Method for identifying strike-slip fault layer through fault dip curve

Abstract

This invention discloses a method for identifying strike-slip faults using fault dip angle curves, relating to the field of sedimentary basin tectonic analysis and seismic interpretation technology. The invention first obtains fault interpretation results for the study area, then measures fault dip angle data based on the obtained results. Next, it plots dip angle curves and dip angle change rate curves based on the obtained dip angle data, and finally identifies strike-slip faults using these curves. This invention proposes a method for identifying strike-slip faults based on fault dip angle and dip angle change rate curve patterns, enabling direct identification of strike-slip faults using seismic profiles. It overcomes the problem of lacking a unified standard to distinguish strike-slip faults from normal / reverse faults, and proposes an intuitive identification chart with qualitative-semi-quantitative characteristics, resulting in more reliable predictions.

Description

Technical Field

[0001] This invention relates to the field of sedimentary basin tectonic analysis and seismic interpretation, and more specifically to a method for identifying strike-slip faults using fault dip curves. Background Technology

[0002] In oil and gas basins, strike-slip faults play a crucial role in controlling the migration, accumulation, and formation of oil and gas reservoirs, as well as the physical properties of tight reservoirs. Identifying strike-slip faults is fundamental to seismic interpretation and tectonic analysis of strike-slip faults.

[0003] Theoretically, strike-slip faults are nearly vertical. Therefore, in seismic / geological profiles, strike-slip faults are usually identified by their near-vertical cross-sectional features. This is the simplest and most commonly used method for qualitative identification of strike-slip faults. However, in nature, strike-slip faults typically exhibit complex tectonic deformations and fracture combinations, forming complex strike-slip fault zones. These faults develop various types of intricate, flower-like structures on the profile, exhibiting characteristics of normal or reverse faults. Therefore, in sedimentary basins where the seismic response of deep strike-slip faults is unclear, it is difficult to distinguish between strike-slip faults and normal / reverse faults from seismic profiles.

[0004] For example, the published text of the invention patent application, entitled "A Method and System for Identifying Strike-Slip Faults," with an application publication date of September 5, 2023, publication number CN116699688A, utilizes 3D seismic data, structural maps, and other data to obtain the dip angle of the fault to be measured and the angle between the fault to be measured and its branch faults, thereby obtaining the lateral plunge angle of the fault intersection line and the fault to be measured, and quantitatively identifying strike-slip faults. However, it does not utilize the fault dip angle data on the cross-section to distinguish between strike-slip faults and normal / reverse faults.

[0005] For example, Yang Gang et al. (2018) and He Kefeng et al. (2023) identified strike-slip faults by high-dipping faults, which is consistent with the principle of identifying strike-slip faults by the characteristics of nearly vertical cross sections. They did not measure the changes in the fault dip angle on the cross section in detail, nor did they involve identifying strike-slip faults by the data on the changes in the fault dip angle on the cross section.

[0006] Therefore, many strike-slip fault zones lack effective seismic response in the deep part of the basin, while exhibiting normal or reverse fault characteristics in the shallow part. It is difficult to distinguish between strike-slip faults and normal / reverse faults on the cross section. Strike-slip faults are usually identified by multiple markers on the plane and cross section.

[0007] As mentioned above, previous studies lacked a method for identifying strike-slip faults using fault dip profile curve patterns on seismic profiles. Summary of the Invention

[0008] To overcome the defects and shortcomings of the existing technology, this invention provides a method for identifying strike-slip faults using fault dip angle curves. The purpose of this invention is to address the difficulty in distinguishing strike-slip faults from normal / reverse faults based on fault characteristics in seismic profiles during seismic interpretation. This invention provides a method for identifying strike-slip faults using fault dip angle profile curve patterns from seismic / geological profiles, providing technical support for fault property identification in seismic interpretation and tectonic analysis.

[0009] To address the problems existing in the prior art and achieve effective identification of strike-slip faults on seismic profiles, the present invention is implemented through the following technical solution.

[0010] This invention provides a method for identifying strike-slip faults using fault dip curves, the method comprising the following steps: S1. Obtain fault interpretation results for the study area; S2. Measure the fault dip angle data based on the fault interpretation results obtained in step S1; S3. Based on the fault dip angle data obtained in step S2, draw dip angle curves and dip angle change rate curves. S4. Identify strike-slip faults using fault dip angle curves and dip angle change rate curves.

[0011] In a further preferred embodiment, if the study area already has seismic profile fault interpretation results or has geological profiles, then the existing fault interpretation results in the study area can be directly obtained.

[0012] Further preferably, if no fault interpretation results are available for the study area, fault interpretation results for the study area can be obtained through the following steps, the specific steps of which include: S101. Obtain seismic and drilling data for the study area; S102. Based on the seismic and drilling data of the study area, conduct detailed stratigraphic interpretation; S103. Based on the stratigraphic interpretation results obtained in step S102, conduct fault profile interpretation of the study area.

