Fault detection method based on local angle domain reflection angle imaging gather

Abstract

The invention provides a fault detection method based on a local angle domain reflection angle imaging gather, and relates to the technical field of oil exploration and development. Comprising the following steps: S1, carrying out pre-stack pretreatment on an omnibearing local angle domain reflection angle imaging gather; s2, determining a sub-azimuth division scheme; s3, according to the azimuth division scheme in the step S2, performing sub-azimuth superposition on all-dimensional local angle domain reflection angle imaging gather data to obtain a sub-azimuth superposition imaging data body; s4, seismic attribute calculation is carried out according to the sub-azimuth superposition imaging data volume obtained in the step S3; s5, principal component analysis and multi-attribute fusion are carried out according to the seismic attributes obtained in the step S4, and a fusion attribute body is calculated; and S6, according to the fusion attribute body obtained in the step S5, fault interpretation and analysis are performed in a three-dimensional space, and a fault three-dimensional space distribution map is obtained. According to the method, the identification precision of the main fault and the secondary fault is improved, so that the fault detection precision is improved.

Description

Technical Field

[0001] This invention belongs to the field of petroleum exploration and development technology, specifically relating to a method for fault detection based on local angle domain reflection angle imaging gathers, and more specifically to a method for fault detection based on all-around local angle domain reflection angle imaging gathers. Background Technology

[0002] Faulting activity makes carbonate reservoirs near faults prone to fracturing, becoming conduits for oil and gas migration. Intense faulting activity is crucial for reservoir stimulation and also significantly influences oil and gas distribution. Reservoir development is controlled by a multi-phase strike-slip fault system and fault dissolution.

[0003] The Ordovician system is generally oil-bearing, and high- and stable-production wells are mainly distributed along the main fault zones, indicating that hydrocarbon accumulation is primarily controlled by fault zones. With the development of computing technology, the processing and analysis capabilities of seismic data have been greatly improved. Among these methods, omnidirectional local angle domain imaging is a commonly used seismic data processing technique. The resulting pre-stack omnidirectional local angle domain reflection angle gathers can provide richer subsurface information, helping to improve the accuracy of fault identification.

[0004] Chinese invention patent CN115877446A discloses a method, computer device, and computer-readable storage medium for generating azimuth reflection angle gathers. The method includes the following steps: during a reverse-time migration process based on excitation amplitude imaging conditions, recording the excitation amplitude information of the forward propagation wavefield of the seismic source, including the excitation time corresponding to the excitation amplitude and the direction vector corresponding to the excitation amplitude; approximately reconstructing the forward propagation wavefield of the seismic source using a high-dimensional wavelet function in conjunction with the excitation amplitude information, and applying cross-correlation imaging conditions to obtain the imaging result; calculating the direction vector of the backpropagation wavefield at the receiver point during the reverse-time extension process; calculating the azimuth and reflection angle of the wavefield illumination at the subsurface imaging point by combining the recorded direction vector corresponding to the excitation amplitude with the direction vector of the backpropagation wavefield at the receiver point; and assigning the imaging result to the corresponding azimuth and reflection angles to obtain the azimuth reflection angle gather.

[0005] Chinese invention patent CN118244347A discloses a method for generating reverse-time offset reflection angle gathers, an electronic device, and a storage medium. The method includes the following steps: extrapolating the reverse-time wavefields of the shot point and receiver point, and constructing an energy target functional under gradient constraints on each time slice; iteratively solving the wavefield vector directions at the shot point end and receiver point end at the current moment; constructing an adaptive threshold through global amplitude scanning, filtering and generating a table of valid points at the current moment, and calculating the reflection angle and / or azimuth of the valid points in the table; interpolating the reflection angle or azimuth of invalid points within a set range for each valid point in the table; and applying the azimuth domain cross-correlation imaging conditions to determine the gathers at the underground imaging points.

[0006] The existing fault detection technology has the following problems: (1) Due to the deep burial of the Ordovician target layer, there are multiple sets of volcanic rock velocity anomalies above the target layer, resulting in azimuth anisotropy in the deep layer, which poses a challenge to the identification and analysis of faults; (2) Strike-slip faults are mostly developed at high angles or vertically, which causes azimuth anisotropy when seismic waves propagate, which further increases the difficulty of fault detection; (3) When processing post-stack seismic data, the existing fault detection technology has difficulties in identifying secondary faults in beaded development areas due to the low signal-to-noise ratio and poor resolution, which greatly troubles the identification and analysis of faults and is not conducive to the study of Ordovician fault-controlled reservoirs.

