Five-dimensional seismic multi-scale dominant azimuth fusion fault description method

Abstract

The application provides a five-dimensional seismic multi-scale advantage azimuth fusion fault description method, and the fault description method comprises the following steps: S1, acquiring the basic geological profile of a research area; S2, generalized transform spectral decomposition, constructing a frequency domain optimized frequency volume; S3, constructing a frequency division and advantage azimuth fusion volume based on the optimized frequency volume; and S4, describing multi-scale and multi-azimuth complex fractures based on RGB-IHS transformation. Based on the frequency division and advantage azimuth fusion volume, different strikes and different scales of fractures are all displayed on a structure map, and the method has high practical value and strong operability.

Description

Technical Field

[0001] This invention relates to the field of oil and gas exploration technology, and in particular to a five-dimensional seismic multi-scale dominant orientation fusion fault description method. Background Technology

[0002] Exploration practice shows that with the increasing demand for oil and gas energy, fault interpretation is becoming an increasingly important and challenging aspect of exploration. Multi-scale, multi-directional faults play a controlling role in trap formation, reservoir improvement, oil and gas sealing, and oil and gas conduit transportation. Therefore, in-depth research on multi-scale, multi-directional fault description techniques is both necessary and significant.

[0003] It is well known that the azimuth perpendicular to the fault strike, also known as the dominant azimuth, provides the best imaging results. However, fault distribution in each zone has multiple directions, requiring multiple dominant azimuths for zone fault distribution imaging. Furthermore, the fault scale varies within each zone; different frequency seismic data can detect faults of different scales. How can the detection results of faults at different scales and with multiple dominant azimuths be fused and displayed on a single structural map? This is a problem that five-dimensional seismic tectonic interpretation needs to solve. In recent years, with the development of five-dimensional seismic technology, a high-quality data foundation has been provided for the detailed interpretation of multi-azimuth and multi-scale faults. Its wide azimuth, wide bandwidth, and high density characteristics can improve the detailed identification of multi-azimuth and multi-angle faults. However, existing research mainly focuses on the selection of azimuth and offset stacking parameters.

[0004] Chinese patent application number CN20210508976X discloses a method for identifying low-order faults in the pre-stack OVT domain based on azimuth and frequency domain control. The method mainly includes the following steps: performing anisotropy analysis of pre-stack OVT domain gathers; analyzing the tectonic stress characteristics of the target area, optimizing and dividing the OVT domain gather data by azimuth angle, and performing partial data overlay on the OVT gathers; performing improved generalized S-transform spectral decomposition to construct data volumes with different azimuth angles and frequency domain controls; extracting coherence class attribute analysis; and drawing a fault distribution plan map of the target area.

[0005] Although this technique considers the anisotropy and frequency domain variation characteristics of low-order faults, it can reflect low-order faults that are difficult to identify using conventional data volumes. However, its drawback is that it only uses the optimal parameter combination of azimuth and frequency domain controlled by the low-order faults to identify them, thus missing a large amount of useful information. This results in unsatisfactory multi-scale, multi-azimuth fault detection, and consequently, the multi-scale, multi-azimuth fault detection results cannot be fused and displayed on a single structural map, causing significant inconvenience to oil and gas exploration. Currently, researchers both domestically and internationally lack a clear technique for five-dimensional seismic multi-scale dominant azimuth fusion fault description. Therefore, we have invented a new five-dimensional seismic multi-scale dominant azimuth fusion fault description technique, filling the gap in this field where similar research is lacking. Summary of the Invention

[0006] In view of the above problems, the present invention is proposed to provide a five-dimensional seismic multi-scale dominant orientation fusion fault description method that overcomes or at least partially solves the above problems.

[0007] According to one aspect of the present invention, a five-dimensional seismic multi-scale dominant azimuth fusion fault description method is provided, the fault description method comprising:

[0008] Step S1: Obtain the basic geological overview of the study area;

[0009] Step S2: Generalized transform spectral decomposition, constructing frequency domain optimized frequency division body;

[0010] Step S3: Based on the optimized frequency division body, construct a frequency division and advantageous orientation fusion body;

[0011] Step S4: Describe complex fractures of multiple scales and orientations based on RGB-IHS transformation.

[0012] Optionally, step S1: obtaining the basic geological overview of the study area specifically includes:

[0013] To obtain the basic geological overview of the study area, collect relevant data on tectonic evolution, understand the tectonic movements and stress directions experienced by the study area, and ensure the rationality of the tectonic interpretation results.

