A 3D fault / fracture network modeling method and device under a thrust nappe system based on the discrete element method

Abstract

The present invention discloses a three-dimensional fault / fracture network modeling method and device under a thrust nappe system based on the discrete element method, which relates to the technical field of three-dimensional fault modeling, and includes constructing an initial fault plane model based on the seismic logging data parameters of the target area; extracting the formation parameters of the target area, and combining with the balanced profile restoration method to determine the deformation process; calibrating the mesoscopic parameters of the discrete element according to the formation parameters, depositing the first discrete element model, optimizing and generating the second discrete element model, setting boundary conditions for thrust nappe simulation, and adjusting the model parameters through the comparison between the output results of the second discrete element model and the actual geological profile until the two match, establishing a three-dimensional fault and fracture network, analyzing and establishing the spatial distribution characteristics of the target area, and dynamically evaluating and trend predicting the activity of the three-dimensional fault. The present invention integrates a geomechanical model, overcomes the subjectivity of manual interpretation, and effectively avoids problems such as mesh reconstruction and fault tip extension.

Description

Technical Field

[0001] The present invention relates to the technical field of three-dimensional tomography modeling research, in particular to a three-dimensional fault / fracture network modeling method and device under a thrust nappe system based on the discrete element method. Background Art

[0002] Faults and fractures, as important products of geological tectonic activities, are key geological elements that control hydrocarbon migration, accumulation, and reservoir formation. A fault refers to a structure in which a rock formation fractures under the action of tectonic stress and undergoes significant displacement, while a fracture represents a discontinuous interface formed by rock rupture. The complex network system composed of the two not only directly affects the distribution law of hydrocarbon reservoir spaces, but also continuously transforms the trap integrity and fluid conduction ability through the dynamic evolution process. Therefore, constructing a three-dimensional fault / fracture network model has become the core technical link in cracking the tectonic reservoir control mechanism in oil and gas exploration and development.

[0003] Current three-dimensional geological modeling faces dual challenges: on the one hand, the surface and deep fault / fracture systems have significant spatial heterogeneity and geometric discontinuity, and their original three-dimensional observation data often exhibit fragmented characteristics. The complex fault structures cut each other, resulting in serious damage to the continuity of the strata. Various spatial interpolation algorithms and fault construction methods for surface models and volume models are no longer applicable; on the other hand, traditional modeling methods are mostly limited to the reconstruction of static layered structures. When constructing a complex fault model with many layers, it will greatly increase the modeling difficulty and complexity, and it is difficult to effectively depict the thrust nappe system formed by the superposition of multiple phases of tectonic movements. Especially when it comes to complex processes such as stress singularity at the fault tip, interactive propagation of multiple faults, and dynamic reorganization of the fracture network, conventional modeling techniques often have significant deviations in prediction results due to problems such as difficult grid reconstruction and lack of evolution process. This limitation is particularly prominent in hydrocarbon-bearing basins with strong tectonic transformation characteristics, making the multi-solution problem of two-dimensional structural interpretation unable to be fundamentally solved through simple three-dimensional visualization.

[0004] The basic idea of the discrete element simulation (Discrete Element Method) is to regard individual discrete particles at the mesoscopic scale inside the material as a discrete unit, regard the aggregate of particles as a collection of several discrete units, and simulate the mechanical behavior of materials science through a series of discrete units. It has great advantages in studying problems of discontinuous medium fracture and large deformation problems. The three-dimensional fault / fracture modeling technology of the thrust nappe system based on the discrete element method improves the traditional modeling paradigm. This method integrates dynamic elements such as the evolution of the stress field and the law of fault nucleation and propagation in geological history into the modeling process, and uses discrete element numerical simulation to reproduce the tectonic deformation sequence. This research method and device are making a leap from static description to dynamic prediction in three-dimensional geological modeling, providing a new technical method for oil and gas exploration in complex tectonic areas. Summary of the Invention

[0005] In view of the significant limitations of existing three-dimensional fault and fracture modeling methods based on seismic data when dealing with complex deformation regions such as nappe tectonic zones, for example: the distribution of fault structures is complex, the spatial heterogeneity is strong, geological data is fragmented, and traditional methods cannot dynamically invert the fracture evolution process, resulting in it being difficult to balance the spatial accuracy and geological rationality of the model, and the prediction results having a large deviation. In addition, conventional grid reconstruction has problems with stress singularities and modeling obstacles that are difficult to describe during processes such as fault tip rupture, fault intersection extension, and fracture dynamic evolution. The present invention is proposed.

[0006] Therefore, the problem to be solved by the present invention is how to construct a high-precision three-dimensional modeling method that combines geomechanical mechanisms, can dynamically simulate the formation and evolution process of faults and fractures, and is applicable to thrust nappe tectonic zones, in order to accurately depict the spatio-temporal distribution characteristics of complex fracture systems, dynamically evaluate fault activity, and overcome the deficiencies of traditional methods in modeling accuracy, evolution process reconstruction, and multi-phase tectonic superposition expression.

[0007] To solve the above technical problems, the present invention provides the following technical solutions:

[0008] In a first aspect, the present invention provides a three-dimensional fault / fracture network modeling method under a thrust nappe system based on the discrete element method, which includes,

[0009] Based on the seismic logging data parameters of the target area, construct an initial fault plane model, and use an encrypted grid method to extract basic fault point set data along the strike direction of the initial fault plane model;

[0010] Extract the formation parameters of the target area, and combine the balanced cross-section restoration method to determine the deformation process of the target area in historical periods;

[0011] Calibrate the mesoscopic parameters of the discrete element according to the formation parameters, deposit the first discrete element model, construct a fault function, and optimize to generate the second discrete element model;

[0012] Based on the second discrete element model, set boundary conditions for thrust nappe simulation, and adjust the model parameters by comparing the output results of the second discrete element model with the actual geological section until they match;

[0013] Based on the simulation results, establish a three-dimensional fault and fracture network, analyze and establish the spatial distribution characteristics of the three-dimensional fault and fracture network in the target area, and dynamically evaluate and predict the trend of the activity of the three-dimensional fault.

