A rock mechanics layer-constrained ground stress prediction method

Abstract

A rock mechanics layer constraint under the ground stress prediction method is aimed at frequent interbedded lithology stratum, and includes the following steps: first, well-seismic joint inversion constructs rock mechanics parameter volume; second, well-seismic calibration divides large, medium and small scale rock mechanics layers; third, the equivalent lithology of the rock mechanics layer is determined; fourth, the equivalent mechanical parameters, interface type and stress state of the small scale rock mechanics layer are determined; fifth, the ground stress is quantitatively predicted under the constraint of the rock mechanics layer. The rock mechanics layer constraint under the ground stress prediction method is proposed, the problem that the existing ground stress prediction method under the complex lithology background is difficult to combine with the actual production is solved, and the scientific prediction and evaluation of the reservoir stress are realized.

Description

Technical Field

[0001] This invention presents a method for predicting geostress under rock mechanical layer constraints, belonging to the field of reservoir geomechanics. Background Technology

[0002] Actual geological strata are often highly heterogeneous and discontinuous media. The anisotropic differences and defects within these strata further complicate their rock mechanical properties. With the deepening of research into geostress, many scholars have discovered that even within blocks with similar regional tectonic environments, the magnitude, direction, and distribution of actual geostress can vary to some extent. Numerous theoretical studies have shown that the spatial anisotropy of lithofacies fabric is the fundamental cause of the heterogeneity of rock mechanical parameters, and lithology directly influences the distribution of geostress through its own mechanical properties.

[0003] Lithology (attributes reflecting rock characteristics, such as color, composition, structure, cements and cement types, and special minerals) is the material basis for the evolution of rock mechanical properties. The lithological combination of composite rock strata determines the differences in their stress field distribution patterns. Therefore, accurate characterization of rock mechanical strata is crucial for the effective application of reservoir geomechanical modeling, and it determines the methods for predicting reservoir stress. Currently, it is difficult to quantify the degree to which the lithological distribution characteristics of composite rock strata influence the stress field distribution patterns. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a method for predicting in-situ stress under the constraint of rock mechanical layers. This method overcomes the drawbacks of large differences in stress field distribution caused by abrupt changes in single or interbedded lithologies. It focuses on considering interbedded lithologies and their interlayer bonding relationships. Through the division of rock mechanical layers and the calculation of equivalent mechanical parameters, it clarifies the characteristics of in-situ stress distribution under the control of rock mechanical layers. This solves the problem that existing in-situ stress prediction methods in complex lithological backgrounds are difficult to integrate with actual production, thus achieving the scientific prediction and evaluation of reservoir stress.

[0005] The technical solution provided by this invention is as follows:

[0006] According to the first aspect, one embodiment provides a method for predicting geostress under rock mechanical layer constraints, targeting strata with frequent interbedded lithologies, including the following steps:

[0007] The first step is to construct a rock mechanics parameter volume through well-seismic joint inversion;

[0008] The static-dynamic mechanical parameters of the rock are converted to determine the static rock mechanical parameters of the entire well section. The static rock mechanical parameters are then jointly inverted with the seismic impedance data to obtain the seismic data volume of the static rock mechanical parameters. A reservoir geological model is then constructed, and the seismic data volume of the static rock mechanical parameters is resampled into the geological model to obtain a three-dimensional heterogeneous rock mechanical parameter volume.

[0009] The second step is to use well-seismic calibration to delineate large, medium, and small-scale rock mechanical layers;

[0010] In the first step of the geological model, large-scale rock mechanical layers with clear interfaces are divided, and on the basis of the large-scale rock mechanical layers, meso-scale rock mechanical layers with clear interfaces are divided.

[0011] Based on the mesoscale rock mechanics layer, the center point data of the mesoscale rock mechanics parameter volume element grid are extracted. The half-amplitude points where the elastic modulus, Poisson's ratio and density data change under the constraint of the mesoscale rock mechanics layer are used as small-scale mechanical interfaces to divide the small-scale rock mechanics layer.

[0012] The third step is to determine the equivalent lithology of the rock mechanical layer;

[0013] The fourth step is to determine the equivalent mechanical parameters, interface types, and stress states of small-scale rock mechanical layers.

[0014] Based on the small-scale mechanical interfaces defined in the second step, the small-scale rock mechanical parameter volume is determined in the three-dimensional heterogeneous rock mechanical parameter volume in the first step.

