Simulation method and device for tectonic stress field

Abstract

The application provides a simulation method and device for constructing a stress field, and relates to the technical field of stress simulation. The method comprises the following steps: obtaining tectonic data of a working area reservoir; constructing a geological model according to the tectonic data of the working area reservoir; determining mechanical properties, stress loading modes, boundary constraint conditions and rock physical parameters of the geological model through test data of uniaxial and triaxial rock mechanics tests of the working area reservoir; and determining the tectonic stress field distribution of the reservoir by using a finite element numerical simulation method according to the mechanical properties, stress loading modes, boundary constraint conditions and rock physical parameters of the geological model. The application determines the mechanical parameters and boundary stress conditions of the geological barrier based on the geological model and the mechanical model, thereby simulating the tectonic stress field distribution of the reservoir, accurately revealing the ground stress distribution characteristics of the reservoir in the research area, and having wide applicability and providing a theoretical support for predicting favorable areas of the oil and gas reservoir.

Description

Technical Field

[0001] This invention relates to the field of stress simulation technology, and more particularly to a method and apparatus for simulating a constructed stress field. Background Technology

[0002] This section is intended to provide background or context for embodiments of the present invention. The description herein is not intended to imply that it is prior art simply because it is included in this section.

[0003] The stresses within the Earth are collectively referred to as geostress, which consists of tectonic stress, static rock stress, pore fluid pressure, and thermal stress. Among these, static rock stress, pore fluid pressure, and thermal stress at any point in the Earth's crust are isotropic. In geology, the stresses caused by gravity and tectonic movements are primarily discussed. Gravity-induced stress is static rock stress, and its magnitude is a function of depth. Tectonic stress refers to a stress state added on top of the static rock stress state, or the portion of geostress that deviates from the static rock stress state. It is the main force forming various geological structural phenomena in the Earth's crust, and in particular, the magnitude of the tectonic differential stress controls the intensity of various tectonic deformations.

[0004] The spatial distribution of tectonic stress is called a tectonic stress field. The stresses that create geological structures during geological history are paleostresses, and their spatial distribution is called the paleotectonic stress field. The stresses existing or currently acting in the modern crust are called the modern tectonic stress field, typically referring to the stress field during the neotectonic period since the Middle Pleistocene (0.7 Ma). Extensive data indicate that fractures in low-permeability oil and gas reservoirs are mainly tectonic fractures formed under the influence of paleotectonic stress fields during geological history. The principal stress direction of the paleotectonic stress field controls the direction of fracture extension, and the differential stress value determines the degree of fracture development. Tectonic deformation during the neotectonic period is relatively stable, with relatively low tectonic stress values, and no intense tectonic deformation occurred within continental plates. Therefore, the paleotectonic stress field determines the distribution of structural fractures in the reservoir, while the present-day stress field mainly affects the preservation state of fractures and their permeability. Therefore, the analysis of paleotectonic and present-day stress fields in sedimentary basins is of great significance for studying the fracture distribution patterns in low-permeability reservoirs and for predicting the "sweet spot" intervals of oil and gas reservoirs.

[0005] Currently, there are many methods for studying stress fields, including experimental tests such as the Kaiser test; conventional hydraulic fracturing stress models; sonic logging; and, in addition, interpreting the fracture propagation direction through FMI imaging logging as the direction of the maximum principal stress. In recent years, finite element numerical simulation has also gradually become a major research method for stress fields. However, there is currently a lack of effective evaluation methods for the geostress field in complex structural areas. Conventional testing methods can effectively recover the stress in a single well, but in areas with complex structural development, the magnitude and direction of stress are often significantly affected by the structure, resulting in substantial variations. This makes it difficult for conventional methods to effectively predict the planar stress field of the entire study area, leading to large errors in the predicted stress field results.

[0006] In summary, there is an urgent need for a technical solution that can overcome the above-mentioned shortcomings, improve the stress field simulation and prediction method, and enhance the effectiveness of the prediction. Summary of the Invention

[0007] To address the shortcomings of existing technologies in effectively predicting stress fields in areas with complex geological structures, which leads to significant errors in the predicted stress fields, this invention proposes a method and apparatus for simulating tectonic stress fields. Based on geological and mechanical models, the mechanical parameters and boundary stress conditions of geological isolation bodies are determined, thereby simulating the distribution of tectonic stress fields in reservoirs and accurately revealing the geostress distribution characteristics of reservoirs in the study area, thus solving the problems existing in the prior art.

[0008] In a first aspect of the present invention, a method for simulating a structural stress field is proposed, the method comprising:

[0009] Obtain structural data of the reservoir in the working area;

[0010] Based on the structural data of the reservoirs in the work area, a geological model is constructed;

[0011] The mechanical properties, loading methods, boundary constraints, and rock physical parameters of the geological model were determined using test data from uniaxial and triaxial rock mechanics tests of the reservoir in the working area.

[0012] Based on the mechanical properties, loading methods, boundary constraints, and rock physical parameters of the geological model, the tectonic stress field distribution of the reservoir is determined using the finite element numerical simulation method.

[0013] In a second aspect of the present invention, a device for simulating a structural stress field is provided, the device comprising:

[0014] The acquisition module is used to acquire the structural data of the reservoir in the working area;

[0015] The model building module is used to build a geological model based on the structural data of the reservoir in the working area;

[0016] The condition determination module is used to determine the mechanical properties, loading methods, boundary constraints, and rock physical parameters of the geological model based on test data from uniaxial and triaxial rock mechanics tests of the reservoir in the working area.

[0017] The calculation module is used to determine the tectonic stress field distribution of the reservoir using the finite element numerical simulation method based on the mechanical properties, loading method, boundary constraints and rock physical parameters of the geological model.

[0018] In a third aspect of the present invention, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement a method for simulating a stress field.

[0019] In a fourth aspect of the present invention, a computer-readable storage medium is provided, the computer-readable storage medium storing a computer program that, when executed by a processor, implements a method for simulating a stress field.

[0020] In a fifth aspect of the present invention, a computer program product is provided, the computer program product comprising a computer program that, when executed by a processor, implements a method for simulating a constructed stress field.

[0021] The proposed method and apparatus for simulating tectonic stress fields establishes geological isolation bodies based on the fault development characteristics of reservoirs, determines the boundary conditions of these isolation bodies, and uses pre-defined rock physical parameters, geological models, and boundary conditions to infer the stress conditions during the formation of structures and tectonic fractures. This determines the loading method, magnitude, and boundary conditions for forward modeling, thereby establishing a geological model. Based on the mechanical parameters and boundary stress conditions of this model, the finite element method is used to simulate the distribution of the tectonic stress field in the reservoir. This method considers the tectonic characteristics of the study area, accurately reveals the geostress distribution characteristics of areas with complex tectonic development based on the establishment of multiple models, reduces the error in stress field prediction results, and has wide applicability, providing theoretical support for the prediction of favorable areas for oil and gas reservoirs. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of a method for simulating a structural stress field according to an embodiment of the present invention.