[0014] As a preferred embodiment of the three-dimensional fault / fracture network modeling method under the thrust nappe system based on the discrete element in the present invention, it includes: Based on the matched model results, establish and analyze the spatial distribution characteristics of the three-dimensional fault and fracture network in the target area, and conduct dynamic evaluation and trend prediction of the activity of the three-dimensional fault, including:

[0015] Based on the particle coordinates of the evolution result of the second discrete element model, different particle displacement gradient tensors are derived according to the relative position vectors between particles.

[0016] According to the particle displacement gradient tensors of the evolution result of the second discrete element model, draw the strain tensors of different profiles to obtain the three-dimensional faults with spatial distribution.

[0017] Based on the bonding relationship between particles in the evolution result of the second discrete element model, determine whether the bonding between particles is damaged.

[0018] According to the judgment result, record the time, location, and type of the bonding failure between particles, where the type includes tensile fracture and shear fracture.

[0019] Mark the bonding state between particles as the crack generation point, where the crack generation point is the situation where the bonding state between particles changes from the bonding compression state or bonding tension state to the non-bonding contact state or the state of losing interaction.

[0020] Conduct characteristic analysis on the tensile fracture type and shear fracture type, where the tensile fracture type is manifested as the failure perpendicular to the direction of the maximum principal stress; the shear fracture type is manifested as the failure developing along the direction of the minimum principal stress.

[0021] Based on the advancement of the loading process, continuously update the information on the bonding failure between particles and establish a fracture network database, where the fracture network database includes the particle coordinates, failure time, and failure type of the particles where the bonding failure has occurred.

[0022] Based on the fracture network database, conduct quantitative analysis of the fracture network and calculate statistical indicators, where the statistical indicators include fracture density, average fracture length, and fracture direction distribution.

[0023] Draw the spatial distribution characteristic diagrams of the fracture network under different spatiotemporal evolutions through the statistical indicators.

[0024] As a preferred embodiment of the three-dimensional fault / fracture network modeling method under the thrust nappe system based on the discrete element in the present invention, it includes: Based on the second discrete element model, set boundary conditions for thrust nappe simulation, and adjust the model parameters by comparing the output result of the second discrete element model with the actual geological profile until the two match, including:

[0025] Set the trailing edge of the second discrete element model as the active boundary and the remaining boundaries as fixed boundaries;

[0026] Refer to the fault displacement amount and the restored shortening amount of the balanced profile in the target area, and apply motion to the active boundary;

[0027] Control the motion of the active boundary. When the extrusion amount equal to the restored shortening amount of the balanced profile is reached, stop the operation of the second discrete element model;

[0028] Extract the simulation results of the second discrete element model, and conduct a consistency comparison between the simulation results and the actual geological profile;

[0029] If the simulation results do not match the actual geological profile, finely adjust the discrete element particle parameters or the boundary motion conditions, and repeat the above steps until the simulation results match the actual geological profile;

[0030] If the simulation results match the actual geological profile, perform three-dimensional fault / fracture network construction.

[0031] As a preferred solution of the three-dimensional fault / fracture network modeling method under the thrust nappe system based on discrete element according to the present invention, wherein: calibrate the mesoscopic parameters of the discrete element according to the formation parameters, deposit the first discrete element model, construct a fault function, and optimize and generate the second discrete element model, including:

[0032] Establish a mesoscopic parameter system of the discrete element, wherein the mesoscopic parameter system includes particle parameters and particle bonding parameters;

[0033] Determine the state relationship between adjacent particles of the discrete element, and calibrate the mesoscopic parameters of the particle materials of each formation through triaxial compression experiments, wherein the state relationship includes bonded compression state, bonded tension state, non-bonded contact state, and particle loss of interaction state;

[0034] Based on the corresponding space of the target area, randomly distribute particles with a normally distributed radius, and establish the corresponding relationship between the mesoscopic parameters of the particles and the macroscopic properties of the formation, and endow each particle with physical properties and interaction parameters, wherein the physical properties include radius and density; the interaction parameters include normal stiffness, shear stiffness, and friction coefficient;

[0035] Let the endowed particles freely settle until the system is stable, record the position parameters of the particles in each formation, and complete the construction of the first discrete element model;

[0036] Based on the calibrated particle bonding parameters and the formation information of the target area, set the bonding relationship between the particles in the first discrete element model;

[0037] Refine the first discrete element model to establish the mesoscopic parameters and mechanical relationships of particles at different horizons in the target area;

[0038] Based on the fault point set data Fault, establish the main fault model function isInsideFault, where the main fault model function is used to determine whether the coordinate pt of any particle is inside the fault point set Fault;

[0039] Based on the judgment result, cancel the bonding between particles on the fault plane and at the same time reduce the friction coefficient between fault particles to form a second discrete element model.

[0040] As a preferred scheme of the three-dimensional fault / fracture network modeling method under the thrust nappe system based on discrete element of the present invention, wherein: extract the formation parameters of the target area, and combine the balanced profile restoration method to determine the deformation process of the target area in the historical period, including:

[0041] Based on the initialized fault plane model, collect the drilling data of the target area and obtain core samples from the drilling data;

[0042] Conduct laboratory analysis on the core samples to measure the physical property parameters of different formations, where the physical property parameters include lithology, porosity and permeability;

[0043] Collect and analyze the logging data of the target area to obtain detailed information of the underground formations, where the logging data includes resistivity logging data and natural gamma ray logging data;

[0044] Analyze the seismic profile data to extract information of different formations in the target area, where the information of different formations includes formation lithology, mechanical parameters and spatial distribution characteristics; the mechanical parameters include elastic modulus and Poisson's ratio;

[0045] Comprehensively analyze the information of different formations, the physical property parameters and the detailed information to obtain the complete formation parameters of the target area;

[0046] Based on the complete formation parameters, use the balanced profile restoration method to model the target area;

[0047] Determine the deformation process of the target area in the historical period through the balanced profile restoration method and identify the multi-stage activities of faults;

[0048] Conduct quantitative comparative analysis on the restored balanced profile generated by the balanced profile restoration method and the original profile, and calculate the extrusion deformation displacement caused by each stage of fault activity.