[0015] Based on the small-scale mechanical interfaces identified in the second step, determine the type of small-scale rock mechanical interfaces;

[0016] Determine the stress state at the interface and outside the small-scale rock mechanical layer.

[0017] The fifth step is the quantitative prediction of geostress under the constraint of rock mechanical layers;

[0018] The geological model constructed in the first step is converted and imported into finite element software to construct a geological digital model.

[0019] The equivalent rock mechanics parameters from step four are discretized and assigned to each grid of the geological digital model to complete the establishment of the geomechanical model.

[0020] The geomechanical model was calculated using finite element software to obtain a quantitative prediction of geostress under the constraint of rock mechanical layers.

[0021] According to the above embodiment, a geostress prediction method under the constraint of rock mechanical layers simulates geostress as a whole, which solves the drawback that it is difficult to quantitatively characterize the geostress prediction results of interbedded lithologies, improves the objectivity and rationality of geostress prediction results, and is suitable for quantitative geostress prediction of complex interbedded lithologies reservoirs.

[0022] The above-described method for predicting geostress under the constraint of rock mechanics layers innovatively forms a new method for predicting geostress under the constraint of rock mechanics layers, based on traditional geostress prediction, and has practical geological significance. Attached Figure Description

[0023] Figure 1 A flowchart of a method for predicting geostress under rock mechanical layer constraints;

[0024] Figure 2 A schematic diagram of a horizontally layered rock mass lacking cohesion;

[0025] Figure 3 A schematic diagram of a horizontally layered rock mass with cohesive forces;

[0026] Figure 4 Results of rock mechanical layer division at different scales;

[0027] Figure 5 This represents the predicted geostress results under the constraint of rock mechanical layers. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of this application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to this application are not shown or described in the specification. This is to avoid obscuring the core parts of this application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0029] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.

[0030] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages).

[0031] Example:

[0032] Please refer to Figure 1According to the first aspect, one embodiment provides a method for predicting geostress under rock mechanical layer constraints, targeting strata with frequent interbedded lithologies, comprising the following steps:

[0033] The first step is to construct a rock mechanics parameter volume through well-seismic joint inversion;

[0034] Rock mechanics experiments were conducted on standard plunger samples of sandstone and mudstone at similar depths to the target layer to obtain static rock mechanics parameters.

[0035] Dynamic rock mechanics parameters were calculated by combining data such as sonic transit time, rock density, clay content, and rock porosity. Static rock mechanics parameters for the entire well section were determined through the conversion between dynamic and static rock mechanics parameters. The relevant calculation formulas are as follows:

[0036]

[0037]

[0038]

[0039] S c =E d [0.008V sh +0.0045(1-V sh (4)

[0040]

[0041] In formulas (1), (2), (3), (4), (5), E d For dynamic Young's modulus, MPa; μ d The dynamic Poisson's ratio is dimensionless; ρ b Density of rock, kg / m³ 3 ;Δt p and Δt s These are the P-wave time difference and S-wave time difference, respectively, in μs / ft; S c V is the uniaxial compressive strength, MPa; C is the rock cohesion, MPa; V sh Φ represents the volumetric content of clay, dimensionless; φ represents the logging porosity, %. φ represents the internal friction angle, °.

[0042] Arithmetic averaging and coarsening are performed on the resolution of well logging and seismic data to ensure that the resolutions of the two are consistent. Seismic impedance data and static rock mechanics parameter data of the whole well section are jointly inverted to obtain the seismic data volume of static rock mechanics parameters.

[0043] Using Petrel geological modeling software as a platform, the actual underground geological morphology is reproduced to the greatest extent possible, and a reservoir geological model that couples the stratigraphic model and the fault model is constructed. The unit grid length of the geological model is x*y*z, where x, y, and z are the resolutions of the seismic data in the X, Y, and Z directions, respectively.

[0044] The static rock mechanics parameters of the seismic data are sampled into the geological model to obtain a three-dimensional heterogeneous rock mechanics parameter volume. These rock mechanics parameters include Young's modulus, Poisson's ratio, internal friction angle, cohesion, and compressive strength.

