Identification method of apparent strike-slip faults with superposition of multi-phase tectonic stress fields

Abstract

The present invention provides a method for identifying apparent strike-slip faults with multi-phase tectonic stress field superposition. The method for identifying apparent strike-slip faults with multi-phase tectonic stress field superposition includes: Step 1, based on the logging and mud logging data of the drilled wells, conducting fine structural interpretation of the standard layer; Step 2, performing characterization of the direction conversion of the multi-phase tectonic stress field; Step 3, performing characterization of the changes in the strike-slip component and the extension component; Step 4, identifying the nature of the apparent strike-slip faults. The method for identifying apparent strike-slip faults with multi-phase tectonic stress field superposition systematically analyzes from three aspects of geometry, kinematics and dynamics, and takes the ratio of the calculated fault extension component to the strike-slip component as the basis for identifying apparent strike-slip faults, with high practical value and strong operability.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas exploration, and particularly to a method for identifying apparent strike-slip faults with superimposed multi-phase tectonic stress fields. Background Art

[0002] Exploration practices have shown that with the increasing demand for oil and gas energy, the exploration of strike-slip structure oil and gas has become the focus of exploration. In the Cenozoic of the Jiyang Depression, it generally experiences the superposition of multi-phase tectonic stress fields, making the faults very complex. Strike-slip faults play a controlling role in trap formation, reservoir improvement, oil and gas sealing or communication and transportation. Therefore, it is very necessary and significant to conduct in-depth research on strike-slip faults with superimposed multi-phase tectonic stress fields.

[0003] Currently, domestic and foreign researchers do not have a clear method for identifying apparent strike-slip faults with superimposed multi-phase stress fields, which brings a lot of inconvenience to the exploration work of strike-slip structure oil and gas.

[0004] In the Chinese patent application with the application number: CN201510853883.5, it involves a seismic identification method for low-order strike-slip faults in complex structural areas. The seismic identification method for low-order strike-slip faults in complex structural areas is as follows: analyze the quality of post-stack seismic data, process to obtain the dominant frequency division phase band, process to obtain the main direction Sobel operator, process to obtain the Sobel operator in any direction, extract the multi-direction low-order strike-slip fault system, and verify the reliability of the low-order strike-slip faults. This invention is suitable for the seismic identification and reliability verification of low-order strike-slip faults in any complex structural belt, can intuitively reflect the combination mode and spatial position of low-order strike-slip faults on the plane, is an effective means to determine low-order hidden faults in areas with low signal-to-noise ratio and low-frequency seismic data, and is an important basis for ensuring the re-understanding of the oil control law of hidden faults, increasing reserves and production, and deploying and adjusting development plans in complex structural oil and gas fields or fault-block oil and gas fields.

[0005] In the Chinese patent application with the application number: CN201810287211.6, it involves a method for analyzing the tectonic evolution of strike-slip faults. By calculating the paleo-throw of the strike-slip fault at different positions, analyze the periodic rhythm change of the paleo-throw of the strike-slip fault along the strike direction; use the restored horst-graben structure on both sides of the strike-slip fault at different times to determine the basin prototype before the deposition of different strata on both sides of the strike-slip fault, and identify the "damping section" of the strike-slip fault; by calculating the unit activity intensity of the fault, characterize the strike-slip amount of the strike-slip fault; use the calculated strain energy release rate of the strike-slip fault to analyze the dynamic mechanism of different parts of the strike-slip fault; use numerical simulation of tectonic stress fields to explain the fault from the dynamic aspect and verify the genetic mechanism of the strike-slip fault. This invention systematically proposes a method for analyzing the genetic mechanism and evolution process of strike-slip faults from three aspects of geometry, kinematics and dynamics, from the four-dimensional perspective of time and space.

[0006] In the Chinese patent application with the application number: CN202010497453.5, a method for identifying weak strike-slip faults based on a tectonic lithology stress field is involved, including the following steps: S1 Establish the relationship between curvature, lithology parameters, tectonic deformation and stress field; S2 Establish the connection between wellbore P-S wave data and seismic attributes, obtain the Poisson's ratio data volume and Young's modulus data volume, where the Young's modulus is E and the Poisson's ratio is ν; S3 Take the derivative of the 3D seismic data volume to obtain the 3D curvature volume, and the curvatures are Kx, Ky, and Kxy respectively; S4 Substitute the Poisson's ratio data volume and Young's modulus data volume obtained in step S2 and the 3D curvature volume obtained in step S3 into the formula obtained in step S1 to obtain the 3D tectonic lithology stress field data volume; and S5 Identify weak strike-slip faults based on the tectonic lithology stress field data volume obtained in step S4. By establishing the curvature-strain-stress formula, the organic combination of well-seismic information and tectonic stress field is realized, and by using the method of multiple linear fitting, the tectonic stress field can be quickly obtained.

[0007] All the above prior arts are quite different from the present invention and fail to solve the technical problems we want to solve. Therefore, we have invented a new method for identifying apparent strike-slip faults by superimposing multi-stage tectonic stress fields. Summary of the Invention

[0008] The object of the present invention is to provide a method for identifying apparent strike-slip faults by superimposing multi-stage tectonic stress fields, which is of great significance for the exploration of Cenozoic strike-slip structures.

[0009] The object of the present invention can be achieved by the following technical measures: A method for identifying apparent strike-slip faults by superimposing multi-stage tectonic stress fields, which includes:

[0010] Step 1, based on the logging and mud logging data of the drilled wells, conduct a fine tectonic interpretation of the standard layer;

[0011] Step 2, perform the characterization of the direction conversion of multi-stage tectonic stress fields;

[0012] Step 3, perform the characterization of the changes in strike-slip components and extensional components;

[0013] Step 4, identify the nature of apparent strike-slip faults.

[0014] The object of the present invention can also be achieved by the following technical measures:

[0015] This method for identifying apparent strike-slip faults by superimposing multi-stage tectonic stress fields further includes, before step 1, obtaining the basic geological overview of the study area, collecting relevant information on tectonic evolution, and understanding the tectonic movements and stress directions experienced by the study area.

[0016] In Step 1, understand the basic geological overview of the study area, the tectonic movements experienced, and the regional stress direction. Based on the well logging and mud logging data of the drilled wells, conduct a fine structural interpretation of the standard layer.

[0017] In Step 1, according to the well logging curves such as acoustic travel time and density, make synthetic seismograms to calibrate the strata, and conduct stratum and fault interpretations. During the interpretation process, check whether the interpreted horizons and faults are closed.

