Finite element method-based strike-slip fault zone activity ability evaluation method

Abstract

The invention discloses a strike-slip fault zone activity ability evaluation method based on a finite element method, and the method comprises the steps: determining the three-dimensional space distribution characteristics of a strike-slip fault zone, determining the evaluation range of the activity ability of the strike-slip fault zone, determining the ground stress state of a research region, carrying out the finite element stress analysis, and carrying out the simulation data of the ground stress distribution, thereby achieving the evaluation of the activity ability of the strike-slip fault zone. The method comprises the following steps: calculating the acting force of different parts of a strike-slip fault zone, calculating two parameters for evaluating the activity capability of the strike-slip fault zone, optimizing the data distribution range of the two parameters according to the strike-slip fault zone activity capability evaluation threshold values of the two parameters, and screening the data capable of being used for evaluating the activity capability of the strike-slip fault zone by utilizing a cumulative multiplication method, so as to evaluate the activity capability of the strike-slip fault zone. The invention relates to a method for finely evaluating active parts of strike-slip fault zones and activity of different parts. According to the method, the activity capability difference of different parts of the strike-slip fault zone can be quantitatively judged, and an effective scheme is provided for professional technicians for researching activity capability evaluation of the strike-slip fault zone and well location deployment.

Description

Technical Field

[0001] This application relates to the field of strike-slip fault zone activity capacity evaluation technology, and in particular to a strike-slip fault zone activity capacity evaluation method based on the finite element method. Background Technology

[0002] Strike-slip fault zones, as an important structural type widely developed in the Earth's crust, play a crucial role in controlling oil and gas migration, trap formation and modification, and reservoir distribution. In recent years, with continuous breakthroughs in oil and gas exploration and development in deep-to-ultra-deep carbonate strike-slip fault zones within my country's cratonic basins, it has become increasingly clear that strike-slip fault zones are not only "highways" for oil and gas migration but also important reservoir spaces for oil and gas in carbonate strata. Furthermore, the differences in activity levels at different locations within strike-slip fault zones have a vital impact on the distribution of oil and gas enrichment areas, posing new challenges to drilling deployment and oilfield development plans targeting strike-slip fault zones. However, current research on the activity of strike-slip fault zones largely focuses on evaluation based on the reading of geometric and kinematic parameters, while the analysis of the activity capacity of strike-slip fault zones under the influence of geostress and the quantitative evaluation of strike-slip fault zone activity remain relatively weak. The difference in strike-slip fault activity in deep to ultra-deep carbonate rocks can increase the geometric complexity and heterogeneity of underground strike-slip fault zones, thereby causing disturbances in the geostress field.

[0003] Currently, research on the activity capacity of strike-slip fault zones is mostly conducted by reading geometric and kinematic parameters. However, this method of manually reading data from a section perpendicular to the strike-slip fault zone after interpreting the fracture profile is not only labor-intensive and time-consuming, but also highly subjective and prone to human error. Therefore, this approach to studying the activity of strike-slip fault zones is prone to significant errors.

[0004] From the perspective of current oilfield development, research on the quantitative evaluation of the activity of different parts of strike-slip fault zones based on the restoration of deep-ultra-deep geostress states and geostress is relatively weak. Therefore, the research results on strike-slip fault activity have insufficient guidance for actual production. Summary of the Invention

[0005] This application provides a method for evaluating the activity capacity of strike-slip fault zones based on the finite element method. It aims to solve the problems of existing technologies that rely on interpreting fracture profiles and then manually reading data from profiles perpendicular to the strike-slip fault zone to study its activity. This method is not only labor-intensive and time-consuming, but also highly subjective and prone to human error.

[0006] A method for evaluating the activity capacity of strike-slip fault zones based on the finite element method, the method comprising:

[0007] S1: Determine the three-dimensional spatial distribution characteristics of the strike-slip fault zone, clarify the evaluation range of the activity capacity of the strike-slip fault zone, determine the geostress state of the target study area, conduct finite element stress analysis, and obtain simulation data of geostress distribution in the target study area;

[0008] S2: Based on the simulation data of the ground stress distribution, the magnitude of the force at different parts of the strike-slip fault zone is obtained, and two parameters are calculated to evaluate the activity capacity of the strike-slip fault zone.

[0009] S3: Based on the threshold values ​​for evaluating the activity capacity of strike-slip fault zones using the two parameters, optimize the data distribution range of the two parameters, construct comprehensive parameters for evaluating the activity capacity of strike-slip fault zones, and assess the active locations of strike-slip fault zones and the strength of activity in different locations.

