A method and system for predicting fold-related cracks based on the principle of stress superposition.

Abstract

This application discloses a method and system for predicting fold-related fractures based on the principle of stress superposition, belonging to the field of geological analysis technology. The method includes: acquiring past 3D seismic data and past regional stress tensors of a region, and constructing a high-precision structural grid cell on the top surface of the target reservoir; based on the high-precision structural grid cell, determining the fracture type and fracture orientation according to the sliding window-least squares surface fitting joint method, the principle of stress superposition, and rock fracture criteria, thus obtaining a fracture prediction model; acquiring the current 3D seismic data and current regional stress tensor of the target region, and inputting them into the fracture prediction model to obtain the current fracture type and current fracture orientation. This application achieves accurate prediction of the type and orientation of fold-related fractures.

Description

Technical Field

[0001] This application relates to the field of geological analysis technology, and in particular to a method and system for predicting fold-related cracks based on the principle of stress superposition. Background Technology

[0002] Fractured reservoirs play a crucial role in global oil and gas exploration and development, especially in tight reservoirs such as carbonate and igneous rocks, where the fracture system is a key factor controlling oil and gas flow and production capacity. Accurately predicting the distribution, direction, and density of fractures is of significant engineering importance for optimizing drilling trajectory design, improving oil and gas recovery rates, and reducing development operation risks.

[0003] However, fracture systems are highly heterogeneous and complex, making their prediction a persistent technical challenge in the fields of petroleum geology and engineering. Fold structures, as a widespread tectonic form in the Earth's crust, significantly control the development and propagation of fractures. During fold formation, the local stress field undergoes complex changes, particularly the superposition of curvature-related tensile stress and regional tectonic stress, which often dominates the type and orientation of fractures.

[0004] Traditional methods for predicting fractures mainly include single-region stress field analysis and single-tectonic curvature analysis, but both have significant limitations. The regional stress field method focuses on the control effect of far-field tectonic stress on the regional fracture system, but it is difficult to accurately characterize the fracture system caused by local folding and bending. Although the tectonic curvature analysis method can reflect the degree of local bending of rock strata, the fracture orientation predicted by this method (usually perpendicular to the direction of maximum curvature) often does not match the actual observed fracture orientation, which is deflected by regional stress.

[0005] Therefore, current technology has failed to effectively achieve coupled analysis of regional stress fields and local fold stress fields, making it difficult to accurately predict crack systems under complex stress regimes. Summary of the Invention

[0006] The purpose of this application is to provide a method and system for predicting fold-related cracks based on the principle of stress superposition, which solves the problem of insufficient prediction accuracy caused by single curvature analysis and single stress analysis, and realizes accurate prediction of the type and orientation of fold-related cracks.

[0007] To achieve the above objectives, this application provides a method for predicting fold-related cracks based on the principle of stress superposition, comprising the following steps:

[0008] Obtain historical 3D seismic data and historical regional stress tensor for a given area;

[0009] Based on past 3D seismic data, a high-precision structural grid unit is constructed for the top surface of the target reservoir.

[0010] Based on high-precision constructed grid cells, and according to the sliding window-least square surface fitting joint method, stress superposition principle and rock fracture criterion, the fracture type and fracture orientation are determined, and a fracture prediction model is obtained.

[0011] The current 3D seismic data and stress tensor of the target area are obtained and input into the crack prediction model to obtain the current crack type and current crack orientation.

[0012] Based on high-precision constructed mesh elements, and according to the sliding window-least-less-squares surface fitting joint method, stress superposition principle, and rock fracture criterion, the past fracture types and directions are determined, resulting in a fracture prediction model that includes:

[0013] By fitting a secondary trend surface on a high-precision constructed mesh element through a sliding window, solving for the principal curvature and principal curvature direction, and then calculating the local tensile stress to construct the local tensile stress tensor;

[0014] After transforming the local tensile stress tensor and the regional stress tensor to the same geographic coordinate system, they are superimposed to obtain the composite principal stress and the dominant direction of crack orientation.