[0014] Optionally, step S1: obtaining the basic geological overview of the study area further includes:

[0015] To obtain the basic geological overview of the study area, the tectonic movements it has experienced, and the regional stress direction, and to conduct a detailed structural interpretation of the standard layers based on the well logging and well logging data of the drilled wells.

[0016] Optionally, the detailed construction interpretation of the standard layer specifically includes:

[0017] Based on the actual well logging data of the study area, the principal stress direction and the measured fault strike were determined, providing a basis for the optimal selection of azimuth data.

[0018] Optionally, the method based on actual well logging data of the study area may further include: performing fracture enhancement preprocessing on the seismic data volume.

[0019] Optionally, obtaining the basic geological overview, tectonic movements, and regional stress direction of the study area specifically includes:

[0020] Based on well logging curves such as sonic transit time and density, synthetic records are created to calibrate the formation, and formation and fault interpretation is performed. During the interpretation process, it is necessary to check whether the interpreted layers and faults are closed.

[0021] Optionally, step S2: generalized transform spectral decomposition, constructing a frequency domain optimized frequency divider specifically includes:

[0022] Spectral analysis was performed on the earthquake data collected for the study to determine the dominant frequency and frequency band range of the earthquake data, which were divided into three frequency bands: low, medium and high.

[0023] Optionally, step S2: Generalized transform spectral decomposition and construction of frequency domain optimized frequency division body further includes: when performing frequency division processing on seismic data, selecting a more accurate generalized S-transform algorithm for time-frequency analysis, selecting frequencies that can reflect multi-scale faults, and constructing a frequency domain optimized frequency division body.

[0024] Optionally, step S3: constructing a frequency division and advantageous orientation fusion body based on the optimized frequency division body specifically includes:

[0025] Based on the actual fracture characteristics, the direction of maximum principal stress, and the imaging effect after gather stacking, the azimuth range of the OVT data in the study area was optimized.

[0026] Optionally, step S3: constructing a frequency division and dominant azimuth fusion body based on the optimized frequency division body further includes:

[0027] Based on low, medium and high frequency subdivisions, azimuth data volumes that can reflect the dominant orientation of multi-scale faults are selected on the low, medium and high frequency subdivisions respectively.

[0028] OVT gathers are superimposed by azimuth angle, and the three dominant azimuth arrays based on frequency dividers are fused to construct a frequency divider and dominant azimuth fusion array.

[0029] Optionally, step S4: describing multi-scale, multi-directional complex fractures based on RGB-IHS transform specifically includes:

[0030] Based on the frequency division and dominant orientation fusion body, the RGB-IHS transformation fusion method is applied to map the RGB and IHS image fusion methods based on the frequency division and dominant orientation fusion body to each other, so that multi-scale and multi-directional tomography can be clearly displayed on the plane.

[0031] This invention provides a five-dimensional seismic multi-scale dominant azimuth fusion fault description method, comprising: Step S1: obtaining the basic geological overview of the study area; Step S2: generalized transform spectral decomposition to construct a frequency domain optimized frequency division body; Step S3: based on the optimized frequency division body, constructing a frequency division and dominant azimuth fusion body; Step S4: describing multi-scale, multi-azimuth complex faults based on RGB-IHS transform. Based on the frequency division and dominant azimuth fusion body, faults of different orientations and scales are all displayed on a single structural map, possessing high practical value and strong operability.

[0032] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 A flowchart of a five-dimensional seismic multi-scale dominant orientation fusion fault description method provided in an embodiment of the present invention;

[0035] Figure 2 This is a multi-attribute fusion processing flow based on RGB-IHS transformation in a specific embodiment of the present invention. Detailed Implementation

[0036] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0037] The terms "comprising" and "having," and any variations thereof, in the specification, embodiments, claims, and drawings of this invention are intended to cover non-exclusive inclusion, such as including a series of steps or units.

[0038] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0039] like Figure 1 As shown, Figure 1 This is a flowchart of the five-dimensional seismic multi-scale dominant azimuth fusion fault description technology of the present invention. The five-dimensional seismic multi-scale dominant azimuth fusion fault description technology includes the following steps:

[0040] In step 1, the basic geological conditions, tectonic movements, and regional stress directions of the study area are understood. Based on well logging and well logging data from existing wells, a detailed structural interpretation of the standard layers is performed. Based on actual well logging data from the study area, the principal stress directions and measured fault strikes are determined, providing a basis for the optimal selection of azimuth data. Fault enhancement preprocessing is performed on the seismic data volume to provide better seismic data for subsequent multi-scale, multi-dominant azimuth fault identification. In step 1, based on well logging curves such as sonic transit time and density, synthetic records are created to calibrate the strata, and stratigraphic and fault interpretation is performed. During the interpretation process, it is necessary to check whether the interpreted layers and faults are closed.