[0010] Optionally, in the above scheme, S1 includes:

[0011] S11: Based on the three-dimensional seismic data, the three-dimensional spatial distribution characteristics of the strike-slip fault zone are characterized by utilizing the fault-sensitive seismic attributes.

[0012] S12: Based on actual production needs, clarify the depth and planar range for evaluating the activity capacity of the strike-slip fault zone;

[0013] S13: Based on the actual research space, conduct analysis and calculation of the geostress state in the target research area;

[0014] S14: Complete the reasonable construction of the mathematical model of the target research area and conduct finite element stress analysis.

[0015] Optionally, in the above scheme, when characterizing the three-dimensional spatial distribution features of strike-slip fault zones in the study area, three-dimensional seismic data is used as the basis. By extracting three-dimensional seismic attributes that are sensitive to the fault, a two-way three-dimensional spatial distribution feature characterization of strike-slip fault zones with the assistance of artificial interpretation and seismic attributes is achieved. Among them, the three-dimensional seismic attributes that are sensitive to the fault include coherence attributes and curvature attributes.

[0016] In the above scheme, optionally, the magnitude of geostress can be calculated by using conventional or special logging data from actual well locations within the study area. The geostress calculation method is selected specifically for different regions and lithologies, and the geostress direction is selected based on literature review of the geostress direction of the tectonic unit where the study area is located.

[0017] Optionally, based on the actual stratigraphic distribution characteristics, the three-dimensional spatial distribution characteristics of strike-slip fault zones, and the spatial stress state of the study area, a reasonable mathematical model of the study area can be constructed. During the construction process, fine meshing can be performed at the distribution locations of strike-slip fault zones.

[0018] Optionally, in the above scheme, S2 includes:

[0019] S21: Extract the three-dimensional geostress distribution data of the study area after finite element simulation, and select data to characterize the three-dimensional spatial stress state of the strike-slip fault zone based on the three-dimensional spatial distribution characteristics of the strike-slip fault zone.

[0020] S22: Based on the screening results of stress state data, and according to the statistical results of the differences in strike and dip angles of different parts of the strike-slip fault zone, the magnitude of the force at different parts of the strike-slip fault zone is obtained;

[0021] S23: Based on the statement of the magnitude of the force, calculate two parameters to evaluate the activity capacity of the strike-slip fault zone.

[0022] Optionally, in the above scheme, in step S21,

[0023] After completing the finite element simulation, the three-dimensional geostress distribution data of the study area were extracted. Then, based on the coordinate data of the three-dimensional spatial distribution characteristics of the bidirectional strike-slip fault zone characterized by manual interpretation and seismic attribute assistance, the data with the same or closest coordinates in the three-dimensional geostress distribution data of the study area after the finite element simulation were selected as data to characterize the three-dimensional spatial stress state of the strike-slip fault zone.

[0024] When matching the coordinate data of the three-dimensional spatial distribution feature characterization result of the strike-slip fault zone with the coordinates in the three-dimensional geostress distribution data, if the coordinates are completely consistent during the matching, the three-dimensional geostress distribution data is directly assigned to the coordinate data of the three-dimensional spatial distribution feature characterization result. If the coordinates are not completely consistent during the matching, the point in the three-dimensional geostress distribution data that is closest to the coordinate data of the three-dimensional spatial distribution feature characterization result of the strike-slip fault zone is selected in space, and its three-dimensional geostress distribution data is assigned to the coordinate data of the three-dimensional spatial distribution feature characterization result of the strike-slip fault zone.

[0025] Optionally, in the above scheme, in step S22,

[0026] Based on the statistical results of the differences in strike and dip angles at different parts of the strike-slip fault zone, and combined with the three-dimensional spatial distribution characteristic coordinate data of the strike-slip fault zone with completed geostress data assignment, the magnitude of the force at different parts of the strike-slip fault zone is calculated. The magnitude of the force includes the magnitude of the normal stress and the magnitude of the shear stress at the cross section.

[0027] Optionally, in the above scheme, S3 includes:

[0028] S31: After completing the evaluation of the two parameters of the activity capacity of the strike-slip fault zone, clarify the threshold values ​​of the two parameters that can be used to evaluate the activity capacity of the strike-slip fault zone, and optimize the data distribution range of the two parameters;

[0029] S32: Based on the optimization results, the cumulative multiplication method is used to construct the comprehensive parameters for evaluating the activity capacity of strike-slip fault zones, and the data distribution intervals for the comprehensive parameters for evaluating the activity capacity of strike-slip fault zones are selected.

[0030] S33: Based on the data distribution range of the comprehensive parameters for evaluating the activity capacity of strike-slip fault zones, assess the active parts of strike-slip fault zones and the strength of activity in different parts.

[0031] Optionally, in the above scheme, in step S31,

[0032] The threshold values ​​for the two parameters are determined based on the meaning of their respective data.