[0045] The second step is to use well-seismic calibration to delineate large, medium, and small-scale rock mechanical layers;

[0046] In the geological model, the development characteristics of faults, large-scale fractures, and unconformities are clearly defined. Stratigraphic interfaces restricting the vertical extension of faults and large-scale fractures are designated as large-scale mechanical interfaces, and the stratigraphic units between adjacent interfaces are large-scale lithomechanical layers. It should be noted that the division of large-scale lithomechanical layers considers not only tectonic phases and patterns but also crucial mechanical layer components such as fault and large-scale fracture density, stratigraphic thickness, and layering interfaces. Based on the above division method, a comprehensive process integrating single-well interpretation, well-connection identification, and seismic 3D characterization is used to complete the division of large, medium, and small-scale lithomechanical layers.

[0047] Based on large-scale rock mechanics layers, ① the stratigraphic interfaces that limit the stratigraphic lithological assemblage, sedimentary filling sequence, tectonic deformation characteristics, low-order faults, and mesoscale fracture development are called mesoscale mechanical interfaces, and the stratigraphic units between adjacent interfaces are mesoscale rock mechanics layers; ② for fractured reservoirs, the stratigraphic interfaces where small- to medium-scale fractures vertically extend and terminate are considered mesoscale mechanical interfaces; ③ for fracture-free reservoirs, sedimentary microfacies interfaces and sequence boundaries are considered mesoscale mechanical interfaces.

[0048] Based on the mesoscale rock mechanics layer, the center point data of the mesoscale rock mechanics parameter volume unit grid is extracted. The center point data of the unit grid includes x-coordinate, y-coordinate, z-coordinate, elastic modulus, Poisson's ratio data, and z-coordinate depth curve data sampled at average intervals. The half-amplitude points of the abrupt changes in elastic modulus, Poisson's ratio, and density data under the constraint of the mesoscale rock mechanics layer (25% curve amplitude difference) are taken as small-scale mechanical interfaces. The stratigraphic units between adjacent interfaces are small-scale rock mechanics layers, and the rock mechanics parameter volumes between adjacent interfaces are small-scale rock mechanics parameter volumes. The basis for this is that rock mechanics parameters are the most intuitive data reflecting the rock mechanics properties.

[0049] The third step is to determine the equivalent lithology of the rock mechanical layer;

[0050] Collect detailed data from drilling cores and cuttings logging to ensure that the lithological information from logging is consistent with the actual lithology from core samples. Treat rocks of the same type with complex mineral composition, similar logging responses, and inconsistent grain sizes as one type of lithology. For example, coarse sandstone, medium sandstone, fine sandstone, siltstone, and argillaceous sandstone are considered as sandstone; and sandy mudstone and mudstone are considered as mudstone.

[0051] Based on the small-scale rock mechanics layers obtained in the second step, the equivalent lithology is defined as follows: when the small-scale rock mechanics layer is thick sandstone interbedded with thin mudstone (sandstone / mudstone thickness ratio > 1.5), the equivalent lithology is defined as equivalent sandstone; when the thick mudstone interbedded with thin sandstone (sandstone / mudstone thickness ratio < 0.7), the equivalent lithology is defined as equivalent mudstone; when the mudstone interbedded with sandstone or sandstone interbedded with rock (0.7 ≤ sandstone / mudstone thickness ratio ≤ 1.5), the equivalent lithology is defined as alternating sandstone and mudstone.

[0052] The fourth step is to determine the equivalent mechanical parameters, interface types, and stress states of small-scale rock mechanical layers.

[0053] The small-scale rock mechanics parameter volume is defined as an array set; the data in this array set includes x-coordinate, y-coordinate, z-coordinate, Young's modulus, Poisson's ratio, and density data, with the z-coordinate being data sampled at a single depth interval; a three-dimensional For loop program automatically reads the data center point data of this array set according to the depth value, and uses the "centroid" search method to take the average value of Young's modulus, Poisson's ratio, and density data in this array set as the equivalent mechanical parameters of the small-scale rock mechanics layer.

[0054] Based on the small-scale mechanical interfaces determined in the second step, unconformities, sandstone-sandstone joints, and mudstone-mudstone joints are defined as uncohesive interfaces, with the stratigraphic units between these interfaces being uncohesive layered rock masses. Sandstone-mudstone joints are defined as cohesive interfaces, with the stratigraphic units between these interfaces being cohesive layered rock masses.

[0055] The focus is on the stress state of horizontally layered rock masses that lack cohesion.

