A seismic oil and gas detection method and system

Abstract

The present invention relates to a seismic oil and gas detection method and system, the method comprising the following steps: obtaining common center point gather data; extracting azimuth common center point gather data of multiple different azimuth ranges according to preset different azimuth ranges from the common center point gather data; obtaining AVO features of each azimuth common center point gather; performing pairwise cross-correlation calculation on the AVO features of all azimuth common center point gathers, and selecting a reference gather; the AVO features of the reference gather have the lowest correlation with the AVO features of other azimuth common center point gathers; obtaining difference common center point gather data according to the reference gather and other azimuth common center point gather data; the difference common center point gather data is the average value after difference and superposition of other azimuth common center point gathers and the reference gather; obtaining the gradient attribute and intercept attribute of the difference common center point gather data, and performing oil and gas detection according to the gradient attribute and intercept attribute. The accuracy of reservoir oil and gas detection is improved.

Description

Technical Field

[0001] The invention relates to a seismic oil and gas detection method and system, belonging to the technical field of seismic exploration and seismic oil and gas detection. Background Art

[0002] In the past 20 years of oil and gas exploration, seismic oil and gas detection methods have played an important role in determining the effectiveness of reservoirs and have greatly improved the success rate of exploration. At present, conventional seismic oil and gas detection methods can be generally divided into two categories: post-stack seismic oil and gas detection methods and pre-stack seismic oil and gas detection methods. The post-stack seismic oil and gas detection method analyzes the oil and gas content of the reservoir through the amplitude and frequency anomalies of the fluid-containing reservoir on the post-stack seismic data body, while the pre-stack seismic oil and gas detection technology is based on the Zoplitz equation, using the relationship between the reflection coefficient and the longitudinal wave velocity, shear wave velocity and lithology density of the formation, and judging the oil and gas content of the reservoir through the influence of changes in formation elastic parameters on seismic amplitude. Recently, a method has been developed based on pre-stack seismic oil and gas detection technology that uses velocity dispersion characteristics, namely frequency-variable AVO technology, to determine the oil and gas content of the reservoir. Judging from the current application results of these technologies, both conventional post-stack seismic oil and gas detection technology and pre-stack use of seismic amplitude characteristics or velocity dispersion characteristics to identify reservoir oil and gas content have large errors and multiple solutions. The reason is that when seismic waves propagate in underground media, the strata have inherent attenuation characteristics for attributes such as amplitude, frequency, and velocity. This attenuation characteristic is not only related to whether the strata contain oil and gas, that is, some strata are not ideal reservoirs, but when seismic waves pass through these strata, the amplitude, frequency, velocity and other attributes will also be attenuated. Summary of the invention

[0003] The purpose of the present invention is to provide a seismic oil and gas detection method and system to solve the problem that the existing seismic oil and gas detection technology cannot accurately judge the oil and gas content of the reservoir.

[0004] To achieve the above object, the solution of the present invention includes:

[0005] A seismic oil and gas detection method of the present invention comprises the following steps:

[0006] 1) Obtain common center point gather data;

[0007] 2) extracting a plurality of azimuth common center point gather data in different azimuth ranges from the common center point gather data according to preset different azimuth ranges;

[0008] 3) Obtain the AVO characteristic curves of the common center point gathers at each azimuth;

[0009] 4) Carry out pairwise cross-correlation calculation on the AVO characteristic curves of all azimuth common center point gathers, and select reference gathers;

[0010] The AVO characteristic curve of the reference gather has the lowest correlation with the AVO characteristic curves of other azimuth common center point gathers;

[0011] 5) obtaining difference common center point gather data according to the reference gather and other azimuth common center point gather data;

[0012] The difference common center point gather data is the average value of the difference and superposition of the common center point gathers at other azimuth angles and the reference gathers;

[0013] 6) Obtaining the gradient attribute and intercept attribute of the difference common center point gather data, and performing oil and gas detection according to the gradient attribute and intercept attribute.

[0014] Furthermore, in step 2), each azimuth angle range covers 0 to 180 degrees without overlapping each other.

[0015] Furthermore, the number of azimuth angle ranges is 3 to 5.