[0033] When the sliding tendency coefficient is greater than 0.6, the fracture is in a critical stress state.

[0034] When the fault shear index is greater than 1, shear slip will occur between the two sides of the fault.

[0035] In S32, the optimized two-parameter data are used to calculate the product of the data at the same coordinates of the two parameters by the cumulative multiplication method, thereby constructing a comprehensive parameter for evaluating the activity capacity of the strike-slip fault zone.

[0036] In step S33, based on the comprehensive parameters for evaluating the activity capacity of strike-slip fault zones calculated in actual research, and according to the data distribution range of the comprehensive parameters for evaluating the activity capacity of strike-slip fault zones, the active parts of the strike-slip fault zones and the strength of their activity capacity in different parts are assessed.

[0037] Compared with the prior art, this application has at least the following beneficial effects:

[0038] This application, based on further analysis and research into the problems of existing technologies, recognizes that existing methods for studying strike-slip fault zone activity through manual data reading of profiles perpendicular to the strike-slip fault zone after interpreting the fracture profile. This approach is not only labor-intensive and time-consuming but also highly subjective and prone to human error. This application addresses these issues by defining the three-dimensional spatial distribution characteristics of strike-slip fault zones, clarifying the evaluation range of their activity capacity, determining the geostress state of the study area, conducting finite element stress analysis, and calculating the magnitude of forces acting on different parts of the strike-slip fault zone based on simulated geostress distribution data. Two parameters for evaluating the activity capacity of the strike-slip fault zone are then calculated. Based on the evaluation thresholds for these two parameters, the data distribution range of the two parameters is optimized, and a cumulative multiplication method is used to screen data suitable for evaluating the activity capacity of the strike-slip fault zone. This method allows for a precise assessment of the active locations of the strike-slip fault zone and the strength of activity at different locations. This approach can quantitatively determine the differences in activity capacity at different locations of the strike-slip fault zone, providing an effective solution for professionals researching strike-slip fault zone activity capacity evaluation and well location deployment. Attached Figure Description

[0039] Figure 1 A flowchart illustrating a method for evaluating the activity capacity of strike-slip fault zones based on the finite element method, provided in one embodiment of this application;

[0040] Figure 2 A cross-sectional normal stress plan view provided for one embodiment of this application;

[0041] Figure 3 A cross-sectional shear stress plan view provided for one embodiment of this application;

[0042] Figure 4 A planar diagram of the sliding trend coefficients provided in one embodiment of this application;

[0043] Figure 5 A plan view of the torsional shear index difference provided in one embodiment of this application;

[0044] Figure 6 A plan view of comprehensive parameters for evaluating the activity capacity of a strike-slip fault zone provided in one embodiment of this application. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0046] In one embodiment, such as Figure 1 As shown, a method for evaluating the activity capacity of strike-slip fault zones based on the finite element method is provided, including the following steps:

[0047] S1: Determine the three-dimensional spatial distribution characteristics of strike-slip fault zones, clarify the evaluation range of the activity capacity of strike-slip fault zones, determine the geostress state of the study area, and conduct finite element stress analysis.

[0048] S2: Based on the simulation data of geostress distribution, the magnitude of the force at different parts of the strike-slip fault zone is obtained, and two parameters are calculated to evaluate the activity capacity of the strike-slip fault zone, including the magnitude of the slip trend coefficient and the fault shear index.

[0049] S3: Based on the threshold values ​​for evaluating the activity capacity of strike-slip fault zones using two parameters, optimize the data distribution range of the two parameters, construct comprehensive parameters for evaluating the activity capacity of strike-slip fault zones, and accurately assess the active locations of strike-slip fault zones and the strength of activity in different locations.

[0050] In this embodiment, step S1 includes:

[0051] S11: Based on three-dimensional seismic data, the three-dimensional spatial distribution characteristics of strike-slip fault zones are characterized by utilizing fault-sensitive seismic attributes.

[0052] S12: Based on actual production needs, clarify the depth and planar range for evaluating the activity capacity of strike-slip fault zones.

[0053] S13: Based on the actual research space, conduct analysis and calculation of the geostress state in the research area.

[0054] S14: Complete the reasonable construction of the mathematical model of the study area and conduct finite element stress analysis.

