Crack detection method based on transverse wave velocity change rate, storage medium and equipment

Abstract

The invention relates to a fracture detection method based on a shear wave velocity change rate, a storage medium and equipment, and the detection method comprises the steps: carrying out three-parameter AVO inversion through a Zoeppritz Akilinear equation according to pre-stack CRP gather data and a seismic velocity, and obtaining the shear wave velocity change rate [delta] Vs / Vs data of a to-be-detected region; extracting the maximum amplitude diagram and the RMS amplitude diagram of the transverse wave velocity change rate delta Vs / Vs data of the Ordovician stratum, and / or the plane diagram of the minimum value of the transverse wave velocity relative value rVs; and delineating a high-amplitude abnormal region on the maximum amplitude diagram and the RMS amplitude diagram of the transverse wave speed change rate delta Vs / Vs, and / or delineating a low-value abnormal region on the plane diagram of the minimum relative value rVs, and the delineating abnormal region is a fracture development region or a fracture-cavity development region. According to the method, the shear wave velocity reflectivity is obtained through AVO three-parameter inversion, and direct and effective crack detection is achieved by searching for abnormity of a high-amplitude region of delta Vs / Vs or a low-value region of channel integral data of delta Vs / Vs.

Description

Technical Field

[0001] The present invention relates to the field of crack parameter prediction, and particularly to a crack detection method, a storage medium and a device based on the shear wave velocity change rate. Background Art

[0002] In the exploration and development of unconventional natural gas (including shale gas, tight sandstone gas, etc.), there are still a series of problems to be solved urgently. Among them, the crack seismic prediction technology is an extremely key technology. For example, in the Ordovician carbonate reservoir in Tahe, the reservoir body is mainly karst fissures and caves, and there is also a relatively large demand for crack detection or prediction in this area.

[0003] Crack seismic prediction is mainly based on the study of azimuthal anisotropy of wide-azimuth seismic data, that is, the elastic parameters are different in different directions. By using the ellipse fitting technology, the fast direction and slow direction of the elastic parameters (such as the fast shear wave, slow shear wave direction and magnitude) are found, so as to determine the main direction of elastic parameter anisotropy (the fast direction is the long axis direction of the ellipse) and the anisotropy intensity (the ratio of the long axis to the short axis of the ellipse). Inversion based on azimuthal anisotropy requires the use of wide-azimuth seismic data. However, at present, wide-azimuth seismic data is not common. In areas without wide-azimuth seismic data, how to improve the accuracy and reliability of crack detection is an urgent problem to be solved. The previous methods based on seismic attributes such as coherence, structural curvature and ant body mainly detect large-scale small faults, not cracks or fissures, and the crack detection accuracy is low.

[0004] The patent with the patent number CN104678434B discloses a method for predicting the development parameters of reservoir cracks. The two-way travel time values of the target layer are extracted from seismic data with different azimuth angles, and after normalization processing, the two-way travel time values of each target layer after normalization processing are obtained; then, seismic rose diagrams and comprehensive crack development intensity plane diagrams are respectively generated for each point on the set grid, and after the two diagrams are superimposed and displayed, a crack parameter plane diagram is obtained.

[0005] The patent with the patent number CN108562936A discloses a crack prediction method, system, storage medium and terminal. According to the OVT gather and seismic velocity data, n azimuth incident angle gathers are obtained; then, any seismic attribute is selected from a preset seismic attribute set, and then the seismic attribute is calculated for each of the n azimuth incident angle gathers respectively to obtain the intensity of the seismic attribute in the azimuth corresponding to each of the n azimuth incident angle gathers; anisotropy calculation is performed on the attribute intensities of the n azimuths to obtain a calculation result; according to the calculation result, the cracks in the area to be predicted are processed to obtain the development density and dominant azimuth direction of the cracks.

[0006] Both of the above two disclosed methods require wide-azimuth seismic data during application. When detecting in areas without wide-azimuth seismic data, the accuracy and reliability of crack detection are poor. Summary of the Invention

[0007] The present invention solves the problem of poor accuracy and reliability of fracture seismic prediction in areas without wide-azimuth seismic data, and provides a fracture detection method, storage medium and device based on the shear wave velocity change rate to solve this technical problem. The shear wave velocity reflectivity is obtained by AVO three-parameter inversion, and by searching for Δ the strong amplitude area of Vs / Vs or the anomaly in the low value area of its trace integral data, fractures can be detected accurately and efficiently.