[0007] Based on the defects and shortcomings of traditional methods for fault identification using post-stack seismic data, this invention provides a method for fault detection based on omnidirectional local angle domain reflection angle imaging gathers. This method improves the accuracy of fault detection in ultra-deep Ordovician carbonate rocks and provides new technical support for oil and gas exploration and development. Summary of the Invention

[0008] This invention addresses the problems existing in the prior art by providing a method for fault detection based on local angular domain reflection angle imaging gathers. It fully utilizes the differences in seismic anomalies caused by geological discontinuities formed by faults at different observation azimuths, performs azimuth-specific stacking of gather data, and then calculates seismic attributes such as coherence volume, curvature, and maximum likelihood for the azimuth-specific stacked data volume to improve the identification accuracy of main and secondary faults.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] First, this invention provides a method for tomography based on local angular domain reflection angle imaging gathers, comprising the following steps:

[0011] Step S1: Preprocessing of the image gathers for omnidirectional local angular domain reflection angle imaging before stacking;

[0012] Step S2: Determine the azimuth division scheme;

[0013] Step S3: Based on the azimuth division scheme in step S2, perform azimuth-based superposition on the omnidirectional local angle domain reflection angle imaging gather data to obtain the azimuth-based superimposed imaging data volume.

[0014] Step S4: Calculate seismic attributes based on the azimuth-stacked imaging data volume obtained in Step S3;

[0015] Step S5: Perform principal component analysis (PCA) and multi-attribute fusion based on the seismic attributes obtained in step S4, and calculate the fused attribute volume;

[0016] Step S6: Based on the fusion attribute volume obtained in step S5, perform fault interpretation and analysis in three-dimensional space to obtain a three-dimensional spatial distribution map of the fault.

[0017] Preferably, in step S1, the preprocessing specifically involves: performing signal-to-noise ratio analysis on the omnidirectional local angle domain reflection angle imaging gather, and using methods such as random noise attenuation and multiple wave coherent noise suppression to improve the quality of the local angle domain reflection angle imaging gather data.

[0018] Preferably, in step S1, the purpose of the preprocessing is to remove noise and improve the quality of the data. The noise removal is mainly achieved by performing time-frequency analysis on the fully stacked seismic data and then using bandpass filtering to remove high and low frequency noise outside the effective frequency band, thereby improving the signal-to-noise ratio of the data.

[0019] Preferably, the determination of the azimuth division scheme in step S2 specifically involves: dividing different azimuth sectors according to the fracture direction in the study area, superimposing the local angle domain reflection angle imaging gathers, and selecting the optimal azimuth division scheme based on the identifiability of the fracture in the superimposed imaging results.

[0020] Preferably, in step S4, the seismic attributes include coherence volume attributes, curvature attributes, and maximum likelihood attributes.

[0021] Preferably, discontinuity detection is performed at step S4.

[0022] Preferably, in step S5, the calculation of the fused attribute body specifically involves: extracting feature information of different seismic attributes, selecting the feature vector corresponding to the largest feature value as the main feature of the multi-type seismic attributes, reconstructing the data based on the main feature, and calculating the fused attribute body.

[0023] Preferably, the fault interpretation and analysis described in step S6 specifically involves: based on the coherence and maximum likelihood data volume obtained in step S4, extracting the root mean square amplitude attribute along the target layer to obtain a planar plot of the coherence and maximum likelihood attributes of the target layer, thus obtaining the planar distribution morphology of the fault in the target layer; then, using the coherence and maximum likelihood data volume obtained in step S4 to constrain the azimuth-divided superimposed data volume obtained in step S3, interpreting the fault on the seismic profile, with the plane orientation of the fault referring to the coherence and maximum likelihood attribute planar plots during interpretation; finally, combining the projection points of the fault interpreted on the profile onto the target layer in a planar manner, and mapping the spatial fault surface of the fault to obtain the final fault interpretation result.

[0024] Then, the present invention provides a three-dimensional spatial distribution map of the fault, obtained by the above method.

[0025] Finally, this invention provides applications of the above-described method in oil and gas exploration, geological structure analysis, or computer data processing.