[0055] In this embodiment, in step S11,

[0056] When characterizing the three-dimensional spatial distribution of strike-slip fault zones in the study area, it is necessary to use three-dimensional seismic data as a foundation. This involves extracting fault-sensitive three-dimensional seismic attributes, such as coherence and curvature attributes, to achieve a bidirectional characterization of the three-dimensional spatial distribution of strike-slip fault zones through a combination of manual interpretation and seismic attribute assistance. This ensures a complete depiction of the spatial outline and internal structure of the strike-slip fault zones, which is a key component in finite element analysis. Particular attention must be paid to accurately characterizing the spatial distribution of strike-slip fault zones to achieve the statistical goal of clearly defining the differences in strike and dip angles at different locations within the fault zone. Furthermore, detailed characterization is required at the overlapping areas of different fault segments and at the junctions of strike-slip faults of different grades. The accuracy of these two characterizations determines the accuracy of the activity capacity assessment after applying stress using the finite element method.

[0057] In this embodiment, in step S12, since the actual production of the oilfield is mostly concentrated in one or several fixed layers, it is possible to effectively reduce the amount of data when conducting three-dimensional finite element simulation by clarifying the depth range for evaluating the activity capacity of the strike-slip fault zone, rather than evaluating a complete strike-slip fault zone. Furthermore, by clarifying the planar range, the structural morphology of the area to be simulated and the actual distribution of well location data can be determined first.

[0058] In this embodiment, in step S13, based on the actual research space, the magnitude of in-situ stress can be calculated using conventional or special logging data from actual well locations within the research area. The in-situ stress calculation method needs to be selected specifically for different regions and lithologies. The direction of in-situ stress can be selected based on literature review, focusing on the in-situ stress direction of the structural unit where the research area is located.

[0059] In this embodiment, due to the different actual research spatial ranges, different combinations of geostress may occur in the longitudinal direction after geostress calculation. If the research area only exhibits a single stress state, such as: If the stress is applied in the longitudinal direction, it is relatively simple to apply stress during the three-dimensional finite element simulation. If the study area exhibits a combination of the above three stress states in the longitudinal direction, it proves that there is a stress transition surface in the space of the study area. In this case, the stress applied in the longitudinal direction during the three-dimensional finite element simulation needs to be adjusted according to the actual situation. Using the same set of force application scheme will lead to errors in the spatial stress simulation results.

[0060] In this embodiment, in step S13, a reasonable mathematical model of the study area is built based on the actual stratigraphic distribution characteristics, the three-dimensional spatial distribution characteristics of the strike-slip fault zone, and the spatial stress state. When building the model, it is important to perform fine meshing at the distribution location of the strike-slip fault zone to more accurately reflect the differences in stress characteristics at different locations of the strike-slip fault zone.

[0061] In this embodiment, step S2 includes:

[0062] S21: Extract the three-dimensional geostress distribution data of the study area after finite element simulation, and select data to characterize the three-dimensional spatial stress state of the strike-slip fault zone based on the three-dimensional spatial distribution characteristics of the strike-slip fault zone.

[0063] S22: Based on the screening results of stress state data, and according to the statistical results of the differences in strike and dip angles of different parts of the strike-slip fault zone, the magnitude of the force at different parts of the strike-slip fault zone is calculated.

[0064] S23: Based on the magnitude of the force, calculate two parameters to evaluate the activity capacity of the strike-slip fault zone.

[0065] In this embodiment, in step S21, after completing the finite element simulation, only the three-dimensional geostress distribution data of the study area needs to be extracted. Then, based on the coordinate data of the three-dimensional spatial distribution characteristics of the bidirectional strike-slip fault zone characterized by manual interpretation and seismic attribute assistance, the data with the same or closest coordinates in the three-dimensional geostress distribution data of the study area after the finite element simulation are selected as data to characterize the three-dimensional spatial stress state of the strike-slip fault zone.

[0066] In this embodiment, when matching the coordinate data of the three-dimensional spatial distribution feature characterization result of the strike-slip fault zone with the coordinates in the three-dimensional geostress distribution data, there are two situations: if the coordinates are completely consistent during matching, the three-dimensional geostress distribution data can be directly assigned to the coordinate data of the three-dimensional spatial distribution feature characterization result; if no completely consistent coordinates are found during matching, the point in the three-dimensional geostress distribution data that is closest to the coordinate data of the three-dimensional spatial distribution feature characterization result of the strike-slip fault zone is selected in space, and its three-dimensional geostress distribution data is assigned to the coordinate data of the three-dimensional spatial distribution feature characterization result of the strike-slip fault zone.

[0067] In this embodiment, in step S22, based on the statistical results of the differences in strike and dip angles at different locations of the strike-slip fault zone, and combined with the three-dimensional spatial distribution characteristic coordinate data of the strike-slip fault zone with completed geostress data assignment, the magnitude of the force at different locations of the strike-slip fault zone can be calculated. The magnitude of the force to be calculated in this study includes the magnitude of the normal stress at the cross-section, and its calculation formula is as follows:

[0068] .