[0015] Based on the rock fracture criterion, the fracture type and fracture orientation are determined according to the combined principal stress and the dominant direction of the fracture, thus obtaining a fracture prediction model.

[0016] Preferably, the high-precision structural grid unit for constructing the top surface of the target reservoir based on past 3D seismic data includes:

[0017] The layer depth data of the target reservoir is extracted from the 3D seismic data, and the layer depth data is discretized into a 2D rectangular grid with a unified spatial coordinate system through an interpolation algorithm.

[0018] The depth difference between the top and bottom surfaces of the reservoir is obtained, and the formation thickness corresponding to the two-dimensional rectangular grid is calculated based on the depth difference to obtain a high-precision structural grid cell.

[0019] Preferably, after fitting a quadratic trend surface onto a high-precision constructed mesh element using a sliding window, solving for the principal curvature and its direction, and then calculating the local tensile stress to construct the local tensile stress tensor, the following steps are taken:

[0020] On a high-precision constructed mesh cell, a sliding window of size n×n is defined, and the sliding window is translated cell by cell to obtain the three-dimensional coordinate data of all mesh nodes within the sliding window;

[0021] Based on three-dimensional coordinate data, a secondary trend surface is obtained by fitting with the least squares method. By calculating the second derivative matrix of the secondary trend surface, the maximum principal curvature, minimum principal curvature, direction of maximum principal curvature, and direction of minimum principal curvature of the center point of the sliding window are obtained.

[0022] Acquire past logging data and calculate Young's modulus based on the past logging data;

[0023] Calculate the maximum and minimum principal curvature, Young's modulus, and formation thickness;

[0024] Construct a local tensile stress tensor based on the direction of maximum principal curvature, the direction of minimum principal curvature, the maximum principal stress, and the minimum principal stress.

[0025] Preferably, the formulas for calculating the maximum and minimum claimed stresses are as follows:

[0026] ;

[0027] ;

[0028] in, R Let be the radius of curvature. k For the maximum principal curvature and the minimum principal curvature, For the maximum and minimum assertion stresses, E For Young's modulus, T This refers to the thickness of the formation.

[0029] Preferably, after transforming the local tensile stress tensor and the regional stress tensor to the same geographic coordinate system and superimposing them, the composite principal stress and the dominant direction of crack orientation are obtained, including:

[0030] The local tensile stress tensor is in the coordinate system of the principal direction of local curvature;

[0031] The regional stress tensor is in the coordinate system of the principal directions of the regional stress;

[0032] After transforming the local tensile stress tensor to the coordinate system of the principal directions of regional stress, it is superimposed with the regional stress tensor to obtain the composite stress tensor.

[0033] The composite stress tensor is decomposed into eigenvalues ​​to obtain the maximum and minimum composite principal stresses, i.e., the composite principal stresses, and the azimuth angle of the maximum composite principal stress, i.e., the dominant direction of crack orientation.

[0034] Preferably, the expression for the local tensile stress tensor is:

[0035] ;

[0036] in, For the local tensile stress tensor, For maximum assertive stress, Minimum assertion stress;

[0037] The expression for the stress tensor of the region is:

[0038] ;

[0039] in, For the region stress tensor, The maximum horizontal principal stress in the region, This represents the minimum horizontal principal stress in the region.

[0040] The expression for the composite stress tensor is:

[0041] ;

[0042] in, For composite stress tensor, β This is the relative rotation angle.

[0043] Preferably, the crack types include tensile cracks and shear cracks.

[0044] Preferably, the determination condition for the tensile crack is: the minimum composite principal stress is less than or equal to the tensile strength of the rock, and the crack direction is parallel to the direction of the maximum composite principal stress;

[0045] The conditions for determining the shear crack are: the composite principal stress satisfies the Coulomb criterion, and the crack direction is the direction of the maximum composite principal stress deflected by an internal friction angle.