[0024] Figure 2 This is a schematic diagram of the process of constructing a geological model according to an embodiment of the present invention.

[0025] Figure 3 This is a schematic diagram of the process of determining the tectonic stress field distribution of a reservoir using the finite element numerical simulation method according to an embodiment of the present invention.

[0026] Figure 4 This is a schematic diagram of the study area modeling and meshing according to an embodiment of the present invention.

[0027] Figure 5 This is a schematic diagram of the stress field calculation process according to an embodiment of the present invention.

[0028] Figure 6 This is a schematic diagram of stress field result analysis according to an embodiment of the present invention.

[0029] Figure 7 This is a graph showing the uniaxial compressive stress-strain relationship of rock according to an embodiment of the present invention.

[0030] Figure 8 This is a schematic diagram of the paradigm equivalent stress distribution characteristics according to an embodiment of the present invention.

[0031] Figure 9 This is a schematic diagram of the principal stress vector distribution characteristics in the study area according to an embodiment of the present invention.

[0032] Figure 10 This is a schematic diagram of the distribution characteristics of the compression deformation in the study area according to an embodiment of the present invention.

[0033] Figure 11 This is a schematic diagram of the shear stress distribution characteristics in the study area according to an embodiment of the present invention.

[0034] Figure 12 This is a schematic diagram of the tensile stress distribution characteristics in the study area according to an embodiment of the present invention.

[0035] Figure 13 This is a schematic diagram of the normal stress distribution characteristics in the study area according to an embodiment of the present invention.

[0036] Figure 14 This is a schematic diagram of the maximum principal stress distribution characteristics in the study area according to an embodiment of the present invention.

[0037] Figure 15 This is a schematic diagram of the distribution characteristics of the principal stress in the middle of the study area according to an embodiment of the present invention.

[0038] Figure 16 This is a schematic diagram of the minimum principal stress distribution characteristics in the study area according to an embodiment of the present invention.

[0039] Figure 17 This is a schematic diagram of the structure of a simulation device for constructing a stress field according to an embodiment of the present invention.

[0040] Figure 18 This is a schematic diagram of a computer device structure according to an embodiment of the present invention. Detailed Implementation

[0041] The principles and spirit of the invention will now be described with reference to several exemplary embodiments. It should be understood that these embodiments are given merely to enable those skilled in the art to better understand and implement the invention, and are not intended to limit the scope of the invention in any way. Rather, these embodiments are provided to make this disclosure more thorough and complete, and to fully convey the scope of this disclosure to those skilled in the art.

[0042] Those skilled in the art will recognize that embodiments of the present invention can be implemented as a system, apparatus, device, method, or computer program product. Therefore, this disclosure can be specifically implemented in the following forms: entirely hardware, entirely software (including firmware, resident software, microcode, etc.), or a combination of hardware and software.

[0043] According to an embodiment of the present invention, a method and apparatus for simulating a stress field are proposed, relating to the field of stress simulation technology.

[0044] The principles and spirit of the present invention will be explained in detail below with reference to several representative embodiments.

[0045] Figure 1 This is a schematic flowchart of a method for simulating a structural stress field according to an embodiment of the present invention. Figure 1 As shown, the method includes:

[0046] S101, Obtain structural data of the reservoir in the working area;

[0047] S102, Construct a geological model based on the structural data of the reservoir in the working area;

[0048] S103. Using test data from uniaxial and triaxial rock mechanics tests of the reservoir in the working area, determine the mechanical properties, loading methods, boundary constraints, and rock physical parameters of the geological model.

[0049] S104. Based on the mechanical properties, loading method, boundary constraints, and rock physical parameters of the geological model, the finite element numerical simulation method is used to determine the tectonic stress field distribution of the reservoir.

[0050] To provide a clearer explanation of the above-mentioned method for simulating the structural stress field, each step will be described in detail below.

[0051] In one embodiment, for S101, structural data of the reservoir in the working area is acquired. In practical applications, structural data of the reservoir in the working area can be acquired through methods such as geological surveys, geophysical exploration, and well logging techniques.

[0052] In one embodiment, for S102, a geological model is constructed based on the structural data of the reservoir in the working area.

[0053] refer to Figure 2 Specific methods include:

[0054] S201, Establishing geological isolation bodies based on structural data of reservoirs in the working area;

[0055] S202, Determine the boundary conditions of the geological isolation body based on well logging data;

[0056] S203, by back-calculating the stress conditions during the formation of structures and tectonic fractures using preset rock physical parameters, geological models, and boundary conditions of the geological isolation body, the loading method, magnitude, and boundary conditions during forward modeling are determined.

[0057] S204. Construct a geological model based on the loading method, size, and boundary conditions used in the forward modeling calculation.

[0058] Furthermore, the method also includes:

[0059] Based on the geological model, an inversion standard is proposed, which includes at least: a deformation standard and an absolute inversion standard. The deformation standard is used to determine the consistency of the structural pattern. If the deformation of the geological isolator after being subjected to different stresses is consistent with the structural pattern before deformation, then the stress application method is considered reasonable. The absolute inversion standard is used to select the stress value, deformation value, and rock fracture strength value of the reservoir structure in the simulation of the current stress field.

[0060] For the absolute inversion standard, the absolute inversion standard of stress value, deformation value, and rock fracture strength value of the selected reservoir structure is calculated using a linear superposition method. The calculation method is as follows:

[0061] Define N parameters P1, P2, ..., P that need to be determined through inversion. N ;

[0062] Collect M measured calibration data points Q1, Q2, ..., Q. M M>N;

[0063] Take a parameter P i Perform inversion calculations for i = 1, i = 1, 2, ..., N to determine the correction point and parameter value a. ij ,i=1,2,…,N,j=1,2,…,M;

[0064] Based on the determined correction points, parameter values, and correction data, linear superposition yields M equations:

[0065]

[0066] Solving M equations using the least squares method yields N parameters P1, P2, ..., P N The absolute inversion standard is determined by repeatedly calculating until the parameters that meet the requirements are obtained; if the calculation result reaches the absolute inversion standard during the calculation process, the numerical simulation result is determined to be correct.

[0067] In one embodiment, for S103, the mechanical properties, loading methods, boundary constraints, and rock physical parameters of the geological model are determined using test data from uniaxial and triaxial rock mechanics tests of the reservoir in the working area.

[0068] Specifically, by conducting uniaxial and triaxial rock mechanics tests, the rock physical parameters required for numerical simulation of tectonic stress field and tectonic cracks are determined; the rock physical parameters include rock mechanical properties such as density, tensile strength, elastic modulus, Poisson's ratio, cohesion, internal friction angle, and shear strength.

[0069] Among them, the bulk density method is used to calculate the mechanical density of rock, and the calculation formula is as follows:

[0070] r0 = M0 / V;

[0071] In the formula, r0 is the natural density of the specimen, representing the mechanical density of the rock; M0 is the natural mass of the specimen; and V is the volume of the specimen.

[0072] The tensile strength of rock is determined by splitting tensile test, and the calculation formula is as follows:

[0073] S t =2P max / (DH);

[0074] Among them, S t P represents the uniaxial tensile strength of the specimen, and P represents the tensile strength of the rock. max The load is the destructive load; D and H are the diameter and height of the specimen, respectively.

