A method for determining evolution period of strike-slip fault at craton edge based on multi-source data analysis

Abstract

The present application belongs to the technical field of determining the evolution period of strike-slip faults in the edge of craton, and particularly relates to a method for determining the evolution period of strike-slip faults in the edge of craton based on multi-source data analysis. Three-dimensional reflection seismic data, well logging data and core samples from multiple wells in the target area are collected, and the core samples are from Sinian, Cambrian, Permian and Triassic strata. The seismic data is interpreted to determine the seismic reflection layer and make a coherent attribute map and a time domain structure map, and the fracture plane distribution characteristics and profile structure style are analyzed. The petrology of the core samples is characterized, including scanning electron microscope observation, energy spectrum testing, cathodoluminescence microscope observation, identification of fracture filling characteristics, cutting relationship and diagenetic mineral filling generation, and fluid inclusion analysis of the fracture filling vein samples.

Description

Technical Field

[0001] This invention belongs to the technical field of determining the evolution stages of strike-slip fractures at the edge of a craton, and particularly relates to a method for determining the evolution stages of strike-slip fractures at the edge of a craton based on multi-source data analysis. Background Technology

[0002] The evolutionary stages of strike-slip faults at the craton margin directly constrain the reconstruction of regional tectonic dynamics and the deployment of oil and gas and other mineral resource exploration. Their formation and evolution are influenced by the superposition of multiple regional tectonic events, such as supercontinental breakup and plate subduction and collision, resulting in complex tectonic styles and intense alteration. Traditional identification methods often rely on single seismic interpretations or limited core observations, making it difficult to comprehensively capture the spatiotemporal evolution characteristics of faults in both plane and profile. This is especially true for atypical strike-slip faults at the craton margin affected by local geological conditions such as gypsum-salt rock detachment and magmatic hydrothermal activity, making it difficult to accurately distinguish the fault activity responses at different tectonic stages.

[0003] On the one hand, the lack of systematic integration and quantitative analysis of multi-source data makes it impossible to effectively correlate key information such as seismic tectonic patterns, rock fracture cutting relationships, fluid activity trajectories, and changes in paleostress fields; On the other hand, numerical methods such as discrete element simulation have insufficient precision in calibrating micro-parameters and do not adequately consider the controlling effect of pre-existing basement fractures, resulting in deviations between simulation results and actual geological phenomena. This makes it difficult to accurately invert the evolution process of multiple superimposed fractures, and there is an urgent need for a comprehensive calibration method that takes into account the comprehensiveness of data, the accuracy of analysis, and the reliability of simulation. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned technical problems by providing a method for determining the evolution stages of strike-slip fractures at the edge of a craton based on multi-source data analysis.

[0005] In view of this, the present invention provides a method for determining the evolution stages of strike-slip faults at the edge of a craton based on multi-source data analysis, comprising the following steps: Step 1: Collect three-dimensional reflection seismic data, well logging data, and core samples from multiple wells in the target area. The core samples are from the Sinian, Cambrian, Permian, and Triassic strata. Step 2: Interpret the seismic data, determine the seismic reflection layer, and create a coherence body attribute map and a time-domain structural map to analyze the characteristics of the fault plane distribution and the structural style of the cross section. Step 3: Perform petrological characterization on the core samples, including scanning electron microscopy, energy dispersive spectroscopy, and cathodoluminescence microscopy, to identify fracture filling characteristics, cutting relationships, and diagenetic mineral filling generations; Step 4: Perform fluid inclusion analysis on the fracture-filled vein samples to obtain homogenization temperature and freezing point temperature data, and determine the spatiotemporal relationship between fluid activity and fracture development. Step 5: Conduct acoustic emission tests on samples from different strata to determine the stress value corresponding to the Kaiser point and classify the tectonic movement periods; Step 6: Establish a numerical model based on the discrete element method, input the stratigraphic mechanical parameters, and simulate the two-stage superimposed evolution process of the strike-slip fault; Step 7: Based on the combined results of seismic interpretation, petrological characterization data, fluid inclusion analysis data, acoustic emission test data, and discrete element simulation results, determine the evolution stages of the strike-slip fault.

[0006] Preferably, in step two, the seismic interpretation uses an interpretation grid spacing of 100m×100m, and the determined seismic reflection layers include the top boundary of the Cambrian, the top boundary of the Silurian, the top boundary of the Permian, and the top boundary of the Triassic Xujiahe Formation.

[0007] Preferably, in step three, after the core sample is prepared into a thin rock section, it is tested. The scanning electron microscope observation is carried out in BSED mode with an HV of 20kV. The cathodoluminescence experiment test conditions are a vacuum of 0.003mBar, an electron gun beam current of about 240μA, and an accelerating voltage of 13kV.

[0008] Preferably, in step four, the fluid inclusion analysis is performed using a Linkam THNS 600G hot and cold stage with an analysis accuracy of ±0.1℃, and is accompanied by an Olympus 100x 8mm telephoto lens for microscopic observation. The samples were taken from the Sinian Dengying Formation, the Cambrian Longwangmiao Formation, the Xixiangchi Formation, and the Permian Qixia Formation and Maokou Formation.

[0009] Preferably, in step five, the rock acoustic emission test uses a GCTS RTR-1000 testing system with a triaxially loaded sample. Acoustic emission information is collected by an SAEU2S detector. The Kaiser point is determined by the jump in acoustic emission energy value and the abrupt change in ring count.

[0010] Preferably, in step six, the discrete element simulation uses PFC3D software. The model includes two deformation stages: State I, which extends in a northeast-southwest direction, and State II, which compresses in a south-north direction. The formation mechanical parameters are obtained through triaxial compression experiments and Brazilian splitting experiments, and are calibrated using an adaptive proportional feedback control algorithm and an internal and external dual-loop strategy.

[0011] Preferably, the State I model contains 344,781 particles with a minimum particle radius of 0.06 meters and a maximum radius / minimum radius ratio of 1.66. The State II model is generated by trimming the State I model and contains 239,776 particles with a gravity load of 1g.

[0012] Preferably, in step seven, during the comprehensive analysis, the evolution stages are determined by combining the layered distribution characteristics of the fracture plane, the vertical extension law of the profile, the multi-stage crack cutting-constraint relationship, the uniform temperature cluster distribution characteristics of fluid inclusions, and the division of stress intervals at Kaiser points.

[0013] Preferably, the defined stages of strike-slip fracture evolution include an early extensional stage and a late compressional alteration stage.

[0014] Preferably, the target area is a strike-slip fault zone at the edge of a craton, particularly applicable to the SBF17 strike-slip fault zone in the Yuanba and Tongnanba areas of northern Sichuan Basin.

[0015] The beneficial effects of this invention are as follows: By integrating multi-source data from 3D seismic interpretation, petrological characterization, fluid inclusion testing, rock acoustic emission testing, and discrete element numerical simulation, a dual support system of geological evidence and numerical verification is constructed, overcoming the limitations of traditional single-data methods. It not only accurately identifies the planar layered distribution characteristics, vertical extension patterns of cross-sections, and multi-stage fracture cutting-constraint relationships of strike-slip faults, but also clarifies the spatiotemporal boundaries of the late Hercynian and early Yanshanian evolution stages through the homogeneous temperature cluster distribution of fluid inclusions and the division of stress intervals at Kaiser points. This achieves quantitative and high-precision determination of the evolution stages of atypical strike-slip faults at the craton margin.