[0018] In Step 2, analyze the fault plane and cross-section structural styles, and clarify the direction conversion of the multi-stage tectonic stress field.

[0019] In Step 3, calculate the fracture density and the cumulative fracture length, denoted as D n 、L n respectively. This parameter provides a parameter to characterize the strike-slip component and extensional component intensities of faults with different periods and different strikes.

[0020] In Step 3, the calculation formula for the fracture density is:

[0021]

[0022] In formula (1), D n is the fracture density, that is, the number of faults per unit area, in pieces; T i is the number of faults, in pieces; S is the area of the study area, in km 2 ; the fracture density represents the strike-slip component intensity of the fracture.

[0023] In Step 3, the calculation formula for the cumulative fracture length is:

[0024]

[0025] In formula (2), L n is the cumulative fracture length of fractures with different strikes, in km; L i is the cumulative length of faults with a certain strike, in km; the cumulative fracture length represents the extensional component intensity of the fault.

[0026] In Step 3, calculate the ratio of the extensional component to the strike-slip component, denoted as K n . This parameter provides a parameter to characterize the relative strength of the extensional component and strike-slip component of faults with different periods and different strikes.

[0027] In Step 3, the calculation formula for the ratio of the extensional component to the strike-slip component is:

[0028]

[0029] In formula (3), Kn is the relative strength of the extensional component and strike-slip component of faults with different periods and different strikes; D nis the fracture density, i.e., the number of faults per unit area, in number; Ln is the cumulative length of fractures with different strikes, in km;; T i The number of faults, in number; L i is the cumulative length of faults with a certain strike, in km; S is the area of the study area, in km 2 ; The larger Kn is, the greater the intensity of the extensional component is than that of the strike-slip component.

[0030] In step 4, when the ratio range of the extensional component to the strike-slip component is within 0.19 - 0.43, i.e., 0.19 < K n <0.43, and the included angle between the fault strike and the extensional direction is between 10° and 80°, such faults are considered as apparent strike-slip faults.

[0031] The method for identifying apparent strike-slip faults by superposition of multi-stage tectonic stress fields in the present invention is as follows: First, understand the basic geological situation of the study area, the tectonic movements experienced and the regional stress direction, and interpret the structural map of the standard horizon according to the well logging and mud logging data of the drilled wells. Second, characterize the direction conversion of multi-stage tectonic stress fields. Third, characterize the changes of the strike-slip component and the extensional component. Finally, identify the nature of the apparent strike-slip faults.

[0032] The advantages and positive effects of the present invention are as follows:

[0033] For the method for identifying apparent strike-slip faults by superposition of multi-stage tectonic stress fields provided by the present invention, there is no clear method for domestic and foreign researchers at present. The present invention creatively introduces the "non-linear" mathematical analysis method into the identification of apparent strike-slip faults, which has significant progress compared with the traditional identification criteria for strike-slip faults. The present invention systematically analyzes from three aspects of geometry, kinematics and dynamics, and uses the ratio of the calculated extensional component to the strike-slip component of the fault as the basis for identifying apparent strike-slip faults, which has high practical value and strong operability, and can provide a reference basis for the study of strike-slip structures related to oil and gas in the Jiyang Depression and even the Bohai Bay Basin. Brief Description of the Drawings

[0034] Figure 1 is a flowchart of a specific embodiment of the method for identifying apparent strike-slip faults by superposition of multi-stage tectonic stress fields of the present invention;

[0035] Figure 2 is a schematic diagram of the crossline 2420 seismic profile of the Changdi Fault Zone in a specific embodiment of the present invention;

[0036] Figure 3 is the seismic profile of different sections of the Changdi Fault in a specific embodiment of the present invention;

[0037] Figure 4 is the structural map of the T2 standard horizon of the Changdi Fault Zone in a specific embodiment of the present invention;

[0038] Figure 5 Structural map of the standard layer of the Changdi Fault Zone (a total of 4 layers) in a specific embodiment of the present invention;

[0039] Figure 6 Quantitative statistical graph of the geometry of the apparent strike-slip fault in the northern section of the Changdi Fault Zone in a specific embodiment of the present invention;

[0040] Figure 7 Schematic diagram of the distribution of active faults in different periods of the Cenozoic in the Changdi area of the northern section of the Changdi Fault Zone in a specific embodiment of the present invention;

[0041] Figure 8 Schematic diagram of oblique extension, extension, and strike-slip actions in a specific embodiment of the present invention;

[0042] Figure 9 Schematic diagram of the seismic profile of the high-precision line 1184 in the Yidong Fault Zone in a specific embodiment of the present invention;

[0043] Figure 10 Structural map of the standard layer of the Yidong Fault Zone (a total of 5 layers) in a specific embodiment of the present invention;

[0044] Figure 11 Schematic diagram of the seismic profiles in different sections of the Yidong Fault Zone in a specific embodiment of the present invention;

[0045] Figure 12 Structural map of the T4 standard layer of the Yidong Fault Zone in a specific embodiment of the present invention;

[0046] Figure 13 Quantitative statistical graph of the geometry of the apparent strike-slip fault in the northern section of the Yidong Fault Zone in a specific embodiment of the present invention;

[0047] Figure 14 Schematic diagram of the distribution of active faults in different periods of the Cenozoic in the Yidong Fault Zone in a specific embodiment of the present invention;

[0048] Figure 15 Schematic diagram of the north-south seismic profile of the Gaoqing-Pingnan Fault Zone in a specific embodiment of the present invention;

[0049] Figure 16 Structural map of the standard layer of the Gaoqing-Pingnan Fault Zone (a total of 4 layers) in a specific embodiment of the present invention;

[0050] Figure 17 Seismic profiles in different sections of the Gaoqing-Pingnan Fault Zone in a specific embodiment of the present invention;

[0051] Figure 18 Schematic diagram of the distribution of active faults in the first member of the Shahejie Formation in the Gaoqing-Pingnan Fault Zone in a specific embodiment of the present invention;

[0052] Figure 19Schematic diagram of the horizontal slice of the Gaoqing-Pingnan fault zone in the specific embodiment of the present invention;

[0053] Figure 20 Quantitative statistical chart of the apparent strike-slip fault geometry of the Gaoqing-Pingnan fault zone in the specific embodiment of the present invention;

[0054] Figure 21 Schematic diagram of the distribution of active faults in different periods of the Cenozoic era in the Gaoqing-Pingnan fault zone in the specific embodiment of the present invention. Detailed implementation manners

[0055] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0056] It should be noted that the terms used herein are only for describing the specific implementation manners and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they specify the presence of features, steps, operations, and / or combinations thereof.