[0075] The formula for calculating uniaxial compressive strength is:

[0076] σ c =P max / A;

[0077] Where, σ c P represents uniaxial compressive strength. max A represents the maximum failure load of the rock specimen; A is the area of ​​the specimen subjected to pressure.

[0078] The formulas for calculating the elastic modulus and Poisson's ratio of uniaxial rock are as follows:

[0079] E = c 50 / h 50 ;

[0080] υ=d 50 / h 50 ;

[0081] In the formula, E is the elastic modulus of the specimen, representing the uniaxial elastic modulus of the rock; c 50 50% of the uniaxial compressive strength of the specimen; h 50 d 50 c 50 The corresponding axial compressive strain and radial tensile strain at the location; υ is Poisson's ratio, representing the Poisson's ratio of the uniaxial rock;

[0082] The elastic modulus and Poisson's ratio of triaxial rocks are:

[0083] E' = Δσ / Δε;

[0084] υ′=-Δε2 / Δε1;

[0085] In the formula, E' is the elastic modulus of the triaxial rock; Δσ is the axial stress increment; Δε is the axial strain increment; Δε1 and Δε2 represent the transverse and longitudinal strain increments, respectively; υ' represents the elastic modulus and Poisson's ratio.

[0086] Using the Coulomb criterion to determine rock shear failure:

[0087]

[0088] In the formula, σ1′ represents the axial stress on the specimen; σ3′ represents the confining pressure; and C is the cohesion. The internal friction angle is denoted by ctg; ctg represents the arctangent calculation formula; when the inequality holds, the rock fails.

[0089] Based on the failure strength values ​​of rocks under different confining pressures, the cohesion and internal friction angle of the rocks are obtained through regression analysis.

[0090] The shear strength of rocks under different normal stress conditions is expressed as:

[0091] σ n =(σ1+σ3) / 2-(σ1-σ3) / 2cos2θ;

[0092] τ m = (σ1-σ3) / 2sin2θ;

[0093] In the formula, σ1 represents the maximum principal stress; σ3 represents the minimum principal stress; σ nτ represents normal stress; θ represents the fracture angle; τ represents the normal stress. m The shear strength is represented by the measured values ​​of the maximum principal stress σ1, the minimum principal stress σ3, and the fracture angle θ. The normal stress σ in the rock is then determined. n Shear strength τ m .

[0094] In one embodiment, for S104, based on the mechanical properties, loading method, boundary constraints, and rock physical parameters of the geological model, the finite element numerical simulation method is used to determine the tectonic stress field distribution of the reservoir, with reference to... Figure 3 Specific methods include:

[0095] S301 discretizes a continuous geological isolation body into finite continuous elements; where each element is connected by nodes and each element is assigned rock mechanical parameters.

[0096] S302, based on the boundary force conditions and the equilibrium conditions of the nodes, establish a joint equation system with nodal displacements and element internal stresses as unknowns and the overall stiffness matrix as coefficients.

[0097] S303 uses a construction interpolation function to calculate the displacement at each node in the joint equation system, determines the approximate values ​​of stress and strain in each unit, and obtains the structural stress field distribution of the reservoir.

[0098] The following is an illustration using a specific embodiment, taking a study area to be simulated as an example. Based on the structural conditions of the study area to be simulated, a complex structural model is established. Combined with the rock mechanical characteristics of the reservoirs in the study area, values ​​are assigned to the model, and the model is meshed, as shown below. Figure 4 As shown; the left figure is the model of the study area, including faults; the right figure is a schematic diagram of the gridding.

[0099] In this embodiment, a geological body of the Qingyi shale oil reservoir in the central depression was established, a discrete fault body was implanted, and the stress distribution characteristics of the study area were predicted and analyzed using the 3D-FEM method.

[0100] The reservoir physical properties and loading conditions are input into the model, and the direction of geostress in the study area is determined as a reference for the confining pressure at the model boundary.

[0101] Numerical modeling, meshing the model, applying confining pressure to the model boundaries, and finally post-processing to obtain the stress field results. The stress field calculation process is as follows: Figure 5 As shown.

[0102] Stress field results analysis, such as Figure 6As shown, the model can output equivalent stress (to obtain the comprehensive stress distribution of the study area), stress vector (to obtain the stress field distribution direction of the study area), shear stress (to determine the dominant development area of ​​shear joints in the study area), and tensile stress (to determine the dominant development area of ​​tension joints in the study area).

[0103] Step 1: Establish and construct a numerical model.

[0104] The finite element method (FEM) is employed to calculate structural deformation and stress distribution. It is a numerical solution method that approximates general continuous problems. The basic idea is to discretize a continuous geological body into finite continuous elements connected by nodes. Each element is assigned actual rock mechanics parameters. Based on boundary stress conditions and nodal equilibrium conditions, a joint equation system is established and solved, with nodal displacements or element stresses as unknowns and the global stiffness matrix as coefficients. An interpolation function is constructed to obtain the displacement at each node, and then approximate values ​​of stress and strain within each element are calculated. Assuming each element is homogeneous, the combination of sufficiently numerous and small elements can simulate real geological bodies with complex shapes, loads, and boundary conditions. As the number of elements increases and the element subdivisions become smaller, more closely resembling the actual geological body, it gradually approaches the true solution.

[0105] For a loaded elastic body, deformation can be represented by the displacement vector [μ] at each point within the body:

[0106] [μ]=(μνω) T (1)

[0107] In the formula:

[0108]

[0109] μ, ν, and w represent the displacement components of a point along three directions, which are functions of x, y, and z. The stress state of an elastic body can be represented by the stress vector [σ] at each point within the body:

[0110] [σ]=(σ x σ y σ z τ xy τ yz τ zx ) T (3)

[0111] [σ] represents the stress vector; σ x σ y σ z These are the normal stresses along the x, y, and z directions, respectively. They represent the force per unit area in the corresponding directions; positive values ​​represent tensile force, and negative values ​​represent compressive force. τ xy τyz τ zx τ represents shear stress. xy τ represents the shear stress along the y-direction in the x-plane (the plane perpendicular to the x-axis). yz τ represents the shear stress along the z-direction in the y-plane (the plane perpendicular to the y-axis). zx This represents the shear stress along the x-direction in the z-plane (the plane perpendicular to the z-axis), reflecting the shearing effect within the material in different directional planes. T represents transpose.

[0112] The strain state of an elastic body can be represented by the strain vector [ε] at each point within the body:

[0113] [ε]=(ε x ε y ε z γ xy γ yz γ zx ) T (4)

[0114] [ε] represents the strain vector; ε x ε y ε z These are the normal strains along the x, y, and z directions, representing the relative changes in length in the corresponding directions; γ xy γ yz γ zx γ represents shear strain. xy γ represents the strain caused by the change in angle between the x and y directions. yz γ represents the strain caused by the change in angle between the y and z directions. zx It represents the strain caused by the change in angle between the z and x directions, reflecting the shear deformation of the material in different directions.