[0016] This innovative method introduces an adaptive proportional feedback control algorithm and an internal / external dual-loop strategy, solving the challenge of calibrating micro-parameters in discrete element simulations. The simulation results show extremely high agreement with actual geological structures, successfully reconstructing the two-stage superimposed evolution process of early extension and late compression under the control of pre-existing basement normal faults. Its findings not only clarify the coupling relationship between strike-slip faults and major regional tectonic events such as supercontinent breakup and plate collisions, but also provide a standardized technical paradigm for the dynamic study of strike-slip fault zones at the craton margins, offering significant guidance for the exploration and deployment of oil, gas, and other mineral resources. Attached Figure Description

[0017] Figure 1 This is a time-domain tectonic plan view of the No. 17 strike-slip fault in the Sichuan Basin within the study area of ​​this invention. A1-A3: Cambrian top boundary; B1-B3: Silurian top boundary; C1-C3: Upper Permian top boundary; D1-D3: Upper Triassic Xujiahe Formation top boundary. Figure 2 This is a typical seismic interpretation profile of the strike-slip fault No. 17, the subject of this invention. The profile location is shown in [link to profile]. Figure 1 D1; Figure 3The images show (A) photographs of core samples collected within the study area of ​​this invention, and (B, C, F) observations of the prepared thin sections under a conventional microscope; (D, E, G) observations under a cathodoluminescence microscope; (H, I) observations under a scanning electron microscope; and (J, K, L) results of energy dispersive spectroscopy analysis. Figure 4 Microscopic observation of inclusions in thin sections made from core samples from the study area of ​​this invention: (A,B) Dengying Formation sample from well RT1 (Sinian); (C,D) Longwangmiao Formation sample from well RT1 (Cambrian); (E) Xixiangchi Formation sample from well RT1 (Cambrian); (F,G,H) Qixia Formation and Maokou Formation sample from well YB6 (Permian); (I) Maokou Formation sample from well YB8. Figure 5 for Figure 4 The distribution of (A) homogenization temperature and (B) freezing point temperature of fluid inclusions observed in the sample shown. Figure 6 This is a graph showing the changes in cumulative ringing count and cumulative energy as applied stress in acoustic emission experiments of core samples from well YB6 (A,B,C,D), the Triassic Xujiahe Formation; well LB1 (E,F,G,H), the Triassic Feixianguan Formation; well YB3 (I,J,K,L), the Permian Maokou Formation; and well RT1 (M,N,O,P), all within the study area of ​​this invention. Figure 7 Analysis diagram for determining the fluid injection period by projecting (A) Permian samples and (B) Sinian-Cambrian samples of the study area of ​​this invention onto the burial history-thermal history diagram of the corresponding well location; Figure 8 The stress distribution diagram of the Kaiser effect points identified in the acoustic emission experiments of this invention; Figure 9 This is a diagram showing the evolution of the tectonic stress field in the study area, reconstructed by integrating the regional stress field environment, crack intersection characteristics, fluid filling stages, and acoustic emission test results. Figure 10 This is a planar distribution diagram of the basement fracture in the study area proposed in this invention; Figure 11 The discrete element numerical model of this invention is established in three dimensions (A, B) and corresponding two-dimensional top views (C, D), vertical cross-sections (E, F) of the numerical model, and (G) the division of different rock mechanical layers; (H) shows the three ways in which contact fracture between particles forms cracks in the discrete element model. Figure 12 (A) calibration logic and (B) loop method for calibrating the microscopic parameters of the discrete element model used in this invention; Figure 13 The present invention presents the (A) stress field simulation results and fracture propagation process and (B) local strain field evolution process of the first stage evolution of strike-slip fracture based on discrete element theory. Figure 14 The present invention presents the (A) stress field simulation results and fracture propagation process and (B) local strain field evolution process of the second stage evolution of strike-slip fracture based on discrete element theory. Figure 15 This is the simulation result of the strike-slip fracture interpretation profile based on discrete element theory in this invention; Figure 16 This is a flowchart of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0019] This invention interprets and produces seismic data interpretation profiles and coherence property maps for the SBF17 strike-slip fault zone in the northern Sichuan Basin. It analyzes 33 dolomite cement samples and their surrounding rocks from the Sinian, Cambrian, Permian, and Triassic systems, as well as 22 vertical well core samples. Analytical methods include scanning electron microscopy and energy dispersive spectroscopy, cathodoluminescence microscopy, fluid inclusion analysis, and rock acoustic emission analysis. The discrete element method (DEM) is used to simulate the multi-stage superposition formation process of the SBF17 strike-slip fault zone in the study area.

[0020] This invention utilizes three-dimensional reflection seismic data from the Yuanba-Tongnanba area in the northern Sichuan Basin, acquired by Sinopec Exploration Company, covering two rectangular work areas with a total area of ​​approximately 6000 square kilometers. A 100m × 100m interpretation grid spacing was selected to complete the seismic interpretation of the SBF17 strike-slip fault zone. Using well logging data for calibration, four seismic reflection layers between the Cambrian and Jurassic systems were identified and compared, including the Cambrian top interface (…). The top boundary of the Silurian (TS), the top boundary of the Permian (TP2), and the top boundary of the Triassic Xujiahe Formation (TT3x) are identified. To achieve high-precision boundary constraint and tectonic deformation feature identification of strike-slip fault zones in planar views, we created coherent volume property maps for these four boundaries and provided time-domain structural maps of these four boundaries.

[0021] Based on the lithological description and fracture observation of core samples from 22 wells in the study area, 33 thin sections were prepared from the dolomite core sample of the Permian Qixia Formation in well LB1. These thin sections were observed using conventional microscopy, scanning electron microscopy, and cathodoluminescence microscopy. Petrological characterization of the core thin sections was performed using optical microscopy. Scanning electron microscopy observation and energy dispersive spectroscopy (EDS) were conducted using a FEIQUANTA 200F at the State Key Laboratory of Oil and Gas Reservoir Development, China University of Petroleum, with an HV of 20 kV in BSED mode. EDS point analysis was performed under accelerating voltage of 20 kV and a working distance of 10 mm. Cathodoluminescence experiments were conducted at the Mineral Typology Laboratory of the Center for Genetic Mineralogy, China University of Geosciences (Beijing), using a Leica DM2500P microscope, a CL8200MK5-2 cathodoluminescence analyzer, and a Leica DFC310FX camera. The testing conditions were a vacuum of 0.003 mBar, an electron gun beam current of approximately 240 μA, and an accelerating voltage of 13 kV. The results of conventional microscopy observations are used to identify the filling characteristics and cutting relationships of fractures, while the results of scanning electron microscopy and cathodoluminescence experiments are used to identify the composition and contact relationships of fracture cement and to characterize the filling generations of diagenetic minerals.