[0057] As Figure 1 shown, Figure 1 is a flow chart of the method for identifying apparent strike-slip faults by superimposing multi-stage tectonic stress fields according to the present invention. The method for identifying apparent strike-slip faults by superimposing multi-stage tectonic stress fields includes the following steps:

[0058] Step 1: Obtain the basic geological overview of the study area, collect relevant information on tectonic evolution, and understand the tectonic movements and stress directions experienced by the study area.

[0059] Step 2: Understand the basic geological overview of the study area, the tectonic movements experienced, and the regional stress directions. Based on the well logging and mud logging data of the drilled wells, conduct a fine structural interpretation of the standard layer;

[0060] According to the logging curves such as acoustic travel time and density, make synthetic seismograms to calibrate the strata, and conduct stratum and fault interpretations. During the interpretation process, check whether the interpreted horizons and faults are closed.

[0061] Step 3: Calculate the fracture density and the cumulative fracture length, which are respectively represented as D n and L n . This parameter provides a parameter for characterizing the strike-slip component and the extension component intensity of faults with different orientations in different periods.

[0062]

[0063] In Equation (1), D n is the fracture density, which is the number of faults within 2 km 2 , expressed as number of faults per 2 km 2 ; T i is the number of faults with different strike directions, expressed as number of faults; S is the area of the study area, in km 2 . The fracture density represents the degree of development of the fracture zone. An increase in the fracture density usually indicates an increase in the strike-slip component of the fracture.

[0064]

[0065] In Equation (2), L n is the cumulative length of fractures with different strike directions, in km; L i is the cumulative length of faults in a certain strike direction, in km; the cumulative fracture length represents the scale of the fracture zone. An increase in the fracture length usually indicates an increase in the extensional component of the fracture.

[0066] In Step 3, calculate the ratio of the extensional component to the strike-slip component, denoted as K n , which provides a parameter characterizing the relative strength of the extensional component to the strike-slip component of faults with different strike directions.

[0067]

[0068] In Equation (3), Kn is the relative strength of the extensional component to the strike-slip component of faults with different strike directions. D n is the fracture density, which is the number of faults per unit area, expressed as number of faults; Ln is the cumulative length of fractures with different strike directions, in km; the larger K n , the stronger the extensional component is compared to the strike-slip component.

[0069] In Step 4, when the ratio range of the extensional component to the strike-slip component is within 0.19 - 0.43, i.e., 0.19 < K n < 0.43, and the angle between the fault strike and the extensional direction is between 10° and 80°, such faults are considered apparent strike-slip faults.

[0070] The following are several specific embodiments of applying the present invention.

[0071] Embodiment 1

[0072] In a specific embodiment 1 of applying the present invention, the Changdi Fault Zone in the eastern part of the Zhanhua Sag in the Jiyang Depression is the boundary fault between the Gubei Sag, the Zhuangxi buried hill and the Changdi buried hill. The Changdi Fault Zone has experienced multi-stage tectonic evolution, and there are obvious differences in the tectonic evolution of each tectonic unit inside. Due to this difference, the Changdi Fault is not a single fault, but consists of multiple groups of faults with different directions and natures in different periods. Although some faults in the Cenozoic have characteristics of en echelon arrangement and flower-like strike-slip faults, it is difficult to determine their fault nature compared with typical strike-slip faults, and there are great controversies. Therefore, it is necessary to conduct in-depth research on the identification method of apparent strike-slip faults superimposed by multi-stage tectonic stress fields.

[0073] Such as Figure 1 is the flow chart of the identification method of apparent strike-slip faults superimposed by multi-stage tectonic stress fields of the present invention.

[0074] In this embodiment, the identification method of apparent strike-slip faults superimposed by multi-stage tectonic stress fields of the present invention includes the following steps:

[0075] In step 101, understand the basic geological situation of the study area, collect relevant information on tectonic evolution, and be familiar with the tectonic movements and stress directions experienced by the study area. The main purpose of this step is to understand the basic geological framework of the study area and ensure the rationality of the tectonic interpretation results.

[0076] Chen Shuping believes that during the sedimentary period of the Kongdian Formation - Sha 4 Member in the Jiyang Depression, the whole area was in a tensile creep-dispersive environment, and multi-directional faults (including NW, NE, NEE, and EW faults) were active; dextral strike-slip activities began during the sedimentary period of the Sha 3 Member, and dextral strike-slip activities occurred again during the sedimentary period of the Sha 1 Member - Dongying Formation; since the Guantao Formation, it has entered the depression period, and it is still in a strike-slip stress field today, and the main stress direction is nearly EW.

[0077] In step 101, interpret the structural map of the Cenozoic standard layer. According to the logging data of the drilled wells, interpret the strata and faults according to the conventional stratigraphic interpretation process. This step is the basis of the present invention. Figure 2 is the seismic profile for interpreting the Cenozoic standard layer using Geoframe interpretation software. The specific interpretation steps are to import curves such as AC (acoustic travel time), Den (density), etc. into the seismic interpretation software - calibrate the strata with synthetic seismograms - interpret the strata and faults. During the interpretation process, check whether the interpreted horizons and faults are closed. A total of 4 standard layers of T1’, T1, T2, and T6 are interpreted ( Figure 5 ). The process enters step 102.

[0078] In step 102, analyze the planar and sectional structural styles of the faults, and clarify the characterization of the direction conversion of multi-stage tectonic stress fields. This step is the basis of the present invention.

[0079] In the cross-section, obvious changes occurred in the fault systems above and below the T6, T2, and T1 interfaces, forming four sets of fault systems, corresponding to four periods (Kongdian - Member 4 of Shahejie Formation, Member 3 - Member 2 of Shahejie Formation, Member 1 of Shahejie Formation - Dongying Formation, Guantao Formation - Minghuazhen Formation). Taking the T2 (equivalent to the bottom of Member 1 of Shahejie Formation) seismic reflection layer as the boundary, two sets of fault systems, deep and shallow, developed ( Figure 2 ). The deep fault system is mainly characterized by single faults, and the shallow fault system is a combination of fault steps and negative flower structures. In the deep fault system, taking the T6 (equivalent to the bottom of Member 3 of Shahejie Formation) seismic reflection layer as the boundary, two sets of fault systems developed. The faults in Member 4 of Shahejie Formation below T6 are listric normal faults with relatively gentle dips, and the secondary faults above T6 (equivalent to the bottom of Member 3 of Shahejie Formation) match the main faults to form structural patterns such as "Y" - shaped or fault step. In the shallow fault system, taking the T1 (equivalent to the bottom of Guantao Formation) seismic reflection layer as the boundary, two sets of fault systems developed. The secondary faults above T1 match the main faults to form a composite "Y" - shaped structural pattern, and below T1 are single - fault or "Y" - shaped structural patterns ( Figure 3 ).