[0056] Assume that the underground horizontal layered rock mass is composed of three types of rocks, A, C, and B, with different lithologies and gradually increasing burial depths, and mechanical interfaces, with no cohesion between the rock interfaces. Define the elastic modulus and Poisson's ratio of rocks A, B, and C as E, respectively. A E B E C μ A μ B μ C It is subjected to uniform compressive stress σ in the x, y, and z directions respectively. x σ y σ z The effect of uniform compressive stress σz Uniform compressive stress σ acting in the vertical direction of the layered rock mass x σ y The effect is on the horizontal direction of the layered rock mass; please refer to the following content. Figure 2 Through mechanical analysis of the variable elastic modulus unit, the stress at the interface between rocks A and C is obtained as follows:

[0057]

[0058]

[0059]

[0060] In formulas (6), (7) and (8): This represents the stress in the z-direction of rocks A and C at the interface between rocks A and C. This represents the stress in the x-direction of rocks A and C at the interface between rocks A and C. This represents the stress in the y-direction of rocks A and C at the interface between rocks A and C; σ' xA ,σ' xC σ' represents the frictional constraint stress experienced by rocks A and C in the x-direction, respectively; yA ,σ' yC Let f represent the frictional constraint stresses experienced by rocks A and C in the y-direction, respectively. xAC f yAC These represent the coefficients of friction between rocks A and C in the x and y directions, respectively.

[0061] Similarly, the stress at the interface between rocks B and C is:

[0062]

[0063]

[0064]

[0065] In formulas (9), (10), (11): This represents the stress in rock B in the z, x, and y directions at the interface between rocks B and C. This represents the stress in rock C in the z, x, and y directions at the interface between rocks B and C, σ”. xB ,σ” xC σ represents the frictional constraint stress in the x-direction experienced by rocks B and C. yB ,σ” yC f represents the frictional constraint stress in the y-direction experienced by rocks B and C. xBC f yBCThese represent the coefficients of friction between rocks B and C in the x and y directions, respectively.

[0066] The focus is on the axial stress state of horizontally layered rock masses with cohesive forces.

[0067] Assume an underground horizontal layered rock mass is composed of three types of rocks (A, B, and C) with different lithologies and gradually increasing burial depths, along with their mechanical interfaces, and that there is cohesion between these interfaces. The rock mass is subjected to uniform compressive stress σ in the x, y, and z directions. x σ y σ z The effect of uniform compressive stress σ z Uniform compressive stress σ acting in the vertical direction of the layered rock mass x σ y The effect is on the horizontal direction of the layered rock mass; please refer to the following content. Figure 3 Define the elastic modulus and Poisson's ratio of rocks A, B, and C as E, respectively. A E B E C μ A μ B μ C Furthermore, the elastic modulus and Poisson's ratio of rocks A, B, and C in this layered rock mass have the following relationships:

[0068]

[0069] Through mechanical analysis of the variable elastic modulus unit, the interface between rocks A and B in the layered rock mass is at σ. z σ x σ y Under triaxial compressive stress, the stress components at the interface between rocks A and B are:

[0070]

[0071]

[0072] in

[0073]

[0074]

[0075]

[0076] In formulas (12), (13), (14), (15), (16), (17): This represents the principal stresses of rock A in the z, x, and y directions at the interface between rocks A and B in a horizontally layered rock mass. K represents the principal stresses of rock B in the z, x, and y directions at the interface between rocks A and B in a horizontally layered rock mass. 1AB K 2AB K5 is the stress coefficient.

[0077] Similarly, in a layered rock mass, the interface between rocks B and C is located at σ z σ x σ y Under triaxial compressive stress, the stress components at the interface between rocks B and C are:

[0078]

[0079]

[0080] in

[0081]

[0082]

[0083]

[0084] In formulas (18), (19), (20), (21), (22): This represents the principal stresses of rock B in the z, x, and y directions at the interface between rocks B and C in a horizontally layered rock mass. This represents the principal stresses of rock C in the z, x, and y directions at the interface between rocks B and C in a horizontally layered rock mass.

[0085] Rocks A, B, and C outside the layered rock interface area are still under tricompression stress σ because they are not affected by the bond-constraint stress at the rock interface, or the effect is negligible. z σ x σ y The triaxial compressive stress state under action, i.e.