[0046] Preferably, based on high-precision constructed mesh elements, and according to the sliding window-least-less-squares surface fitting joint method, stress superposition principle, and rock fracture criterion, the past crack types and past crack orientations are determined, and the crack prediction model further includes:

[0047] Obtain historical actual well point data;

[0048] The fracture prediction model was optimized by adjusting the past regional stress parameters, Young's modulus, and formation thickness to fit the past fracture types and fracture orientations with past actual well point data.

[0049] This application also provides a fold-related crack prediction system based on the stress superposition principle, used to implement the above-mentioned fold-related crack prediction method based on the stress superposition principle, including:

[0050] The data acquisition module is used to acquire past 3D seismic data and past regional stress tensors for a region.

[0051] The grid cell construction module is used to construct high-precision structural grid cells for the top surface of the target reservoir based on past 3D seismic data.

[0052] The model building module is used to determine the crack type and crack orientation based on high-precision constructed mesh elements, the sliding window-least square surface fitting joint method, the stress superposition principle and the rock fracture criterion, and obtain the crack prediction model.

[0053] The crack prediction module is used to acquire the current 3D seismic data and the current regional stress tensor of the target area, and input them into the crack prediction model to obtain the current crack type and current crack orientation.

[0054] In summary, the fold-related crack prediction method and system based on the stress superposition principle provided in this application have the following advantages compared with traditional technologies: by constructing a crack prediction model, the regional tectonic stress field and the local fold stress field are effectively coupled, thereby realizing the quantitative prediction of crack type and orientation.

[0055] The technical methods of this application will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0056] Figure 1 This is a flowchart of a method for predicting fold-related cracks based on the principle of stress superposition in this application;

[0057] Figure 2 This is a diagram showing the relationship between the high-precision constructed mesh element division and curvature distribution in this application;

[0058] Figure 3 This is a flowchart illustrating the construction process of the crack prediction model in this application;

[0059] Figure 4 This is a diagram showing the fracture prediction results of a reservoir in a structural zone of a basin, as presented in this application.

[0060] Figure 5 This is a schematic diagram of a fold-related crack prediction system based on the stress superposition principle in this application. Detailed Implementation

[0061] The technical methods of this application will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application.

[0062] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the scope of this application and its application or use.

[0063] Techniques, systems, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the instruction manual.

[0064] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0065] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning as understood by a person of ordinary skill in the art to which this application pertains.

[0066] A method for predicting fold-related cracks based on the principle of stress superposition, such as Figure 1 As shown, it includes the following steps:

[0067] S1. Acquire past 3D seismic data, past well logging data, past imaging well logging data, past rock mechanics parameters, and past regional stress tensor for a region.

[0068] S2. Based on past 3D seismic data, past well logging data, past imaging well logging data, and past rock mechanics parameters, construct a high-precision structural grid unit for the top surface of the target reservoir.

[0069] Furthermore, step S2 specifically includes the following steps:

[0070] Step S201: Extract the layer depth data of the target reservoir from the 3D seismic data, and discretize the layer depth data into a two-dimensional rectangular grid with a unified spatial coordinate system using an interpolation algorithm. Each two-dimensional rectangular grid is assigned a unique coordinate value. The interpolation algorithm includes either Kriging interpolation or discrete smoothing interpolation.

[0071] Step S202: Obtain the depth difference between the top and bottom surfaces of the reservoir, and calculate the formation thickness corresponding to the two-dimensional rectangular grid based on the depth difference to obtain a high-precision structural grid cell. The formation thickness is the burial depth of the lower surface minus the burial depth of the upper surface.

[0072] S3. Based on high-precision constructed grid units, and according to the sliding window-least square surface fitting joint method, stress superposition principle and rock fracture criterion, the crack type and crack direction are determined, and a crack prediction model is obtained.