[0080] In the plane, the Changdi fault shows a gentle "S" - shaped distribution. The middle section trends nearly north - south and is the main body of the fault. There are associated end - branch faults in the north and south sections, and branch feather - like faults are associated on both sides of the fault ( Figure 4 ). On the structural maps of T6, T2, T1, and T1' in the Changdi fault zone ( Figure 5 ), the Changdi fault zone gradually changes from a continuous main fault to an en echelon combination composed of discontinuous secondary faults, reflecting that the strike - slip intensity gradually weakens from bottom to top. From T6 - T2 - T 1- T1', the dominant fault strike gradually changes from northeast - north - east - east - west, corresponding to the development periods of the four sets of fault systems: Kongdian - Member 4 of Shahejie Formation, Member 3 - Member 2 of Shahejie Formation, Member 1 of Shahejie Formation - Dongying Formation, Guantao Formation - Minghuazhen Formation ( Figure 5 ), and the regional extensional stress direction gradually changes from northwest - west in Member 3 - Member 2 of Shahejie Formation to north - south in Member 1 of Shahejie Formation - Dongying Formation.

[0081] Next, taking the northern section of the Changdi fault zone as an example, it is illustrated how to identify apparent strike - slip faults under the superposition of multi - stage tectonic stress fields. The process enters step 103.

[0082] In step 103, faults in nature that are only affected by one kind of stress are rare. Commonly, they are the result of the combined action of two kinds of stresses. This invention creatively introduces the "non - linear" analysis method to deeply study the fault density and the cumulative length of faults. By clarifying the relative changes of the strike - slip component and the extensional component of faults with different periods and different strikes, it lays a foundation for identifying apparent strike - slip faults. This step is the core of this invention.

[0083] In step 103, the fault density is calculated and denoted as Dn This parameter provides a parameter to characterize the strength of the strike-slip component of faults in different periods and directions.

[0084]

[0085] In formula (1), D n is the fracture density, i.e. 2km 2 Number of internal faults, faults / 2km 2 ;T i The number of faults with different strikes, S is the area of the study area, km 2 The fault density represents the strength of the strike-slip component of the fault.

[0086] In the northern section of the Changdi fault zone, the fault density increased significantly during the Sha3-Sha2 and Sha1-Dongying periods ( Figure 6 The middle pie chart is the fault density, indicating 2km 2 An increase in fault density generally indicates an increase in the number of strike-slip faults. This suggests that the northern section of the Changdi Fault Zone was primarily formed during the Shahejie Formation III-Shahejie Formation II and Shahejie Formation I-Dongying Formation periods. It also suggests that the zone experienced two phases of strike-slip, with the strike-slip intensity of the Shahejie Formation I-Dongying Formation being relatively weaker than that of the Shahejie Formation III-Shahejie Formation II period.

[0087] In step 103, the cumulative length of fractures in different directions is calculated. It is expressed as L n This parameter provides a parameter to characterize the strength of the extension component of faults in different periods and directions.

[0088]

[0089] In formula (2), L n is the cumulative length of faults with different directions, km; L i It is the cumulative length of faults in a certain direction, km; the cumulative length of faults represents the strength of the fault extension component.

[0090] "Nonlinearity" refers to the mathematical relationship between two variables. The two variables interact with each other. It is this interaction that makes the whole no longer simply equal to the sum of its parts, and gains or losses different from "linear superposition" may occur.

[0091] This invention creatively incorporates a nonlinear mathematical analysis method into the cumulative length of faults with different strikes, providing a basis for identifying apparent strike-slip faults. For example, if the cumulative length of faults with different strikes shows only one peak during a given period, it indicates that the fault formed during that period has a roughly identical strike to the pre-existing fault. If the fault length shows two peaks, it indicates that the fault formed during that period is oblique to the pre-existing fault.

[0092] The cumulative length of fractures is generally the largest during the Kongdian - Sha 4 Member and Sha 1 Member - Dongying Formation periods, and relatively smaller during the Sha 3 Member - Sha 2 Member and Guantao - Minghuazhen Formation periods. There are two peaks during both the Kongdian - Sha 4 Member and Sha 1 Member - Dongying Formation periods, indicating that the faults formed during the Kongdian - Sha 4 Member and Sha 1 Member - Dongying Formation periods are oblique to the pre - existing faults. There is a single peak during both the Sha 3 Member - Sha 2 Member and Guantao - Minghuazhen Formation periods, indicating that the faults formed during the Sha 3 Member - Sha 2 Member and Guantao - Minghuazhen Formation periods are basically parallel to the pre - existing faults( Figure 6 )

[0093] Figure 7 Figure 1 is the distribution map of active faults in different periods of the Cenozoic in the Changdi Fault Zone. Generally speaking, the pre - existing NNE - trending Changdi Fault was affected by NW - trending oblique extensional stress during the Sha 3 Member - Sha 2 Member period, resulting in NE - trending faults that are oblique to the NNE - trending Changdi Fault. Then, the NE - trending faults generated during the Sha 3 Member - Sha 2 Member period were affected by NS - trending oblique extensional stress during the Sha 1 Member - Dongying Formation period, resulting in EW - trending faults that are oblique to the NE - trending faults( Figure 7 )

[0094] In step 103, calculate the ratio of the extensional component to the strike - slip component, denoted as K n , which provides a parameter to characterize the relative strength of the extensional component and the strike - slip component of faults with different strikes

[0095]

[0096] In formula (3), Kn is the relative strength of the extensional component and the strike - slip component of faults with different strikes. D n is the fracture density, that is, the number of faults per unit area, in pieces; Ln is the cumulative length of fractures with different strikes, in km; the larger K n , the greater the strength of the extensional component is than that of the strike - slip component

[0097] Table 1 Statistical table of the ratio of the extensional component to the strike - slip component of faults with different strikes in the Changdi Fault Zone

[0098]

[0099] As can be seen from Table 1, the ratio K of the extensional component to the strike - slip component of faults with different strikes in the Changdi Fault Zone nVariation pattern. The ratio of extensional component to strike-slip component is the largest during the Kongdian Formation - Member 4 of Shahejie Formation and Member 1 of Shahejie Formation - Dongying Formation. The ratio of extensional component to strike-slip component during the Member 3 of Shahejie Formation - Member 2 of Shahejie Formation and the Guantao - Minghuazhen Formation is relatively small. Generally, the ratio of extensional component to strike-slip component of faults with different strikes is within the range of 0.02 - 0.59. Through comprehensive analysis, it is considered that the ratio range of extensional component to strike-slip component of apparent strike-slip faults is within 0.22 - 0.59, that is, 0.20 < K n <0.59. The process proceeds to step 104.