[0013] In a further preferred embodiment, in step S101, based on the seismic and drilling data of the study area, the geological background and fault distribution of the study area are analyzed, and typical faults of typical fault zones are selected for research.

[0014] In a further preferred embodiment, in step S102, when performing detailed stratigraphic interpretation, a seismic profile with high seismic resolution and significant stratigraphic and fault response characteristics is selected. Strata with clear stratigraphic positions are used as the main target layers for stratigraphic interpretation. Seismic-geological stratigraphic positioning is performed, and detailed stratigraphic interpretation is carried out, while also taking into account the number of layers for densification interpretation above and below.

[0015] In a further preferred embodiment, in step S103, when interpreting fault profiles in the study area, a typical seismic profile with good quality perpendicular to the fault strike is selected, the seismic response characteristics of the fault are analyzed, and fault profile interpretation is performed.

[0016] In a further preferred embodiment, step S103 involves analyzing the seismic response characteristics of the fault and interpreting the fault profile. Specifically, this means determining the stratified morphology of the fault, analyzing the strata crossed by the fault, clarifying the relationship between the fault location and the fault combination, and interpreting the fault displacement and dip angle of the crossed strata in detail.

[0017] More preferably, step S2, measuring the fault dip angle data, specifically includes the following steps: S201. Select typical seismic profiles with large fault displacements perpendicular to the fault strike, and check and verify the stratigraphic and fault interpretation results of the measured locations. S202. Measure the dip angles of multiple fault zones on the same cross section separately, and measure the dip angles of fault combinations with large differences between the upper and lower parts of the same fault zone separately. When measuring multiple fault zones on the same cross section separately, keep the measured strata the same, starting from the stratum with significant fault displacement at the upper part of the fault, and then measure the apparent dip angles of two different strata downwards in sequence. In strata with large dip angle changes, carry out detailed interpretation and densified measurements. S203. For fault zones with small upper fault displacement, insignificant downward fault points, and large deep stratum intervals, the analysis and data measurement results of adjacent profiles are selected as auxiliary data.

[0018] In a further preferred embodiment, step S3 specifically involves, based on the tilt angle data measurement in step S2, verifying and statistically analyzing the tilt angle measurement data, and compiling a tilt angle curve and a tilt angle change rate curve.

[0019] In a further preferred embodiment, when compiling dip angle curves, the dip angle data of the profile is statistically analyzed, the dip angle data is checked and corrected, and dip angle data tables of different faults and different layers are compiled respectively. The depth-dip angle curves are then plotted using the dip angle data corresponding to the time depth of different layers.

[0020] Furthermore, when compiling dip curves for the same fault zone, dip data from the same stratum are selected.

[0021] Furthermore, when plotting the dip angle change rate curve, the uppermost layer with a significant fault displacement is selected from the same fault breaks, and its dip angle is used as the initial value A0. The dip angles A of different layers at different depths are then calculated sequentially downwards. i rate of change A c The calculation method is A c =(A i -A0) / A0, where A0 represents the dip angle of the uppermost layer, A iTo measure the dip angle of the layer segment, i is the layer segment number from top to bottom, i=1,2,3….

[0022] In a further preferred embodiment, step S4 involves identifying strike-slip faults using fault dip angle curves and dip angle change rate curves. Specifically, this means comparing and analyzing the dip angle curves and dip angle change rate curves of the seismic profiles of faults in the study area, and using the curve distribution patterns to identify strike-slip faults.

[0023] More preferably, if the fault dip curve shows a linear updip or the dip change rate curve shows a wavy change, then the fault corresponding to the dip curve or dip change rate curve is identified as a strike-slip fault.

[0024] Compared with the prior art, the beneficial technical effects of the present invention are as follows: 1. This invention innovatively proposes a unique method for identifying strike-slip faults based on fault dip angle and dip angle change rate curve patterns, making it possible to directly identify strike-slip faults from seismic profiles, greatly improving the pertinence and accuracy of strike-slip fault identification. It effectively solves the dilemma in existing technologies of lacking a unified standard to distinguish strike-slip faults from normal / reverse faults, constructing a qualitative-semi-quantitative and highly intuitive identification chart, significantly improving the reliability and credibility of strike-slip fault prediction results, and reducing the risk of misjudgment.

[0025] 2. This invention is specifically applicable to identifying strike-slip faults using seismic time profiles in sedimentary basin scenarios. The operation process is simple and easy to implement and promote, significantly reducing the technical threshold and labor costs of strike-slip fault identification. It allows for flexible acquisition of fault interpretation results based on the actual conditions of the study area. Whether directly utilizing existing results or obtaining data through rigorous multi-step data collection and analysis when no results are available, the method's universality and practicality are ensured. During the measurement of fault dip angle data, multi-dimensional measurement strategies, such as targeted measurements of different types of fault zones, data verification, and statistical analysis, ensure the accuracy and completeness of the dip angle data. This lays a solid foundation for the subsequent accurate plotting of dip angle curves and dip angle change rate curves, effectively improving the scientific rigor and precision of the entire strike-slip fault identification process.