[0049] As a preferred solution of the three-dimensional fault / fracture network modeling method under the thrust nappe system based on the discrete element in the present invention, wherein: the construction method of the initialized fault plane model is as follows,

[0050] Obtain the seismic logging data parameters of the target area, and preprocess the seismic logging data parameters;

[0051] Based on the preprocessed seismic logging data parameters, select the seismic profiles that clearly show the characteristics of the target fault, and give priority to areas showing displacement;

[0052] Based on the seismic profiles, extract coordinate data, stratification data, and fault data;

[0053] Analyze the seismic profiles, identify and extract the relevant parameters of the main faults with large displacement and in the extrusion direction, where the relevant parameters include the dip of the fault plane, the dip angle of the fault plane, the sliding distance along the fault plane, the sliding direction along the fault plane, and the relative displacement of the strata on both sides of the fault;

[0054] Based on the relevant parameters, extract the three-dimensional geometric shape of the main faults;

[0055] Process the three-dimensional geometric shape by using the encrypted grid method;

[0056] Based on the processed three-dimensional geometric shape, extract the basic fault point set data along the strike direction of the main faults. Let the basic fault point set data be Fault, which includes n three-dimensional points S = {p1, p2,..., p n}, where p n is the nth three-dimensional point on the fault plane;

[0057] Construct an initialized fault plane model according to the basic fault point set data.

[0058] In the second aspect, the present invention provides a three-dimensional fault / fracture network modeling device under the thrust nappe system based on the discrete element, which includes:

[0059] A fault module, which constructs an initialized fault plane model based on the seismic logging data parameters of the target area, and uses the encrypted grid method to extract the basic fault point set data along the strike direction of the initialized fault plane model;

[0060] An inversion module, which is used to observe the geology of the target area, analyze the seismic data in this area, extract the formation information and deformation process, and invert the seismic analysis map to obtain the spatial evolution process of the faults;

[0061] A model module, which calibrates the discrete element mesoscopic parameters according to the formation parameters, deposits the first discrete element model, constructs a fault function, and optimizes to generate the second discrete element model;

[0062] The deformation module, based on the second discrete element model, sets boundary conditions for thrust nappe simulation, and adjusts the model parameters by comparing the output results of the second discrete element model with the actual geological profile until they match.

[0063] The modeling module, based on the matched model results, establishes and analyzes the spatial distribution characteristics of the three-dimensional fault and fracture network in the target area, and dynamically evaluates and predicts the activity trend of the three-dimensional fault.

[0064] In a third aspect, the present invention provides a computer device, including a memory and a processor, where the memory stores a computer program, and: when the processor executes the computer program, any step of the above-mentioned three-dimensional fault / fracture network modeling method based on the discrete element under the thrust nappe system is implemented.

[0065] In a fourth aspect, the present invention provides a computer-readable storage medium, on which a computer program is stored, and: when the computer program is executed by a processor, any step of the above-mentioned three-dimensional fault / fracture network modeling method based on the discrete element under the thrust nappe system is implemented.

[0066] Compared with the prior art, the beneficial effects of the present invention are as follows: by introducing the discrete element method to dynamically simulate the fault fracture system, it effectively avoids the problem that the fracture propagation behavior at the fault tip is difficult to accurately depict due to the difficulty of grid reconstruction in traditional modeling; by integrating geomechanical parameters and tectonic evolution processes in the modeling process, a spatio-temporal coupling relationship between pre-existing faults and newly formed fractures is established, realizing the quantitative analysis of the multi-stage tectonic superposition effect; at the same time, a closed-loop modeling process from tectonic sign inversion to future tectonic evolution prediction is established, significantly improving the geological rationality and prediction ability of the three-dimensional spatial distribution modeling of complex fracture systems, and providing scientific and reliable technical support for the identification of hidden structures, the evaluation of fault sealing properties, and the study of tectonic reservoir control mechanisms in oil and gas exploration. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. Among them:

[0068] Figure 1 It is a schematic flow chart of the three-dimensional fault / fracture network modeling method based on the discrete element under the thrust nappe system.

[0069] Figure 2It is a sedimentation model for a three-dimensional fault / fracture network modeling method under a thrust nappe system based on the discrete element method.

[0070] Figure 3 It is the particle contact and bonding relationship for a three-dimensional fault / fracture network modeling method under a thrust nappe system based on the discrete element method.

[0071] Figure 4 It is an example of the equilibrium profile evolution process for a three-dimensional fault / fracture network modeling method under a thrust nappe system based on the discrete element method.

[0072] Figure 5 It is a schematic diagram of the structure of a simulation device for a three-dimensional fault / fracture network modeling method under a thrust nappe system based on the discrete element method.

[0073] Figure 6 It is a comparison between the discrete element geological model and the actual geological situation in the indicated example area for a three-dimensional fault / fracture network modeling method under a thrust nappe system based on the discrete element method.

[0074] Figure 7 It is the stress-strain curve of the simulated formation for a three-dimensional fault / fracture network modeling method under a thrust nappe system based on the discrete element method.

[0075] Figure 8 It is an example of a seismic profile of the Mazatag structural belt for a three-dimensional fault / fracture network modeling method under a thrust nappe system based on the discrete element method.

[0076] Figure 9 It is an example of a fault combination map for a three-dimensional fault / fracture network modeling method under a thrust nappe system based on the discrete element method.

[0077] Figure 10 It is an example of a longitudinal section of a fault for a three-dimensional fault / fracture network modeling method under a thrust nappe system based on the discrete element method.

[0078] Figure 11 It is an example of a cross-section of a fault for a three-dimensional fault / fracture network modeling method under a thrust nappe system based on the discrete element method.