[0073] Furthermore, step S3 specifically includes the following steps:

[0074] S301. Fit a secondary trend surface onto a high-precision constructed mesh element using a sliding window. After solving for the principal curvature and its direction, calculate the local tensile stress to construct the local tensile stress tensor. Specifically, step S301 includes:

[0075] On a high-precision constructed mesh cell, a sliding window of size n×n is defined, and the sliding window is translated cell by cell to obtain the three-dimensional coordinate data of all mesh nodes within the sliding window.

[0076] Based on three-dimensional coordinate data, a quadratic trend surface is obtained using the least squares method. By calculating the second derivative matrix of the quadratic trend surface, two eigenvalues ​​λ1 and λ2 are obtained, namely the maximum principal curvature λ1 and minimum principal curvature λ2 at the center point of the sliding window, as well as the directions of the maximum and minimum principal curvatures. The direction of the maximum curvature is typically perpendicular to the axis of the anticline, such as... Figure 2 As shown, the sliding window moves continuously until each grid point of the high-precision constructed grid cell is assigned the corresponding principal curvature. This application combines the least squares curvature calculation method with the sliding window technique, which can obtain the principal curvature parameters of the grid points in the entire region with high precision, providing a reliable basis for the calculation of local tensile stress tensors.

[0077] Obtain past logging data and calculate Young's modulus based on the past logging data.

[0078] Calculate the maximum and minimum principal stresses based on the maximum principal curvature, minimum principal curvature, Young's modulus, and formation thickness.

[0079] The formulas for calculating the maximum and minimum claimed stresses are as follows:

[0080] ;

[0081] ;

[0082] in, R Let be the radius of curvature. k For the maximum principal curvature and the minimum principal curvature, For the maximum and minimum assertion stresses, E For Young's modulus, T This refers to the thickness of the formation.

[0083] A local tensile stress tensor is constructed based on the directions of maximum and minimum principal curvature, maximum and minimum principal stresses. The local tensile stress tensor, in a coordinate system based on the principal curvature directions (with the principal curvature directions as axes), characterizes the tensile stress state generated solely by folding morphology at the top of the rock strata.

[0084] S302. After transforming the local tensile stress tensor and the regional stress tensor to the same geographic coordinate system, they are superimposed to obtain the composite principal stress and the dominant direction of crack orientation. Among them, the regional stress tensor is in the coordinate system of the regional stress principal direction.

[0085] Furthermore, step S302 specifically includes the following:

[0086] The local tensor stress tensor is transformed to the coordinate system of the principal directions of the regional stress and then superimposed with the regional stress tensor to obtain the composite stress tensor. The expression for the local tensor stress tensor is as follows:

[0087] ;

[0088] in, For the local tensile stress tensor, For maximum assertive stress, The minimum assertion stress.

[0089] The region stress tensor is a diagonal matrix, expressed as:

[0090] ;

[0091] in, For the region stress tensor, The maximum horizontal principal stress in the region, This represents the minimum horizontal principal stress in the region.

[0092] Since the local tensor stress tensor and the regional stress tensor are in different coordinate systems, they must first be transformed into the same mathematical reference system before they can be superimposed. Therefore, the local tensor stress tensor is transformed into the regional principal stress direction coordinate system, and the geographic coordinate system (north direction) is chosen as the common reference system. Let α be the angle between the direction of the maximum horizontal principal stress in the region and the geographic north axis, and ω be the angle between the direction of the maximum principal curvature and the geographic north axis. Then, the relative rotation angle β can be calculated using the formula: β = α - ω, where the relative rotation angle β represents the angle between the direction of the maximum principal stress and the direction of the maximum horizontal principal stress in the region.

[0093] Using the tensor rotation formula, the local tensile stress tensor L Rotate by angle β to obtain the local tensile stress tensor after rotation. L´ The expression is:

[0094] K = ;

[0095] L´=KLK T =

[0096] = ;

[0097] in, K For rotation matrix, It is the transpose of the rotation matrix.