[0100] In step 104, the nature of apparent strike-slip faults is identified. Although the structural style of the northern section of the Changdi Fault Zone is en echelon arrangement and flower-like structure, its essence is the NE-trending Changdi main fault formed during the Member 3 of Shahejie Formation - Member 2 of Shahejie Formation. It was subjected to north-south extension during the Member 1 of Shahejie Formation - Dongying Formation. And when the ratio range of extensional component to strike-slip component of the fault is within 0.22 - 0.59, the formed pull-apart (oblique extension) structure is not a typical strike-slip structure.

[0101] Based on the above analysis, it is considered that when the ratio range of extensional component to strike-slip component of faults with different periods and strikes in the Changdi Fault Zone is within 0.22 - 0.59, and the included angle between the fault strike and the regional extension direction is between 10° - 80°, such faults can be considered as apparent strike-slip faults ( Figure 8 ).

[0102] Embodiment 2

[0103] In a specific Embodiment 2 of applying the present invention, the Yidong Fault Zone is located in the western part of the Zhanhua Sag in the Jiyang Depression. The west side is the Yihezhuang Uplift, and the east, north, and south sides are adjacent to the Sikou Depression, Guojuzi, and Shaojia Depression. The Yidong Fault intersects with the Yinan Fault to the south and plunges northeastward into the northern part of the Sikou Depression. Since the Cenozoic, the Yidong Fault Zone has experienced multi-stage tectonic evolution and formed a complex fault system composed of NE-trending main faults and NW, EW-trending secondary faults. In the Cenozoic, although some faults have strike-slip fault characteristics such as flower-like structures in their structural styles, it is difficult to determine their fault natures compared with typical strike-slip faults, and there are great controversies. Therefore, it is necessary to conduct in-depth research on the identification method of apparent strike-slip faults superimposed by multi-stage tectonic stress fields.

[0104] In this embodiment, the identification method of apparent strike-slip faults superimposed by multi-stage tectonic stress fields of the present invention includes the following steps:

[0105] In step 101, the structural map of the Cenozoic standard layer is interpreted. According to the logging data of the drilled wells, the strata and faults are interpreted according to the conventional formation interpretation process. This step is the basis of this invention. Such as Figure 9Using the Geoframe interpretation software to conduct structural interpretation of the Cenozoic standard layer. The specific steps are to import curves such as AC (acoustic travel time difference) and Den (density) into the seismic interpretation software - calibrate the strata with synthetic seismograms - interpret the strata and faults. During the interpretation process, it is necessary to check whether the interpreted horizons and faults are closed. A total of 5 standard layers, namely T1, T2, T4, T6, and T7, were interpreted ( Figure 10 ). The process proceeds to step 102.

[0106] In step 102, analyze the fault plane and section structural styles to clarify the characterization of the direction conversion of the multi-stage tectonic stress field. This step is the basis of the present invention.

[0107] In the section, obvious changes have occurred in the fault systems above and below the T6, T2, and T1 interfaces, forming 4 sets of fault systems, corresponding to 4 periods (Kongdian - Sha 4 Member, Sha 3 Member - Sha 2 Member, Sha 1 Member - Dongying Formation, Guantao Formation - Minghuazhen Formation) respectively.

[0108] Taking the T2 (equivalent to the bottom of Sha 1 Member) seismic reflection horizon as the boundary, two sets of deep and shallow fault systems are developed ( Figure 11 ). The deep fault system (including four sedimentary periods from Kongdian Formation to Sha 2 Member) is mainly single - faulted, and the shallow fault system (sedimentary periods after Sha 1 Member, Dongying Formation, and Guantao Formation) is in the combination styles of fault - step and negative flower - like. In the deep fault system, taking the T6 (equivalent to the bottom of Sha 3 Member) seismic reflection horizon as the boundary, two sets of fault systems are developed. The faults in the Sha 4 Member below T6 are listric normal faults with relatively gentle dips, and above T6 (equivalent to the bottom of Sha 3 Member) are in structural styles such as "Y" - shaped or fault - step. In the shallow fault system, taking the T1 (equivalent to the bottom of Guantao Formation) seismic reflection horizon as the boundary, two sets of fault systems are developed. The secondary faults above T1 match with the main fault to form a composite "Y" - shaped structural style, and below T1 is the fault - step ( Figure 11 ).

[0109] In the plane, according to the differences in structural styles, the Yidong fault zone can be divided into the northern, middle, and southern sections. The northern section of the Yidong fault is located in the area where the Yidong fault enters the basin and the Yihezhuang uplift disappears. This section is a right - deflected broom - like spreading end composed of NE - trending main faults combined with NEE - trending and nearly EW - trending secondary faults ( Figure 12 ). The middle section of the Yidong fault is the main body separating the basin and the uplift. In the plane, it is mainly NE - trending main faults supplemented by NE - and NW - trending secondary faults. The southern section of the Yidong fault extends to the Shaojia depression in the Zhanhua sag and is in the "en echelon" type composed of multiple left - stepped NEE - trending faults in the plane.

[0110] In the plane, from the T1, T2, T4, T6, and T7 structural maps of the Yidong fault zone ( Figure 10)In the Sha-4 sedimentary period (T7): The NE-trending main faults are obvious, with obvious extensional components, showing an oblique and comb-like fault combination on the plane. In the Sha-3 sedimentary period (T4-T6): On the plane, the NE-trending main faults and the NEE-trending arc-shaped faults form a right-deflected broom-like fault combination. In the Sha-1-Dongying sedimentary period (T1-T2): The right-deflected broom-like fault combination on the plane further extends to the northeast. It shows that the regional extensional stress direction changes from the NW direction in the Sha-3 to Sha-2 members to the NS direction in the Sha-1 member-Dongying Formation. Here, taking the northern section of the Yidong Fault Zone as an example, it is illustrated how to identify apparent strike-slip faults under the superposition of multi-stage tectonic stress fields. The process enters step 103.