[0008] To solve the above technical problems, the technical solution of the present invention is as follows:

[0009] A fracture detection method based on the shear wave velocity change rate, comprising the following steps:

[0010] S1. According to the pre-stack CRP gather data and seismic velocity, three-parameter AVO inversion is carried out using the Zoeppritz Aki&

[0011] Rechards linear equation to obtain the shear wave velocity change rate Δ Vs / Vs data of the area to be detected;

[0012] S2. Process the shear wave velocity change rate Δ Vs / Vs data of the Ordovician formation in the area to be detected to obtain:

[0013] The maximum amplitude map, RMS amplitude map of the shear wave velocity change rate Δ Vs / Vs, and / or

[0014] Perform trace integral processing on the shear wave velocity change rate Δ Vs / Vs to obtain the relative value rVs of the shear wave velocity Vs, and process to obtain the planar map of the minimum value of the relative value rVs;

[0015] S3. Circle the strong amplitude anomaly area on the maximum amplitude map and RMS amplitude map of the shear wave velocity change rate Δ Vs / Vs, and / or

[0016] Circle the low value anomaly area on the planar map of the minimum value of the relative value rVs;

[0017] S4. The anomaly area is the fracture development area or the fracture-vug development area.

[0018] Preferably, in step S1, the formula for calculating the shear wave velocity change rate is:

[0019]

[0020] Wherein, R is the reflection coefficient; θ is the incident angle, unit: degree; Vp is the longitudinal wave velocity, unit: m / s; Vs is the shear wave velocity, unit: m / s; Δ Vs / Vs is the shear wave velocity change rate, unit: none; ρ is the density, unit: g / cc.

[0021] Preferably, in step S3, the shear wave velocity change rate is calibrated in advance according to the fracture-developed well section Δ The strong amplitude range of the Vs / Vs data and the range of the low value of the relative shear wave velocity rVs, and then the abnormal area is calibrated on the maximum amplitude map, RMS amplitude map of the shear wave velocity change rate Vs / Vs and the plan view of the minimum value of the relative value rVs. Δ On the maximum amplitude map, RMS amplitude map of the shear wave velocity change rate Vs / Vs and the plan view of the minimum value of the relative value rVs.

[0022] Preferably, in step S3, under the condition of delineating the strong amplitude abnormal area and the low value abnormal area at the same time, the strong amplitude abnormal area and the low value abnormal area are mutually verified to improve the judgment accuracy of the fracture-developed area / fracture-cavity developed area, and it can be verified by the actual drilled well.

[0023] Preferably, the applicable conditions of the fracture detection method include: the INLINE direction of seismic acquisition is perpendicular to the main fracture strike of the area to be detected.

[0024] A computer-readable storage medium stores computer-executable instructions, and when the computer-executable instructions are executed by a processor, they are used to implement the above-mentioned fracture detection method based on the shear wave velocity change rate.

[0025] A computer device includes a processor and a memory, the memory stores a computer program, and the computer program is loaded and executed by the processor to implement the above-mentioned fracture detection method based on the shear wave velocity change rate.

[0026] The beneficial technical effects of the technical solution of the present invention:

[0027] This solution uses AVO three-parameter inversion to obtain the shear wave velocity reflectivity, and then directly and effectively detects fractures by finding Δ The strong amplitude area of Vs / Vs or the abnormality of the low value area of its trace integral data. Since this method is based on the theory that the attenuation of the shear wave velocity propagating in the direction perpendicular to the fracture surface is significantly greater than the attenuation of the longitudinal wave velocity, the fracture detection accuracy is higher than that of the post-stack seismic prediction method, and it is especially suitable for detecting fractures in areas lacking wide-azimuth seismic data.

[0028] Meanwhile, this solution also solves the problem of high-precision and effective detection of fractures under the condition of no wide-azimuth seismic data acquisition at present. Using the technical method of the present invention will significantly improve the reliability and accuracy of predicting fractures by conventional seismic attributes, and has more advantages than the conventional seismic attribute fracture detection method. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 FIG. shows a flowchart of a fracture detection method based on the shear wave velocity change rate in an embodiment of the present invention;

[0030] Figure 2 FIG. shows a comparison diagram of synthetic P-wave seismic amplitude attenuation and synthetic S-wave seismic amplitude attenuation of a fractured reservoir in an embodiment of the present invention;

[0031] Figure 3 FIG. shows a comparison diagram of fracture detection of curvature and relative shear wave velocity rVs in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further elaborates in detail the fracture detection method, storage medium and device based on the shear wave velocity change rate proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the accompanying drawings are in a very simplified form and all use non-precise scales, only for the purpose of facilitating and clearly assisting in explaining the embodiments of the present invention. In order to make the objectives, features and advantages of the present invention more obvious and understandable, please refer to the accompanying drawings. It should be noted that the structures, ratios, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those skilled in this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention. Therefore, they do not have technical essence. Any modification of the structure, change of the proportional relationship or adjustment of the size, without affecting the effects that the present invention can produce and the objectives that can be achieved, should still fall within the scope covered by the technical content disclosed by the present invention.