[0022] We collected a series of calcite vein samples from the fracture-filled interiors of the Sinian Dengying Formation, Cambrian Longwangmiao and Xixiangchi Formations, and Permian Qixia and Maokou Formations in wells RT1, YB6, and YB8 in the northern Sichuan Basin for fluid inclusion analysis. Fluid inclusion analysis allows us to determine the relative timing of fluid activity, thus indicating the spatiotemporal relationship between fluid activity and fracture development. We performed fluid inclusion thermometry analysis on thin sections of rocks with multiple fracture filling stages. The fluid inclusion analysis was completed in the Microscopic Hydrocarbon Monitoring Laboratory of the Petroleum Department, College of Resources, China University of Geosciences (Wuhan). Microthermometry was performed on a Linkam THNS 600G hot and cold stage, which has an analytical accuracy of ±0.1℃. Microscopic observation of fluid inclusions was completed using an Olympus with a 100x 8mm telephoto lens.

[0023] When rocks are subjected to stress and deformation, stress concentration zones form around microcracks created by early tectonic movements, and strain energy gradually accumulates. When the external force increases to a certain extent, microscale yielding or deformation occurs at the location of the pre-existing cracks, causing the pre-existing microcracks to expand and thus releasing strain energy. Stress relaxation occurs at the local location where the pre-existing cracks are located, and some of the stored strain energy is released in the form of elastic waves—this is the acoustic emission phenomenon. The loading stress value at which acoustic emission occurs, obtained by an acoustic emission detector, is defined as the Kaiser point. The Kaiser value of rocks under confining pressure loading conditions is determined jointly by the jump in acoustic emission energy value and the abrupt change in ring count. Rock acoustic emission testing was conducted in the Rock Mechanics Laboratory of the State Key Laboratory of Oil and Gas Reservoir Geology and Development Engineering at Southwest Petroleum University. The GCTS RTR-1000 testing system was used to triaxially load the samples, and the SAEU2S detector was used to collect acoustic emission information.

[0024] In this study, we used PFC3D software based on the Discrete Element Method (DEM) to build a numerical model. The DEM, first proposed by Cundall, is a numerical method for studying the mechanical behavior of interactions between discontinuous granular materials under specified force or displacement conditions. The force-displacement law is used to update the contact force generated by the relative motion at each particle contact point, while the velocity and position of each particle are updated according to Newton's second law. The dynamic behavior of the particles is realized through explicit dynamics and a time-stepping algorithm, which assumes that within a sufficiently small time step, the forces acting on a particle and the disturbances generated by its motion are entirely determined by the interactions between it and the particles in contact. Therefore, the interaction between particles is considered a nonlinear dynamic process; when boundary conditions or internal stresses change, the equilibrium state between particles changes. This study established a two-stage superimposed evolution numerical model, including a NE-SW extensional State I and a SNR compressional State II. After State I, we pruned this model and continued to deposit new formation particles to simulate new boundary conditions and natural compaction. In addition to the physical properties of particles, they can also be bonded together by bonds. When the shear / tensile stress exceeds the shear / tensile strength between particles, the contact bond is broken and recorded as a microcrack. Macroscopic fractures are formed by the convergence of several microcracks. The interparticle interactions defined by the Discrete Element Method (DEM) determine that this method is suitable for simulating the deformation of upper crustal rock materials. Based on the above-mentioned fundamental properties of discrete particles, the DEM model can generate fractures and cracks with actual displacements. This capability of the DEM is essential when we attempt to reproduce the strain-fracture process of strata under tectonic stress.

[0025] The SBF17 strike-slip fault zone studied in this study is located in the northern Sichuan Basin, on the northwestern margin of the Yangtze Craton. The studied fault is 32 km long and has an azimuth of approximately 335°, terminating at the Tongnanba anticline on its northwest side. Located on the craton margin, the SBF17 strike-slip fault zone differs significantly from previously discovered intracraton strike-slip fault zones in the central Sichuan Basin and Tarim Basin, exhibiting a non-typical strike-slip fault tectonic style. Through analysis of 3D seismic data, the structural geometry was studied in detail from both planar and cross-sectional perspectives.

[0026] Due to lithological differences and the superimposed effects of multiple tectonic environments, the SBF17 strike-slip fault zone exhibits a distinct layered distribution in plan view. At the Cambrian top interface, short, isolated, and discontinuous faults are observed. A clear three-segment distribution is visible in this plane, each separated by a NNE-SSW trending normal fault. The northern segment features shorter, parallel faults, while the central segment shows greater development and better continuity than the northern segment, with soft connections between multiple faults. Figure 1 A). The southern segment has the lowest degree of fault development, with faults far apart and not forming any composite relationships. At the top interface of the Silurian system, the width of the fault zone increases significantly. The northern segment shows continuous fault development and exhibits the geometry of the Riddle shear zone. The north-northeast-southwest trending normal faults in the north extend to greater lengths. The central segment extends northeastward under the obstruction of the normal fault assemblage, with the fault width being the largest in the middle of the central segment. This indicates that the weak rock mechanics of the Silurian strata led to the release of stratigraphic stress, forming a wide and weak shear zone. Figure 1 B); At the top interface of the Permian, the middle and southern segments continue to extend northeastward, the width of the fault zone decreases, but the fault density increases instead, forming a strong positive undulation with limited linearity in the middle of the fault zone. Due to the modification by late compression, the early normal faults are reversed at both the top interfaces of the Silurian and Permian, exhibiting a local positive undulation structure. Figure 1 C). At the top interface of the Triassic Xujiahe Formation, under the dual control of Yanshanian orogeny and strike-slip faults, compressional-strike-slip faults with similar strikes to the shallow strata developed. This reflects the control of deep strike-slip faults on the development location of shallow thrust structures. Some deep main strike-slip faults, under the compressional strike-slip stress field, broke through the stress release of the Jialingjiang Formation gypsum-salt rocks and developed upwards into the interior of the Xujiahe Formation. Figure 1 D).

[0027] In the cross-sectional view, the SBF17 main fault extends downwards to the Sinian strata and upwards mostly terminates at the bottom of the Triassic Jialingjiang Formation gypsum-salt rock. The secondary faults have a shorter vertical penetration length and mostly terminate at the top interfaces of the Silurian and Permian systems. The Hanjiadian Formation at the top interface of the Silurian system is in parallel unconformity contact with the overlying Liangshan Formation of the Permian system. The Silurian mudstone strata with weaker rock mechanics properties transform into the Permian carbonate strata with stronger rock mechanics properties. The decoupling of rock mechanics properties leads to stress release near this stratum interface. Some deep faults terminate at the top interface of the Silurian system. Figure 2 The termination of some faults at the Maokou Formation is influenced by the Dongwu Movement. During the Dongwu Movement, the study area was uplifted and formed into land, then weathered and eroded, resulting in a parallel unconformity between the Upper and Lower Permian strata. Until the end of the Late Permian, the study area was subjected to NE-SW trending extensional stress, and the SBF17 strike-slip fault zone developed normal faults under this stress. However, due to intense compression and alteration of the basin margin in the later period, the normal faults formed during this period were modified, and only a few normal faults were observed on the seismic profile. Figure 2 (B, C). The SBF17 strike-slip fault zone terminates upwards at the base of the Triassic Jialingjiang Formation gypsum-salt rock, due to stress release caused by the weak rock mechanics of the gypsum-salt rock. Typical salt structures such as salt domes and salt pillows have formed within the gypsum-salt rock. Thrust faults develop in the strata above the Triassic Xujiahe Formation, sliding downwards into the Jialingjiang Formation gypsum-salt rock. Furthermore, a salt dome structure usually corresponds above the main SBF17 fault, demonstrating the control of deep strike-slip faults over the development of shallow thrust structures. The strike of the thrust faults and the strike-slip faults also conform to the Riddle geometric shear fault assemblage.