[0026] 3. By systematically acquiring seismic data, drilling data, and existing fault interpretation results (if any) of the study area, this invention effectively integrates multi-source geological data, fully explores the potential value of various types of data in strike-slip fault identification, reduces the waste of data resources, and improves the overall utilization efficiency of geological exploration data.

[0027] 4. When performing detailed stratigraphic interpretation and fault profile interpretation, this invention carefully selects seismic profiles with high seismic resolution and significant stratigraphic and fault response characteristics, and clearly identifies the main target layer with clear stratigraphic position and reasonably densifies the number of interpretation layers above and below the stratigraphic position. This enables extremely accurate determination of stratigraphic structural morphology and various characteristics of faults, including fault crossing position, fault location, fault displacement and dip angle, etc., providing extremely detailed and reliable basic geological structural information for the accurate identification of strike-slip faults.

[0028] 5. In the stage of measuring fault dip angle data, this invention has formulated differentiated measurement schemes for different types of fault zones (such as typical seismic profiles with large fault displacement perpendicular to the fault strike, fault zones with small upper fault displacement and large deep layer intervals, etc.). Furthermore, it measures multiple fault zones and fault combinations with large differences between the upper and lower parts of the same fault zone on the same profile. It also conducts detailed interpretation and densified measurement in the segments with large dip angle changes. From multiple dimensions, it ensures the comprehensiveness, accuracy and representativeness of fault dip angle measurement data, thereby significantly improving the accuracy and reliability of strike-slip fault identification based on dip angle data.

[0029] 6. This invention is based on rigorous dip angle measurement data verification and statistical analysis to compile dip angle curves and dip angle change rate curves. By reasonably selecting data sources for plotting depth-dip angle curves (such as dip angle data from statistical analysis profiles, checking and correcting dip angle data, selecting dip angle data from the same stratum, etc.) and accurately calculating the change rate value of the dip angle change rate curve, the plotted curves can scientifically and intuitively reflect fault characteristics. This provides a powerful visualization analysis tool for accurately identifying strike-slip faults using curve distribution patterns, greatly improving the intuitiveness and accuracy of strike-slip fault identification.

[0030] 7. This invention has broad regional applicability. Because this method can flexibly adjust the way fault interpretation results are obtained according to the actual situation of the study area, and considers coping strategies under different geological conditions in each data processing and analysis stage, such as for seismic profiles of different qualities and different types of fault zones, this method has strong regional adaptability. It is not only applicable to sedimentary basins, but also has high application and promotion value for other areas with similar geological structural features or exploration needs. It can effectively expand the application scope of strike-slip fault identification technology and promote the development of the geological exploration industry in different regions. Attached Figure Description

[0031] Figure 1 This is a flowchart of the method for identifying strike-slip faults using fault dip curves according to the present invention; Figure 2 These are typical dip angle curves of strike-slip faults, normal faults, and reverse faults that extend to the basement, varying with depth. Figure 3The dip angle curves of strike-slip faults in shallow layers, similar to normal / reverse faults, are shown on the cross-section, illustrating curve patterns such as linear growth, wavy fluctuation, and constant-growth of the dip angle of strike-slip faults. Figure 4 These are typical dip angle variation rate curves of strike-slip faults, normal faults, and reverse faults that extend to the basement, as a function of depth. Figure 5 The dip angle change rate curves of shallow strike-slip faults resembling normal / reverse faults on the cross-section show linear growth, horizontal linear, and wavy rate change curve patterns of strike-slip faults. Figure 6 This is a typical seismic profile; the dotted lines represent stratigraphic horizons (labeled C1-C11), the thick dotted lines represent the main seismic-geological horizons, the thin dotted lines represent the auxiliary horizons, and the solid lines represent faults (F1, F1-1, F1-2, F2, F2-1, F2-2 fault numbers). Figure 7 for Figure 6 The seismic profile diagram shows the dip angle curves of the upper and lower parts of the two faults; Figure 8 for Figure 6 The seismic profile diagram shows the rate of change of the dip angle of the upper and middle-lower parts of the two faults. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1 As a preferred embodiment of the present invention, please refer to the appendix to the specification. Figure 1 As shown in the figure, this embodiment discloses a method for identifying strike-slip faults by fault dip curves. In this embodiment, the study area is a mature oil and gas exploration area with relatively complete seismic profile fault interpretation results and geological profile data.

[0034] First, perform step S1 to directly obtain existing fault interpretation data within the study area.