[0115] For a loaded elastic body in equilibrium, there are certain relationships between strain and displacement, and between stress and external force. These relationships are called the fundamental equations of elasticity. Combined with given boundary conditions, these equations form the basis for solving problems in elasticity. In practical calculations, by solving the fundamental equations of elasticity, the direction and magnitude of the maximum principal stress, intermediate principal stress, and minimum principal stress of each finite element in a geological body can be obtained.

[0116] After calculating the stress field, the stress is obtained on each element as follows:

[0117]

[0118] By using orthogonal similarity transformation, a real matrix can be simplified into a diagonal matrix, whose diagonal elements are the three eigenvalues ​​of the matrix:

[0119]

[0120] [σ] is the stress tensor; P is the transformation matrix; P -1 λ1, λ2, and λ3 are the transformed principal stress values; σ1, σ2, and σ3 are the principal stress components of the original stress tensor in a specific coordinate system. These three eigenvalues ​​are the three principal stress values, and their corresponding eigenvalue vectors are the cosines of the three principal stress directions.

[0121] Establish a heterogeneous geological model:

[0122] The geological model is the foundation and prerequisite for the entire numerical simulation, directly determining the appropriate selection of the mechanical and mathematical models. The geological model mainly includes the selection of geological isolates and faults, and the determination of boundary conditions and inversion criteria. It is proposed based on a comprehensive study of geological laws, including the structural evolution of the oilfield, the distribution characteristics and causes of fractures, etc. Then, using seismic, logging, and drilling data, the paleotectonic development history profile is reconstructed according to the principle of balanced profiles to establish simulated geological isolates. Simultaneously, based on a comprehensive analysis of the longitudinal evolution history of the regional and local stress fields, and using data from each well point (including core, logging, and dynamic data), preliminary boundary conditions for the geological bodies are determined, and inversion criteria are proposed.

[0123] Selection of Geological Isolators: After studying the distribution characteristics and causes of fractures and analyzing the longitudinal evolution of the stress field, a structural planar map of the fracture formation period was selected to establish the geological isolates. The x-axis direction of the geological isolates was chosen as the direction of maximum principal stress, and the y-axis direction was perpendicular to the x-axis. The simulated target layer thickness varied according to the actual thickness of the reservoir.

[0124] Step 2, Determining boundary conditions:

[0125] Boundary conditions refer to the nature, magnitude, and loading and constraint methods of external far-field stresses acting on the boundary of a geological isolator, including both force-based and constraint-based boundary conditions. For different geological periods, the distribution characteristics of the tectonic stress field vary, resulting in inconsistent simulated boundary conditions. Based on a comprehensive analysis of the principal stress orientation, maximum principal stress magnitude, and tectonic differential stress magnitude obtained from previous studies of tectonic stress fields, the initial boundary conditions for numerical simulation are set as follows: The maximum horizontal stress orientation in the study area is near-horizontal (NE, 77°-93°), the simulated stress loading direction is determined, the maximum principal stress is 30.64 MPa, the minimum principal stress orientation is perpendicular to the maximum principal stress, the minimum principal stress is 21.90 MPa, and the vertical principal stress is 39.38 MPa. The final boundary conditions for the numerical simulation are determined by selecting the optimal scheme after numerous inversion calculations. Boundary conditions in numerical simulation primarily involve stress loading conditions. Stress loading involves the magnitude and direction of the applied stress. The stress direction can be referenced from the "World Geostress Database". The magnitude of the boundary stress can be calculated from the shear wave data of well logging data to obtain the current structural differential stress value.

[0126] The constrained boundary conditions are the initial constraints on the boundaries and corners of the geological isolator. To prevent the geological isolator from drifting, the y-axis boundary of the isolator is constrained in the x-direction in the simulation, while the other boundaries are free boundaries. The isolator is subjected to in-situ stress and is subjected to horizontal force and deformation, which is consistent with the geological conditions of the area. From the actual simulation results, this boundary is quite reasonable.

[0127] Step 3, Calculation of stress field results:

[0128] Determining the inversion criteria: Due to the multiplicity and complexity of geological structural genesis, it is difficult to accurately determine the factors and boundary conditions that affect the distribution of tectonic stress field and reservoir structural fractures. Therefore, the simulation calculation of tectonic stress field and reservoir structural fractures is actually an iterative inversion and forward modeling process.

[0129] First, the stress conditions during the tectonic and fracture formation periods are inferred from the initially established rock physics parameters, geological model, and boundary conditions, thereby determining the loading method, magnitude, and boundary conditions for forward modeling. Since the parameters to be determined in the inversion are not unique, the inversion results will also not be unique. Therefore, a series of geological inversion standards need to be developed based on accurate and actual geological data of the study area to verify the accuracy of the calculation results. To date, there is no simple and reliable method or standard suitable for different geological conditions; in practice, hundreds of calculation schemes often need to be tested. Based on previous practice, the following are some feasible inversion standards in numerical modeling:

[0130] Deformation criterion: If the deformation of the geological body after loading is consistent with the actual paleotectonic pattern, then the loading method is considered to be basically reasonable.

[0131] The principal stress orientation criteria in the tectonic stress field calculation stage: Under different stress conditions, the directions and dip angles of the three principal stresses are regularly distributed. In the extensional tectonic region, the minimum principal stress (σ3) and intermediate principal stress (σ2) are nearly horizontal, while the maximum principal stress (σ1) is nearly vertical, consistent with the Anderson model. In the compressional tectonic stress field, the maximum principal stress (σ1) and minimum principal stress (σ3) are nearly horizontal, while the intermediate principal stress (σ2) is nearly vertical, consistent with the stress state experienced during shear crack formation. After simulation, the directions of the maximum and minimum principal stresses within each element are approximately the same as the direction of the boundary forces.

[0132] Fracture orientation criteria in reservoir structural fracture calculation stage: On the core, the structural fracture system, orientation and dip angle can be quantitatively described by various methods. The simulated structural fracture system orientation and dip angle distribution should be consistent with the description results.

[0133] Absolute inversion criteria: Since the absolute values ​​of the in-situ stress in certain oil wells of an oilfield can be measured using various methods when calculating the in-situ stress field, absolute inversion criteria are generally used in the simulation of the in-situ stress field. Specific criteria can be selected from stress values, deformation values, rock fracture strength values, etc. For these inversion criteria with defined values, the principle of linear superposition can be used for calculation. The specific process is as follows:

[0134] Define N parameters P1, P2, ..., P that need to be determined through inversion. N ;

[0135] Collect M measured calibration data points Q1, Q2, ..., Q. M M>N;

[0136] Take a parameter P i Perform inversion calculations for i = 1, i = 1, 2, ..., N to determine the correction point and parameter value a. ij ,i=1,2,…,N,j=1,2,…,M;

[0137] Based on the determined correction points, parameter values, and correction data, linear superposition yields M equations:

[0138]

[0139] Solving the M equations using the least squares method yields N parameters P1, P2, ..., P N This process can be repeated until the requirements are met.