[0069] The formula for calculating the magnitude of the cross-sectional shear stress is as follows:

[0070] .

[0071] in, Normal stress acting on the cross section, MPa; Shear stress acting on the cross-section, MPa;

[0072] Local maximum horizontal principal stress, MPa; Local horizontal minimum principal stress, MPa; Local vertical principal stress, MPa; for Angle with the outer normal of the fracture, °; for Angle with the outer normal of the fracture, °; for Angle with the outer normal of the fracture, °; The angle between the direction of the maximum horizontal principal stress and the fracture orientation, in °; Fracture angle, °;

[0073] In this embodiment, in step S23, based on the calculated magnitudes of the cross-sectional normal stress and cross-sectional shear stress, two parameters for evaluating the activity capacity of different parts of the strike-slip fault zone can be obtained. First, the slip tendency coefficient used to characterize whether the underground fault is in a critical stress state is obtained. The calculation formula is as follows: .

[0074] Secondly, the fault shear index, used to characterize whether shear slip will occur in the underground fault, is determined. The calculation formula is as follows: .

[0075] Here It is the sum of the inherent shear strength of the fault zone material and the frictional force on the fault plane, i.e. .

[0076] in, It is the normal stress acting on the surface of the natural crack, in MPa; It is the shear stress acting on the surface of a natural crack, in MPa; Inherent shear strength; is the internal friction coefficient.

[0077] In this embodiment, step S3 includes:

[0078] S31: After completing the evaluation of the two parameters for the activity capacity of strike-slip fault zones, it is necessary to clarify the threshold values ​​of the two parameters that can be used to evaluate the activity capacity of strike-slip fault zones, and optimize the data distribution range of the two parameters.

[0079] S32: Based on the optimization results, the comprehensive parameters for evaluating the activity capacity of strike-slip fault zones are constructed using the cumulative multiplication method, and the data distribution intervals for the comprehensive parameters for evaluating the activity capacity of strike-slip fault zones are selected.

[0080] S33: Based on the data distribution range of the comprehensive parameters for evaluating the activity capacity of strike-slip fault zones, accurately assess the active parts of strike-slip fault zones and the strength of activity in different parts.

[0081] In this embodiment, in step S31, the meanings of the two parameters representing the activity capacity of different parts of the strike-slip fault zone vary depending on their data distribution. Therefore, it is necessary to first determine the threshold values ​​of the two parameters based on their respective data meanings.

[0082] Regarding the slip tendency coefficient, according to the critical stress hypothesis, when the slip tendency coefficient ( When the stress ratio is greater than 0.6, the fracture is in a critical stress state and is prone to sliding, allowing underground fluids to seep through the fracture.

[0083] As for the fault shear index, when the fault shear index ( When the fault shear index is greater than 1, it is considered that shear slip will occur between the two sides of the fault, causing changes in the physical properties of the fault zone. If the fault shear index ( ) > 1 and the normal stress on the fault plane is compressive stress (i.e. When the fault undergoes compressional shear displacement on both sides, the existing pores and fractures that allow oil and gas to seep through the fault zone are closed under shearing action, thus strengthening the fault's sealing ability and increasing its capacity to block oil and gas. Conversely, when... When tensional shear displacement occurs on both sides of a fault, the existing pores, fractures, and other oil and gas seepage channels will expand under the tension. Simultaneously, due to the shear displacement of the two sides, new fractures may be generated in the fault zone, increasing the degree of fault opening and creating favorable channels for oil and gas migration. Furthermore, when the fault shear index (… When the fault shear index is ≤1, the fault only tends to undergo shear displacement; the two sides of the fault will not experience relative displacement, the physical properties of the fault zone material do not change significantly, and the impact on the fault sealing can be ignored. Therefore, for the fault shear index ( Only when and Only when the fracture is in a valid active position can it be considered.

[0084] Therefore, based on the threshold values ​​of the two parameters for evaluating the effective active parts of the fracture, data smaller than their respective threshold ranges can be set to 0, while data exceeding the threshold ranges can be left at their original size without processing. This method optimizes the data distribution range of the two parameters, filters and retains only the data that reflects the effective active parts of the fracture, and effectively eliminates the impact of useless data on subsequent calculations.

[0085] In this embodiment, in step S32, the optimized two-parameter data are used to calculate the product of data from locations with the same coordinates using the cumulative multiplication method, thereby constructing a comprehensive parameter for evaluating the activity capacity of the strike-slip fault zone. The calculation formula is as follows: .

[0086] in, The sliding trend coefficient is dimensionless. The fault shear index is dimensionless.