[0028] Based on the fracture morphology and cathodoluminescence patterns observed in the Permian Qixia Formation core from well LB1, three stages of calcite veins can be identified, and the fractures can be sequentially divided into three groups: F1, F2, and F3. Figure 3 The three sets of cracks show a clear cutting relationship. Crack F1 is a high-angle vertical crack, exhibiting bright red fluorescence. The crack surface is smooth and flat, with a width of approximately 2 mm, and is completely filled with calcite. Crack F2 is a medium-angle shear crack, exhibiting weak dark red fluorescence. The inclination angle is 60°, the crack surface is rough and tortuous, and the crack width is approximately 6 mm, completely filled with calcite. Fluorite minerals are present in the crack. Crack F3 is a high-angle near-vertical shear crack, exhibiting no fluorescence. The crack surface is straight, with a width of approximately 3 mm, and is completely filled with calcite minerals. Figure 3 A).

[0029] Core observations revealed a clear intersection and confinement relationship among the three sets of fractures. The angle between fracture F1 and F2 was 23°, and the angle between F2 and F3 was 45.71°. The high-angle fracture F1 was confined by the medium-angle fracture F2, indicating that fracture F1 formed earlier than fracture F2. The high-angle fracture F3 clearly cut and discontinuously severed fractures F1 and F2, indicating that fracture F3 formed the latest. Therefore, based on the development characteristics and cutting relationships of the fractures, the formation order of the three sets of fractures can be determined as: fracture F1, fracture F2, fracture F3. Figure 3 A, B). Figure 3 C and F show the cutting and confinement relationship of three sets of cracks, F1, F2, and F3, under an orthogonal light microscope. The filling material at the cut location of crack F2 is fluorite. During the cutting process of crack F2, the calcite and fluorite minerals filling crack F2 separated along the fault direction to form branch cracks. The orientation and morphology of the fluorite minerals also indicate that after being cut by crack F3, the fluorite particles were faulted to both sides of crack F3. Figure 3 Cathodes D, E, and G show the matrix composition as primarily dolomite under cathodoluminescence microscopy. The surrounding rock is generally dark red. The calcite in the high-angle fracture F1 is bright red, and fracture F1 is confined by fractures F2 and F3. The calcite in fracture F2 exhibits slight luminescence, appearing dark red, while the fluorite filling it is bluish-purple. The calcite filling in fracture F3 does not emit light and remains dark red. Figure 3 G indicates that a large-scale magmatic-hydrothermal activity occurred after the deposition of the Qixia Formation, resulting in irregular fluorite minerals being replaced within the dolomite. This suggests that the Late Permian Emeishan basalt eruption affected the northeastern part of the Sichuan Basin. The fact that the fluorite minerals formed by this magmatic-hydrothermal activity were cut by F3 also indicates that the formation of the F3 fracture occurred later than the Late Permian. The near-vertical dip angle of the F3 fracture suggests that it may have formed in a horizontal compressive stress environment. Figure 3 H,I show the cutting relationship between the cracks observed under a scanning electron microscope. Figure 3 J,K,L presents energy dispersive spectroscopy (EDS) data of fluorite, calcite, and dolomite matrix in the fracture filling material and the surrounding rock.

[0030] Methane-containing gas-liquid two-phase brine inclusions and pure gaseous methane inclusions were observed in samples from the Dengying Formation of Well RT1. Calcite or quartz-filled fractures or dissolution pores were the main hosts for these inclusions. They were mostly distributed in clusters, and the inclusions were relatively small, approximately 5 micrometers in size. Figure 4A, B); Gas-phase inclusions, single-phase brine inclusions, and two-phase brine inclusions were observed in calcite minerals within veins and pores of the Longwangmiao Formation. The brine inclusions ranged in size from 2 to 60 micrometers, exhibiting irregular shapes such as triangles and rectangles. They were mainly distributed in bands along the healed microfractures of calcite minerals within the veins, appearing colorless or light brown and showing no fluorescence. Two-phase brine inclusions were often associated with single-phase brine inclusions. Gas-phase inclusions were generally less developed, with sizes ranging from 5 to 15 micrometers, mostly square in shape, and mainly distributed in lines / bands along the healed fissures of calcite minerals. Figure 4 C, D); Fluid inclusions found in the Xixiangchi Formation samples were mainly hosted within vein-type calcite minerals. The inclusions were diverse, including gaseous and brine inclusions. The brine inclusions ranged in size from 2 to 28 micrometers, were rectangular in shape, and were mainly distributed in bands along the healed micro-fractures of the calcite minerals. None of them showed fluorescence. Figure 4 E). In samples from the Qixia and Maokou Formations of Well YB6, clusters of gas-liquid two-phase brine inclusions were found developed within fracture-filled calcite veins. These inclusions were quadrilateral in shape and ranged in size from 3 to 11 micrometers. Figure 4 F, G, H); In samples from the Maokou Formation of well YB8, gas-liquid two-phase inclusions were found to be distributed in a banded pattern along the bright calcite veins filling the fractures. The inclusions ranged in size from 3 to 7 micrometers and were mostly square in shape. Figure 4 I).

[0031] Microthermography was performed on 108 samples from the Sinian Dengying Formation, Cambrian Longwangmiao Formation, Cambrian Xixiangchi Formation, Permian Qixia Formation, and Permian Maokou Formation in the Yuanba area to obtain homogeneous temperatures from brine inclusions associated with methane inclusions. Only samples from the Cambrian Longwangmiao Formation, Cambrian Xixiangchi Formation, and Permian Maokou Formation yielded freezing point temperatures. The results are summarized in […]. Figure 5A. All analyzed fluid inclusions were in a homogeneous liquid state. The homogenization temperatures of fluid inclusions in the fractures of the Dengying Formation in well RT1 mainly fell within four ranges, with median values ​​of 118℃, 146℃, 242℃, and 283℃, respectively. The homogenization temperatures of fluid inclusions found in the Longwangmiao Formation of well RT1 mainly fell within three ranges, with median values ​​of 100℃, 111℃, and 120℃, respectively. The homogenization temperatures of fluid inclusions found in the Xixiangchi Formation of well RT1 mainly fell within two ranges, with median values ​​of 108℃ and 129℃, respectively. Y The homogenization temperatures of fluid inclusions found in the Qixia Formation of Well B6 are mainly distributed in three ranges, with medians of 72℃, 108℃, and 170℃, respectively; the homogenization temperatures of fluid inclusions found in the Maokou Formation of Well YB8 are mainly distributed in four ranges, with medians of 96℃, 114℃, 129℃, and 150℃, respectively; the homogenization temperatures of fluid inclusions found in the Maokou Formation of Well YB6 are mainly distributed in two ranges, with medians of 116℃ and 146℃, respectively; the obtained freezing point temperature and homogenization temperature exhibit a non-linear relationship and a clustered distribution characteristic. Figure 5 B). These homogenization temperatures indicate that different strata have undergone multiple phases of fracturing and fluid activity.