[0140] Other standards:

[0141] a. The simulated paleostress values ​​(mainly the maximum principal stress and differential stress values) should be close to the values ​​estimated by other methods and consistent with current understanding;

[0142] b. The simulated fracture density distribution is basically consistent with existing geological data and oilfield dynamic data.

[0143] If the above inversion criteria can be met in the calculation, the numerical simulation results are basically reliable, and then production data can be used to verify them.

[0144] Establishing a mechanical model: The mechanical model is crucial for numerical simulation and should be built upon the geological model. It includes determining the mechanical properties of the geological body, the loading and constraint methods, the treatment of thin oil layers, and the determination of rock physical parameters. Determining the mechanical properties, loading and constraint methods of the geological body: Determining the mechanical properties of the geological body involves identifying its mechanical characteristics and the governing differential equations. This includes treating the geological body as an elastic, elastoplastic, or viscoelastic body, and whether the deformation is large or small.

[0145] Rock mechanics tests show that the overall properties of the rock are brittle, exhibiting a significant stress drop after fracture. Therefore, the geological body is treated as an elastic body, and linear elasticity is calculated using a plate-shell model. Since the thickness of the reservoir sandstone varies with sedimentation, the rock mechanics parameters of the reservoir also change accordingly. Therefore, based on the percentage of sandstone and mudstone in the sedimentary zone, a weighted average method is used to obtain the rock mechanics parameters for different sandstone thickness zones. Within the same sandstone thickness zone, the reservoir is defined as having the same material properties, while different sandstone thickness zones are bonded together, forming a heterogeneous body.

[0146] To reflect the complex and heterogeneous geological bodies caused by sedimentation, and to avoid overly coarse meshes in areas of complex shape, a free meshing method was adopted. The mesh size was controlled using several default levels, each with pre-defined parameter values; there were ten levels in total, with higher levels indicating coarser meshing. Analysis of the results showed that level 3 performed best, automatically optimizing the mesh and resulting in more uniform meshing for the same material. In complex areas of key regions, the mesh was denser, while in other areas, the mesh size was relatively larger.

[0147] Static structural analysis is performed, and its static equations are as follows:

[0148]

[0149] In the formula, [K] is called the global stiffness matrix. Let be the displacement vector of the node, and the first term on the right-hand side of the equation. It is a reaction load, the second term. It is the load applied to the node, the third term. It is the load applied to the element. Each element in [K] is related to the node coordinates in the structural model. In order to ensure that the [K] matrix can reflect the true stiffness of the structure, in addition to the establishment of a solid model that can accurately reflect the geometry of the simulated shell structure, an accurate mechanical model should also be established, and external loads and boundary constraints should be applied.

[0150] Before performing stress field analysis, boundary conditions and loads must be applied to the finite element elements. Based on geological conditions, the initial loading method for the geological body is to apply horizontal compressive forces to the stress nodes at all four boundaries. The magnitude of these forces is determined based on the stress field analysis results. The final boundary conditions for the simulation are determined through numerous forward and inverse calculations. Constraints are applied in the x-direction on the northwest and west boundaries of the model, while other boundaries are free boundaries.

[0151] Determination of Rock Physical Parameters: Rock mechanical properties directly affect rock deformation behavior, thus influencing the formation and development of rock fractures. Therefore, conducting uniaxial and triaxial rock mechanics tests can provide practical rock physical parameters for numerical simulation of tectonic stress fields and tectonic fractures, including rock mechanical properties such as density, elastic modulus (E), Poisson's ratio (υ), cohesion (C), and internal friction angle. Shear strength (τ) m ) and tensile strength (S) t )wait.

[0152] Rock density is measured using an electronic balance and calculated using the bulk density method. The formula is as follows:

[0153] r0 = M0 / V; (9)

[0154] In the formula, r0 is the natural density of the specimen (g / cm³). 3 M0 represents the rock's mechanical density; M0 is the specimen's natural mass (g); V is the specimen's volume (cm³). 3 );

[0155] The tensile strength of the rock is directly measured by a splitting tensile test. The rock splitting tensile test is performed on a universal testing equipment. The formula for calculating the rock splitting tensile test is:

[0156] S t =2P max / (DH); (10)

[0157] Among them, S t P represents the uniaxial tensile strength (MPa) of the specimen, and P represents the tensile strength of the rock. max The destructive load is (N); D and H are the diameter and height of the specimen, respectively (mm).

[0158] Uniaxial compression and deformation tests on rocks were conducted on an experimental platform consisting of an electronic pressure testing machine, pressure sensors, a control recorder, and a data processing system including a computer and plotter. The uniaxial compressive stress-strain curves of the rocks are shown below. Figure 7 Formula for calculating uniaxial compressive strength:

[0159] σ c =P max / A;(11)

[0160] Where, σ c P represents the uniaxial compressive strength (MPa). max A represents the maximum failure load (N) of the rock specimen; A represents the pressure-bearing area of ​​the specimen (mm²). 2 );

[0161] The formulas for calculating the elastic modulus (E) and Poisson's ratio (υ) of rock are as follows:

[0162] E = c 50 / h 50 (12)

[0163] υ=d 50 / h 50 (13)

[0164] In the formula, E is the elastic modulus of the specimen (GPa), representing the uniaxial elastic modulus of the rock; c 50 The value is 50% (MPa) of the uniaxial compressive strength of the specimen; h 50 d 50 c 50 The corresponding axial compressive strain and radial tensile strain at the location; υ is Poisson's ratio, representing the Poisson's ratio of the uniaxial rock;

[0165] High-temperature and high-pressure triaxial rock mechanics experiments were conducted on a high-temperature and high-pressure triaxial rock mechanics testing platform consisting of a hydraulic press, autoclave, confining pressure system, and automatic data acquisition system. Before the experiment, the samples were processed into cylindrical specimens conforming to the ISRM international rock mechanics standard. Based on the rock sample experiments, the stress-strain curves of the rock and the failure strength of the rock under different confining pressures were first obtained. The elastic modulus (E') and Poisson's ratio (υ') of the rock were:

[0166] E'=Δσ / Δε;(14)

[0167] υ′=-Δε2 / Δε1;(15)

[0168] In the formula, E' is the elastic modulus of the triaxial rock; Δσ is the axial stress increment; Δε is the axial strain increment; Δε1 and Δε2 represent the transverse and longitudinal strain increments, respectively; υ' represents the elastic modulus and Poisson's ratio.

[0169] Whether a rock sample has undergone shear failure can be determined using the Coulomb criterion:

[0170]

[0171] In the formula, σ1′ represents the axial stress on the specimen; σ3′ represents the confining pressure; and C is the cohesion. The internal friction angle is represented by ctg; ctg represents the arctangent calculation formula.