[0033] The following will Figures 1 to 3 and specific embodiments elaborate in detail the technical solutions of the fracture detection method, storage medium and device based on the shear wave velocity change rate of the present invention.

[0034] Embodiment

[0035] As Figures 1 to 3 shown, the fracture detection method based on the shear wave velocity change rate in this embodiment includes the following steps:

[0036] S1. According to the pre-stack CRP gather data and seismic velocity, using Zoeppritz Aki&

[0037] Perform three-parameter AVO inversion using the Rechards linear equation to obtain the shear wave velocity change rate in the area to be detected. Δ The Vs / Vs data, and the formula for calculating the shear wave change rate is;

[0038]

[0039] Where R is the reflection coefficient; θ is the incident angle, unit: degree; Vp is the P-wave velocity, unit: m / s; Vs is the S-wave velocity, unit: m / s; Δ Vs / Vs is the shear wave velocity change rate, unit: none; ρ is the density, unit: g / cc.

[0040] S2. Process the shear wave velocity change rate Δ Vs / Vs data of the Ordovician formation in the area to be detected to obtain:

[0041] The shear wave velocity change rate Δ The maximum amplitude map, RMS amplitude map of Vs / Vs, and / or

[0042] Perform trace integration on the shear wave velocity change rate Δ Vs / Vs to obtain the relative value rVs of the shear wave velocity Vs, and process to obtain the plan view of the minimum value of the relative value rVs;

[0043] S3. Circumscribe the strong amplitude anomaly area on the maximum amplitude map, RMS amplitude map of the shear wave velocity change rate Δ Vs / Vs, and / or

[0044] Circumscribe the low value anomaly area on the plan view of the minimum value of the relative value rVs;

[0045] S4. The anomaly area is a fracture development area or a fracture-vug development area. For example Figure 3 In, the area where the relative value rVs of the shear wave velocity is less than 2492 in the left figure is the fracture development area. During actual detection, either the strong amplitude anomaly area or the low value anomaly area of the relative value can be used for judgment. Of course, under the condition that the strong amplitude anomaly area and the low value anomaly area are circumscribed at the same time, the strong amplitude anomaly area and the low value anomaly area can be mutually verified to improve the judgment accuracy of the fracture development area / fracture-vug development area.

[0046] The purpose of the present invention is to solve the problem of achieving high-precision fracture detection in areas without wide-azimuth seismic data. First, use AVO three-parameter inversion to obtain the shear wave velocity reflectivity, and directly and effectively detect fractures by finding the strong amplitude area of ΔVs / Vs or the anomaly of the low value area of its trace integration data. The applicable condition of this method is that the INLINE direction of seismic acquisition is basically perpendicular to the main fracture strike (i.e., the approximate extension direction of fractures) in this area.

[0047] In the absence of wide-azimuth seismic data, shear wave velocity is the most sensitive parameter reflecting fractures, and shear wave velocity is not affected by fluids.

[0048] The present invention provides a method for detecting fractures by using the shear wave velocity change rate under the condition of no wide-azimuth seismic data, that is, by obtaining the maximum value of the shear wave velocity change rate obtained from pre-stack inversion or the low value of the Vs relative value to detect fractures. This method is applicable to the fracture prediction of restricted platform carbonates.

[0049] In the deep layer of the Tarim Basin, the lithology is relatively simple (at least in the target interval), and the reservoirs are mainly fracture-vug type or fault-karst type. In the developed sections (areas) of these reservoirs, the longitudinal and shear wave velocities of the reservoirs are significantly lower than those of the surrounding rocks. Therefore, the reflection characteristics of the longitudinal and shear waves at the top of the reservoir show strong reflections, and the reflection amplitude of the shear wave is stronger because, relative to the longitudinal wave, the shear wave velocity decreases faster when encountering fractures (provided that it is in the direction perpendicular to the fracture strike, because the main survey line direction of seismic acquisition is mostly perpendicular to the main structure or fault). Specifically, for the well-free inversion results of longitudinal and shear wave seismology, the fracture sections (areas), including the developed areas of fault-karst bodies, show low velocity and low impedance, especially the shear wave velocity or shear wave impedance.