[0041] In step 2, spectral analysis is performed on the acquired seismic data to determine the dominant frequency and frequency band range, which are then divided into low, medium, and high frequency bands, laying a solid foundation for constructing an optimized frequency division system in the frequency domain. When processing the seismic data for frequency division, the more accurate generalized S-transform algorithm is preferred for time-frequency analysis, selecting frequencies that best represent multi-scale faults to construct an optimized frequency division system in the frequency domain.

[0042] In step 3, based on the actual fracture characteristics, the direction of maximum principal stress, and the imaging effect after gather stacking, the azimuth range of the OVT data in the study area is optimized. Based on low, medium, and high frequency subdivisions, azimuth data volumes that can reflect the dominant azimuth of multi-scale faults are selected on the low, medium, and high frequency subdivisions respectively. Then, OVT gathers are stacked by azimuth, and the three dominant azimuth volumes based on the frequency subdivisions are fused to finally construct a frequency-subdivision and dominant azimuth fused body.

[0043] In step 4, based on the frequency division and dominant orientation fusion body, the RGB-IHS transformation fusion method is applied to map the RGB and IHS image fusion methods based on the frequency division and dominant orientation fusion body to each other, so that the multi-scale and multi-directional tomography can be clearly displayed on a single structural map.

[0044] The following are specific embodiments of the application of the present invention.

[0045] Example 1

[0046] In a specific embodiment of the present invention, the study area is characterized by numerous faults and small fault blocks, with almost all traps, large and small, related to faults. The main faults trend north-south, northeast, and northwest, with low-order faults well-developed. How to display faults of different trends and scales on a single structural map is a pressing problem. Therefore, it is necessary to conduct in-depth research on five-dimensional seismic multi-scale dominant azimuth fusion fault description technology.

[0047] like Figure 1 This is a flowchart of the five-dimensional seismic multi-scale dominant orientation fusion fault description technology of the present invention.

[0048] In this embodiment, the five-dimensional seismic multi-scale dominant azimuth fusion fault description technology of the present invention includes the following steps:

[0049] In step 101, we learn about the basic geological conditions of the study area, collect relevant data on tectonic evolution, and become familiar with the tectonic movements and stress directions experienced by the study area. The main purpose of this step is to understand the basic geological framework and tectonic stress field of the study area to ensure the rationality of the fault interpretation results.

[0050] In step 101, based on the actual well logging data of the study area, the direction of principal stress and the measured strike of the fault are determined, providing a basis for the optimal selection of azimuth data. The wellbore collapse method for in-situ stress analysis mainly utilizes formation dip logging and imaging logging data. Based on the wellbore collapse azimuth image of the Sha-3 section in a certain area, it is considered that the direction of the maximum principal stress in that area is near northeast-east.

[0051] In step 101, fracture strengthening pretreatment is performed, which is the basis of this invention.

[0052] The main faults in a certain area exhibit three dominant trends: east-west, northeast, and northwest. The azimuth perpendicular to the fault trend, i.e., the dominant azimuth, provides the best imaging results. Therefore, fault enhancement preprocessing is performed in three azimuths: north-south, northeast, and northwest. Consequently, the azimuth- and offset-based stacked profiles show decreased continuity of phase axes and a reduced signal-to-noise ratio compared to the all-round, full-offset stacked profiles. To mitigate the reduced signal-to-noise ratio caused by azimuth- and offset-based stacking, signal-to-noise ratio and resolution improvement processing is necessary.

[0053] Fault enhancement preprocessing mainly involves dip-guided filtering of 3D seismic data. First, the dip and dip azimuth angles of the seismic data are estimated. Then, correlation-weighted median filtering is applied along the direction of the seismic reflection axis to remove random noise. Dip-guided filtering of the original 3D seismic data increases the continuity of the seismic reflection axis and highlights fault zone information.

[0054] A comparison of seismic profiles before and after dip-guided filtering shows that the continuity of seismic phase axes is enhanced, the discontinuities are more distinct, and the ability to identify small faults is improved, which can provide a better seismic data basis for subsequent seismic identification of strike-slip fault zones.