[0016] Furthermore, in step 3), the AVO characteristic curves of the common center point gathers at each azimuth angle are obtained according to the change of the amplitude at the top of the reservoir section with the offset distance.

[0017] Further, in step 5), the difference common center point gather data is calculated according to the following formula:

[0018]

[0019] Among them, Y(IL,CL,off,i) is the difference common center point gather data, M is the number of azimuth ranges, X(IL,CL,off,Azi O ,i) is the reference gather, X(IL,CL,off,Azi k ,i) is the azimuth common center point gather of the kth azimuth range, k = 0,1…M.

[0020] Further, in step 6), the gradient attribute and the intercept attribute are multiplied together to form a detection data volume for oil and gas detection.

[0021] A seismic oil and gas detection system of the present invention includes a processor, and the processor executes instructions to implement the following method steps.

[0022] 1. Data preparation: Collect 3D prestack time migration common center point gathers in the work area;

[0023] 2. The 3D prestack time migration common center point gathers collected in the work area are divided into multiple center point gathers with different azimuths according to the azimuth information;

[0024] 3. Analyze the relationship between the amplitude and offset distance of the common center point gathers at different azimuths in the reservoir section, and obtain the characteristic curve of the amplitude at the top of the reservoir changing with the offset distance of the common center point gathers at different azimuths, that is, the AVO characteristic curve;

[0025] 4. Analyze the AVO characteristic curves of different azimuth common center point gathers at the top of the reservoir section, and determine the azimuth common center point gather with the largest difference from the AVO characteristic curves of other azimuth common center point gathers at the top of the reservoir section as the reference gather;

[0026] 5. Use the reference gathers obtained in step 4 and other common center point gathers to construct difference common center point gathers;

[0027] 6. Using the difference common center point gathers obtained in step 5, the AVO approximate equation Shuey equation is used to calculate the gradient P and intercept G attribute bodies. The P×G attribute body is the final high-precision oil and gas detection result.

[0028] The present invention divides the 3D prestack time migration common center point gathers according to the azimuth information to obtain a plurality of common center point gathers with different azimuths. On this basis, by constructing differential common center point gathers, AVO inversion is performed to obtain high-precision oil and gas detection results, which produces the following beneficial effects: (1) the oil and gas detection results are less affected by non-reservoir factors, reducing the multi-solution nature of conventional oil and gas detection results; (2) the oil and gas detection accuracy is high, which can improve the drilling success rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flow chart of a seismic oil and gas detection method of the present invention;

[0030] Figure 2 This is a common center point gather of 3D prestack time migration in a certain depression;

[0031] Figure 3 It is the azimuth 1 common center point gather divided by azimuth of the 3D prestack time migration common center point gather;

[0032] Figure 4 It is the azimuth 2 common center point gather of 3D prestack time migration common center point gather divided by azimuth;

[0033] Figure 5 It is the azimuth 3 common center point gather of 3D prestack time migration common center point gather divided by azimuth;

[0034] Figure 6 The AVO characteristic curve of the top of the reservoir section of the common center point gathers at different azimuths;

[0035] Figure 7 is the difference common center point gather;

[0036] Figure 8 For high-precision oil and gas detection profile;

[0037] Fig. 9 It is a conventional oil and gas detection profile;

[0038] Fig.10 It is a structural schematic diagram of the seismic oil and gas detection system of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0040] Method Example:

[0041] The process of a seismic oil and gas detection method of the present invention is as follows: Figure 1 As shown, the following steps are included:

[0042] 1. Data preparation: Obtain a 3D prestack time migration common center point gather of a depression. In this embodiment, the data was collected in 2016, the bin is 12.5m*12.5m, and the sampling interval is 2ms. Figure 2 As shown;

[0043] 2. Set the main survey line IL, tie line CL, offset off, azimuth Azi, and seismic signal of sampling point i in step 1 as X(IL, CL, off, Azi, i), where the azimuth Azi ranges from 0° to 180°. The azimuth is divided into M azimuth ranges according to Δθ as equal intervals, where M is 180 / Δθ rounded to the integer.