[0086]

[0087] In formula (23): σ zA σ xA σ yA σ represents the stress in rock A within a horizontally layered rock mass in the z, x, and y directions; zB σ xB σ yB σ represents the stress in rock B within a horizontally layered rock mass in the z, x, and y directions; zC σ xC σ yCThese represent the stresses of rock C in the horizontally layered rock mass in the z, x, and y directions, respectively.

[0088] Through the stress-strain analysis of the horizontally layered rock mass using formulas (12) to (23), it can be seen that at the rock interface, the stress state changes due to the generation of bond-constrained stress, mainly manifested in the horizontal stress. Regarding the increase or decrease of numerical values, rocks A, B, and C, located outside the rock interface layer, are still under the influence of σ. z σ x σ y The triaxial stress state under action.

[0089] The fifth step is the quantitative prediction of geostress under the constraint of rock mechanical layers;

[0090] Based on the geological model constructed in the first step, extract the fault and stratigraphic data from the geological model, import them into AutoCAD software to construct a 3D digital model. Please refer to [link / reference needed]. Figure 4 The 3D digital model is then imported back into ANSYS software for geological digital model construction. The choice of mesh step size generally involves a comprehensive consideration of expected accuracy and computational efficiency. The resulting mesh should not be too large or too small. The geological digital model is then divided into nodes and meshes at seismic resolution.

[0091] The equivalent rock mechanics parameters under the equivalent lithological constraints, as described in the fourth step of the "centroid" search method, are discretely assigned to each grid of the geological digital model to complete the establishment of the geomechanical model.

[0092] The initial values ​​of boundary conditions are generally determined based on the macroscopic analysis of the structure. This study uses acoustic emission experiments, downhole microseismic monitoring, and geotectonic background data, with single-well test geostress data as constraints, to iteratively select the appropriate boundary load loading method.

[0093] The basic idea of ​​the finite element numerical simulation method is as follows: divide the continuous rock mass into several elements connected by nodes, and assign realistic mechanical properties to each element. The process of solving the continuous function of the rock mass is equivalent to solving the problem of solving the function values ​​at the nodes of discrete elements composed of stress, strain, and displacement. In this way, a combined equation is established with nodal displacement and unit internal force as parameters and the global rigidity matrix as coefficients. The deformation of each node is solved by interpolation, thereby solving for the stress and strain at each node.

[0094] The system of finite element linear algebraic equations with displacement as the fundamental variable is as follows:

[0095]

[0096] In formula (24), U is the nodal displacement vector, K is the stiffness matrix, P is the equivalent nodal force vector of the body load p, and Q is the equivalent nodal force vector of the force load q on the boundary surface, defined as follows:

[0097]

[0098] In formula (25), N is the displacement interpolation shape function matrix, and "t" represents transpose.

[0099] For a three-dimensional elastic problem, its stress and strain tensors can be expressed as:

[0100] σ=[σ x σ y σ z τ xy τ yz τ zx ] t (26)

[0101] ε=[ε x ε y ε z γ xy γ yz γ zx ] t (27)

[0102] In formulas (26) and (27), σ is the stress tensor, ε is the strain tensor, and the superscript "t" represents transpose.

[0103] The constitutive equation can be written as:

[0104] σ=Dε (28)

[0105] In formula (28), D is the flexibility matrix, and its mathematical expression is represented by the matrix as follows:

[0106]

[0107] In formula (29), E is the elastic modulus and μ is Poisson's ratio.

[0108] The in-situ stress prediction results are automatically generated by ANSYS software. By setting the stress loading method, the actual in-situ stress field is simulated and predicted. If the predicted stress field does not match the measured results, the stress loading method is repeatedly adjusted until the relative error between the predicted and measured results reaches less than 10%. The simulation is then terminated, and the results are output. Please refer to the provided documentation. Figure 5 This completes the quantitative prediction of geostress under the constraint of rock mechanical layers.