[0079] Figure 12 It is an example of the fracture density statistics for a three-dimensional fault / fracture network modeling method under a thrust nappe system based on the discrete element method. Specific implementation manners

[0080] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following provides a detailed description of the specific embodiments of the present invention in conjunction with the accompanying drawings of the specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0081] In the following description, numerous specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the spirit of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0082] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it an isolated or alternative embodiment that mutually excludes other embodiments.

[0083] The present invention is described in detail in conjunction with schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views showing the device structure are enlarged locally out of the general scale, and the schematic diagrams are only examples and should not limit the scope of protection of the present invention herein. In addition, in actual production, three-dimensional spatial dimensions including length, width, and depth should be included.

[0084] Meanwhile, in the description of the present invention, it should be noted that the orientation or positional relationships indicated by terms such as "upper, lower, inner, and outer" are based on the orientation or positional relationships shown in the drawings. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first, second, or third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0085] Unless otherwise clearly defined and limited in the present invention, the terms "mounted, connected, and coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can also be a mechanical connection, an electrical connection, or a direct connection, or can be indirectly connected through an intermediate medium, or can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0086] Embodiment 1

[0087] Refer to Figures 1 to 5, which is the first embodiment of the present invention. This embodiment provides a three-dimensional fault / fracture network modeling method under a thrust nappe system based on the discrete element method, including:

[0088] S1: Based on the seismic logging data parameters of the target area, construct an initial fault plane model, and use the encrypted grid method to extract the basic fault point set data along the strike direction of the initial fault plane model.

[0089] Specifically, the method for constructing the initial fault plane model is to obtain the seismic logging data parameters of the target area and preprocess the seismic logging data parameters.

[0090] In an alternative embodiment, the seismic logging data parameters of the target area are obtained through geological surveys and seismic data analysis, and after preprocessing the seismic logging data parameters using Petrol and LandMark software, it includes noise removal and reflection wave extraction.

[0091] Furthermore, based on the preprocessed seismic logging data parameters, select the seismic profiles that clearly show the characteristics of the target fault, and give priority to the areas showing displacement; based on the seismic profiles, extract coordinate data, stratification data, and fault data; analyze the seismic profiles, identify and extract the relevant parameters of the main faults with large displacement and in the squeezing direction, where the relevant parameters include the dip of the fault plane, the dip angle of the fault plane, the sliding distance along the fault plane, the sliding direction along the fault plane, and the relative displacement of the strata on both sides of the fault; based on the relevant parameters, extract the three-dimensional spatial geometry of the main faults; process the three-dimensional spatial geometry using the encrypted grid method.

[0092] Preferably, based on the processed three-dimensional spatial geometry, extract the basic fault point set data along the strike direction of the main fault. Let the basic fault point set data be Fault, including n three-dimensional points S = {p1, p2,..., p n}, where p n is the nth three-dimensional point on the fault plane;

[0093] Even further, construct an initial fault plane model according to the basic fault point set data.

[0094] S2: Extract the formation parameters of the target area, and combine the balanced profile restoration method to determine the deformation process of the target area in historical periods.

[0095] Specifically, collect the drilling data of the target area and obtain core samples from the drilling data; conduct laboratory analysis on the core samples to measure the physical property parameters of different formations, where the physical property parameters include lithology, porosity, and permeability; collect and analyze the logging data of the target area to obtain detailed information of the underground formations, where the logging data includes resistivity logging data and natural gamma ray logging data.

[0096] It should be noted that the detailed information of the underground formation includes formation thickness, lithological boundary, and fluid saturation.

[0097] Furthermore, analyze the seismic profile data to extract the information of different formations in the target area. The information of different formations includes formation lithology, mechanical parameters, and spatial distribution characteristics; the mechanical parameters include elastic modulus and Poisson's ratio; comprehensively analyze the information of different formations, physical property parameters, and detailed information to obtain the complete formation parameters of the target area; based on the complete formation parameters, use the balanced cross-section restoration method to model the target area.

[0098] It should be noted that the balanced cross-section restoration method is implemented through balanced cross-section restoration software, and the balanced cross-section restoration software is 3dmove.

[0099] Even further, as Figure 4 shown, determine the deformation process of the target area in the historical period through the balanced cross-section restoration method, and identify the multi-stage activities of faults; conduct a quantitative comparative analysis of the restored balanced cross-section and the original cross-section generated by the balanced cross-section restoration method, and calculate the extrusion deformation displacement caused by each stage of fault activity.

[0100] S3: Calibrate the mesoscopic parameters of the discrete element according to the formation parameters, deposit the first discrete element model, construct a fault function, and optimize to generate the second discrete element model.

[0101] Specifically, as Figure 2 shown, establish a discrete element mesoscopic parameter system, where the discrete element mesoscopic parameter system includes particle parameters and particle bonding parameters.

[0102] It should be noted that the particle parameters describe the mechanical properties of the particles themselves and the contact behavior between particles; the particle bonding parameters describe the bonding effect between particles and are applicable to simulating cementitious materials (such as consolidated rocks). The relationship between particle contact and bonding is as Figure 3 shown.

[0103] In an alternative implementation, establish a constitutive model of particle contact based on the Hertz-Mindlin theory. In the constitutive model, elastic-frictional contact characteristics are assigned to the particles; define the mechanical response when particles contact, including the normal stress and the shear stress between particles , where the normal stress is related to the normal stiffness between particles and the overlap amount between particles; the shear stress between particles is related to the shear stiffness between particles and the shear offset amount at the center of the particles; and The values are all non-linear quantities related to the contact area of overlapping particles and are related to the particle shear modulus and Poisson's ratio and are related.

[0104] Furthermore, determine the state relationship between adjacent particles in the discrete element method, and calibrate the mesoscopic parameters of the particle materials in each formation through triaxial compression tests. The state relationships include bonded compression state, bonded tension state, non-bonded contact state, and the state where particles lose interaction.

[0105] Illustrated by examples, the triaxial compression test uses the radius expansion method to establish an initial model of 1:1:2. In the initial model, the top and bottom walls move towards the center of the specimen at the same speed, and different confining pressures are set around. Obtain the stress-strain curve of the triaxial compression test specimen at a strain of 20%. Through post-processing the stress-strain curve, parameters such as the cohesion and friction coefficient of the specimen are obtained. Establish the corresponding relationship between the mesoscopic parameters of the particles and the macroscopic properties of the formation.