[0032] The number of Kaiser points obtained from different stratigraphic samples varies. Cambrian Longwangmiao Formation and Permian Maokou Formation samples generally have 4 Kaiser points, Triassic Feixianguan Formation has 2 Kaiser points, and Triassic Xujiahe Formation has 3 Kaiser points. Figure 6 These Kaiser points correspond to different stress field intensities, which means that the intersecting cracks may be the product of different tectonic movements.

[0033] This invention obtained three core geological evidences through seismic interpretation, petrological characterization, fluid inclusion testing, and acoustic emission experiments: (1) the characteristics of fracture plane distribution and profile structure; (2) the relationship between multi-stage fluid filling and multi-stage fracture cutting-constraint; and (3) the periodization of paleostress fields. The above evidence provides a direct basis for the establishment of subsequent geological evolution models.

[0034] The large-scale thrusting and compression at the late basin margin severely altered the original morphology of the SBF17 strike-slip fault, a point that needs to be distinguished from the typical strike-slip faults within the cratons of the central Sichuan and Shunbei regions, which have already been described in detail. The SBF17 strike-slip fault exhibits a banded distribution with poor continuity but relatively wide fault widths in plan view. Figure 1B, C), this is likely controlled by late-stage thrusting and the stratification characteristics of the rock mechanics. Thrusting alters the direction of the local stress field, causing early, well-connected fractures to deflect and break, and also changing the nature of the fractures. This explains why only a few near-north-south trending normal fractures parallel to the direction of the maximum principal stress of the compressive stress field were found in the seismic data. Under the stress release effect of the regional gypsum-salt rock weak layers, thrust faults formed in the shallow Triassic strata under the action of the compressive stress field. Figure 1 D), whose development location is controlled by strike-slip faults, indicates the evolutionary history of the SBF17 strike-slip fault, which underwent two phases of superimposed modification: early extension and late compression. On the seismic profile, we discovered a series of normal faults penetrating into the basement rocks within the deep Sinian strata, which may be evidence of the extension of the Sichuan Basin during the Rodinian period. Figure 2 The main faults in the Paleozoic strata exhibit good vertical continuity. However, due to the reactivation of these faults caused by later thrusting, the termination points of secondary faults cannot serve as direct evidence of the different periods of fault activity. The few normal faults developed in the Paleozoic strata indicate the presence of early extensional processes. It is noteworthy that the control of these normal faults over the strata appears to terminate at the top boundary of the Permian system. Figure 2 (B,C), which indirectly reflects that the normal fault formed no later than the end of the Permian. Based on the above analysis, the SBF17 strike-slip fault zone underwent two phases of evolution: early extension and late compressional alteration. The vertical combination of Paleozoic residual normal faults and Triassic reverse faults provides direct evidence for this view.

[0035] Microthermography was performed on inclusions in the deep Sinian Dengying Formation, Cambrian Longwangmiao Formation and Xixiangchi Formation, and the shallow Permian Qixia Formation and Maokou Formation in the study area. It should be noted that we have preliminarily screened out the secondary inclusion data associated with the fracture filling process for analysis. By projecting the homogenized temperature onto the corresponding burial-thermal history, we infer that the northern Sichuan region experienced two stages of secondary fracture formation and fluid filling: (1) The first stage occurred in the late Hercynian period, Late Permian to End of Permian (269.3-253.7 Ma). The secondary fractures formed in the deep Sinian and Cambrian samples during this period captured the associated fluid inclusions ( Figure 7 A); (2) The second stage occurred in the early Yanshanian Movement, Middle Jurassic (177.5-155.7 Ma). This period corresponds to the uplift stage of the Micangshan-Dabashan tectonic belt in the northern Sichuan Basin. At this time, the Permian strata were subjected to compressive stress field, forming shear fractures that once again captured the fluid inclusions associated with the fractures. Figure 8 B). In summary, fluid inclusion data indicate that the northern Sichuan Basin experienced two phases of secondary fracture formation-fluid inflow events: the late Hercynian phase and the early Yanshanian phase.

[0036] Kaiser points, detected through time-series acoustic emission monitoring of rocks, can indicate the tectonic alteration periods experienced by rock strata. This study conducted systematic acoustic emission tests on different strata in the northern Sichuan Basin, and the detected Kaiser points were compiled into... Figure 8 The Kaiser points obtained from the Cambrian Longwangmiao Formation include 59.14 MPa, 84.78 MPa, 94.08 MPa, 99.79 MPa, 123.44 MPa, 142.12 MPa, 159.44 MPa, and 176.49 MPa; the Kaiser points obtained from the Permian Maokou Formation include 52.59 MPa, 82 MPa, 85 MPa, 93.24 MPa, 98.34 MPa, 118.36 MPa, 131.9 MPa, 141.11 MPa, and 156.49 MPa. 74 MPa; the Kaiser points obtained from the Triassic Feixianguan Formation include 40.55 MPa, 44.72 MPa, 49.86 MPa, 82.35 MPa, 85.69 MPa, 92.37 MPa, and 97.33 MPa; the Kaiser points obtained from the Triassic Xujiahe Formation include 38.66 MPa, 43.45 MPa, 45.4 MPa, 48.07 MPa, 53.14 MPa, 60.32 MPa, 82.03 MPa, 89.76 MPa, and 99.08 MPa.

[0037] At different burial depths, the magnitude of the vertical principal stress increases linearly with density and burial depth. However, the Kaiser point stress values ​​monitored by acoustic emission indicate the magnitude of the maximum principal stress in different tectonic periods. The maximum principal stress is often the horizontal principal stress. Therefore, the Kaiser points monitored in different strata can indicate the tectonic movements that have experienced the maximum principal stress values. Thus, if Kaiser points with the same stress value range are monitored in different strata, we can assume that the two strata experienced the same tectonic movement. In short, the number of Kaiser points directly indicates the number of key tectonic movements experienced by the corresponding strata. We found that the Kaiser points of the Cambrian Longwangmiao Formation and the Permian Maokou Formation are concentrated in three intervals: Phase I: 38.66MPa-59.14MPa, Phase II: 82.03MPa-99.79MPa, and Phase III: 118.36MPa-159.44MPa. The Kaiser point data obtained from the Triassic samples are distributed in Phase I and Phase II. It should be noted that these three phases do not represent the chronological order of occurrence. Figure 8This indicates that the Permian Maokou Formation and its deeper strata experienced three phases of tectonic activity, while the Triassic strata only experienced two phases. Acoustic emission experiments show that after the deposition of the Triassic Xujiahe Formation, the northern Sichuan Basin experienced two more phases of tectonic activity, with acoustic emission events recorded in both Cambrian and Triassic strata. From the deposition of the Permian Maokou Formation until the deposition of the Triassic Feixianguan Formation, the northern Sichuan Basin experienced one phase of tectonic activity, and acoustic emission events from this phase were only recorded in the Permian and its deeper strata.