[0026] Preferably, the application is in high-precision tomography.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. This invention provides a method for fault detection based on the azimuth-based superposition of omnidirectional local angle domain reflection angle imaging gather data. It fully utilizes the differences in seismic anomalies caused by geological discontinuities formed by faults at different observation azimuths, and uses principal component analysis technology for multi-attribute fusion, which can significantly improve the identification accuracy of main faults and secondary faults, thereby improving the accuracy of fault detection and providing strong support for oil and gas exploration and development.

[0029] 2. The method of the present invention has been tested and applied in some fault zones in the Shunbei area of ​​the Tarim Basin, and has achieved significant improvement results.

[0030] 3. The fault detection method based on omnidirectional local angle domain reflection angle imaging gathers provided by this invention can be applied to fields such as oil and gas exploration, geological structure analysis, and computer data processing. Especially in oil and gas exploration, this method can improve the accuracy of fault detection in ultra-deep Ordovician carbonate rocks, thereby increasing the success rate of oil and gas exploration and meeting the demand for efficient and accurate oil and gas exploration technology.

[0031] 4. The method of this invention, when applied to geological structure analysis, can more accurately identify and analyze faults, thereby providing a better understanding of the formation and evolution of geological structures. Furthermore, the method of this invention can also be applied to computer data processing technology, improving the processing and analysis capabilities of seismic data and providing new technical approaches for the effective utilization of seismic data. Attached Figure Description

[0032] Figure 1 This is a flowchart of the method for tomography based on omnidirectional local angle domain reflection angle imaging gathers according to the present invention.

[0033] Figure 2 This is a cross-sectional comparison of the omnidirectional superimposed data volume and the azimuth-specific superimposed data volume of the local angular domain reflection angle imaging gather in an embodiment of the present invention.

[0034] Figure 3 This is a comparison diagram of the property planes of the omnidirectional superimposed data volume and the azimuth-divided superimposed data coherence volume of the local angular domain reflection angle imaging gather in an embodiment of the present invention.

[0035] Figure 4 This is a planar diagram showing the fracture properties of the top surface of the target layer in an embodiment of the present invention.

[0036] Figure 5 This is a three-dimensional spatial distribution map of the faults in the study area according to an embodiment of the present invention. Detailed Implementation

[0037] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following content is merely an exemplary description of the scope of protection claimed by the present invention, and those skilled in the art can make various changes and modifications to the present invention based on the disclosed content, and such changes should also fall within the scope of protection claimed by the present invention.

[0038] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0039] The present invention will be further described below by way of specific embodiments. Unless otherwise specified, all reagents and equipment used in the embodiments of the present invention are obtained through conventional commercial means.

[0040] Example 1

[0041] The study area is Block 12 of Shunbei Oilfield.

[0042] A method for tomography based on omnidirectional local angular domain reflection angle imaging gathers is as follows:

[0043] Step S1: Perform signal-to-noise ratio analysis on the omnidirectional local angle domain reflection angle imaging gather. Use methods such as random noise attenuation and multiple wave coherent noise suppression to improve the quality of the local angle domain reflection angle imaging gather data. Noise removal is mainly achieved by performing time-frequency analysis on the fully stacked seismic data, and then using bandpass filtering to remove high and low frequency noise outside the effective frequency band, thereby improving the signal-to-noise ratio of the data.

[0044] Step S2: Based on the fracture orientation in the study area, divide the local angle domain reflection angle imaging gathers into different azimuth sectors and overlay them. Based on the identifiability of the fracture in the overlaid imaging results, select the optimal azimuth division scheme.

[0045] In this embodiment, the main faults in the study area are trending northeast. By performing superimposed imaging experiments at different azimuth angles, it was found that after superimposing at azimuth angles of 20°-50°, the fault points are clearly visible in the superimposed profile, and the identification accuracy is the highest.

[0046] Step S3: Based on the azimuth division scheme in Step S2, perform azimuth-based superposition on the omnidirectional local angle domain reflection angle imaging gather data. Specifically, select 20°-50° azimuth gather data for superposition imaging to obtain the azimuth-based superimposed imaging data volume.

[0047] Step S4: Perform discontinuity detection, and calculate coherence volume, curvature, and maximum likelihood seismic attributes based on the azimuth stacked imaging data volume obtained in Step S3.

[0048] Step S5: Perform principal component analysis (PCA) on the seismic attributes obtained in step S4 to extract the feature information of different seismic attributes, and select the feature vector corresponding to the largest feature value as the main feature of the multi-type seismic attributes. Reconstruct the data based on the main features and calculate the fused attribute volume.