[0035] Next, in step S2, based on the obtained results, typical seismic profiles with vertical fault strikes and large displacements are selected. After carefully checking and verifying the stratigraphic and fault interpretation results of the measured area, multiple fault zones on the same profile are measured separately. During the measurement, the same stratigraphic level is maintained. Starting from the upper part of the fault with a significant displacement, the apparent dip angles of different stratigraphic levels are measured sequentially downwards. In particular, detailed interpretation and densified measurements are carried out in the stratigraphic levels with large dip angle changes. At the same time, dip angle measurements are also carried out separately for fault combinations with large differences between the upper and lower parts of the same fault zone.

[0036] Then, proceed to step S3. Based on the dip angle data obtained in step S2, perform dip angle measurement data verification and statistical analysis. Statistically analyze the dip angle data of the profile and check and correct it. Compile dip angle data tables for different faults and different layers. Plot depth-dip angle curves using dip angle data corresponding to different layer depths over time. When compiling dip angle curves for the same fault zone, strictly select dip angle data from the same layer. When plotting the dip angle change rate curve, select the uppermost layer with a significant fault displacement at the break of the same fault, and use its dip angle as the initial value A0, according to formula A... c =(A i -A0) / A0 are used to calculate the fault dip angle A at different depths of different layers downwards. i rate of change A c .

[0037] Finally, in step S4, the dip angle curves and dip angle change rate curves of the seismic profiles of the faults in the study area were compared and analyzed. It was found that the dip angle curve of a certain fault showed a linear upward dip. According to the identification rules, the fault was determined to be a strike-slip fault.

[0038] Example 2 As another preferred embodiment of the present invention, please refer to the appendix to the specification. Figure 1 As shown in the figure, this embodiment discloses a method for identifying strike-slip faults by fault dip curves. In this embodiment, the study area is a new exploration area with no existing fault interpretation results.

[0039] In step S101, seismic and drilling data of the study area are collected, and the geological background and fault distribution of the study area are analyzed in depth. Typical faults of representative typical fault zones are selected as the key research objects.

[0040] In step S102, seismic profiles with high seismic resolution and significant stratigraphic and fault response characteristics are carefully selected. Strata with clear stratigraphic positions are identified as the main target layers for stratigraphic interpretation. Seismic-geological stratigraphic calibration is carried out, and detailed stratigraphic interpretation is conducted. At the same time, the number of interpretation layers above and below is also considered to obtain detailed stratigraphic interpretation results.

[0041] Step S103 involves selecting typical seismic profiles with good seismic profile quality that are perpendicular to the fault strike, based on the detailed stratigraphic interpretation results mentioned above. This process involves analyzing the seismic response characteristics of the faults, determining the fault stratification, accurately analyzing the strata crossed by the faults, clarifying the fault location and fault combination relationship, and meticulously interpreting the fault displacement and dip angle of the crossed strata. This completes the interpretation of the fault profiles in the study area, thus yielding the fault interpretation results.

[0042] The subsequent steps S2, S3, and S4 are the same as in Example 1. By measuring dip angle data, drawing curves, and analyzing curve distribution patterns, the strike-slip fault in the study area was successfully identified.

[0043] Example 3 As another preferred embodiment of the present invention, please refer to the appendix to the specification. Figure 1 As shown in the figure, this embodiment discloses a method for identifying strike-slip faults by fault dip curves. The study area is a complex geological structure region. There are existing seismic profile fault interpretation results, but data for some areas are missing or inaccurate.

[0044] Step S1 first obtains existing, relatively reliable fault interpretation data.

[0045] For areas with missing or inaccurate data, fault interpretation results are supplemented according to steps S101-S103. In S101, seismic and drilling data for the area are comprehensively collected, and the geological background and fault distribution are analyzed in depth to select key fault zones and faults. In S102, appropriate seismic profiles are selected to conduct detailed stratigraphic interpretation. In S103, fault profile interpretation is performed for the area to determine various fault characteristics.

[0046] Then, step S2 is performed to measure the dip angle data of the faults in the entire study area, including verification measurements of existing results areas and comprehensive measurements of newly acquired results areas. The measurement process follows the principles of selecting typical profiles and measuring multiple fault zones and fault combinations separately.

[0047] Step S3 involves integrating all measurement data for dip angle measurement data verification and statistical analysis, plotting dip angle curves and dip angle change rate curves, selecting data from the same stratigraphic level within the same fault zone to plot dip angle curves, and calculating the change rate according to the formula to plot the change rate curve.

[0048] Finally, in step S4, the dip curves and dip change rate curves of the entire study area are compared and analyzed. Based on the curve distribution pattern, multiple strike-slip faults are identified, and their distribution and characteristics are recorded and analyzed in detail.