[0087] In this embodiment, by using the sliding trend coefficient ( ) and fault shear index ( Multiplying data with the same coordinates amplifies the data on active parts of strike-slip fault zones that are identified by both data sources, while data on active parts of strike-slip fault zones that are identified by only one data source and not by the other are set to zero and then deleted. This further enhances the accuracy of evaluating the activity capacity of different parts of strike-slip fault zones.

[0088] In this embodiment, in step S32, a comprehensive parameter for evaluating the activity capacity of strike-slip fault zones is constructed ( ), can be considered when the comprehensive parameters ( When the comprehensive parameter () > 0, the strike-slip fault zone is in an active state, and the larger the value, the stronger the activity of the strike-slip fault zone. When the value is less than 0, the strike-slip fault zone at that location is considered to be in a static state, and the larger the value, the more likely it is to slip. Therefore, the data distribution range of the comprehensive parameter for evaluating the activity capacity of strike-slip fault zones can be defined based on this data distribution, that is, when the comprehensive parameter ( When the comprehensive parameter () > 0, the strike-slip fault zone is in an active state. When ) < 0, the strike-slip fault zone is in a static state.

[0089] In this embodiment, in step S33, the comprehensive parameters for evaluating the activity capacity of the strike-slip fault zone calculated in actual research are used. Based on the data distribution range of the comprehensive parameters for evaluating the activity capacity of strike-slip fault zones, the active parts of the strike-slip fault zones and the strength of their activity in different parts can be accurately assessed.

[0090] In one specific embodiment, this example applies a finite element method-based method to evaluate the activity capacity of strike-slip fault zones in different locations of the northeast-trending strike-slip fault in the Akkul Uplift of the Tarim Basin.

[0091] First, a three-dimensional spatial characterization of the strike-slip fault zones in the study area was conducted, primarily using artificial interpretation and supplemented by three-dimensional coherent seismic attributes. This characterization aimed to refine the spatial outline, internal structure, overlapping areas of different fault segments, and lap joints of different fault grades within the strike-slip fault zones. Furthermore, it clarified the differences in strike and dip angles at different locations within the strike-slip fault zones. Then, based on the actual production needs of the study area, the spatial range between stratigraphic levels T74 and T76 was determined. The depth range was defined as 100m upwards from T74 as the top interface and 100m downwards from T76 as the bottom interface. The planar range then defined the scope of the study area. After defining this spatial range, the distribution of actual well locations within the study area could be determined, with a focus on identifying conventional and specialized logging data for different well locations to facilitate the calculation of in-situ stress. In this study, the comprehensive results of well logging calculations yielded a maximum horizontal principal stress of 128 MPa and a minimum horizontal principal stress of 105 MPa in the study area. The direction of the maximum horizontal principal stress was 51.2°, obtained from literature review. Furthermore, the stress distribution results from conventional well logging data of four wells in the study area indicate that there is no stress transition surface within the target layer. Therefore, applying stress in the three-dimensional finite element method (3D finite element method) simulation is relatively simple. Finally, based on the actual formation distribution characteristics, the three-dimensional spatial distribution characteristics of the strike-slip fault zone, and the spatial stress state, a mathematical model was constructed, and the distribution area of ​​the strike-slip fault zone was finely meshed.

[0092] After completing the finite element simulation, the coordinate data of the three-dimensional spatial distribution feature characterization of the strike-slip fault zone are matched with the coordinates in the three-dimensional geostress distribution data. The three-dimensional geostress distribution data is then assigned to the coordinate data of the three-dimensional spatial distribution feature characterization of the strike-slip fault zone. Then, based on the statistical results of the differences in strike and dip angles at different locations of the strike-slip fault zone, and combined with the completed geostress data assignment results for different locations of the strike-slip fault zone, the magnitudes of the normal stress and shear stress at different locations of the strike-slip fault zone can be calculated. Figure 2 and Figure 3 As shown, then, based on the calculation results of the normal stress and shear stress of the cross section, the slip trend coefficient for evaluating the activity capacity of different parts of the strike-slip fault zone can be obtained. ) and fault shear index ( Two parameters, such as Figure 4 and Figure 5 As shown. Since determining the threshold range is necessary when using two parameters to evaluate the activity capacity of strike-slip fault zones, the data from both parameters should be processed first. Based on the slip trend coefficient ( >0.6 and fault shear index ( ) > 1 and The principle that a value greater than 0 indicates a fracture is considered to be in an effective active region is applied. Data values ​​below their respective threshold ranges are treated as 0, while data values ​​exceeding the threshold range are left unchanged. This optimizes the data distribution range of the two parameters, filtering and retaining only data reflecting the effective active region of the fracture. This method effectively eliminates useless data and reduces the burden of subsequent calculations. After processing the two parameters in this calculation using this method, it was found that the slip trend coefficient (… Among the values ​​> 0.6, the maximum value is 0.9887, and the percentage of data treated as 0 is 89.74%; fault shear index ( ) > 1 and Among the values ​​>0, the maximum value is 0.8896, and the data with a value of 0 account for 93.58%. Using the optimized two-parameter data, the data from locations with the same coordinates are multiplied using the cumulative multiplication method to construct a comprehensive parameter for evaluating the activity capacity of the strike-slip fault zone. )like Figure 6 As shown. Based on the data distribution range, the active parts of the strike-slip fault zone and the strength of activity in different parts can be accurately assessed.