[0098] Under a unified public coordinate system (geographic coordinate system), the regional stress tensor is... S With the local tensile stress tensor after rotation L´By performing direct matrix addition, the composite stress tensor is obtained. R The expression for the composite stress tensor is: R=S+L´ .Right now,

[0099] .

[0100] Composite stress tensor R It represents the total stress state acting on the rock, while also including the contributions of regional tectonic forces and local folding forces.

[0101] Eigenvalue decomposition of the composite stress tensor yields the maximum composite principal stress. and minimum composite principal stress This refers to the composite principal stress, and the azimuth angle θ of the maximum composite principal stress, which is the dominant direction of the crack orientation.

[0102] This application superimposes the regional stress tensor and the local tensile stress tensor into a coordinate system, fully considering the combined control of far-field tectonic stress and near-field folding and bending stress on crack development, and significantly improves the accuracy of crack orientation, type and density prediction.

[0103] S303. Based on rock fracture criteria, and according to the principal stress and the dominant direction of fracture orientation, the fracture type and fracture orientation are determined, resulting in a fracture prediction model. The fracture types include tensile fractures and shear fractures.

[0104] The condition for determining tensile cracks is: minimum composite principal stress. Less than or equal to the tensile strength of the rock - T 0, that is The crack direction is parallel to the maximum composite principal stress. The direction.

[0105] The conditions for determining the shear crack are: the combined principal stresses satisfy the Coulomb criterion, and the crack direction is a deflection of the direction of the maximum combined principal stress by an internal friction angle. This typically occurs when the combined principal stress difference (…) Large enough, and the rock cohesion C When θ and the internal friction angle Φ are permissible, i.e. The shear cracks formed two sets of conjugate cracks, with their orientations being respectively... Z 1 and Z 2, relative to The direction (i.e., θ) deflects by an angle related to the internal friction angle, which ultimately results in two sets of orientations for shear cracks. Z 1 and Z The azimuth angles of 2 are respectively and .

[0106] This application adopts the rock fracture criterion (Coulomb criterion) to determine the fracture type, making the classification of fracture types more theoretically based and in line with actual geomechanical laws.

[0107] In an exemplary embodiment of this application, step S3 further includes the following steps:

[0108] S304. Obtain past actual well point data.

[0109] S305. Adjust past regional stress parameters, Young's modulus, and formation thickness to fit past fracture types and orientations with past actual well point data, thereby optimizing the fracture prediction model. The fracture prediction model's predictions must match the actual well point data to ensure its geological reliability. Through statistical and visual comparisons, systematically evaluate the fracture prediction model's error and use this information to guide adjustments to the input parameters, minimizing prediction errors. This involves continuously adjusting regional stress parameters (such as direction and magnitude) and rock mechanics parameters (such as Young's modulus and layer thickness) to optimize the model, ensuring the predicted fracture orientation and density best fit actual observations.

[0110] This application introduces a fracture prediction model verification and optimization step, and adjusts parameters in reverse using actual well point data to ensure the geological reliability and statistical validity of the prediction results, providing precise technical support for oil and gas field drilling design and development scheme optimization.

[0111] S4. Obtain the current 3D seismic data and current regional stress tensor of the target area, and input them into the crack prediction model to obtain the current crack type and current crack orientation.

[0112] This application achieves effective coupling between regional tectonic stress fields and local fold stress fields through five core steps: data preparation and structural modeling, curvature analysis and local stress field calculation, stress superposition and composite stress field solution, crack type determination, and model verification and optimization. Figure 3 As shown, in the process of constructing the fracture prediction model, by inputting past 3D seismic data, past regional stress tensors and past actual well point data, local stress calculation, stress superposition processing, fracture judgment and output, result verification and parameter optimization are performed in sequence. This not only yields the fracture prediction results, but also improves the accuracy of fracture prediction.