[0106] Even further, based on the corresponding space of the target area, randomly distribute particles with a radius following a normal distribution, and establish the corresponding relationship between the mesoscopic parameters of the particles and the macroscopic properties of the formation. Assign physical properties and interaction parameters to each particle. The physical properties include radius and density; the interaction parameters include normal stiffness, shear stiffness, and friction coefficient. Let the assigned particles freely settle until the system is stable, and record the position parameters of the particles in each formation to complete the construction of the first discrete element model.

[0107] Specifically, based on the calibrated particle bonding parameters and the formation information of the target area, set the bonding relationship between the particles in the first discrete element model.

[0108] It should be noted that the bonding relationship defines the failure criterion of the bonding between particles through parameters such as bonding strength, tensile strength, and internal friction angle.

[0109] Furthermore, refine the first discrete element model to establish the mesoscopic parameters and mechanical relationships of the particles at different layers in the target area; according to the fault point set data Fault, establish the main fault model function isInsideFault, where the main fault model function is used to judge whether any particle coordinate pt is inside the fault point set Fault.

[0110] It should be noted that when the particle coordinate pt is inside the fault plane defined by the fault point set Fault, the main fault model function isInsideFault returns true, and when the particle coordinate pt is outside the fault plane defined by the fault point set Fault, the main fault model function isInsideFault returns false.

[0111] Furthermore, based on the judgment result, the bonding between particles on the fault plane is cancelled, and at the same time, the friction coefficient between fault particles is reduced to form a second discrete element model.

[0112] S4: Based on the second discrete element model, set boundary conditions for the thrust nappe simulation, and adjust the model parameters by comparing the output result of the second discrete element model with the actual geological profile until the two match.

[0113] Specifically, setting boundary conditions for the thrust nappe simulation includes: setting the trailing edge of the second discrete element model as the active boundary and the remaining boundaries as fixed boundaries; referring to the fault displacement amount and the shortening amount recovered by the balanced profile in the target area, applying motion to the active boundary; controlling the motion of the active boundary, and stopping the operation of the second discrete element model when the extrusion amount equal to the shortening amount recovered by the balanced profile is reached.

[0114] Further, extract the simulation result of the second discrete element model, and conduct a consistency comparison between the simulation result and the actual geological profile; if the simulation result does not match the actual geological profile, slightly adjust the discrete element particle parameters or the boundary motion situation, and repeat the above steps until the simulation result matches the actual geological profile; if the simulation result matches the actual geological profile, perform the three-dimensional fault / fracture network construction.

[0115] S5: Based on the matched model result, establish and analyze the spatial distribution characteristics of the three-dimensional fault and fracture network in the target area, and conduct dynamic evaluation and trend prediction on the activity of the three-dimensional fault.

[0116] Specifically, based on the particle coordinates of the evolution result of the second discrete element model, different particle displacement gradient tensors are derived according to the relative position vectors between particles; according to the particle displacement gradient tensors of the evolution result of the second discrete element model, the strain tensors of different profiles are drawn to obtain the spatially distributed three-dimensional fault.

[0117] Further, the three-dimensional fault includes: dividing the space of the second discrete element model into the control volume of each particle, where the initial position of particle i is , and the current position is , and the position of neighbor particle j is ; assign a cell to each particle, where the cell includes the set of all spatial points closest to this particle , satisfying the condition: for all particle points .

[0118] Furthermore, based on the positions of the particles in the reference state and the current state, the displacement vector and the relative position vector are calculated, and the relevant formulas are as follows:

[0119]

[0120] ;

[0121] Among them, is the displacement vector of particle j relative to particle i, is the position vector of particle j relative to particle i, is the displacement vector of particle j, is the displacement vector of particle i, is the position coordinate of particle j in the current state, is the position coordinate of particle j in the initial reference state, is the position coordinate of particle i in the current state, is the position coordinate of particle i in the initial reference state.

[0122] Furthermore, according to the displacement vector and the relative position vector, calculate the displacement gradient tensor, and the specific formula is as follows:

[0123] ;

[0124] Among them, is the displacement gradient tensor of particle i, is the position vector of particle j relative to particle i.

[0125] Preferably, calculate the strain tensor according to the displacement gradient tensor, draw the strain tensor distribution of different profiles, and obtain a three-dimensional fault with spatial distribution.

[0126] It should be noted that the specific formula of the strain tensor is as follows:

[0127] ;

[0128] Among them, is the strain tensor of particle i, is the displacement gradient tensor of particle i, is the transpose of the displacement gradient tensor of particle i.

[0129] Specifically, based on the bonding relationship between particles in the evolution result of the second discrete element model, judge whether the bonding between particles is damaged.

[0130] It should be noted that if the stress value is greater than the preset bonding strength, it is determined that the bonding between particles is damaged; if the stress value is less than or equal to the preset bonding strength, it is determined that the bonding between particles is not damaged.

[0131] Further, record the time, location, and type of inter-particle bond failure according to the judgment result, where the type includes tensile fracture and shear fracture; mark the inter-particle bond state as the crack generation point, where the crack generation point is the situation where the inter-particle bond state changes from the bonded compression state or the bonded tension state to the non-bonded contact state or the state of losing interaction.

[0132] Furthermore, conduct characteristic analysis on the tensile fracture type and the shear fracture type, where the tensile fracture type is manifested as the failure perpendicular to the direction of the maximum principal stress; the shear fracture type is manifested as the failure developing along the direction of the minimum principal stress.

[0133] Specifically, based on the progress of the loading process, continuously update the information of inter-particle bond failure, and establish a crack network database, where the crack network database includes the coordinates of the particles with bond failure, the failure time, and the failure type; based on the crack network database, conduct quantitative analysis of the crack network and calculate statistical indicators, where the statistical indicators include crack density, average crack length, and crack direction distribution;

[0134] Further, draw the spatial distribution characteristic diagram of the crack network under different spatio-temporal evolutions through the statistical indicators.