[0172] When the inequality holds, the rock fails. Based on the failure strength values ​​of the rock under different confining pressures, the rock's C and... can be obtained through regression analysis. Value. Different normal stresses (σ) n Shear strength (τ) of rock under the following conditions m This can be represented as:

[0173] σ n =(σ1+σ3) / 2-(σ1-σ3) / 2cos2θ; (17)

[0174] τ m =(σ1-σ3) / 2sin2θ;(18)

[0175] In the formula, σ1 represents the maximum principal stress; σ3 represents the minimum principal stress; σ n τ represents normal stress; θ represents the fracture angle; τ represents the normal stress. m The shear strength is represented by the measured values ​​of the maximum principal stress σ1, the minimum principal stress σ3, and the fracture angle θ. The normal stress σ in the rock is then determined. n Shear strength τ m Alternatively, one can use the method of drawing Mohr's circle to find its envelope to obtain the shear strength of each rock under different normal stress conditions.

[0176] Establishing a mathematical model: A mathematical model is the means of quantitatively predicting structural stress fields and reservoir structural fractures. It mainly includes numerical calculation methods determined based on mechanical models, and methods determined based on geological and mechanical models. For the finite element method, the most important aspects are determining the element type, the principle of element division, the treatment of faults and thin oil layers, and the specific implementation plan based on the geological and mechanical models. A suitable finite element calculation program is selected, and corresponding supporting programs are developed. Actual rock fracture criteria are established to calculate the stress field and rock fracture. After multiple inversions, the geological and mechanical models are revised, supplemented, and improved until they meet various geological inversion standards and the actual geological conditions of the oilfield.

[0177] Numerical simulation of tectonic stress field: Based on the planar tectonic characteristics of the study area, the following reasonable geological model is established ( Figure 1Based on the mechanical and mathematical models, and according to the actual rock mechanics parameters and boundary stress conditions assigned to each unit, the finite element numerical simulation technique was used to calculate the distribution of the tectonic stress field. For reservoir fracture calculations, the maximum principal stress (σ1) and minimum principal stress (σ3) are primarily used to represent the stress. Compression is considered positive, and tension is considered negative. From the simulation results (reference...), Figures 8 to 16 The magnitudes of the maximum and minimum principal stresses vary considerably and are related to the heterogeneous distribution of the reservoir. Among them, Figure 8 This shows the distribution characteristics of the paradigm equivalent stress (Von-Mises-equivalent stress). Figure 9 This shows the distribution characteristics of the principal stress vectors in the study area. Figure 10 This shows the distribution characteristics of tectonic compression deformation in the study area. Figure 11 The study area is shown to have shear stress distribution characteristics. Figure 12 The tensile stress distribution characteristics of the study area are shown. Figure 13 The study area is shown to have the characteristics of normal stress distribution. Figure 14 This shows the distribution characteristics of the maximum principal stress in the study area. Figure 15 This shows the distribution characteristics of the central principal stress in the study area. Figure 16 The distribution characteristics of the minimum principal stress in the study area are shown.

[0178] For details, please refer to Figure 9 It is evident that the principal stress direction does not change significantly in areas with underdeveloped faults, while stress reversal frequently occurs in fault-developed zones. The shear stress in the study area is mainly concentrated in the northeast, indicating areas prone to shear failure. Figure 11 The tensile stress is affected by the fault distribution and is locally concentrated in the study area. Figure 12 ).

[0179] Step 4, Stress field result analysis:

[0180] The orientation of the maximum principal stress in the tectonic stress field is near the EW direction, while the orientation of the minimum principal stress is near the SN direction. Stress concentrates and reverses near the fault, and stress concentration easily forms at the fault tip. With increasing burial depth, both the maximum and minimum principal stresses tend to increase. The distribution characteristics of shear elastic deformation and shear stress indicate that shear fractures are prone to form in the northeastern part of the study area. The distribution characteristics of tensile stress suggest that tensile fractures are prone to form in localized areas in the northern and eastern parts of the study area. Principal stresses tend to concentrate near the fault, and the stress direction is prone to reversal. The areas in the study area prone to deformation are mainly concentrated in the central and eastern parts, while strain decreases near the fault, possibly because fault slippage leads to energy loss, reducing stress-strain.

[0181] Finite element numerical simulation analysis revealed significant variations in the magnitudes of the maximum and minimum principal stresses, which are related to the heterogeneous distribution of the reservoir. Currently, the orientation of the maximum principal stress in the tectonic stress field is near the EW direction, while the orientation of the minimum principal stress is near the SN direction. Stress concentrations occur near faults and exhibit reversals, with stress concentrations easily forming at fault tips. In the study area, the maximum and minimum principal stresses tend to increase with increasing burial depth. The distribution characteristics of shear elastic deformation and shear stress indicate a tendency for shear fractures to form in the northeastern part of the study area. The distribution characteristics of tensile stress suggest that tensile fractures are prone to form in localized areas in the northern and eastern parts of the study area.

[0182] It should be noted that although the operation of the method of the present invention has been described in a specific order in the above embodiments and figures, this does not require or imply that the operations must be performed in that specific order, or that all the operations shown must be performed to achieve the desired result. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps.

[0183] After introducing the method of exemplary embodiments of the present invention, the following references are made. Figure 17 An apparatus for simulating a structural stress field according to an exemplary embodiment of the present invention will be described.

[0184] The implementation of the stress field simulation device can refer to the implementation of the above method, and will not be repeated. The term "module" or "unit" used below can refer to a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0185] Based on the same inventive concept, this invention also proposes a device for simulating a structural stress field, such as... Figure 17 As shown, the device includes:

[0186] Module 1710 is used to acquire structural data of the reservoir in the working area.

[0187] The model building module 1720 is used to build a geological model based on the structural data of the reservoir in the working area;

[0188] The condition determination module 1730 is used to determine the mechanical properties, loading mode, boundary constraint conditions and rock physical parameters of the geological model based on the test data of uniaxial and triaxial rock mechanics tests of the reservoir in the working area.

[0189] The calculation module 1740 is used to determine the tectonic stress field distribution of the reservoir using the finite element numerical simulation method based on the mechanical properties, loading method, boundary constraints and rock physical parameters of the geological model.

[0190] In one embodiment, the model building module 1720 is specifically used for:

[0191] Establish geological isolation bodies based on the structural data of the reservoir in the working area;

[0192] The boundary conditions of the geological isolation body are determined based on well logging data;

[0193] By back-calculating the stress conditions during the formation of structures and tectonic fractures using preset rock physical parameters, geological models, and boundary conditions of the geological isolation body, the loading method, magnitude, and boundary conditions for forward modeling are determined.

[0194] A geological model is constructed based on the loading method, size, and boundary conditions used in the forward modeling calculation.

[0195] In one embodiment, the model building module 1720 is further configured to:

[0196] Based on the geological model, an inversion standard is proposed, which includes at least: a deformation standard and an absolute inversion standard. The deformation standard is used to determine the consistency of the structural pattern. If the deformation of the geological isolator after being subjected to different stresses is consistent with the structural pattern before deformation, then the stress application method is considered reasonable. The absolute inversion standard is used to select the stress value, deformation value, and rock fracture strength value of the reservoir structure in the simulation of the current stress field based on the absolute inversion standard.