[0093] This embodiment provides a method for studying the differences in activity capacity of different locations within strike-slip fault zones in deep-to-ultra-deep carbonate reservoirs. This method involves defining the three-dimensional spatial distribution characteristics of the strike-slip fault zone, clarifying the evaluation range of its activity capacity, determining the geostress state of the study area, conducting finite element stress analysis, and calculating the magnitude of forces acting on different locations within the strike-slip fault zone based on simulated geostress distribution data. Two parameters for evaluating the activity capacity of the strike-slip fault zone are then calculated. Based on the evaluation thresholds for these two parameters, the data distribution range of the two parameters is optimized. Data suitable for evaluating the activity capacity of the strike-slip fault zone is then selected using a cumulative multiplication method. This allows for a precise assessment of the locations of active strike-slip faults and the strength of activity at different locations. This patent addresses the current problems in the study of the activity of strike-slip fault zones in deep-to-ultra-deep carbonate reservoirs, which are characterized by high workload, time-consuming and labor-intensive methods, strong subjectivity, high human error, and a lack of geostress-based research, resulting in insufficient practical production guidance from strike-slip fault activity research findings.

[0094] This embodiment provides a method for studying the differences in activity capacity of different parts of strike-slip fault zones in deep-ultra-deep carbonate reservoirs. This method involves defining the three-dimensional spatial distribution characteristics of the strike-slip fault zone, clarifying the evaluation range of its activity capacity, determining the geostress state of the study area, conducting finite element stress analysis, and calculating the magnitude of the forces acting on different parts of the strike-slip fault zone based on simulated geostress distribution data. Two parameters for evaluating the activity capacity of the strike-slip fault zone are then calculated. Based on the evaluation thresholds for these two parameters, the data distribution range of the two parameters is optimized. Finally, a cumulative multiplication method is used to screen data suitable for evaluating the activity capacity of the strike-slip fault zone, thus precisely assessing the active parts of the strike-slip fault zone and the strength of activity at different parts. This method can quantitatively determine the differences in activity at different locations within a strike-slip fault zone. It also addresses current challenges in studying the activity of strike-slip fault zones in deep-to-ultra-deep carbonate reservoirs, such as the large workload, time-consuming nature, high subjectivity, and significant human error associated with manually reading data from profiles, as well as the lack of ground-stress-based research and insufficient practical guidance for actual production. This provides a practical and effective solution for professionals researching strike-slip fault activity assessment and well location deployment.

[0095] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A method for evaluating the activity capacity of strike-slip fault zones based on the finite element method, characterized in that, The method includes: S1: Determine the three-dimensional spatial distribution characteristics of the strike-slip fault zone, clarify the evaluation range of the activity capacity of the strike-slip fault zone, determine the geostress state of the target study area, conduct finite element stress analysis, and obtain simulation data of geostress distribution in the target study area; S2: Based on the simulation data of the ground stress distribution, the magnitude of the force at different parts of the strike-slip fault zone is obtained, and two parameters are calculated to evaluate the activity capacity of the strike-slip fault zone. S3: Based on the threshold values ​​for evaluating the activity capacity of strike-slip fault zones using the two parameters, optimize the data distribution range of the two parameters, construct comprehensive parameters for evaluating the activity capacity of strike-slip fault zones, and assess the active locations of strike-slip fault zones and the strength of activity in different locations.

2. The method according to claim 1, characterized in that, S1 includes: S11: Based on the three-dimensional seismic data, the three-dimensional spatial distribution characteristics of the strike-slip fault zone are characterized by utilizing the fault-sensitive seismic attributes. S12: Based on actual production needs, clarify the depth and planar range for evaluating the activity capacity of the strike-slip fault zone; S13: Based on the actual research space, conduct analysis and calculation of the geostress state in the target research area; S14: Complete the reasonable construction of the mathematical model of the target research area and conduct finite element stress analysis.