[0135] Furthermore, referring to Figure 5 , this embodiment also provides a three-dimensional fault / crack network modeling device based on the discrete element method under the thrust nappe system, including:

[0136] Fault module, based on the seismic logging data parameters of the target area, construct an initial fault plane model, and extract the basic fault point set data along the strike direction of the initial fault plane model by using the encrypted grid method;

[0137] Inversion module, used to observe the geology of the target area and analyze the seismic data of the area, extract the formation information and deformation process, and invert the spatial evolution process of the fault for the seismic analysis map;

[0138] Model module, calibrate the discrete element mesoscopic parameters according to the formation parameters, deposit the first discrete element model, construct a fault function, and optimize to generate the second discrete element model;

[0139] Deformation module, based on the second discrete element model, set boundary conditions for thrust nappe simulation, and adjust the model parameters by comparing the output results of the second discrete element model with the actual geological profile until the two match;

[0140] Modeling module, based on the matched model results, establish and analyze the spatial distribution characteristics of the three-dimensional fault and crack network in the target area, and conduct dynamic evaluation and trend prediction on the activity of the three-dimensional fault.

[0141] This embodiment also provides a computer device, which is applicable to the case of the three-dimensional fault / fracture network modeling method under the reverse thrust nappe system based on the discrete element method. The computer device includes a memory and a processor. The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to implement the three-dimensional fault / fracture network modeling method under the reverse thrust nappe system based on the discrete element method as proposed in the above embodiment.

[0142] This computer device can be a terminal. The computer device includes a processor, a memory, a communication interface, a display screen, and an input device connected through a system bus. Among them, the processor of this computer device is used to provide computing and control capabilities. The memory of this computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The communication interface of this computer device is used to communicate with an external terminal in a wired or wireless manner. The wireless manner can be implemented through WIFI, a carrier network, NFC (Near Field Communication), or other technologies. The display screen of this computer device can be a liquid crystal display screen or an electronic ink display screen. The input device of this computer device can be a touch layer covered on the display screen, or a button, a trackball, or a touchpad set on the shell of the computer device, or an external keyboard, a touchpad, or a mouse, etc.

[0143] This embodiment also provides a storage medium, on which a computer program is stored. When the program is executed by a processor, it implements the three-dimensional fault / fracture network modeling method under the reverse thrust nappe system based on the discrete element method as proposed in the above embodiment.

[0144] The storage medium proposed in this embodiment and the data storage method proposed in the above embodiment belong to the same inventive concept. The technical details not described in detail in this embodiment can be referred to the above embodiment, and this embodiment has the same beneficial effects as the above embodiment.

[0145] In summary, the present invention effectively avoids the problem that the fracture propagation behavior at the fault tip is difficult to accurately depict due to the difficulty of grid reconstruction in traditional modeling by introducing the discrete element method to dynamically simulate the fault fracture system; by integrating geomechanical parameters and the tectonic evolution process during the modeling process, a spatio-temporal coupling relationship between pre-existing faults and newly formed fractures is established, realizing the quantitative analysis of the multi-stage tectonic superposition effect; at the same time, a closed-loop modeling process from tectonic indication inversion to future tectonic evolution prediction is established, significantly improving the geological rationality and prediction ability of the three-dimensional spatial distribution modeling of complex fracture systems, and providing scientific and reliable technical support for the identification of hidden structures, the evaluation of fault sealing properties, and the study of tectonic hydrocarbon control mechanisms in oil and gas exploration.

[0146] Embodiment 2

[0147] Reference Figure 4 、 Figures 6 to 12 This is the second embodiment of the present invention, which provides a three-dimensional fault / fracture network modeling method under a thrust nappe system based on the discrete element method. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0148] Taking the middle section of the southern margin of Bachu Uplift in the western Tarim Basin as the research object, a typical thrust nappe structure area where the intersection of the Niushan, Mazatag, and Luostag structural belts is distributed internally is selected as the target area. Due to multi-stage tectonic superposition and transformation in this area, the fault system is dense and complex, with typical nappe deformation characteristics. The extrusion and convergence between multiple structural belts not only result in the diversity and heterogeneity of the fault system but also breed rich oil and gas resources. It is of great significance to clarify the deep fault distribution and structural style for improving the efficiency of oil and gas exploration.

[0149] The origin of the Niushan structural belt can be regarded as the result of the differential evolution of the late advancing rates of the Mazatag structural belt on the east side and the Luostag structural belt on the west side. Its structural evolution is mainly simulated and inferred based on the seismic data of the Mazatag and Luostag structural belts. Therefore, first, high-resolution seismic profiles are selected, preprocessed, and fault identification is carried out to extract clear fault reflection characteristics. As Figure 8 shown, a northward thrust main fault F1 is identified within the Mazatag structural belt, and multiple branch antithetic faults developed along this main fault are observed. For each fault, spatial coordinate information (including lateral, longitudinal positions, and time / depth) is extracted at the positions where the reflection axes on the hanging wall and footwall are suddenly interrupted or displaced, and the two-dimensional seismic information is converted into a three-dimensional coordinate point set. Finally, the Luostag fault point set p1 and the Mazatag fault data point p2 are respectively constructed, providing a structural boundary basis for subsequent discrete element modeling.

[0150] In order to accurately construct the formation mechanical properties and fracture evolution process, the mesoscopic parameters of the particles are further calibrated by triaxial compression experiments. As Figure 7 shown, in the experiment, the sample is constructed by the radius expansion method, and isostrain compression loading is applied through the top and bottom two-sided walls. At the same time, the stress-strain response of the sample is tested under confining pressures of 5 - 80 MPa, and the curve at 20% strain is recorded. The results show that the macroscopic response cohesion of the model particles is about 32.8 MPa and the friction angle is 29.4°, which is similar to the brittle formation parameters of the target area, verifying the rationality of the parameter settings.