[0050] In Figure 2 , the lithologies of the fractured reservoir and the tight layer are both dolomite, and the porosities are the same. Relative to the tight layer below the target layer, the synthetic longitudinal wave seismic amplitude decays by 9%, while the synthetic shear wave seismic amplitude decays by 22%.

[0051] This solution uses AVO three-parameter inversion to obtain the shear wave velocity reflectivity, and realizes direct and effective fracture detection by finding Δ the strong amplitude area of Vs / Vs or the abnormal low value area of its trace integral data. The applicable condition of this method is that the INLINE direction of seismic acquisition is basically perpendicular to the strike of the main fault in this area (i.e., the approximate extension direction of the fracture). Since this method is based on the theory that the attenuation of the shear wave velocity propagating in the direction perpendicular to the fracture surface is significantly greater than that of the longitudinal wave velocity, the accuracy of fracture detection is higher than that of post-stack seismic prediction methods.

[0052] This embodiment also discloses a computer-readable storage medium and a computer device. The computer-readable storage medium stores computer-executable instructions, which are used to implement the above-mentioned fracture detection method based on the shear wave velocity change rate when executed by a processor.

[0053] The computer device includes a processor and a memory. The memory stores a computer program, which is used to implement the above-mentioned fracture detection method based on the shear wave velocity change rate when loaded and executed by the processor.

[0054] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0055] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A crack detection method based on the shear wave velocity change rate, characterized in that, Including the following steps: S1. Based on the pre-stack CRP gather data and seismic velocity, perform three-parameter AVO inversion using the Zoeppritz Aki&Rechards linear equation to obtain the shear wave velocity change rate Δ Vs / Vs data in the area to be detected; S2. Shear wave velocity change rate of the Ordovician formation in the area to be detected Δ Process the Vs / Vs data to obtain: Shear wave velocity change rate Δ Maximum amplitude plot of Vs / Vs, RMS amplitude plot, and / or Perform trace integration on the shear wave velocity change rate Δ Vs / Vs to obtain the relative value rVs of the shear wave velocity Vs, and process to obtain a planar map of the minimum value of the relative value rVs; S3. On the maximum amplitude map and RMS amplitude map of the shear wave velocity change rate Δ Vs / Vs, delineate strong amplitude anomaly areas, and / or Circling a low-value anomaly area on the planar graph of the minimum relative value rVs; S4. The anomaly area is a fracture-developed area or a fracture-vug developed area.

2. The crack detection method based on the shear wave velocity change rate according to claim 1, wherein, In step S1, the formula for calculating the shear wave velocity change rate is: In the formula, R is the reflection coefficient; θ is the incident angle, unit: degree; Vp is the longitudinal wave velocity, unit: m / s; Vs is the shear wave velocity, unit: m / s; Δ Vs / Vs is the shear wave velocity change rate, unit: none; ρ is the density, unit: g / cc.

3. A crack detection method based on the shear wave velocity change rate according to claim 1, characterized in that, In step S3, the change rate of shear wave velocity is calibrated in advance according to the fracture-developed well section. Δ Based on the strong amplitude range of Vs / Vs data and the range of the relative shear wave velocity rVs low value, the abnormal area is calibrated on the maximum amplitude map of the shear wave velocity change rate Δ Vs / Vs, the RMS amplitude map, and the plan view of the minimum value of the relative value rVs.

4. The crack detection method based on the shear wave velocity change rate according to claim 1, characterized in that, In step S3, under the condition of simultaneously circling the strong amplitude anomaly area and the low-value anomaly area, the strong amplitude anomaly area and the low-value anomaly area are mutually verified to improve the judgment accuracy of the fracture-developed area / fracture-vug developed area, and verification can be carried out through actual drilled wells.

5. A crack detection method based on the shear wave velocity change rate as described in claim 1, characterized in that, The applicable conditions of the fracture detection method include: the INLINE direction of seismic acquisition is perpendicular to the main fracture strike of the area to be detected.

6. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions, and when the computer-executable instructions are executed by a processor, they are used to implement the fracture detection method based on the shear wave velocity change rate according to any one of claims 1 to 5.

7. A computer device, characterized in that, The computer device includes a processor and a memory, and the memory stores a computer program, and the computer program is loaded and executed by the processor to implement the fracture detection method based on the shear wave velocity change rate according to any one of claims 1 to 5.

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