[0055] In step 101, the structural map of the Cenozoic standard stratigraphic layers is interpreted. Based on the well logging data from the drilled wells, the stratigraphy and faults are interpreted according to the conventional stratigraphic interpretation process. This step is the foundation of this invention. The specific interpretation steps are as follows: import the AC (acoustic transit time), Den (density), and other curves into the seismic interpretation software—synthetic record calibration of stratigraphy—stratigraphic and fault interpretation. During the interpretation process, it is necessary to check whether the interpreted layers and faults are closed. A total of two standard layers, T4 and T7, are interpreted. The process then proceeds to step 102.

[0056] In step 102, spectral analysis is performed on the seismic data of the study area to determine the dominant frequency and frequency band range of the seismic data. Spectral analysis of high-density 3D seismic data from a certain area shows that the dominant frequency of the actual seismic data is 25Hz, and the frequency band range is 5-45Hz. Based on this, the low, medium, and high frequency bands of the actual seismic data can be determined to be 1-10Hz, 11-25Hz, and 26-45Hz, respectively. Coherence slices from different frequency subdivisions at 10Hz, 25Hz, and 40Hz reflect information about faults at different scales. Low frequencies clearly and continuously identify main faults, while high frequencies are more sensitive to lower-order faults. The main east-west trending faults are clearly visible on the 10Hz frequency subdivision slice, while smaller faults are clearly visible on the 40Hz slice. The process then proceeds to step 103.

[0057] In step 103, the dominant azimuth is selected. The main fault trends in a certain region are east-west, northeast, and northwest. The azimuth perpendicular to the fault trend is the dominant azimuth. For large east-west trending faults, north-south trend is selected as the dominant azimuth on the 10Hz frequency division. For medium-sized northeast trending faults, northwest trend is selected as the dominant azimuth on the 25Hz frequency division. For low-order northwest-northwest trending faults, northeast trend is selected as the dominant azimuth.

[0058] In step 103, a frequency division and dominant azimuth fusion body is constructed based on the optimized frequency division body. Based on the 10Hz, 25Hz, and 40Hz frequency division bodies, azimuths such as north-south, northeast, and northeast-northeast are selected, and then OVT gathers are superimposed to finally form the frequency division and dominant azimuth fusion body. The process then proceeds to step 104.

[0059] In step 104, RGB-IHS transformation fusion processing is performed based on the frequency division and dominant orientation fusion.

[0060] Multi-attribute fusion processing flow based on RGB-IHS transformation ( Figure 2 (a) Extraction of multiple seismic attributes: Through comparative analysis with actual drilling results, three sensitive attributes are selected. (b) Each sensitive attribute is optimized by noise reduction, outlier removal, etc., and normalized to the range of 0 to 255. (c) The normalized sensitive attributes are mapped to the RGB color space. There are six mapping modes: RGB, RBG, GRB, GBR, BRG, and BGR, which need to be determined according to the fusion effect. (d) The normalized sensitive attributes are mapped to the IHS color space through RGB-IHS forward transformation, and then the final fused image is output through RGB-IHS inverse transformation. (e) By comparing and analyzing with the original sensitive attributes and the actual drilling results, if the fusion effect is considered poor, return to (c), change the RGB mapping mode, and re-fuse. If the fusion effect is considered good, the multi-attribute fused image can be applied.

[0061] By applying five-dimensional multi-directional and multi-scale fusion fault description technology, the identification and description of multi-directional and multi-scale faults have been significantly improved, and the fault characterization has become more refined. For frequency-domain-based optimized frequency division bodies, a fusion body of dominant frequency division and dominant azimuth is constructed. On the one hand, the dominant azimuth angle body merges multiple dominant azimuth bodies to reflect the development characteristics of faults with different strikes throughout the region; on the other hand, the dominant frequency division body reflects multi-scale faults, and the characterization of faults with different azimuths and scales is more comprehensive and detailed.

[0062] Beneficial Effects: The five-dimensional seismic multi-scale dominant azimuth fusion fault description technology provided by this invention is currently a method that researchers both domestically and internationally have not yet clearly defined. This invention creatively integrates two fusion technologies (based on dominant frequency division and dominant azimuth fusion) and one color fusion technology (RGB-IHS transformation technology), clearly displaying all multi-scale and multi-azimuth faults on a single structural map. This represents a significant improvement over traditional fault identification markers. This invention has high practical value and strong operability, and can provide a reference for the description and research of multi-azimuth and multi-scale faults related to oil and gas.