[0049] Step S6: Based on the fusion attributes obtained in Step S5, perform fault interpretation and analysis in three-dimensional space: Based on the coherence and maximum likelihood data volume obtained in Step S4, extract the root mean square amplitude attribute along the target layer to obtain the coherence and maximum likelihood attribute planar plots of the target layer, thus obtaining the planar distribution morphology of the fault in the target layer; then, using the coherence and maximum likelihood data volume obtained in Step S4, constrain the azimuth-divided superimposed data volume obtained in Step S3, and interpret the fault on the seismic profile. During interpretation, the plane orientation of the fault is referenced to the coherence and maximum likelihood attribute planar plots; finally, combine the projection points of the fault interpreted on the profile onto the target layer in a plane, and map the spatial fault surface of the fault to obtain the final fault interpretation result; obtain the three-dimensional spatial distribution map of the fault.

[0050] Figure 2 A comparative cross-sectional view of local angular domain reflection angle imaging gather omnidirectional stacked data (Comparative Example 1) and azimuth-based stacked data (Example 1) according to an embodiment of the present invention is provided. Figure 2 As shown, on the seismic profile, comparing the azimuth-based superimposed data with the all-around azimuth superimposed data, the fault points and cross-sectional features on the azimuth-based superimposed data profile of this invention are clearer, and the fault identification accuracy is improved.

[0051] Figure 3 A coherence attribute plane comparison diagram is provided for omnidirectional overlay data (Comparative Example 1) and azimuth-based overlay data (Example 1) according to an embodiment of the present invention. Figure 3 As shown, by extracting omnidirectional superimposed coherent attribute plane maps and azimuthal superimposed coherent attribute plane maps from two stratigraphic levels, T80 (the top surface of the Cambrian System) and T81 (the top of the Awatag Formation of the Middle Cambrian), the azimuthal superimposed attribute plane maps of this invention are superior to the omnidirectional superimposed plane maps, and the fault direction on the plane is clearer, which is more beneficial for subsequent fault interpretation. Figure 3 W1 and W2 in the diagram represent the numbers of the two wells, respectively.

[0052] Figure 4 A planar diagram showing the fusion of fracture properties at the top surface of the target layer in the study area according to an embodiment of the present invention is provided. For example... Figure 4 As shown, based on the coherence volume, curvature, and maximum likelihood seismic attribute volume obtained in step S4, principal component analysis is used to extract feature information from different seismic attributes, and the feature vector corresponding to the maximum eigenvalue is selected as the main feature of multiple types of seismic attributes. Based on the main feature, data reconstruction is performed to calculate the fused attribute volume. Figure 4 The fusion attribute contains information from the fusion of multiple attributes. Compared with the single attribute, the fusion attribute shows obvious high-value anomalies in the main and secondary fault zones, which can more clearly characterize the fault development features in the study area. Figure 4 W1 and W2 in the diagram represent the numbers of the two wells, respectively.

[0053] Figure 5 A three-dimensional spatial distribution map of faults in the study area according to an embodiment of the present invention is shown. Figure 5 As shown, using the fusion attribute volume obtained in step S5, the root mean square amplitude attribute along the target layer is extracted to obtain the fusion attribute plane map of the target layer, which is the planar distribution morphology of the fault in the target layer. On the cross section, using the fusion attribute volume obtained in step S5, the sub-azimuth superposition data volume obtained in step S3 is constrained, and the fault is interpreted on the cross section. During the interpretation, the plane orientation of the fault is referenced to the fusion attribute plane map of the target layer. Finally, the projection points of the fault interpreted on the cross section onto the target layer are combined in a plane, and the fault is plotted in three-dimensional space to obtain the final three-dimensional spatial distribution map of the fault.

[0054] Comparative Example 1

[0055] Step S1: Same as in Example 1;

[0056] Step S2: Perform omnidirectional stacking of the local angular domain reflection angle imaging gathers to obtain an omnidirectional angle scheme; such as Figure 2 As shown, on the seismic profile, comparing the azimuth-based superimposed data (Example 1) with the all-around azimuth superimposed data (Comparative Example 1), the fault points and cross-sectional features on the azimuth-based superimposed data profile of Example 1 are clearer, and the fault identification accuracy is improved.