[0049] Example 3 As another preferred embodiment of the present invention, please refer to the appendix to the specification. Figure 1As shown in the figure, this embodiment discloses a method for identifying strike-slip faults by fault dip curves. The study area is a complex geological structure area, where seismic data is difficult to obtain and of inconsistent quality, and there are no readily available fault interpretation results.

[0050] In step S101, we painstakingly acquired seismic and drilling data for the study area using advanced detection technologies. Despite fluctuations in data quality, we carefully analyzed the geological background and fault distribution, and selected relatively reliable typical fault zones and faults for further study.

[0051] In step S102, among a limited number of high-quality seismic profiles, profiles with relatively high seismic resolution and relatively obvious stratigraphic and fault response characteristics are selected to determine the main target layers for seismic-geological stratigraphic calibration and fine stratigraphic interpretation, while taking into account the number of densified interpretation layers above and below as much as possible.

[0052] Step S103 utilizes high-quality seismic profiles perpendicular to the fault strike to analyze the seismic response characteristics of the fault in detail. Even with poor data quality, various technical means are used to repeatedly determine the fault layer structure, fault crossing horizons, fault location and fault combination relationships, as well as fault displacement and dip angle, to obtain preliminary fault interpretation results.

[0053] In step S2, due to data quality issues, greater emphasis is placed on data verification and multi-section auxiliary measurements when measuring dip angle data. Relatively reliable typical seismic profiles with vertical fault strikes and large fault displacements are selected to check and calibrate the stratigraphic and fault interpretation results at the measurement locations. Multiple fault zones on the same profile are measured separately, and dip angle measurements are performed on fault combinations with significant differences between the upper and lower fault zones, keeping the measurement horizons consistent. Starting from the upper fault segment with a significant fault displacement, the apparent dip angles of two different lower layers are measured sequentially. In segments with large dip angle changes, detailed interpretation and densified measurements are conducted. For fault zones with small upper fault displacements, insignificant downward fault points, and large intervals between deep layers, the analysis and measurement results of adjacent profiles are fully utilized as auxiliary data.

[0054] Step S3 involves verifying and statistically analyzing the measured dip angle data, compiling dip angle curves and dip angle change rate curves. When compiling dip angle curves for the same fault zone, dip angle data from the same stratum are selected. When plotting the dip angle change rate curve, the uppermost stratum with a significant fault displacement at the point where the same fault breaks is selected, and its dip angle is used as the initial value A0. The fault dip angles A at different depths are then calculated sequentially downwards. i rate of change A c The calculation method is A c =(A i -A0) / A0.

[0055] Step S4 involves comparing and analyzing the dip angle curves and dip angle change rate curves of the seismic profiles of the faults in the study area. Although the curves exhibit some fluctuations, the strike-slip faults in the study area were successfully identified based on the curve distribution pattern, providing crucial fault information for deep-sea geological exploration and resource development.

[0056] Example 5 As another preferred embodiment of the present invention, please refer to the appendix to the specification. Figure 1 Appendix Figure 2 Appendix Figure 3 Appendix Figure 4 and attached Figure 5 As shown in the figure, this embodiment provides a method for identifying strike-slip faults using fault dip angle curves from seismic profiles. The steps are as follows: S1. Obtain fault interpretation results for the study area. If seismic profile fault interpretation results or geological profiles are available, the existing fault interpretation results can be used directly. If there are no seismic profile fault interpretation results, follow these steps for fault interpretation: ① Load seismic data. Load seismic and drilling data for the study area and analyze the regional fault distribution characteristics; ② Conduct detailed stratigraphic interpretation. Prioritize seismic profiles with high seismic resolution and significant stratigraphic and fault response characteristics, perform seismic-geological stratigraphic calibration, and conduct stratigraphic interpretation. ③ Conduct fault profile interpretation. Select typical seismic profiles with good quality perpendicular to the fault strike, analyze the seismic response characteristics of the fault, and conduct fault profile interpretation.

[0057] S2. Measure the fault dip angle data based on the fault interpretation results obtained in step S1; the specific steps are as follows: ①Section selection. Select typical seismic sections with large displacement perpendicular to the fault strike, especially sections where the dip angle may change, and verify the stratigraphic and fault interpretation results.

[0058] ② Measure fault dip angle data. Within the same fault zone, starting from the segment with significant fault displacement at the top of the fault, measure the dip angle (A) of different layers sequentially downwards. i (where i is the specific segment number). In depth-migrated seismic profiles, assuming consistent longitudinal and transverse scales, the measured dip angle represents the true dip angle. If the scales are inconsistent, or if the fault dip angle measured on a time-seismic profile is the apparent dip angle, then in densely packed segments with similar dip angles, some segment data can be omitted; however, in segments with large dip angle variations, more detailed interpretation and denser measurements are required.