[0197] In one embodiment, the model building module 1720 is further configured to:

[0198] For the absolute inversion standard, the absolute inversion standard of stress value, deformation value, and rock fracture strength value of the selected reservoir structure is calculated using a linear superposition method. The calculation method is as follows:

[0199] Define N parameters P1, P2, ..., P that need to be determined through inversion. N ;

[0200] Collect M measured calibration data points Q1, Q2, ..., Q. M M>N;

[0201] Take a parameter P i Perform inversion calculations for i = 1, i = 1, 2, ..., N to determine the correction point and parameter value a. ij ,i=1,2,…,N,j=1,2,…,M;

[0202] Based on the determined correction points, parameter values, and correction data, linear superposition yields M equations:

[0203]

[0204] Solving the M equations using the least squares method yields N parameters P1, P2, ..., P N The absolute inversion standard is determined by repeatedly calculating until the parameters that meet the requirements are obtained; if the calculation result reaches the absolute inversion standard during the calculation process, the numerical simulation result is determined to be correct.

[0205] In one embodiment, the condition determination module 1730 is specifically used for:

[0206] By conducting uniaxial and triaxial rock mechanics tests, the rock physical parameters required for numerical simulation of tectonic stress field and tectonic fracture were determined; the rock physical parameters include rock mechanical properties such as density, tensile strength, elastic modulus, Poisson's ratio, cohesion, internal friction angle, and shear strength.

[0207] Specifically, the bulk density method is used to calculate the mechanical density of rock. The calculation formula is as follows:

[0208] r0 = M0 / V;

[0209] In the formula, r0 is the natural density of the specimen, representing the mechanical density of the rock; M0 is the natural mass of the specimen; and V is the volume of the specimen.

[0210] The tensile strength of rock is determined by splitting tensile test, and the calculation formula is as follows:

[0211] S t =2P max / (DH);

[0212] Among them, S t P represents the uniaxial tensile strength of the specimen and represents the tensile strength of the rock. max The load is the destructive load; D and H are the diameter and height of the specimen, respectively.

[0213] The formula for calculating uniaxial compressive strength is:

[0214] σ c =P max / A;

[0215] Where, σ c P is the uniaxial compressive strength. max A represents the maximum failure load of the rock specimen; A is the area of ​​the specimen subjected to pressure.

[0216] The formulas for calculating the elastic modulus and Poisson's ratio of uniaxial rock are as follows:

[0217] E = c50 / h 50 ;

[0218] υ=d 50 / h 50 ;

[0219] In the formula, E is the elastic modulus of the specimen, representing the uniaxial elastic modulus of the rock; c 50 50% of the uniaxial compressive strength of the specimen; h 50 d 50 c 50 The corresponding axial compressive strain and radial tensile strain at the location; υ is Poisson's ratio, representing the Poisson's ratio of the uniaxial rock;

[0220] The elastic modulus and Poisson's ratio of triaxial rocks are:

[0221] E' = Δσ / Δε;

[0222] υ′=-Δε2 / Δε1;

[0223] In the formula, E' is the elastic modulus of the triaxial rock; Δσ is the axial stress increment; Δε is the axial strain increment; Δε1 and Δε2 represent the transverse and longitudinal strain increments, respectively; υ' represents the elastic modulus and Poisson's ratio.

[0224] Using the Coulomb criterion to determine rock shear failure:

[0225]

[0226] In the formula, σ1′ represents the axial stress on the specimen; σ3′ represents the confining pressure; and C is the cohesion. The internal friction angle is denoted by ctg; ctg represents the arctangent calculation formula; when the inequality holds, rock failure occurs.

[0227] Based on the failure strength values ​​of rocks under different confining pressures, the cohesion and internal friction angle of the rocks are obtained through regression analysis.

[0228] The shear strength of rocks under different normal stress conditions is expressed as:

[0229] σ n =(σ1+σ3) / 2-(σ1-σ3) / 2cos2θ;

[0230] τ m = (σ1-σ3) / 2sin2θ;

[0231] In the formula, σ1 represents the maximum principal stress; σ3 represents the minimum principal stress; σ n τ represents normal stress; θ represents the fracture angle; τ represents the normal stress. m The shear strength is represented by the measured values ​​of the maximum principal stress σ1, the minimum principal stress σ3, and the fracture angle θ. The normal stress σ in the rock is then determined.n Shear strength τ m .

[0232] In one embodiment, the calculation module 1740 is specifically used for:

[0233] A continuous geological isolation body is discretized into finite continuous units; where each unit is connected by nodes and each unit is assigned rock mechanical parameters.

[0234] Based on the boundary stress conditions and the equilibrium conditions of the nodes, a joint equation system is established with nodal displacements and element internal stresses as unknowns and the global stiffness matrix as coefficients.

[0235] The displacement at each node in the joint equation system is calculated by constructing an interpolation function, and the approximate values ​​of stress and strain in each unit are determined to obtain the structural stress field distribution of the reservoir.

[0236] It should be noted that although several modules of the simulation device for constructing the stress field have been mentioned in the detailed description above, this division is merely exemplary and not mandatory. In fact, according to embodiments of the present invention, the features and functions of two or more modules described above can be embodied in one module. Conversely, the features and functions of one module described above can be further divided and embodied by multiple modules.

[0237] Based on the aforementioned inventive concept, such as Figure 18 As shown, the present invention also proposes a computer device 1800, including a memory 1810, a processor 1820, and a computer program 1830 stored in the memory 1810 and executable on the processor 1820. When the processor 1820 executes the computer program 1830, it implements the aforementioned method for simulating the structural stress field.

[0238] Based on the aforementioned inventive concept, the present invention proposes a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the aforementioned method for simulating a structural stress field.

[0239] Based on the aforementioned inventive concept, the present invention proposes a computer program product, which includes a computer program that, when executed by a processor, implements a method for simulating a stress field.

[0240] The proposed method and apparatus for simulating tectonic stress fields establishes geological isolation bodies based on the fault development characteristics of reservoirs, determines the boundary conditions of these isolation bodies, and uses pre-defined rock physical parameters, geological models, and boundary conditions to infer the stress conditions during the formation of structures and tectonic fractures. This determines the loading method, magnitude, and boundary conditions for forward modeling, thereby establishing a geological model. Based on the mechanical parameters and boundary stress conditions of this model, the finite element method is used to simulate the distribution of the tectonic stress field in the reservoir. This method considers the tectonic characteristics of the study area, accurately reveals the geostress distribution characteristics of areas with complex tectonic development based on the establishment of multiple models, reduces the error in stress field prediction results, and has wide applicability, providing theoretical support for the prediction of favorable areas for oil and gas reservoirs.

[0241] The acquisition, storage, use, and processing of data in this application comply with relevant laws and regulations.

[0242] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, apparatus, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0243] This invention is described with reference to flowchart illustrations and / or block diagrams of methods and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0244] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0245] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0246] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for simulating a structural stress field, characterized in that, The method includes: Obtain structural data of the reservoir in the working area; Based on the structural data of the reservoirs in the work area, a geological model is constructed; The mechanical properties, loading methods, boundary constraints, and rock physical parameters of the geological model were determined using test data from uniaxial and triaxial rock mechanics tests of the reservoir in the working area. Based on the mechanical properties, loading methods, boundary constraints, and rock physical parameters of the geological model, the tectonic stress field distribution of the reservoir is determined using the finite element numerical simulation method.