[0113] An exemplary embodiment of this application describes the fracture prediction of a reservoir in a certain structural zone of a basin, specifically the western anticline fold and the eastern syncline fold, as shown in Table 1.

[0114] Table 1 shows the reservoir parameters.

[0115]

[0116] Crack prediction results are as follows Figure 4As shown, the fracture density is relatively high at the turning point of the fold structure in the reservoir top surface of this region. As the fracture density gradually decreases towards the fold flanks, the development of shear fractures is significantly better than that of tension fractures.

[0117] This application provides a fold-related crack prediction system based on the stress superposition principle, used to implement the aforementioned fold-related crack prediction method based on the stress superposition principle, such as... Figure 5 As shown, it includes:

[0118] The data acquisition module is used to acquire historical 3D seismic data and historical regional stress tensors for a given area.

[0119] The grid cell construction module is used to construct high-precision structural grid cells on the top surface of the target reservoir based on past 3D seismic data, past well logging data, past imaging well logging data, and past rock mechanics parameters.

[0120] The model building module is used to determine the crack type and crack orientation based on high-precision constructed mesh elements, the sliding window-least-square surface fitting joint method, the stress superposition principle and the rock fracture criterion, and obtain a crack prediction model.

[0121] The crack prediction module is used to acquire the current 3D seismic data and the current regional stress tensor of the target area, and input them into the crack prediction model to obtain the current crack type and current crack orientation.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical methods of this application and not to limit them. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical methods of this application, and these modifications or equivalent substitutions cannot cause the modified technical methods to deviate from the spirit and scope of the technical methods of this application.

Claims

1. A method for predicting fold-related cracks based on the principle of stress superposition, characterized in that, Includes the following steps: Obtain historical 3D seismic data and historical regional stress tensor for a given area; Based on past 3D seismic data, a high-precision structural grid unit is constructed for the top surface of the target reservoir. Based on high-precision constructed grid cells, and according to the sliding window-least square surface fitting joint method, stress superposition principle and rock fracture criterion, the fracture type and fracture orientation are determined, and a fracture prediction model is obtained. The current 3D seismic data and stress tensor of the target area are obtained and input into the crack prediction model to obtain the current crack type and current crack orientation. Based on high-precision constructed mesh elements, and according to the sliding window-least-less-squares surface fitting joint method, stress superposition principle, and rock fracture criterion, the past fracture types and directions are determined, resulting in a fracture prediction model that includes: By fitting a secondary trend surface on a high-precision constructed mesh element through a sliding window, solving for the principal curvature and principal curvature direction, and then calculating the local tensile stress to construct the local tensile stress tensor; After transforming the local tensile stress tensor and the regional stress tensor to the same geographic coordinate system, they are superimposed to obtain the composite principal stress and the dominant direction of crack orientation. Based on the rock fracture criterion, the fracture type and fracture orientation are determined according to the composite principal stress and the dominant direction of the fracture, and a fracture prediction model is obtained. After transforming the local tensile stress tensor and the regional stress tensor to the same geographic coordinate system and superimposing them, the composite principal stress and the dominant direction of crack orientation are obtained, including: The local tensile stress tensor is in the coordinate system of the principal direction of local curvature; The regional stress tensor is in the coordinate system of the principal directions of the regional stress; After transforming the local tensile stress tensor to the coordinate system of the principal directions of regional stress, it is superimposed with the regional stress tensor to obtain the composite stress tensor. The composite stress tensor is decomposed into eigenvalues ​​to obtain the maximum and minimum composite principal stresses, i.e., the composite principal stresses, and the azimuth of the maximum composite principal stress, i.e., the dominant direction of crack orientation. The expression for the local tensile stress tensor is: ； in, For the local tensile stress tensor, For maximum assertive stress, Minimum assertion stress; The expression for the stress tensor of the region is: ； in, For the region stress tensor, The maximum horizontal principal stress in the region, This represents the minimum horizontal principal stress in the region. The expression for the composite stress tensor is: ； in, For composite stress tensor, β This is the relative rotation angle.