[0111] In step 103, calculate the fault density, denoted as D n , which provides a parameter to characterize the strike-slip component intensity of faults with different strikes in different periods.

[0112]

[0113] In formula (1), D n is the fault density, that is, the number of faults within 2 km 2 , number / km / 2 km 2 ; T i is the number of faults with different strikes, number; S is the area of the study area, km 2 . The fault density represents the strike-slip component intensity of the faults.

[0114] In the northern section of the Yidong Fault Zone, the fault density has increased significantly during both the Sha-3 to Sha-2 members and the Sha-1 member-Dongying Formation periods ( Figure 13 )( Figure 13 The pie chart in it is the fault density, representing the number of faults within 2 km 2 ). The increase in the fault density usually indicates an increase in the number of strike-slip faults. On the one hand, it shows that the main formation period of the northern section of the Changdi Fault Zone is the Sha-3 to Sha-2 members and the Sha-1 member-Dongying Formation periods. On the other hand, it shows that there have been two periods of strike-slip, and the strike-slip intensity in the Sha-1 member-Dongying Formation is relatively weaker than that in the Sha-3 to Sha-2 members period.

[0115] In step 103, calculate the cumulative length of faults with different strikes. It is denoted as L n , which provides a parameter to characterize the extensional component intensity of faults with different strikes in different periods.

[0116]

[0117] In formula (2), L n is the cumulative length of faults with different strikes, km; L i is the cumulative length of faults with a certain strike, km; The cumulative length of faults represents the extensional component intensity of the faults.

[0118] The intensity of the extensional component of faults with different strikes is the largest during the Kongdian - Member 4 of Shahejie Formation and Member 1 of Shahejie Formation - Dongying Formation periods, and relatively smaller during the Member 3 of Shahejie Formation - Member 2 of Shahejie Formation and Guantao - Minghuazhen Formation periods. There are two peaks during both the Member 3 of Shahejie Formation - Member 2 of Shahejie Formation period and the Member 1 of Shahejie Formation - Dongying Formation period, indicating that the faults formed during the Member 3 of Shahejie Formation - Member 2 of Shahejie Formation and Member 1 of Shahejie Formation - Dongying Formation periods are oblique to the pre - existing faults. There is a single peak during the Guantao - Minghuazhen Formation period, indicating that the faults formed during the Guantao - Minghuazhen Formation period are basically parallel to the pre - existing faults( Figure 13 )。

[0119] Figure 14 It is a schematic diagram of the distribution of active faults in different periods of the Yidong Fault Zone in the Cenozoic era. Generally speaking, under the action of NW - trending oblique extensional stress during the Member 3 of Shahejie Formation - Member 2 of Shahejie Formation period, the pre - existing NNE - trending Yidong Fault produced NE - trending faults that are oblique to the pre - existing NNE - trending Yidong Fault. Then, the NE - trending faults produced during the Member 3 of Shahejie Formation - Member 2 of Shahejie Formation period were under the action of NS - trending oblique extensional stress during the Member 1 of Shahejie Formation - Dongying Formation period, and produced EW - trending faults that are oblique to the NE - trending faults. The faults formed during the Guantao - Minghuazhen Formation period are basically parallel to the pre - existing faults.

[0120] In step 103, calculate the ratio of the extensional component to the strike - slip component, denoted as K n , which provides a parameter to characterize the relative strength of the extensional component and the strike - slip component of faults with different strikes and in different periods.

[0121]

[0122] In formula (3), Kn is the relative strength of the extensional component and the strike - slip component of faults with different strikes and in different periods. D n is the fracture density, that is, the number of faults per unit area, in pieces; Ln is the cumulative length of faults with different strikes, in km; the larger K n , the greater the intensity of the extensional component is than that of the strike - slip component.

[0123] Table 2 Statistical table of the ratio of the extensional component to the strike - slip component of faults with different strikes in the Yidong Fault Zone

[0124]

[0125] It can be seen from Table 2 that the ratio K of the extensional component to the strike - slip component of faults with different strikes in the Yidong Fault Zone nVariation law. The ratio of the extensional component to the strike-slip component during the Kongdian Formation - Member 4 of Shahejie Formation and Member 1 of Shahejie Formation - Dongying Formation is relatively large, while the ratio of the extensional component to the strike-slip component during the Member 3 of Shahejie Formation - Member 2 of Shahejie Formation and Guantao - Minghuazhen Formation is relatively small. Generally, the ratio of the extensional component to the strike-slip component of faults with different strikes is within the range of 0.02 - 0.39. Through comprehensive analysis, it is considered that the ratio of the extensional component to the strike-slip component of apparent strike-slip faults is within the range of 0.11 - 0.39, that is, 0.11 < K n <0.39. The process proceeds to step 104.

[0126] In step 104, the nature of the apparent strike-slip fault is identified. Although the structural pattern in the northern section of the Yidong Fault Zone is en echelon arrangement and flower-like structure, its essence is the NE-trending Yidong main fault formed during the Member 3 of Shahejie Formation - Member 2 of Shahejie Formation. It was stretched in the north-south direction during the Member 1 of Shahejie Formation - Dongying Formation. And when the ratio of the extensional component to the strike-slip component of the fault is within the range of 0.11 - 0.39, the formed pull-apart (oblique extension) structure is not a typical strike-slip structure.

[0127] Based on the above analysis, it is considered that when the ratio of the extensional component to the strike-slip component of faults with different periods and strikes in the Yidong Fault Zone is within the range of 0.11 - 0.39, and the included angle between the fault strike and the regional extensional direction is between 10° - 80°, such faults can be considered as apparent strike-slip faults ( Figure 8 ).

[0128] Embodiment 3

[0129] In a specific Embodiment 3 of applying the present invention, the Gaoqing - Pingnan Fault Zone is located in the southwestern part of the Dongying Sag, Jiyang Depression, and is a long-term active inherited boundary main fault. The Gaoqing - Pingnan Fault Zone has experienced multi-stage tectonic evolution and formed a complex fault system composed of NE-trending main faults and NW, EW-trending secondary faults. In the Cenozoic, although the structural patterns of some faults have characteristics of strike-slip faults such as flower-like structures, it is very difficult to determine their fault natures compared with typical strike-slip faults, and there are great controversies. Therefore, it is necessary to conduct in-depth research on the identification method of apparent strike-slip faults superimposed by multi-stage tectonic stress fields.