[0109] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A method for predicting ground stress under the constraint of rock mechanical layer, characterized in that, Includes the following steps: The first step is to construct a rock mechanics parameter volume through well-seismic joint inversion; The static-dynamic mechanical parameters of rocks are converted to determine the static rock mechanical parameters of the entire well section. They are then combined with seismic impedance data to obtain the seismic data volume of static rock mechanical parameters. A reservoir geological model is constructed, and the seismic data volume of static rock mechanical parameters is resampled into the geological model to obtain a three-dimensional heterogeneous rock mechanical parameter volume. The static rock mechanics parameters include Young's modulus, Poisson's ratio, internal friction angle, cohesion, and compressive strength. Among them, the static mechanical parameters of the rock were obtained by conducting rock mechanics experiments using standard plunger samples of sandstone and mudstone at similar depths to the target layer, and the dynamic mechanical parameters of the rock were obtained by combining data such as sonic transit time, rock density, mud content and rock porosity. The second step is to use well-seismic calibration to delineate large, medium, and small-scale rock mechanical layers; In the first step of the geological model, large-scale rock mechanical layers with clear interfaces are divided, and on the basis of the large-scale rock mechanical layers, meso-scale rock mechanical layers with clear interfaces are divided. Based on the mesoscale rock mechanics layer, the center point data of the mesoscale rock mechanics parameter volume element grid are extracted. The half-amplitude points where the elastic modulus, Poisson's ratio and density data change under the constraint of the mesoscale rock mechanics layer are used as the small-scale mechanical interface to divide the small-scale rock mechanics layer. The term "defined interface" refers to the stratigraphic interface in the geological model that clearly defines the development characteristics of faults, large-scale fractures, and unconformities, and restricts the vertical extension of faults and large-scale fractures. The term "second-level defined interface" refers to the stratigraphic interface within the large-scale petromechanical layer that: ① restricts the development of stratigraphic lithological assemblage, sedimentary infill sequence, tectonic deformation characteristics, low-order faults, and mesoscale fractures; ② for fractured reservoirs, the stratigraphic interface that terminates with the vertical extension of small- to medium-scale fractures; ③ for fracture-free reservoirs, the interface that is defined by sedimentary microfacies interfaces and sequence boundaries. The term "data abrupt change" refers to a 25% difference in curve amplitude. The third step is to determine the equivalent lithology of the rock mechanical layer; The fourth step is to determine the equivalent mechanical parameters, interface types, and stress states of small-scale rock mechanical layers. Based on the small-scale mechanical interfaces defined in the second step, the small-scale rock mechanical parameter volume is determined in the three-dimensional heterogeneous rock mechanical parameter volume in the first step. Based on the small-scale mechanical interfaces identified in the second step, determine the type of small-scale rock mechanical interfaces; Determine the stress state outside and at the interface of small-scale rock mechanical layers; For horizontally layered rock masses with cohesion, the stress state under triaxial compressive stress is determined in the following way: Assume the layered rock mass is composed of rocks A, B, and C with different lithologies, and that there is cohesion between the interfaces of these rocks. It is subjected to uniform compressive stress σ in the x, y, and z directions, respectively. x σ y σ z The function of this method is to obtain the stress components at the rock interface through mechanical analysis of the variable elastic modulus unit. The calculation formula is as follows: ； in ； In the formula: , , This represents the principal stresses of rock A in the z, x, and y directions at the interface between rocks A and B in a horizontally layered rock mass. , , This represents the principal stresses of rock B in the z, x, and y directions at the interface between rocks A and B in a horizontally layered rock mass; K 1AB K 2AB K5 is the stress coefficient; E A E B E C μ A μ B μ C The elastic modulus and Poisson's ratio of rocks A, B, and C are respectively. The fifth step is the quantitative prediction of geostress under the constraint of rock mechanical layers; The geological model constructed in the first step is converted into a three-dimensional digital model that can be recognized by finite element software, and then imported into the finite element software to construct a geological digital model. The equivalent rock mechanics parameters from step four are discretized and assigned to each grid of the geological digital model to complete the establishment of the geomechanical model. The geomechanical model was calculated using finite element software to obtain a quantitative prediction of geostress under the constraint of rock mechanical layers.

2. The method of predicting in-situ stress under the constraint of rock mechanics layer according to claim 1, characterized in that: In the fifth step, the finite element software is used to obtain the quantitative prediction of the in-situ stress under the constraint of rock mechanics layer, and the relative error between the prediction result and the measured result is less than 10% after several cycles of solving, which is the quantitative prediction result of the in-situ stress.

3. The method of predicting in-situ stress under the constraint of rock mechanics layer according to claim 2, characterized in that: If the relative error between the quantitative prediction result and the measured result of the in-situ stress is greater than 10%, the stress loading mode is repeatedly adjusted until the relative error between the prediction result and the measured result is less than 10%.

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