[0038] Cathodoluminescence microscopy and scanning electron microscopy revealed three sets of fractures in the Qixia Formation of the northern Sichuan Basin: F1 high-angle shear fracture, F2 medium-angle tensile fracture, and F3 near-vertical shear fracture. F1 was restricted in its developmental position by F2 and F3. F3 simultaneously dislocated both F1 and F2 by the same distance. The extension direction of F2 was deflected by the earlier orientation of F1. Figure 3 A, B). The cutting of the later-stage fluorite minerals filling the F2 vein and the clockwise deflection of the mineral grain orientation also indicate this cutting relationship ( Figure 3 The fluorite minerals locally filling the tensional fractures in D,H), and F2, as well as the later-stage metasomatic fluorite mineral grains found in the surrounding rock under cathodoluminescence microscopy, are inferred to have been formed by the reaction and precipitation of F-rich deep hydrothermal fluids entering the Permian Qixia Formation fractures along the fractures and reacting with dolomite. This is related to the formation of the Kaijiang-Liangping tensional trough and the activity of deep basement faults. Figure 3 G).

[0039] The maximum principal stress forming the local stress field of F2 is in the vertical direction, while the intermediate and minimum principal stresses are in the horizontal direction, with the direction of the minimum principal stress perpendicular to the direction of F2; the intermediate principal stress forming the local stress field of F3 is in the vertical direction, while the directions of the maximum and minimum principal stresses are in the horizontal direction. Figure 10 The direction of the maximum principal stress is parallel to the angle bisector of the angle between F3 and its conjugate crack. The angle between the tensile crack in F2 and the near-perpendicular shear crack in F3 was measured to be 45.71°. Figure 9 ).

[0040] As mentioned above, the SBF17 strike-slip fault zone in the northern Sichuan Basin has undergone multiple superimposed alteration activities. The normal basement faults found in the seismic data indicate the presence of pre-existing weak basement surfaces constraining the starting point of the strike-slip fault in the study area. The analysis results of fluid inclusions and rock acoustic emission Kaiser points indicate two phases of tectonic activity: (1) Late Hercynian, Late Permian-End of Permian (269.3-253.7 Ma), secondary inclusions associated with fractures indicate the first phase of fluid activity, and the Permian strata and below record Kaiser points of phases III and IV; (2) Early Yanshanian, Middle Jurassic (177.5-155.7 Ma), secondary inclusions associated with fractures indicate the second phase of fluid activity, and the Triassic strata do not record Kaiser points of phases III and IV. Finally, combining the fracture cutting relationship and paleostress field reconstruction, we propose a superimposed evolution model of extension and compression. This model explains the late-stage compressional alteration features of the tectonic geometry of the SBF17 strike-slip fault zone, and can also well explain the spatial relationship between the SBF17 strike-slip fault, the tensional trough, and the Micangshan-Dabashan thrust structure.

[0041] Specifically, under the influence of peripheral magmatism caused by the eruption of the Emei basalt during the Late Hercynian period, two parallel NW-SE trending extensional troughs formed within the Sichuan Basin. At this time, the direction of the minimum principal stress in the regional stress field was perpendicular to the direction of the extensional troughs, at 54.2° N. Under normal fault stress, a medium-angle extensional fracture, represented by F2, was formed. The addition of hydrothermal fluids resulted in the capture of a large number of banded brine inclusions in the F2 fracture. Under regional extensional stress, a high-angle normal fault formed above the stress-weak zone. The normal fault had a short planar extension length and exhibited a banded distribution. During the early Yanshanian orogeny, the southward thrust of the Qinling orogenic belt in the northern Yangtze Craton led to the joint uplift of the Micangshan-Dabashan Mountains, creating a regional stress field environment with the maximum principal stress direction nearly north-south in the study area. Under reverse fault stress, a near-vertical shear fracture, represented by F3, was formed. The early normal faults in the Paleozoic strata were reactivated under the action of a near-north-south compressive stress field, forming a right-lateral strike-slip fault zone. The strata above the gypsum-salt rock of the Triassic Jialingjiang Formation formed a reverse strike-slip fault under a compressive stress field. The fault strike is at a small angle to or parallel to the deep strike-slip fault.

[0042] In the above discussion, we have proposed a two-stage evolutionary model of extension and compression. In the discrete element method, we have established a cubic model, consisting of particles of different diameters and walls as boundary conditions. This model includes two deformation stages, namely State I and State II. Figure 11A, B). The State 1 model consists of four vertical walls and a base plate. To match the direction of the stretching stress during the "stretching" period, we set the angle between the two opposing boundary walls of the State 1 model and the X-axis to 54.2 degrees ( ). Figure 11 A, C). The State I model contains 344,781 particles as sedimentary strata. To avoid particle locking caused by hexagonal particle stacking, the radii of the generated particles are configured according to the Weibull distribution, with a minimum radius of 0.06 meters and a maximum / minimum radius ratio of 1.66. Under gravity, the particles settle to the bottom of the model, releasing internal stress and eventually reaching static equilibrium, i.e., minimizing the unbalanced forces acting on the particles. Then, the model is constructed to the required stratum thickness, after which it needs to reach a stable state again. The State II compression period model is based on the simulation completed by the State I model. The State II model's study rectangular region is divided within the model, generating four new numerical boundary walls and deleting the peripheral particles outside the study region. Figure 11 (B, D). New particles were generated above the rectangular area to form a sedimentary stratum. The process of static particle equilibration, deleting overflowing particles, and rebalancing was then repeated. The final State II model consisted of 239,776 particles. The model's gravity load was 1g.

[0043] The crystalline basement of the Sichuan Basin is composed of mixed granites, gneiss, and metamorphic complex-slate sequences. Seismic data indicate that deep within the Sichuan Basin, there are remnants of subduction associated with the amalgamation of Rodinia. During the subsequent extensional phase, possibly controlled by mantle plume activity, known as the Xingkai rift, the supercontinent Rodinia broke apart. This also led to the formation of multi-trending intracontinental rift valleys within the Neoproterozoic strata of the Sichuan Basin, including the near-east-west trending Qinling Proterozoic Ocean Basin and the northeast-trending Longmenshan Proterozoic Ocean Basin on the northern margin of the Upper Yangtze Craton. Previous reports of Neoproterozoic stratigraphic sequences and U-Pb ages indicate the widespread presence of syn-rift deposits within the Neoproterozoic Sichuan Basin. Rift infill materials are predominantly characterized by bimodal volcanic rocks and marine clastic sediments. Combining our interpreted seismic data with previous research, we summarize the planar distribution of basement normal faults in the Sinian strata. Figure 10 The strike of the basement normal faults mainly includes two groups, one trending northeast-southwest and the other northwest-southeast, parallel to the boundary of the Sichuan Basin. The location of strike-slip faults found in the Paleozoic strata of the Gaoshiti-Moxi area is controlled by the near-east-west trending basement normal faults developed in central Sichuan. Considering the basement normal faults developed in the Sinian strata, we set pre-existing normal faults in the first-phase model. The distribution and dip angle of the faults were set with reference to the seismic interpretation results. Three basement normal faults were set along the fault zones in the Sinian strata. Figure 11C), the northernmost basement normal fault P1 strikes 322° and dips 70° northwest; the central pre-existing fault P2 consists of two parts, one striking 300° and the other striking 322°, both dipping 70° southwest; the southern pre-existing fault P3 strikes 309° and dips 70° northeast.