[0130] In this embodiment, the identification method of apparent strike-slip faults superimposed by multi-stage tectonic stress fields of the present invention includes the following steps:

[0131] In step 101, the structural map of the Cenozoic standard layer is interpreted. According to the logging data of the drilled wells, the strata and faults are interpreted according to the conventional formation interpretation process. This step is the basis of the present invention. For example Figure 15Geoframe interpretation software was used to interpret the structure of the Cenozoic standard layer. The specific steps were to import AC (acoustic time difference) and Den (density) curves into the seismic interpretation software - synthetic record calibration layer - layer and fault interpretation. During the interpretation process, it was necessary to check whether the interpretation layer and fault were closed. A total of 4 standard layers, T1, T2, T6, and T7, were interpreted. Figure 16 ). The process proceeds to step 102.

[0132] In step 102, the fault plane and cross-section structural patterns are analyzed to clarify the characterization of the multi-phase tectonic stress field direction conversion. This step is the basis of this invention.

[0133] On the profile, the fault systems above and below the T6, T2, and T1 interfaces have undergone significant changes, forming four fault systems, corresponding to four stages (Kongdian-Sha 4, Sha 3-Sha 2, Sha 1-Dongying Formation, Guantao Formation-Minghuazhen Formation).

[0134] Taking the T2 (equivalent to the bottom of the first member of Shahejie Formation) seismic reflection layer as the boundary, two sets of fault systems are developed, deep and shallow. The deep fault system (including the four sedimentary periods of the Kongdian Formation-the second member of Shahejie Formation) is mainly single fault, and the shallow fault system (the sedimentary period after the first member of Shahejie Formation, Dongying Formation and Guantao Formation) is a combination of fault steps and negative flower shapes. In the deep fault system, with the T6 (equivalent to the bottom of the third member of Shahejie Formation) seismic reflection layer as the boundary, two sets of fault systems are developed. The fourth member of Shahejie Formation below T6 is a shovel-shaped or horsetail-shaped structure with a relatively gentle dip angle, and the structure above T6 (equivalent to the bottom of the third member of Shahejie Formation) is a "Y"-shaped or fault step. In the shallow fault system, with the T1 (equivalent to the bottom of the Guantao Formation) seismic reflection layer as the boundary, two sets of fault systems are developed. The secondary fault above T1 matches the main fault to form a composite "Y"-shaped structural style, and the structure below T1 is a "Y"-shaped or fault step ( Figure 17 ).

[0135] The Gaoqing-Pingnan Fault Zone generally strikes northeast to southwest, dipping southeast, and has an "S" shape on the plane. The main fault strikes northeast and is in the shape of an arc convex to the northwest. The secondary faults are mainly located in the active plate, matching the main fault to form a right-handed broom-shaped structure with obvious zoning. According to the changes in its strike on the plane, it can be roughly divided into three sections, namely the Huagou section with a near EW trend, the Gaoqing section with a NNE trend, and the Pingnan section with a NE trend ( Figure 18 ).

[0136] On the plane, horizontal slices at 3800ms, 3500ms, 2500ms, 1500ms, and 1000ms from the Yidong fault zone ( Figure 19)It can be seen that the main fault of the Gaoqing fault has changed from single and continuous to complex and discontinuous, and the "S" shape has become more obvious, evolving from a linear - broom - en echelon pattern on the plane. In the northern Pingnan section, secondary faults that intersect obliquely at an acute angle with it have gradually developed, reflecting the extensional nature of the fault in the end section and presenting a broom shape. The fault in the southern Huagou section is relatively simple, but a series of small - scale nearly parallel same - direction and reverse faults have developed in its southern part. This indicates that the direction of the regional extensional stress has changed from the northwest - southeast direction in the Es3 - Es2 formations to the north - south direction in the Es1 - Dongying Formation. Here, taking the northern section of the Gaoqing - Pingnan fault zone as an example, it is explained how to identify apparent strike - slip faults under the superposition of multi - stage tectonic stress fields. The process enters step 103.

[0137] In step 103, calculate the fault density, denoted as D n , which provides a parameter to characterize the strike - slip component intensity of faults with different periods and different strikes.

[0138]

[0139] In formula (1), D n is the fault density, that is, the number of faults within 2 km 2 , number of faults / 2 km 2 ; T i is the number of faults with different strikes, number of faults; S is the area of the study area, km 2 . The fault density represents the intensity of the fault strike - slip component.

[0140] In the northern section of the Gaoqing - Pingnan fault zone, the fault density has increased significantly in the Es3 - Es2 formations ( Figure 20 ). The increase in fault density usually indicates an increase in the number of strike - slip faults. On the one hand, it shows that the main formation period of the northern section of the Gaoqing - Pingnan fault zone is the Es3 - Es2 period. On the other hand, it shows that the strike - slip intensity in the Es1 - Dongying Formation is weaker than that in the Es3 - Es2 period.

[0141] In step 103, calculate the cumulative length of faults with different strikes. Denoted as L n , which provides a parameter to characterize the extensional component intensity of faults with different periods and different strikes

[0142]

[0143] In formula (2), L n is the cumulative length of faults with different strikes, km; L i is the cumulative length of faults with a certain strike, km; The cumulative length of faults represents the intensity of the fault extensional component.

[0144] The intensity of the extensional component of faults with different strikes was the largest during the Sha-3 to Sha-2 Member periods, and relatively smaller during the Sha-1 to Dongying Formation and Guantao to Minghuazhen Formation periods. There were two peaks during the Sha-3 to Sha-2 Member periods, indicating that the faults formed during the Sha-3 to Sha-2 Member periods were oblique to the pre-existing faults. There was a single peak during both the Sha-1 to Dongying Formation and Guantao to Minghuazhen Formation periods, indicating that the faults formed during the Sha-1 to Dongying Formation and Guantao to Minghuazhen Formation periods were basically parallel to the pre-existing faults( Figure 21 ).

[0145] Figure 21 Fig. is a schematic diagram showing the distribution of active faults in different periods of the Cenozoic in the Gaoqing-Pingnan fault zone. Generally speaking, under the action of NW-trending oblique extensional stress during the Sha-3 to Sha-2 Member periods, the pre-existing NNE-trending Gaoqing-Pingnan fault produced NE-trending faults that were oblique to the Gaoqing-Pingnan fault. Then, the NE-trending faults produced during the Sha-3 to Sha-2 Member periods were under the action of NS-trending oblique extensional stress during the Sha-1 to Dongying Formation periods, resulting in EW-trending faults that were oblique to the NE-trending faults.