[0151] In the modeling stage, first, a spatial container with a size of 20 km × 15 km is constructed and filled with a calibrated set of particles to simulate the natural sedimentation process of the formation. After free settlement stabilizes, the top 3.5 km is eroded to reflect the surface uplift history, and the particle position data is output to form the first discrete element model. Subsequently, combining the formation information and the fault structure characteristics, a particle bonding relationship with parameters such as bond strength, tensile strength, and internal friction angle is introduced between the particles to simulate the natural cementation structure of the rock formation. By writing the isInsideFault function, a spatial judgment is made on the particle positions to identify whether they are inside the area defined by the fault planes p1 or p2. If it belongs to the fault plane area, the bonding relationship between the particles is cancelled and the friction coefficient is reduced to simulate the easy-sliding characteristics of the fault plane, thus forming a more realistic second discrete element model; as Figure 6 shown, different particle colors can distinguish the fault zone (red) from the brittle formation (blue, green), clearly showing the model structure hierarchy. The extrusion direction is due north. The main fault plane p1 of the Rostag Fault is on the west side of the fault zone, and the main fault plane p2 of the Mazatag Fault is on the east side of the fault zone.

[0152] During the simulation process of tectonic deformation, referring to the shortening amount obtained by the balanced profile restoration method, a boundary load is applied to the model. The trailing edge of the model is set as the active boundary, and the other three sides are set as fixed boundaries, and the active boundary is continuously extruded until the equivalent displacement of the restored profile is reached (as Figure 4 shown, the deformation amount is 6.59 km), simulating the whole process of tectonic evolution. Comparing the simulation output with the seismic profile results, Figure 9 with Figure 11 the longitudinal profile shown in Figure 8 and the seismic measured results of Figure 10 and Figure 11 are highly consistent, verifying the rationality and accuracy of the modeling method. The profile positions of Figure 9 are shown in detail in Figure 9 ; The simulation results also reveal that, as Figure 10 shown, two oblique en echelon faults are formed between the Rostag Fault point set p1 and the Mazatag Fault data point p2. Their strike intersects with the fault systems of the Rostag and Mazatag tectonic belts and finally disappears. The tectonic characteristics match the geometric shape of the Niushan tectonic belt, verifying the existence of the inferred structure.

[0153] In terms of fracture modeling, the system continuously tracks the change of the bonding failure state between particles. Whenever the stress between particles exceeds the bond strength and the state changes from "bonded compression" or "bonded tension" to "unbonded" or "losing interaction", it is determined as a fracture generation event. The system records the time, location, and type (tensile fracture or shear fracture) of fracture generation, constructing a spatio-temporal evolution fracture database. Tensile fractures mostly occur in the direction perpendicular to the maximum principal stress, and shear fractures expand along the direction of the minimum principal stress. Further, the fracture development in different regions is statistically analyzed, asFigure 12 As shown, with the intensification of boundary extrusion, the number of fractures in the transfer zone increases rapidly. Among them, the fracture density in the central intersection area is the highest, and it is inferred that it has excellent reservoir fracture channel characteristics, providing an important spatial index and target area judgment basis for oil and gas exploration.

[0154] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A three-dimensional fault / fracture network modeling method under a thrust nappe system based on discrete element, characterized in that: including Based on the parameters of seismic logging data in the target area, construct an initial fault plane model, and use the encrypted grid method to extract the basic fault point set data along the strike direction of the initial fault plane model; Extract the formation parameters of the target area, and combine the balanced section restoration method to determine the deformation process of the target area in the historical period; Calibrate the mesoscopic parameters of the discrete element according to the formation parameters, deposit the first discrete element model, construct a fault function, and optimize to generate the second discrete element model; Based on the second discrete element model, set boundary conditions for thrust nappe simulation, and adjust the model parameters by comparing the output results of the second discrete element model with the actual geological section until they match; Based on the matched model results, establish and analyze the spatial distribution characteristics of the three-dimensional fault and fracture network in the target area, and dynamically evaluate and trend predict the activity of the three-dimensional fault; Based on the particle coordinates of the evolution results of the second discrete element model, different particle displacement gradient tensors are deduced according to the relative position vectors between particles; According to the particle displacement gradient tensors of the evolution results of the second discrete element model, draw the strain tensors of different sections to obtain a spatially distributed three-dimensional fault; Based on the bonding relationship between particles in the evolution results of the second discrete element model, judge whether the bonding between particles is damaged; Record the time, location and type of the bonding failure between particles according to the judgment results, where the type includes tensile fracture and shear fracture; Mark the bonding state between particles as the crack generation point, where the crack generation point is the situation where the bonding state between particles changes from the bonding compression state or the bonding tension state to the non-bonding contact state or the state of losing interaction; Conduct characteristic analysis on the tensile fracture type and the shear fracture type, where the tensile fracture type is manifested as the failure perpendicular to the direction of the maximum principal stress; the shear fracture type is manifested as the failure developing along the direction of the minimum principal stress; Based on the progress of the loading process, continuously update the information on the bonding failure between particles, and establish a fracture network database, where the fracture network database includes the particle coordinates, failure time and failure type of the bonded particles that have failed; Based on the fracture network database, conduct quantitative analysis of the fracture network and calculate statistical indicators, where the statistical indicators include fracture density, average fracture length and fracture direction distribution; Draw the spatial distribution characteristic diagrams of the fracture network under different spatio-temporal evolutions through the statistical indicators.

2. The 3D fault / fracture network modeling method under the thrust nappe system based on the discrete element as described in claim 1, wherein: Based on the second discrete element model, set boundary conditions for thrust nappe simulation, and adjust the model parameters by comparing the output results of the second discrete element model with the actual geological section until they match, including: Set the trailing edge of the second discrete element model as the active boundary, and the other boundaries as fixed boundaries; Refer to the fault displacement amount and the balanced section restoration shortening amount of the target area, and apply motion to the active boundary; Control the motion of the active boundary, and stop the operation of the second discrete element model when the extrusion amount equal to the balanced section restoration shortening amount is reached; Extract the simulation results of the second discrete element model, and conduct a consistency comparison between the simulation results and the actual geological section; If the simulation results do not match the actual geological profile, finely adjust the discrete element particle parameters or boundary movement conditions, and repeat the above steps until the simulation results match the actual geological profile; If the simulation results match the actual geological profile, perform three-dimensional fault / fracture network construction.