[0059] S3. Based on the fault dip angle data obtained in step S2, plot the dip angle curve and the dip angle change rate curve; the specific steps are as follows: ① Draw dip angle curves. Statistically analyze the dip angle data of the profile, check and correct the dip angle data, compile dip angle data tables for different layers, and draw depth-dip angle curves (e.g., using dip angle data corresponding to different depths (or time depths)). Figure 2 and Figure 3 ).

[0060] ② Plot the dip angle change rate curve. Select the uppermost layer with a significant fault displacement along the same fault break, and use its dip angle as the initial value (A0). Calculate the dip angles of different layers downwards sequentially (A... i The rate of change of (A) c The calculation method is as follows: A c = (A i -A0) / A0 (where Ai is the dip angle of the measured segment, and i is the segment number from top to bottom: 1, 2, 3, ...). The dip angle change rate can intuitively reflect the dip angle variation characteristics on the profile, avoiding the comparison problems caused by large dip angle value variations and large measurement errors on different profiles. At the same time, if the cross-section on the seismic profile is not significant and the reliability of the dip angle data is low, the dip angle change rate can highlight the dip angle variation and can replace the dip angle curve to identify strike-slip faults.

[0061] S4. Identify strike-slip faults using fault dip angle curves and dip angle change rate curves; the specific steps are as follows: ① Identify strike-slip faults using fault dip angle curves. Generally, strike-slip faults are steep and vertical, with dip angles close to 90°, while normal and reverse faults have smaller dip angles, tending to decrease downwards. Figure 2 Therefore, strike-slip faults can be identified using dip profiles approaching 90°. However, many strike-slip faults also have relatively small dip angles in shallow layers, making them difficult to identify when deep seismic data is unclear. Based on the characteristic that the dip angle of a strike-slip fault increases downwards, while the dip angles of normal and reverse faults decrease, the dip angle profile of a strike-slip fault shows a trend of increasing dip angle with depth, while normal / reverse faults show a trend of decreasing or remaining unchanged. Figure 3 Therefore, based on the curve patterns of linear increase in dip angle, wavy fluctuation, and constant-increase, it can be identified as a strike-slip fault.

[0062] ② Identify strike-slip faults using the dip angle change rate curve. Generally, the dip angle of a strike-slip fault may increase downwards, while the dip angle of a normal / reverse fault may decrease downwards. Therefore, the dip angle change rate of a strike-slip fault shows a positive increasing trend with depth, while the dip angle change rate of a normal / reverse fault shows a negative increasing trend with depth. Figure 4This positively increasing fault dip rate change curve pattern can be identified as a strike-slip fault. In some cases, the dip angles of normal / reverse faults and strike-slip faults in the upper part of the seismic profile may be consistent, and the change rates are not large, making it difficult to identify strike-slip faults using shallow dip angle data. However, by tracing downwards, it is possible to find when the fault dip angle becomes steeper and the dip rate of change is positive ( Figure 5 (This can also be identified as a strike-slip fault.) In summary, the appearance of a linear updip or a wavy updip curve in the fault dip angle can be used to identify strike-slip faults.

[0063] Example 6 As a preferred embodiment of the present invention, please refer to the appendix to the specification. Figure 1 As shown in the figure, this embodiment discloses a method for identifying strike-slip faults through fault dip curves. The method includes the following steps: S1. Obtain fault interpretation results for the study area; S2. Measure the fault dip angle data based on the fault interpretation results obtained in step S1; S3. Based on the fault dip angle data obtained in step S2, draw dip angle curves and dip angle change rate curves. S4. Identify strike-slip faults using fault dip angle curves and dip angle change rate curves.

[0064] Specifically, for the fault interpretation in step S1, the seismic response characteristics of faults on the seismic profile are analyzed, and a detailed interpretation of the faults is carried out. The specific steps are as follows: ① Data loading. Load seismic and drilling data, analyze the regional geological background and fault distribution, and select typical faults in typical fault zones for research.

[0065] ② Stratigraphic Interpretation. Prioritize seismic profiles with high seismic resolution and significant stratigraphic and fault response characteristics, using clearly defined stratigraphic horizons as the primary target horizons for stratigraphic interpretation. Figure 6 (Medium-coarse line stratigraphy), conduct seismic-geological stratigraphic mapping, perform stratigraphic interpretation, and take into account the densification of the upper and lower stratigraphic layers. Figure 6 (Medium-fine line layer).

[0066] ③ Interpretation of fault profiles. Prioritize typical seismic profiles with high quality that are perpendicular to the fault strike. Figure 6 The study analyzes the seismic response characteristics of faults and interprets faults; it focuses on determining the strata of fault layers, analyzing the strata crossed by faults, clarifying the relationship between fault location and fault combination, and interpreting the fault displacement and dip angle of the crossed strata in detail.