2. The method for predicting fold-related cracks based on the principle of stress superposition according to claim 1, characterized in that, Based on past 3D seismic data, the construction of a high-precision structural grid cell for the top surface of the target reservoir includes: The layer depth data of the target reservoir is extracted from the 3D seismic data, and the layer depth data is discretized into a 2D rectangular grid with a unified spatial coordinate system through an interpolation algorithm. The depth difference between the top and bottom surfaces of the reservoir is obtained, and the formation thickness corresponding to the two-dimensional rectangular grid is calculated based on the depth difference to obtain a high-precision structural grid cell.

3. The method for predicting fold-related cracks based on the principle of stress superposition according to claim 1, characterized in that, By fitting a quadratic trend surface onto a high-precision constructed mesh element using a sliding window, and solving for the principal curvatures and their directions, the local tensile stress is calculated. The construction of the local tensile stress tensor includes: On a high-precision constructed mesh cell, a sliding window of size n×n is defined, and the sliding window is translated cell by cell to obtain the three-dimensional coordinate data of all mesh nodes within the sliding window; Based on three-dimensional coordinate data, a secondary trend surface is obtained by fitting with the least squares method. By calculating the second derivative matrix of the secondary trend surface, the maximum principal curvature, minimum principal curvature, direction of maximum principal curvature, and direction of minimum principal curvature of the center point of the sliding window are obtained. Acquire past logging data and calculate Young's modulus based on the past logging data; Calculate the maximum and minimum principal stresses based on the maximum principal curvature, minimum principal curvature, Young's modulus, and formation thickness; Construct a local tensile stress tensor based on the direction of maximum principal curvature, the direction of minimum principal curvature, the maximum principal stress, and the minimum principal stress.

4. The method for predicting fold-related cracks based on the principle of stress superposition according to claim 3, characterized in that, The formulas for calculating the maximum and minimum claimed stresses are as follows: ； ； in, R Let be the radius of curvature. k For the maximum principal curvature and the minimum principal curvature, For the maximum and minimum assertion stresses, E For Young's modulus, T This refers to the thickness of the formation.

5. The method for predicting fold-related cracks based on the principle of stress superposition according to claim 1, characterized in that, The crack types include: tensile cracks and shear cracks; The conditions for determining the tensile crack are: the minimum composite principal stress is less than or equal to the tensile strength of the rock, and the crack direction is parallel to the direction of the maximum composite principal stress. The conditions for determining the shear crack are: the composite principal stress satisfies the Coulomb criterion, and the crack direction is the direction of the maximum composite principal stress deflected by an internal friction angle.

6. The method for predicting fold-related cracks based on the principle of stress superposition according to claim 3, characterized in that, Based on high-precision constructed mesh elements, and according to the sliding window-least-less-squares surface fitting joint method, stress superposition principle, and rock fracture criterion, the past fracture types and directions are determined, resulting in a fracture prediction model that also includes: Obtain historical actual well point data; The fracture prediction model was optimized by adjusting the past regional stress parameters, Young's modulus, and formation thickness to fit the past fracture types and fracture orientations with past actual well point data.

7. A fold-related crack prediction system based on the principle of stress superposition, characterized in that, A method for predicting fold-related cracks based on the stress superposition principle as described in any one of claims 1-6 includes: The data acquisition module is used to acquire past 3D seismic data and past regional stress tensors for a region. The grid cell construction module is used to construct high-precision structural grid cells for the top surface of the target reservoir based on past 3D seismic data. The model building module is used to determine the crack type and crack orientation based on high-precision constructed mesh elements, the sliding window-least square surface fitting joint method, the stress superposition principle and the rock fracture criterion, and obtain the crack prediction model. The crack prediction module is used to acquire the current 3D seismic data and the current regional stress tensor of the target area, and input them into the crack prediction model to obtain the current crack type and current crack orientation.

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