[0044] The parallel bond model requires setting five microscopic parameters: effective modulus, Poisson's ratio, cohesion, tensile / compressive strength ratio, and internal friction angle. During parameter calibration, we constructed two models: a conventional triaxial compression simulation test and a Brazilian splitting simulation test, to obtain five macroscopic parameters for rock testing, including Young's modulus, Poisson's ratio, triaxial compressive strength, internal friction angle, and Brazilian splitting tensile strength. Based on orthogonal experimental results, we found that the response relationship between microscopic parameters and the macroscopic deformation characteristics of rocks is highly complex. The relationship between macroscopic mechanical parameters and microscopic input parameters is not a simple linear one, and macroscopic mechanical parameters are not influenced by a single factor. While we cannot fully understand this response relationship, we can adjust the changes in macroscopic mechanical parameters by adjusting a single factor. Although this method does not follow a strict functional correspondence, it is effective in parameter calibration. Therefore, we propose an automatic calibration program for PBM microscopic parameters based on an adaptive proportional feedback control algorithm (APFC) and an internal and external dual-loop strategy (IODC). The logic diagram of this algorithm is shown below. Figure 12 Simulation calibration results show that the automatic program can calibrate the five micro-parameters to an error of 5%, which meets the simulation requirements.

[0045] In this study, a parallel bonding model was used to simulate the particle contact relationship between deep and shallow strata, while a linear model was used to simulate the high fluidity characteristics of gypsum-salt rocks. The geometric, strength, and stiffness properties of the particles, as well as the contact relationships between them, are shown in Table 2.

[0046] The discrete element method (DEM) simulation results for particles show that the new extension-compression two-stage evolution model is feasible and can well reproduce the tectonic geometry of the SBF17 strike-slip fault zone. Figure 13 ,14). Figure 13A1-10 illustrates the fracture propagation pattern and maximum principal stress evolution characteristics of State I. The direction of fracture propagation is initially controlled by extensional stress, generally parallel to the direction of minimum principal stress. A1-2 represents the initial stage of fracture propagation. At the location of the overlying strata of the Sinian basement normal fault, the maximum principal stress gradually accumulates. Since the tensile strength limit of the strata has not yet been reached, large-scale fracture formation does not occur. Small-sized fracture f1 begins to form in the middle, with its strike angle to the direction of minimum principal stress being approximately 5°. In the northern part of A3, f2 forms in the overlying strata of the pre-existing fault. At this time, f2 consists of two small-sized fractures that have not yet penetrated each other. Because the pre-existing faults P1 and P2 dip in opposite directions, the initial fracture locations of f1 and f2 are relatively far apart. Between f1 and f2 in the north of A4-6, f3 forms. The position of f3 is influenced by the turning point of P2, developing northeast of f1 and f2. Initially straight, it gradually bends towards f2 under stress induction from the f2 fracture. In the south, small-sized normal faults with a right-handed arrangement form, exhibiting Riddle shear geometry. The angle between the fault strike and the direction of minimum principal stress is approximately 5°. In the north of A6-9, f1, f2, and f3 continue to extend along the direction of minimum principal stress, forming a complex planar overlapping distribution pattern. In the south, the f4 fault evolves into the f4, f5, and f6 fault combination, exhibiting a mature Riddle shear geometry. In A10, the southern f4, f5, and f6 merge and develop into the complex extensional fault system f7. The geostress field and deformation strain field indicate that the location of maximum principal stress concentration first appears at the fault ends (…). Figure 13 B1-10), until the maximum principal stress exceeds the tensile strength limit of the rock strata, resulting in localization of deformation strain. High strain zones appear in the direction of fracture propagation. The deformation strain at the junction of f1 and f3 and at f1 and f6 is opposite to the direction of the fracture location, which shows the reverse rotation of the strata caused by the decoupling of the block at the fracture location.

[0047] Figure 14A1-10 shows a top view (XY plane) of the fracture propagation pattern and maximum principal stress evolution characteristics in State II. A1-2 shows the formation of thrust faults f1 and f2 in the overlying strata, which form small angles with the strike of the main basement fault. The faults develop on both sides deviating from the main fault, which is due to the stress release of the gypsum-salt strata, causing the shear stress transmitted from deep to upward to diffuse and form a deformation zone with a larger influence range. A3-4 shows f3, f4, and f5 forming in the shallow strata above the main fault and merging into f6 and f7. f3-f5 exhibit a left-hand tiered distribution, with an angle of about 6° with the main strike-slip fault. f6 deviates in strike as it crosses the main fault, which may be related to the local stress concentration caused by the location of the rotating block formed by the underlying superimposed segment. As compressive stress accumulates in section A5-8, the normal fracture system in the deep strata is activated under the influence of the compressive stress field. At the location where pre-existing fractures overlap, f8 and f9 are activated first, forming localized positive undulations. The deep normal fracture system transforms into a right-lateral compressive-strike-slip fracture system. In section A9-10, after sufficient fracturing within the overlapping segment, stress concentration begins to form outside the strike-slip fault zone, representing the secondary modification process of the strike-slip fault zone extending outwards to form a complex fracture system. Simultaneously, due to boundary effects, low-angle thrust fractures f13-f16 form in the deep strata. The deformation-strain field indicates that the deformation strain in section B1-8 did not change significantly during State 2, suggesting that long-term stress accumulation is required under the compressive-strike-slip stress field, and localization of deformation strain mainly occurs in section B9-10.

[0048] The model accurately reproduces the cross-sectional geometric features of the SBF17 strike-slip fault zone. Figure 15 The simulated strike-slip fault zone appears as a near-vertical fault assemblage in the vertical direction. Figure 15 The AD profile is located close to the source of compressive stress, resulting in strong compressive alteration. A large-scale compressive fracture zone was formed in the deep Sinian strata. A compressive fault with a small dip angle was developed on the southwest side of the main fault. In the Paleozoic strata, the fault developed into a branch fault on the northwest side. The previous development reached the bottom of the Jialingjiang Formation detachment layer, forming a local positive undulation structure. Salt dome structure was formed above the fault on the Jialingjiang Formation detachment layer. High-angle thrust faults were developed in the shallow Triassic strata. Figure 15 EH is the profile in the middle of the model that is far from the stress source. Its profile geometry is more similar to that of the SBF17 strike-slip fault zone. High-angle strike-slip faults are developed at deep depths, extending upwards to the bottom of the detachment layer to form a positive flower-like structure. High-angle thrust fault systems are developed in the shallow Triassic strata.