[0067] For the dip angle measurement in step S2, fault dip angle (A) measurement and analysis are performed on seismic profiles with high reliability in stratigraphic and fault interpretation. The specific steps are as follows: ①Section Selection and Verification. Select typical seismic sections with large displacement perpendicular to the fault strike, especially sections where the dip angle may change (e.g., Figure 6 The stratigraphic and fault interpretation results of the measured area were checked and verified. Two fault zones on the same profile were measured separately, and dip measurements were performed on fault combinations with significant differences above and below the same fault zone. Figure 6 When some stratigraphic interpretations or discontinuities are inaccurate, refer to the results of nearby seismic profiles to verify the relevant interpretations. When the reliability of auxiliary stratigraphic measurement data is low, refer to the interpretation schemes for key stratigraphic levels and the interpretation results of nearby seismic profiles.

[0068] ② Measurement of fault dip angle data. Measurements were conducted separately for the two fault zones, but the stratigraphic levels remained the same. Starting from the segment with significant fault displacement at the upper part of the fault, the apparent dip angles of different stratigraphic levels were measured sequentially downwards. In segments with large dip angle changes, detailed interpretation and densified measurements were carried out to correct the accuracy of the dip angle measurement data.

[0069] ③ Conduct fault dip angle measurements on auxiliary profiles. The upper fault displacement is small and the downward fault point is not significant, while the deep layer intervals are large. Therefore, analysis and data measurement of adjacent profiles are added as an auxiliary measure.

[0070] Regarding the plotting of the dip angle curve and dip angle change rate curve in step S3, based on the dip angle measurements, dip angle measurement data are verified and statistically analyzed to compile dip angle profiles and dip angle change rate profiles. The specific steps are as follows: ① Draw dip angle curves. Statistically analyze the dip angle data of the profile, check and correct the dip angle data, and compile dip angle data tables for different faults and different layers. Plot depth-dip angle curves using the dip angle data corresponding to different time depths in different layers (e.g., Figure 7 When compiling dip profiles for the same fault zone, dip data from the same strata should be selected as much as possible for easy comparison.

[0071] ② Compile a dip angle change rate curve. Select the uppermost layer with a significant fault displacement where the same fault breaks, and use its dip angle as the initial value (A0). Using the method described above, calculate the dip angle change rate (A0) of different layers downwards sequentially. c ) diagram (e.g.) Figure 8 ).

[0072] For the strike-slip fault identification in step S4, a comparative analysis of the faults was conducted. Figure 6 The dip angle and dip angle change rate curves of the seismic profile are used to identify strike-slip faults based on the curve distribution pattern. The specific steps are as follows: ① The upper fault of the second fault zone (F2-1). This fault exhibits downdip characteristics in both the downdip angle curve and the rate of change of dip angle. Figure 7 and Figure 8Furthermore, the detached portion of the fault is far from the lower main strike-slip fault, indicating that it is a later reverse fault.

[0073] ② The upper fault of the first fault zone (F1-1). This fault has a large dip angle, merges downward into the main fault, and exhibits characteristics of upward dip in both the downward dip angle curve and the rate of change of dip angle. Figure 7 and Figure 8 ()) can be identified as a later-stage inherited strike-slip fault.

[0074] ③ Main fault. Although the main fault in the middle and lower part of the second fault zone exhibits layered deformation, the fault dip angle is large, close to 90°, and the dip curve and dip angle change rate show significant upward dip characteristics. Figure 7 and Figure 8 The fault can be identified as a strike-slip fault. The dip angle of the fault in the middle of the first fault zone shows a slight downward decrease, with a certain upward thrust component (F1-2). However, it also shows an upward dip curve and an upward dip rate of change, which are typical dip angle patterns of strike-slip faults. Therefore, it is determined to be a strike-slip fault.

[0075] ④ Comprehensive analysis shows that this area exhibits the superimposed development of multiple fault phases. In the early stage, strike-slip faults developed, followed by localized compressional-torsional deformation during the development of inherited strike-slip faults in the middle stage (F1-2). In the later stage, thrust faults superimposed on the strike-slip faults, and a local fault (F1-1) was incorporated into the main fault through strike-slip deformation. Based on this, the fault interpretation scheme was revised, fault properties were labeled, and a fault interpretation model was provided for seismic interpretation in this area, completing a refined and reasonable interpretation of the faults.

[0076] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for identifying strike-slip faults using fault dip curves, characterized in that, The method includes the following steps: S1. Obtain fault interpretation results for the study area; S2. Measure the fault dip angle data based on the fault interpretation results obtained in step S1; S3. Based on the fault dip angle data obtained in step S2, draw dip angle curves and dip angle change rate curves. S4. Identify strike-slip faults using fault dip angle curves and dip angle change rate curves.

2. The method for identifying strike-slip faults using fault dip curves as described in claim 1, characterized in that: If the study area already has seismic profile fault interpretation results or geological profiles, then the existing fault interpretation results in the study area can be directly obtained.

