-readable storage medium, in which computer-executable instructions are stored. When the computer-executable instructions are executed on a computer, the computer executes the above method.

[0168] The computer-readable storage medium mentioned above can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory, electrically erasable programmable read-only memory, erasable programmable read-only memory, programmable read-only memory, read-only memory, magnetic memory, flash memory, magnetic disk or optical disk. The readable storage medium can be any available medium that can be accessed by a general or special-purpose computer.

[0169] Optionally, a readable storage medium is coupled to a processor so that the processor can read information from the readable storage medium and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can be located in an application specific integrated circuit (ASIC). Of course, the processor and the readable storage medium can also exist in the device as discrete components.

[0170] An embodiment of the present application also provides a computer program product, which includes a computer program. The computer program is stored in a computer-readable storage medium. At least one processor can read the computer program from the computer-readable storage medium. When the at least one processor executes the computer program, the above method can be implemented.

[0171] It should be understood that the present application is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A method for simulating fracture propagation in laminar reservoirs, characterized in that: include: According to the preset polyhedral block, the model corresponding to the laminar reservoir is discretized to obtain at least one discrete matrix unit; Determining at least one property model corresponding to the at least one discrete matrix unit; According to the at least one property model, performing fluid-solid coupling solution on the at least one discrete matrix unit to determine rupture information between adjacent discrete matrix units, fluid pressure distribution between the adjacent discrete matrix units, and stress states of the adjacent discrete matrix units; The fracture information of laminar reservoir fracturing is determined based on the fracture information between all adjacent discrete matrix units, the fluid pressure distribution between all adjacent discrete matrix units, and the stress state of all adjacent discrete matrix units, combined with the laminar characterization parameters of the reservoir.

2. The method according to claim 1, characterized in that The determining of at least one property model corresponding to the at least one discrete matrix unit comprises: constructing a model for the at least one discrete matrix unit according to the discretely generated matrix, fluid, perforation and wellbore unit types to obtain the at least one attribute model; Wherein, the at least one attribute model includes: a matrix grid unit stress attribute model, and / or a matrix grid unit and laminae strength attribute model.

3. The method according to claim 2, characterized in that Each two discrete matrix units include: a first discrete matrix unit and a second discrete matrix unit; Accordingly, performing fluid-solid coupling solution on the at least one discrete matrix unit according to the at least one property model to determine the rupture information between adjacent discrete matrix units, the fluid pressure distribution between the adjacent discrete matrix units, and the stress state of the adjacent discrete matrix units includes: According to the at least one attribute model, a virtual quadrilateral unit is inserted between the first discrete matrix unit and the second discrete matrix unit, a virtual spring is applied to connect the first discrete matrix unit and the second discrete matrix unit, and a pressure acting between the first discrete matrix unit and the second discrete matrix unit is transmitted, and according to a preset failure criterion, the fracture of the virtual spring is determined to characterize the fracture information of the rock as the fracture information between the adjacent discrete matrix units; The finite element method is used to determine the fluid pressure distribution between the first discrete matrix unit and the second discrete matrix unit and the stress state between the adjacent discrete matrix units.

4. The method according to claim 3, characterized in that The preset failure criterion is determined based on the maximum tensile stress criterion and the Mohr-Coulomb criterion.

5. The method according to any one of claims 1 to 4, characterized in that: The laminae characterization parameters of the reservoir are equivalent density, equivalent width and mechanical characteristics.

6. A device for simulating fracture propagation in laminar reservoirs, characterized in that: The device comprises: A processing module, used for discretizing the model corresponding to the laminar reservoir according to the preset polyhedral block to obtain at least one discrete matrix unit; A first determining module, used to determine at least one attribute model corresponding to the at least one discrete matrix unit; A second determination module is used to perform fluid-solid coupling solution on the at least one discrete matrix unit according to the at least one property model to determine the rupture information between adjacent discrete matrix units, the fluid pressure distribution between the adjacent discrete matrix units, and the stress state of the adjacent discrete matrix units; The third determination module is used to determine the fracture rupture information of the laminar reservoir fracturing according to the fracture information between all adjacent discrete matrix units, the fluid pressure distribution between all adjacent discrete matrix units, and the stress state of all adjacent discrete matrix units, combined with the laminar characterization parameters of the reservoir.

7. The device according to claim 6, characterized in that The first determining module is specifically configured to: constructing a model for the at least one discrete matrix unit according to the discretely generated matrix, fluid, perforation and wellbore unit types to obtain the at least one attribute model; Wherein, the at least one attribute model includes: a matrix grid unit stress attribute model, and / or a matrix grid unit and laminae strength attribute model.

8. An electronic device, characterized in that: include: A processor, and a memory communicatively connected to the processor; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory to implement the method according to any one of claims 1 to 5.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, and when the computer-executable instructions are executed by a processor, they are used to implement the method according to any one of claims 1 to 5.

10. A computer program product, characterized in that The computer program product comprises a computer program, which is stored in a computer-readable storage medium. At least one processor can read the computer program from the computer-readable storage medium, and when the at least one processor executes the computer program, the method described in any one of claims 1 to 5 can be implemented.

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