[0146] In step 103, calculate the ratio of the extensional component to the strike-slip component, denoted as K n , which provides a parameter to characterize the relative strength of the extensional component and the strike-slip component of faults with different strikes in different periods.

[0147]

[0148] In formula (3), Kn is the relative strength of the extensional component and the strike-slip component of faults with different strikes in different periods. D n is the fault density, that is, the number of faults per unit area, in pieces; Ln is the cumulative length of faults with different strikes, in km; the larger K n , the stronger the intensity of the extensional component is than that of the strike-slip component.

[0149] Table 3 Statistical table of the ratio of the extensional component to the strike-slip component of faults with different strikes in the Gaoqing-Pingnan fault zone

[0150]

[0151] From Table 3, the variation law of the ratio K n of the extensional component to the strike-slip component of faults with different strikes in the Gaoqing-Pingnan fault zone can be seen. The ratio of the extensional component to the strike-slip component was relatively large during the Kongdian Formation to Sha-4 Member and Sha-3 to Sha-2 Member periods, and relatively small during the Sha-1 to Dongying Formation and Guantao to Minghuazhen Formation periods. Generally, the ratio of the extensional component to the strike-slip component of faults with different strikes was within the range of 0.02 - 0.43. Through comprehensive analysis, it is considered that the ratio range of the extensional component to the strike-slip component of apparent strike-slip faults was within 0.19 - 0.43, 0.19 < K n < 0.43. The process proceeds to step 104.

[0152] In step 104, the nature of the strike-slip fault is identified. Although the structural pattern of the Gaoqing-Pingnan fault zone is en echelon arrangement and flower-like structure, its essence is that during the Sha 3rd - Sha 2nd member period, the pre-existing NNE-trending faults in Kongdian - Sha 4th member were affected by the oblique pull (oblique extension) structure formed by NW-SE extension. These NE-trending faults intersect obliquely with the Gaoqing-Pingnan fault and are not typical strike-slip structures. The ratio range of the extension component to the strike-slip component of these NE-trending faults is within 0.19 - 0.43.

[0153] Based on the above analysis, it is considered that when the ratio range of the extension component to the strike-slip component of the faults with different orientations in different periods in the Gaoqing-Pingnan fault zone is within 0.19 - 0.43, and the included angle between the fault strike and the regional extension direction is between 10° - 80°, such faults can be considered as apparent strike-slip faults ( Figure 8 ).

[0154] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0155] Except for the technical features described in the specification, the rest are well-known technologies to those skilled in the art.

Claims

1. Method for identifying apparent strike-slip faults with superposition of multi-stage tectonic stress fields, characterized in that, The method for identifying apparent strike-slip faults with superimposed multi-phase tectonic stress fields includes: Step 1: Conduct fine structural interpretation of the standard layer based on the logging and mud logging data of the drilled wells; Step 2: Characterize the direction conversion of multi-phase tectonic stress fields; Step 3: Characterize the changes in strike-slip components and extensional components; Step 4: Identify the nature of apparent strike-slip faults; In step 3, the ratio of the extensional component to the strike-slip component is calculated and denoted as K n， The ratio of the extensional component to the strike-slip component provides a parameter for characterizing the relative strengths of the extensional and strike-slip components of faults with different orientations in different periods.

2. The method for identifying apparent strike-slip faults by superimposing multi-stage tectonic stress fields according to claim 1, wherein The method for identifying apparent strike-slip faults with superimposed multi-phase tectonic stress fields further includes, before Step 1, obtaining the basic geological overview of the study area, collecting relevant data on tectonic evolution, and understanding the tectonic movements and stress directions experienced by the study area.

3. The method for identifying apparent strike-slip faults by superimposing multi-stage tectonic stress fields according to claim 1, wherein, In Step 1, understand the basic geological overview, tectonic movements and regional stress directions of the study area, and conduct fine structural interpretation of the standard layer based on the logging and mud logging data of the drilled wells.

4. The method for identifying apparent strike-slip faults by superimposing multi-stage tectonic stress fields according to claim 3, wherein, In Step 1, make synthetic seismograms to calibrate the strata based on logging curves such as acoustic travel time and density, and conduct stratum and fault interpretation. During the interpretation process, check whether the interpreted horizons and faults are closed.

5. The method for identifying apparent strike-slip faults by superimposing multi-stage tectonic stress fields according to claim 1, characterized in that, In Step 2, analyze the fault plane and profile structural patterns to clarify the direction conversion of multi-phase tectonic stress fields.

6. The method for identifying apparent strike-slip faults by superimposing multi-stage tectonic stress fields according to claim 1, wherein, In step 3, the fracture density and the cumulative fracture length are calculated, denoted as D n , L n , respectively. The fracture density and the cumulative fracture length provide a parameter for characterizing the strike-slip component and the extensional component intensity of faults with different trends in different periods.

7. The method for identifying apparent strike-slip faults by superimposing multi-stage tectonic stress fields according to claim 6, characterized in that, In Step 3, the calculation formula for fracture density is: In formula (1), D n is the fracture density, that is, the number of faults per unit area, in pieces; T i is the number of faults, in pieces; S is the area of the study area, in km 2 ; the fracture density represents the intensity of the strike-slip component of the fracture.

8. The method for identifying apparent strike-slip faults by superimposing multi-stage tectonic stress fields according to claim 6, wherein, In Step 3, the calculation formula for cumulative fracture length is: In formula (2), L n is the cumulative length of fractures in different directions, km; L i is the cumulative length of faults in a certain direction, km; the cumulative length of fractures represents the intensity of the fault extension component.

9. The method for identifying apparent strike-slip faults by superimposing multi-stage tectonic stress fields according to claim 1, characterized in that, In Step 3, the formula for calculating the ratio of extensional component to strike-slip component is: In formula (3), Kn is the relative strength of the extensional component and the strike-slip component of faults with different orientations in different periods; D n is the fracture density, that is, the number of faults per unit area, in pieces; Ln is the cumulative length of fractures with different orientations, in km; T i Number of faults, piece; L i Accumulated length of faults in a certain strike, km; S is the area of the study area, km 2 ; The larger Kn is, the greater the intensity of the extensional component is than that of the strike-slip component.

10. The method for identifying apparent strike-slip faults by superimposing multi-stage tectonic stress fields according to claim 1, characterized in that, In step 4, when the ratio range of the extensional component to the strike-slip component is within 0.19 - 0.43, i.e., 0.19 < K n < 0.43, and the included angle between the fault strike and the extensional direction is between 10° and 80°, such a fault is considered a pseudo strike-slip fault.

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