2. The method for simulating the structural stress field according to claim 1, characterized in that, Based on the structural data of the reservoir in the working area, a geological model is constructed, including: Establish geological isolation bodies based on the structural data of the reservoir in the working area; The boundary conditions of the geological isolation body are determined based on well logging data; By back-calculating the stress conditions during the formation of structures and tectonic fractures using preset rock physical parameters, geological models, and boundary conditions of the geological isolation body, the loading method, magnitude, and boundary conditions for forward modeling are determined. A geological model is constructed based on the loading method, size, and boundary conditions used in the forward modeling calculation.

3. The method for simulating the structural stress field according to claim 1, characterized in that, The method also includes: Based on the geological model, an inversion standard is proposed, which includes at least: a deformation standard and an absolute inversion standard. The deformation standard is used to determine the consistency of the structural pattern. If the deformation of the geological isolator after being subjected to different stresses is consistent with the structural pattern before deformation, then the stress application method is considered reasonable. The absolute inversion standard is used to select the stress value, deformation value, and rock fracture strength value of the reservoir structure in the simulation of the current stress field based on the absolute inversion standard.

4. The method for simulating the structural stress field according to claim 3, characterized in that, The method also includes: For the absolute inversion standard, the absolute inversion standard of stress value, deformation value, and rock fracture strength value of the selected reservoir structure is calculated using a linear superposition method. The calculation method is as follows: Define N parameters P1, P2, ..., P that need to be determined through inversion. N ; Collect M measured calibration data points Q1, Q2, ..., Q. M M>N; Take a parameter P i Perform inversion calculations for i = 1, i = 1, 2, ..., N to determine the correction point and parameter value a. ij ,i=1,2,…,N,j=1,2,…,M; Based on the determined correction points, parameter values, and correction data, linear superposition yields M equations: Solving the M equations using the least squares method yields N parameters P1, P2, ..., P N The absolute inversion standard is determined by repeatedly calculating until the parameters that meet the requirements are obtained; if the calculation result reaches the absolute inversion standard during the calculation process, the numerical simulation result is determined to be correct.

5. The method for simulating the structural stress field according to claim 1, characterized in that, Based on the test data from uniaxial and triaxial rock mechanics tests of the reservoir in the working area, the mechanical properties, loading methods, boundary constraints, and rock physical parameters of the geological model were determined, including: By conducting uniaxial and triaxial rock mechanics tests, the rock physical parameters required for numerical simulation of tectonic stress field and tectonic fracture were determined; the rock physical parameters include rock mechanical properties such as density, tensile strength, elastic modulus, Poisson's ratio, cohesion, internal friction angle, and shear strength.

6. The method for simulating the structural stress field according to claim 5, characterized in that, The mechanical density of rock is calculated using the bulk density method. The formula is as follows: r0 = M0 / V; In the formula, r0 is the natural density of the specimen, representing the mechanical density of the rock; M0 is the natural mass of the specimen; and V is the volume of the specimen. The tensile strength of rock is determined by splitting tensile test, and the calculation formula is as follows: S t =2P max / (DH); Among them, S t P represents the uniaxial tensile strength of the specimen and represents the tensile strength of the rock. max The load is the destructive load; D and H are the diameter and height of the specimen, respectively. The formula for calculating uniaxial compressive strength is: s c =P max / A; Where, σ c P is the uniaxial compressive strength. max A represents the maximum failure load of the rock specimen; A is the area of ​​the specimen subjected to pressure. The formulas for calculating the elastic modulus and Poisson's ratio of uniaxial rock are as follows: E=c 50 / h 50 ; u=d 50 / h 50 ; In the formula, E is the elastic modulus of the specimen, representing the uniaxial elastic modulus of the rock; c 50 50% of the uniaxial compressive strength of the specimen; h 50 d 50 c 50 The corresponding axial compressive strain and radial tensile strain at the location; υ is Poisson's ratio, representing the Poisson's ratio of the uniaxial rock; The elastic modulus and Poisson's ratio of triaxial rocks are: E' = Δσ / Δε; υ′=-Δε2 / Δε1; In the formula, E' is the elastic modulus of the triaxial rock; Δσ is the axial stress increment; Δε is the axial strain increment; Δε1 and Δε2 represent the transverse and longitudinal strain increments, respectively; υ' represents the elastic modulus and Poisson's ratio. Using the Coulomb criterion to determine rock shear failure: In the formula, σ1' represents the axial stress on the specimen; σ3' represents the confining pressure; and C is the cohesion. The internal friction angle is denoted by ctg; ctg represents the arctangent calculation formula; when the inequality holds, rock failure occurs. Based on the failure strength values ​​of rocks under different confining pressures, the cohesion and internal friction angle of the rocks are obtained through regression analysis. The shear strength of rocks under different normal stress conditions is expressed as: s n =(σ1+σ3) / 2-(σ1-σ3) / 2cos2θ; t m =(σ1-σ3) / 2sin2θ; In the formula, σ1 represents the maximum principal stress; σ3 represents the minimum principal stress; σ n τ represents normal stress; θ represents the fracture angle; τ represents the normal stress. m The shear strength is represented by the measured values ​​of the maximum principal stress σ1, the minimum principal stress σ3, and the fracture angle θ. The normal stress σ in the rock is then determined. n Shear strength τ m .

7. The method for simulating the structural stress field according to claim 1, characterized in that, Based on the mechanical properties, loading methods, boundary constraints, and rock physical parameters of the geological model, the tectonic stress field distribution of the reservoir is determined using the finite element numerical simulation method, including: A continuous geological isolation body is discretized into finite continuous units; where each unit is connected by nodes and each unit is assigned rock mechanical parameters. Based on the boundary stress conditions and the equilibrium conditions of the nodes, a joint equation system is established with nodal displacements and element internal stresses as unknowns and the global stiffness matrix as coefficients. The displacement at each node in the joint equation system is calculated by constructing an interpolation function, and the approximate values ​​of stress and strain in each unit are determined to obtain the structural stress field distribution of the reservoir.

8. A device for simulating a structural stress field, characterized in that, The device includes: The acquisition module is used to acquire the structural data of the reservoir in the working area; The model building module is used to build a geological model based on the structural data of the reservoir in the working area; The condition determination module is used to determine the mechanical properties, loading methods, boundary constraints, and rock physical parameters of the geological model based on test data from uniaxial and triaxial rock mechanics tests of the reservoir in the working area. The calculation module is used to determine the tectonic stress field distribution of the reservoir using the finite element numerical simulation method based on the mechanical properties, loading method, boundary constraints and rock physical parameters of the geological model.

9. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method of any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the method of any one of claims 1 to 7.

11. A computer program product, characterized in that, The computer program product includes a computer program that, when executed by a processor, implements the method of any one of claims 1 to 7.

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