[0063] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A five-dimensional seismic multi-scale dominant azimuth fusion fault description method, characterized in that, The fault description method includes: Step S1: Obtain the basic geological overview of the study area; Step S2: Generalized transform spectral decomposition, constructing frequency domain optimized frequency division body; Step S3: Based on the optimized frequency division body, construct a frequency division and advantageous orientation fusion body; Step S4: Describe complex fractures of multiple scales and orientations based on RGB-IHS transformation.

2. The five-dimensional seismic multi-scale dominant azimuth fusion fault description method according to claim 1, characterized in that, Step S1: Obtaining the basic geological overview of the study area specifically includes: To obtain the basic geological overview of the study area, collect relevant data on tectonic evolution, understand the tectonic movements and stress directions experienced by the study area, and ensure the rationality of the tectonic interpretation results.

3. The five-dimensional seismic multi-scale dominant azimuth fusion fault description method according to claim 1, characterized in that, Step S1: Obtaining the basic geological overview of the study area also includes: To obtain the basic geological overview of the study area, the tectonic movements it has experienced, and the regional stress direction, and to conduct a detailed structural interpretation of the standard layers based on the well logging and well logging data of the drilled wells.

4. The five-dimensional seismic multi-scale dominant azimuth fusion fault description method according to claim 3, characterized in that, The detailed structural interpretation of the standard layer specifically includes: Based on the actual well logging data of the study area, the principal stress direction and the measured fault strike were determined, providing a basis for the optimal selection of azimuth data.

5. The five-dimensional seismic multi-scale dominant azimuth fusion fault description method according to claim 3, characterized in that, The method based on actual well logging data in the study area also includes: performing fracture enhancement preprocessing on the seismic data volume.

6. The five-dimensional seismic multi-scale dominant azimuth fusion fault description method according to claim 3, characterized in that, The acquisition of the basic geological overview, tectonic movements, and regional stress direction of the study area specifically includes: Based on well logging curves such as sonic transit time and density, synthetic records are created to calibrate the formation, and formation and fault interpretation is performed. During the interpretation process, it is necessary to check whether the interpreted layers and faults are closed.

7. The five-dimensional seismic multi-scale dominant azimuth fusion fault description method according to claim 1, characterized in that, Step S2: Generalized transform spectral decomposition, constructing a frequency domain optimized frequency division body specifically includes: Spectral analysis was performed on the earthquake data collected for the study to determine the dominant frequency and frequency band range of the earthquake data, which were divided into three frequency bands: low, medium and high.

8. The five-dimensional seismic multi-scale dominant orientation fusion fault description method according to claim 1, characterized in that, Step S2: Generalized transform spectral decomposition and construction of frequency domain optimized frequency division body further includes: when performing frequency division processing on seismic data, selecting a more accurate generalized S-transform algorithm for time-frequency analysis, selecting frequencies that can reflect multi-scale faults, and constructing a frequency domain optimized frequency division body.

9. The five-dimensional seismic multi-scale dominant azimuth fusion fault description method according to claim 1, characterized in that, Step S3: Constructing a frequency division and advantageous orientation fusion body based on the optimized frequency division body specifically includes: Based on the actual fracture characteristics, the direction of maximum principal stress, and the imaging effect after gather stacking, the azimuth range of the OVT data in the study area was optimized.

10. The five-dimensional seismic multi-scale dominant azimuth fusion fault description method according to claim 1, characterized in that, Step S3: Constructing a frequency division and dominant azimuth fusion body based on the optimized frequency division body further includes: Based on low, medium and high frequency subdivisions, azimuth data volumes that can reflect the dominant orientation of multi-scale faults are selected on the low, medium and high frequency subdivisions respectively. OVT gathers are superimposed by azimuth angle, and the three dominant azimuth arrays based on frequency dividers are fused to construct a frequency divider and dominant azimuth fusion array.

11. The five-dimensional seismic multi-scale dominant azimuth fusion fault description method according to claim 1, characterized in that, Step S4: Describing multi-scale, multi-directional complex fractures based on RGB-IHS transform specifically includes: Based on the frequency division and dominant orientation fusion body, the RGB-IHS transformation fusion method is applied to map the RGB and IHS image fusion methods based on the frequency division and dominant orientation fusion body to each other, so that multi-scale and multi-directional tomography can be clearly displayed on the plane.

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