3. The method for identifying strike-slip faults using fault dip curves as described in claim 1, characterized in that: If no fault interpretation results are available for the study area, fault interpretation results for the study area shall be obtained through the following steps, the specific steps of which include: S101. Obtain seismic and drilling data for the study area; S102. Based on the seismic and drilling data of the study area, conduct detailed stratigraphic interpretation; S103. Based on the stratigraphic interpretation results obtained in step S102, conduct fault profile interpretation of the study area.

4. The method for identifying strike-slip faults using fault dip curves as described in claim 3, characterized in that: In step S101, based on the seismic and drilling data of the study area, the geological background and fault distribution of the study area are analyzed, and typical faults of typical fault zones are selected for research.

5. The method for identifying strike-slip faults using fault dip curves as described in claim 3, characterized in that: In step S102, when performing detailed stratigraphic interpretation, seismic profiles with high seismic resolution and significant stratigraphic and fault response characteristics are selected. Strata with clear stratigraphic positions are used as the main target layers for stratigraphic interpretation. Seismic-geological stratigraphic positioning is performed, and detailed stratigraphic interpretation is carried out, while also considering the number of layers for densification interpretation above and below.

6. The method for identifying strike-slip faults using fault dip curves as described in claim 3, characterized in that: In step S103, when interpreting fault profiles in the study area, typical seismic profiles with good quality perpendicular to the fault strike are selected, and the seismic response characteristics of the faults are analyzed to interpret the fault profiles.

7. The method for identifying strike-slip faults using fault dip curves as described in claim 6, characterized in that: In step S103, the seismic response characteristics of the fault are analyzed and the fault profile is interpreted. Specifically, this means determining the layered structural morphology of the fault, analyzing the strata crossed by the fault, clarifying the relationship between the fault location and the fault combination, and interpreting the fault displacement and dip angle of the crossed strata in detail.

8. A method for identifying strike-slip faults using fault dip curves as described in any one of claims 1-7, characterized in that: Step S2 specifically includes the following steps for measuring fault dip angle data. S201. Select typical seismic profiles with large fault displacements perpendicular to the fault strike, and check and verify the stratigraphic and fault interpretation results of the measured locations. S202. Measure the dip angles of multiple fault zones on the same cross section separately, and measure the dip angles of fault combinations with large differences between the upper and lower parts of the same fault zone separately. When measuring multiple fault zones on the same cross section separately, keep the measured strata the same, starting from the stratum with significant fault displacement at the upper part of the fault, and then measure the apparent dip angles of two different strata downwards in sequence. In strata with large dip angle changes, carry out detailed interpretation and densified measurements. S203. For fault zones with small upper fault displacement, insignificant downward fault points, and large deep stratum intervals, the analysis and data measurement results of adjacent profiles are selected as auxiliary data.

9. A method for identifying strike-slip faults using fault dip curves as described in any one of claims 1-7, characterized in that: Step S3 specifically involves verifying and statistically analyzing the tilt angle measurement data based on the tilt angle data measured in step S2, and compiling tilt angle curves and tilt angle change rate curves.

10. The method for identifying strike-slip faults using fault dip curves as described in claim 9, characterized in that: When compiling dip angle curves, statistical analysis of the dip angle data of the profile is performed, dip angle data is checked and corrected, and dip angle data tables of different faults and different layers are compiled. Depth-dip angle curves are then plotted using dip angle data corresponding to different time depths in different layers.

11. The method for identifying strike-slip faults using fault dip curves as described in claim 10, characterized in that: When compiling dip curves for the same fault zone, dip data from the same stratum should be selected.

12. The method for identifying strike-slip faults using fault dip curves as described in claim 9, characterized in that: When plotting the dip angle change rate curve, select the uppermost layer with a significant fault displacement that is broken by the same fault, and use its dip angle as the initial value A0. Then, calculate the fault dip angle A at different depths of different layers sequentially downwards. i rate of change A c The calculation method is A c =(A i -A0) / A0, where A0 represents the dip angle of the uppermost layer, A i To measure the dip angle of the layer segment, i is the layer segment number from top to bottom, i=1,2,3….

13. A method for identifying strike-slip faults using fault dip curves as described in any one of claims 1-7, characterized in that: In step S4, strike-slip faults are identified by fault dip angle curves and dip angle change rate curves. Specifically, this involves comparing and analyzing the dip angle curves and dip angle change rate curves of the seismic profiles of faults in the study area, and using the curve distribution patterns to identify strike-slip faults.

14. The method for identifying strike-slip faults using fault dip curves as described in claim 13, characterized in that: If the fault dip curve shows a linear updip or the dip change rate curve shows a wavy change, then the fault corresponding to the dip curve or dip change rate curve is identified as a strike-slip fault.

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