[0057] Step S3: Calculate the coherence volume, curvature, and maximum likelihood seismic properties from the omnidirectional overlay data of Step S2; such as... Figure 3 As shown, by extracting omnidirectional superposition coherence property plane maps (Comparative Example 1) and azimuthal superposition coherence property plane maps (Example 1) from two stratigraphic layers T80 (top of the Cambrian System) and T81 (top of the Middle Cambrian Awatag Formation), the azimuthal superposition property plane maps of Example 1 are superior to the omnidirectional superposition plane maps. The fault direction on the plane is clearer, which is more conducive to the subsequent fault interpretation.

[0058] The remaining steps are the same as in Example 1.

[0059] This invention fully utilizes the differences in seismic anomalies caused by geological discontinuities formed by faults at different observation azimuths. It performs azimuth-based superposition of gather data and outputs azimuth-based data volumes that reflect the true azimuth information of underground reflection points, highlighting fault characteristics and eliminating other noise information, resulting in higher fault detection accuracy and clearer fault points. In contrast, omnidirectional superposition does not consider the differences in seismic anomalies caused by geological discontinuities formed by faults at different observation azimuths. Fault information and noise information are superimposed together, and the noise information affects the detection accuracy of fault information, resulting in lower fault detection accuracy and less clear fault points compared to azimuth-based superposition data volumes.

[0060] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for tomographic detection based on local angular domain reflection angle imaging gathers, characterized in that, Including the following steps: Step S1: Preprocessing of the image gathers for omnidirectional local angular domain reflection angle imaging before stacking; Step S2: Determine the azimuth division scheme; Step S3: Based on the azimuth division scheme in step S2, perform azimuth-based superposition on the omnidirectional local angle domain reflection angle imaging gather data to obtain the azimuth-based superimposed imaging data volume. Step S4: Calculate seismic attributes based on the azimuth-stacked imaging data volume obtained in Step S3; Step S5: Perform principal component analysis and multi-attribute fusion based on the seismic attributes obtained in step S4, and calculate the fused attribute volume; Step S6: Based on the fusion attribute volume obtained in step S5, perform fault interpretation and analysis in three-dimensional space to obtain a three-dimensional spatial distribution map of the fault.

2. The method according to claim 1, characterized in that, In step S1, the preprocessing specifically involves: performing signal-to-noise ratio analysis on the omnidirectional local angle domain reflection angle imaging gather, and using methods such as random noise attenuation and multiple wave coherent noise suppression to improve the quality of the local angle domain reflection angle imaging gather data.

3. The method according to claim 1, characterized in that, In step S1, the purpose of the preprocessing is to remove noise and improve the quality of the data. The noise removal is achieved by performing time-frequency analysis on the fully stacked seismic data and then using bandpass filtering to remove high and low frequency noise outside the effective frequency band, thereby improving the signal-to-noise ratio of the data.

4. The method according to claim 1, characterized in that, Step S2, which involves determining the azimuth division scheme, specifically involves dividing the study area into different azimuth sectors based on the fracture direction, stacking the local angle domain reflection angle imaging gathers, and selecting the optimal azimuth division scheme based on the identifiability of the fracture in the stacked imaging results.

5. The method according to claim 1, characterized in that, In step S4, the seismic attributes include coherence volume attributes, curvature attributes, and maximum likelihood attributes.

6. The method according to claim 1, characterized in that, In step S5, the calculation of the fused attribute body specifically involves: extracting feature information of different seismic attributes, selecting the feature vector corresponding to the largest feature value as the main feature of the multi-type seismic attributes, reconstructing the data based on the main feature, and calculating the fused attribute body.

7. The method according to claim 1, characterized in that, The fault interpretation and analysis described in step S6 are as follows: Based on the coherence and maximum likelihood data volume obtained in step S4, the root mean square amplitude attribute along the target layer is extracted to obtain the coherence and maximum likelihood attribute planar plots of the target layer, that is, the planar distribution morphology of the fault in the target layer is obtained; then, using the coherence and maximum likelihood data volume obtained in step S4, the azimuth-divided superimposed data volume obtained in step S3 is constrained to interpret the fault on the seismic profile, and the plane strike of the fault is referenced to the coherence and maximum likelihood attribute planar plots during interpretation; finally, the projection points of the fault interpreted on the profile onto the target layer are combined in a plane, and the spatial fault surface is mapped to obtain the final fault interpretation result.

8. A three-dimensional spatial distribution map of faults, characterized in that, Obtained by the method described in any one of claims 1-7.

9. The application of the method according to any one of claims 1-7 in oil and gas exploration, geological structure analysis or computer data processing.

10. The application according to claim 9, characterized in that, Specifically, it is used in high-precision tomography.

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