3. The 3D fault / fracture network modeling method under the thrust nappe system based on the discrete element as claimed in claim 2, wherein: Calibrate the mesoscopic parameters of the discrete element according to the formation parameters, deposit the first discrete element model, construct a fault function, and optimize to generate the second discrete element model, including: Establish a mesoscopic parameter system for the discrete element, where the mesoscopic parameter system includes particle parameters and particle bonding parameters; Determine the state relationship between adjacent discrete element particles, and calibrate the mesoscopic parameters of the particle materials of each formation through triaxial compression experiments, where the state relationship includes bonded compression state, bonded tension state, non-bonded contact state, and the state where particles lose interaction; Based on the corresponding space of the target area, randomly distribute particles with a radius following a normal distribution, and establish the corresponding relationship between the mesoscopic parameters of the particles and the macroscopic properties of the formation, and assign physical properties and interaction parameters to each particle, where the physical properties include radius and density; the interaction parameters include normal stiffness, shear stiffness, and friction coefficient; Let the assigned particles freely settle until the system is stable, record the position parameters of the particles in each formation, and complete the construction of the first discrete element model; Based on the calibrated particle bonding parameters and the formation information of the target area, set the bonding relationship between the particles in the first discrete element model; Refine the first discrete element model to establish the mesoscopic parameters and mechanical relationships of the particles at different horizons in the target area; According to the fault point set data Fault, establish the main fault model function isInsideFault, where the main fault model function is used to determine whether any particle coordinate pt is inside the fault point set Fault; Based on the judgment result, cancel the bonding between the particles on the fault plane, and at the same time reduce the friction coefficient between the fault particles to form the second discrete element model.

4. The three-dimensional fault / fracture network modeling method under the reverse thrust nappe system based on the discrete element method according to claim 3, characterized in that: Extract the formation parameters of the target area, and combine the balanced cross-section restoration method to determine the deformation process of the target area in the historical period, including: Based on the initialized fault plane model, collect the drilling data of the target area and obtain core samples from the drilling data; Conduct laboratory analysis on the core samples to measure the physical property parameters of different formations, where the physical property parameters include lithology, porosity, and permeability; Collect and analyze the logging data of the target area to obtain detailed information about the underground formations, where the logging data includes resistivity logging data and natural gamma ray logging data; Analyze the seismic profile data and extract the information of different formations in the target area, where the information of different formations includes formation lithology, mechanical parameters, and spatial distribution characteristics; the mechanical parameters include elastic modulus and Poisson's ratio; Comprehensively analyze the information of different formations, the physical property parameters, and the detailed information to obtain the complete formation parameters of the target area; Based on the complete formation parameters, use the balanced cross-section restoration method to model the target area; Determine the deformation process of the target area in the historical period through the above-mentioned balanced profile restoration method, and identify the multi-stage activities of faults; Conduct a quantitative comparative analysis of the restored balanced profile generated by the balanced profile restoration method and the original profile, and calculate the extrusion deformation displacement caused by each stage of fault activity.

5. The 3D fault / fracture network modeling method under the thrust nappe system based on discrete element as claimed in claim 4, wherein: The construction method of the initialized fault plane model is as follows: Obtain the seismic logging data parameters of the target area, and preprocess the seismic logging data parameters; Based on the preprocessed seismic logging data parameters, select the seismic profiles that clearly show the characteristics of the target fault, and give priority to the areas showing displacement; Based on the seismic profiles, extract coordinate data, stratification data, and fault data; Analyze the seismic profiles, identify and extract the relevant parameters of the main faults with large displacement and in the extrusion direction, where the relevant parameters include the dip of the fault plane, the dip angle of the fault plane, the sliding distance along the fault plane, the sliding direction along the fault plane, and the relative displacement of the strata on both sides of the fault; Based on the relevant parameters, extract the three-dimensional spatial geometry of the main faults; Process the three-dimensional spatial geometry using an encrypted grid method; Based on the processed three-dimensional spatial geometry, extract the basic fault point set data along the strike direction of the main fault. Let the basic fault point set data be Fault, which includes n three-dimensional points S = {p1, p2, …, p n}, where p n is the nth three-dimensional point on the fault plane; Construct an initialized fault plane model according to the basic fault point set data.

6. A three-dimensional fault / fracture network modeling device under a thrust nappe system based on the discrete element method, based on the three-dimensional fault / fracture network modeling method under the thrust nappe system based on the discrete element method according to any one of claims 1 to 5, characterized in that: Including: Fault module, based on the seismic logging data parameters of the target area, construct an initialized fault plane model, and use an encrypted grid method to extract basic fault point set data along the strike direction of the initialized fault plane model; Inversion module, used to observe the geology of the target area and analyze the seismic data in this area, extract the stratigraphic information and deformation process, and invert the seismic analysis map, the spatial evolution process of the fault; Model module, calibrate the discrete element mesoscopic parameters according to the stratigraphic parameters, deposit the first discrete element model, construct a fault function, and optimize to generate the second discrete element model; Deformation module, based on the second discrete element model, set boundary conditions for thrust nappe simulation, and adjust the model parameters by comparing the output results of the second discrete element model with the actual geological profile until they match; Modeling module, based on the matched model results, establish and analyze the spatial distribution characteristics of the three-dimensional fault and fracture network in the target area, and conduct dynamic evaluation and trend prediction on the activity of the three-dimensional faults.

7. A computer device, comprising a memory and a processor, the memory storing a computer program, characterized in that: When the processor executes the computer program, it implements the steps of the three-dimensional fault / fracture network modeling method under the thrust nappe system based on discrete elements according to any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by the processor, it implements the steps of the three-dimensional fault / fracture network modeling method under the thrust nappe system based on discrete elements according to any one of claims 1 to 5.

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