[0049] Based on geological evidence including seismic interpretation, petrology, fluid inclusions, and rock acoustic emission testing, as well as three-dimensional discrete element modeling, the formation and evolution of the SBF17 strike-slip fault zone in the northern Sichuan Basin can be summarized as follows: Under the control of weak rock mechanics surfaces resulting from the development of pre-existing normal faults within the Sinian strata, the Caledonian-Late Hercynian extensional stress field led to the formation of a normal fault assemblage near the overlying strata of the normal faults, extending downwards to the Sinian strata and upwards to the top interface of the Permian. During the Yanshanian period, under the strong compressive stress environment caused by the southward thrusting of the Qinling orogen, the Cambrian-Permian normal fault system was reactivated, forming a right-lateral compressional-strike-slip fault zone. Late-stage modified basaltic structures formed in the deep strata, influenced upwards by the stress release of the Triassic Jialingjiang Formation gypsum-salt rocks. Most strike-slip faults terminated at the bottom of the Jialingjiang Formation, and typical salt structures such as salt domes and salt pillows developed within the Jialingjiang Formation gypsum-salt rocks. The Middle-Upper Triassic Leikoupo and Xujiahe Formations are characterized by a high-angle thrust fault system, whose strike is also controlled by deep strike-slip fault zones. In the proposed two-stage evolution model, the basement normal faults developed in the Sinian strata are a prerequisite for the formation of the SBF17 strike-slip fault zone. Pre-existing faults provide weak zones with low rock mechanical properties, where the rock strength limit is significantly lower than that of the surrounding rock. Therefore, these pre-existing faults preferentially become stress concentration zones and reach the rock fracturing threshold earlier. The results of this simulation verify that the development location of pre-existing faults controls the development scale and strike of later faults.

[0050] In summary, the evolution of the SBF17 strike-slip fault zone is the result of the combined effects of regional tectonic events and local geological conditions. Its dynamic evolution can be summarized as follows: (1) Neoproterozoic-Early Paleozoic (600-450 Ma): The breakup of the Rodinia supercontinent and the subduction of the Shangdan Ocean triggered regional extension, forming the Sinian basement normal fault, laying the foundation for the pre-existing weak zone (the pre-existing fault setting response of the discrete element model); (2) Late Paleozoic Hercynian (269.3-253.7 Ma): The uplift of the Emei mantle plume and the extension of the Mianlue Ocean led to strong regional extension, and the strata overlying the basement normal fault formed a normal fault combination, accompanied by magmatic hydrothermal activity; (3) Early Mesozoic Yanshanian (177.5-155.7 Ma): The southward thrust of the Qinling orogenic belt triggered strong regional compression, and the early normal fault reversed to form a compression-torsion strike-slip fault zone. The gypsum-salt rock detachment layer led to vertical tectonic decoupling. This evolution process clarifies the coupling relationship between the SBF17 strike-slip fault zone and major regional tectonic events such as the Qinling-Yangtze collision and the breakup of the supercontinent. Combined with geological evidence including seismic interpretation, petrology, fluid inclusions and rock acoustic emission tests, and three-dimensional particle discrete element simulation results, it reveals the dynamic evolution process of the strike-slip fault zone at the craton margin.

[0051] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A method for determining the evolution stages of strike-slip faults at the edge of a craton based on multi-source data analysis, characterized in that: Includes the following steps: Step 1: Collect three-dimensional reflection seismic data, well logging data, and core samples from multiple wells in the target area. The core samples are from the Sinian, Cambrian, Permian, and Triassic strata. Step 2: Interpret the seismic data, determine the seismic reflection layer, and create a coherence body attribute map and a time-domain structural map to analyze the characteristics of the fault plane distribution and the structural style of the cross section. Step 3: Perform petrological characterization on the core samples, including scanning electron microscopy, energy dispersive spectroscopy, and cathodoluminescence microscopy, to identify fracture filling characteristics, cutting relationships, and diagenetic mineral filling generations; Step 4: Perform fluid inclusion analysis on the fracture-filled vein samples to obtain homogenization temperature and freezing point temperature data, and determine the spatiotemporal relationship between fluid activity and fracture development. Step 5: Conduct acoustic emission tests on samples from different strata to determine the stress value corresponding to the Kaiser point and classify the tectonic movement periods; Step 6: Establish a numerical model based on the discrete element method, input the stratigraphic mechanical parameters, and simulate the two-stage superimposed evolution process of the strike-slip fault; Step 7: Based on the combined results of seismic interpretation, petrological characterization data, fluid inclusion analysis data, acoustic emission test data, and discrete element simulation results, determine the evolution stages of the strike-slip fault.

2. The method for determining the evolution stages of strike-slip faults at craton edges based on multi-source data analysis according to claim 1, characterized in that: In step two, the seismic interpretation uses an interpretation grid spacing of 100m×100m. The determined seismic reflection layers include the top boundary of the Cambrian, the top boundary of the Silurian, the top boundary of the Permian, and the top boundary of the Triassic Xujiahe Formation.

3. The method for determining the evolution stages of strike-slip faults at craton edges based on multi-source data analysis according to claim 1, characterized in that: In step three, after preparing thin sections of the core sample, the samples were tested. Scanning electron microscopy observation was performed in BSED mode with an HV of 20kV. The cathodoluminescence experiment was conducted under the following conditions: vacuum of 0.003mBar, electron gun beam current of approximately 240μA, and accelerating voltage of 13kV.

4. The method for determining the evolution stages of strike-slip faults at craton edges based on multi-source data analysis according to claim 1, characterized in that: In step four, fluid inclusion analysis was performed using a Linkam THNS 600G hot and cold stage with an analysis accuracy of ±0.1℃, paired with an Olympus 100x 8mm telephoto lens for microscopic observation. The samples were taken from the Sinian Dengying Formation, the Cambrian Longwangmiao Formation, the Xixiangchi Formation, and the Permian Qixia Formation and Maokou Formation.

5. The method for determining the evolution stages of strike-slip faults at craton edges based on multi-source data analysis according to claim 1, characterized in that: In step five, the rock acoustic emission test uses a GCTS RTR-1000 testing system with triaxial loading of the sample. Acoustic emission information is collected by an SAEU2S detector. The Kaiser point is determined by the jump in acoustic emission energy value and the abrupt change in ring count.

6. The method for determining the evolution stages of strike-slip faults at craton edges based on multi-source data analysis according to claim 1, characterized in that: In step six, the discrete element simulation uses PFC3D software. The model includes two deformation stages: State I, which extends in the northeast and southwest directions, and State II, which compresses in the south and north directions. The formation mechanical parameters are obtained through triaxial compression experiments and Brazilian splitting experiments, and are calibrated using an adaptive proportional feedback control algorithm and an internal and external dual-loop strategy.

7. The method for determining the evolution stages of strike-slip faults at craton edges based on multi-source data analysis according to claim 6, characterized in that: The State I model contains 344,781 particles with a minimum radius of 0.06 meters and a maximum radius / minimum radius ratio of 1.

66. The State II model is generated by trimming the State I model and contains 239,776 particles with a gravity load of 1g.

8. The method for determining the evolution stages of strike-slip faults at craton edges based on multi-source data analysis according to claim 1, characterized in that: In step seven, during the comprehensive analysis, the evolution stages are determined by combining the layered distribution characteristics of the fracture plane, the vertical extension law of the profile, the multi-stage crack cutting-constraint relationship, the uniform temperature cluster distribution characteristics of fluid inclusions, and the division of stress intervals at Kaiser points.

9. The method for determining the evolution stages of strike-slip faults at craton edges based on multi-source data analysis according to claim 1, characterized in that: The defined stages of strike-slip fracture evolution include the early extensional stage and the late compressional alteration stage.

10. The method for determining the evolution stages of strike-slip faults at the craton margin based on multi-source data analysis according to claim 1, characterized in that: The target area is a strike-slip fault zone at the edge of a craton, and is particularly applicable to the SBF17 strike-slip fault zone in the Yuanba and Tongnanba areas of northern Sichuan Basin.

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