3. The method according to claim 2, characterized in that, In step S11, when characterizing the three-dimensional spatial distribution features of the strike-slip fault zone in the study area, three-dimensional seismic data is used as the basis. By extracting three-dimensional seismic attributes that are sensitive to the fault, a two-way three-dimensional spatial distribution feature characterization of the strike-slip fault zone with artificial interpretation and seismic attribute assistance is achieved. Among them, the three-dimensional seismic attributes that are sensitive to the fault include coherence attributes and curvature attributes.

4. The method according to claim 2, characterized in that, In S13, the magnitude of geostress is calculated by using conventional or special logging data from actual well locations within the study area. The geostress calculation method is selected specifically for different regions and lithologies, and the geostress direction is selected based on literature review of the tectonic unit where the study area is located.

5. The method according to claim 2, characterized in that, In S13, a reasonable mathematical model of the study area is built based on the actual stratigraphic distribution characteristics, the three-dimensional spatial distribution characteristics of the strike-slip fault zone, and the spatial stress state. During the building process, fine meshing is carried out at the distribution location of the strike-slip fault zone.

6. The method according to claim 1, characterized in that, S2 includes: S21: Extract the three-dimensional geostress distribution data of the study area after finite element simulation, and select data to characterize the three-dimensional spatial stress state of the strike-slip fault zone based on the three-dimensional spatial distribution characteristics of the strike-slip fault zone. S22: Based on the screening results of stress state data, and according to the statistical results of the differences in strike and dip angles of different parts of the strike-slip fault zone, the magnitude of the force at different parts of the strike-slip fault zone is obtained; S23: Based on the statement of the magnitude of the force, calculate two parameters to evaluate the activity capacity of the strike-slip fault zone.

7. The method according to claim 6, characterized in that, In S21, After completing the finite element simulation, the three-dimensional geostress distribution data of the study area were extracted. Then, based on the coordinate data of the three-dimensional spatial distribution characteristics of the bidirectional strike-slip fault zone characterized by manual interpretation and seismic attribute assistance, the data with the same or closest coordinates in the three-dimensional geostress distribution data of the study area after the finite element simulation were selected as data to characterize the three-dimensional spatial stress state of the strike-slip fault zone. When matching the coordinate data of the three-dimensional spatial distribution feature characterization result of the strike-slip fault zone with the coordinates in the three-dimensional geostress distribution data, if the coordinates are completely consistent during the matching, the three-dimensional geostress distribution data is directly assigned to the coordinate data of the three-dimensional spatial distribution feature characterization result. If the coordinates are not completely consistent during the matching, the point in the three-dimensional geostress distribution data that is closest to the coordinate data of the three-dimensional spatial distribution feature characterization result of the strike-slip fault zone is selected in space, and its three-dimensional geostress distribution data is assigned to the coordinate data of the three-dimensional spatial distribution feature characterization result of the strike-slip fault zone.

8. The method according to claim 6, characterized in that, In S22, Based on the statistical results of the differences in strike and dip angles at different parts of the strike-slip fault zone, and combined with the three-dimensional spatial distribution characteristic coordinate data of the strike-slip fault zone with completed geostress data assignment, the magnitude of the force at different parts of the strike-slip fault zone is calculated. The magnitude of the force includes the magnitude of the normal stress and the magnitude of the shear stress at the cross section.

9. The method according to claim 1, characterized in that, S3 includes: S31: After completing the evaluation of the two parameters of the activity capacity of the strike-slip fault zone, clarify the threshold values ​​of the two parameters that can be used to evaluate the activity capacity of the strike-slip fault zone, and optimize the data distribution range of the two parameters; S32: Based on the optimization results, the cumulative multiplication method is used to construct the comprehensive parameters for evaluating the activity capacity of strike-slip fault zones, and the data distribution intervals for the comprehensive parameters for evaluating the activity capacity of strike-slip fault zones are selected. S33: Based on the data distribution range of the comprehensive parameters for evaluating the activity capacity of strike-slip fault zones, assess the active parts of strike-slip fault zones and the strength of activity in different parts.

10. The method according to claim 9, characterized in that, In S31, The threshold values ​​for the two parameters are determined based on the meaning of their respective data. When the sliding tendency coefficient is greater than 0.6, the fracture is in a critical stress state. When the fault shear index is greater than 1, shear slip will occur between the two sides of the fault. In S32, the optimized two-parameter data are used to calculate the product of the data at the same coordinates of the two parameters by the cumulative multiplication method, thereby constructing a comprehensive parameter for evaluating the activity capacity of the strike-slip fault zone. In step S33, based on the comprehensive parameters for evaluating the activity capacity of strike-slip fault zones calculated in actual research, and according to the data distribution range of the comprehensive parameters for evaluating the activity capacity of strike-slip fault zones, the active parts of the strike-slip fault zones and the strength of their activity capacity in different parts are assessed.

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