[0044] According to the divided azimuth, the 3D prestack time migration common center point gather data are extracted to obtain M common center point gathers with different azimuths. The seismic signals of the common center point gathers with different azimuths are recorded as X(IL,CL,off,Azi k ,i), k=1,2,...M.

[0045] In this embodiment, the azimuth angle from 0° to 180° is divided into three azimuth angle ranges of 0° to 60°, 60° to 120°, and 120° to 180° according to the interval of Δθ=60°. The three-dimensional prestack time migration common center point gather data are extracted according to the three divided azimuth angle ranges to obtain three common center point gathers with different azimuth angles. The seismic signals of the three common center point gathers with different azimuth angles are respectively recorded as X(IL, CL, off, Azi 1 ,i), such as Figure 3 As shown; X(IL,CL,off,Azi 2 ,i), such as Figure 4 As shown; X(IL,CL,off,Azi 3,i), such as Figure 5 As shown;

[0046] 3. Analyze the common center point gathers at different azimuths at the top of the reservoir section (such as Figure 2 The amplitude of the oscillation changes with the offset distance, and the AVO characteristic curves of the common center points at different azimuths are obtained, recorded as AVO (IL, CL, Azi k ), k = 1, 2, 3, such as Figure 6 As shown, the green (hollow dots, the two ends of the curve are marked with hollow dots) is AVO (IL, CL, Azi 1 ), red (indicated by a cross “×”, with the two ends of the curve marked with a cross “×”) is AVO (IL, CL, Azi 2 ), blue (solid dots, both ends of the curve are marked with solid dots) is AVO (IL, CL, Azi 3 ); The position of the top of the reservoir segment can be obtained based on other prior knowledge, such as the knowledge of the reservoir obtained through existing technology;

[0047] 4. The AVO characteristic curve AVO(IL,CL,Azi obtained in step 3 k ) to perform pairwise cross-correlation calculations, and select the azimuth common center point gathers with low cross-correlation values ​​with other AVO characteristic curves as the reference gathers X(IL,CL,off,Azi O ,i), in this case, O takes the value of 1;

[0048] 5. Use the reference gather obtained in step 4 and the other common center point gathers with different azimuth angles to calculate the difference common center point gathers Y(IL,CL,off,i) according to the following formula: Figure 7 As shown:

[0049]

[0050] 6. Based on the difference common center point gathers obtained in step 5, the gradient attribute P and intercept attribute G are obtained using the Shuey approximate equation of the AVO equation. The high-precision oil and gas detection data volume is obtained by multiplying the P attribute with the G attribute, as shown in Figure 8 shown.

[0051] Comparative Example:

[0052] Fig. 9 Directly using a 3D prestack time migration common center point gather, the oil and gas detection data volume obtained according to the Shuey approximate equation of the AVO equation is compared Figure 8 and Fig. 9 It can be seen that the vertical resolution of the oil and gas detection data obtained by the patent of this invention is much higher than Fig. 9The oil and gas detection data body is well eliminated, and the influence of non-reservoir sections on the oil and gas detection results is better eliminated, reducing the ambiguity of conventional oil and gas detection results. In addition, by comparing with the drilled wells, the oil and gas detection data body obtained by the present invention is completely consistent with the drilled wells, which greatly improves the accuracy of the oil and gas detection results.

[0053] System Example:

[0054] This embodiment provides a seismic oil and gas detection system, such as Fig.10 As shown, it includes a memory, a processor and an internal bus, and the processor and the memory communicate with each other through the internal bus.

[0055] The processor may be a processing device such as a microprocessor MCU, a programmable logic device FPGA, etc.

[0056] The memory can be various memories that use electrical energy to store information, such as RAM, ROM, etc.; various memories that use magnetic energy to store information, such as hard disks, floppy disks, magnetic tapes, magnetic core memories, bubble memories, USB flash drives, etc.; various memories that use optical methods to store information, such as CDs, DVDs, etc. Of course, there are other types of memory, such as quantum memory, graphene memory, etc.

[0057] The processor can call the logic instructions in the memory to implement a seismic oil and gas detection method of the present invention. The method is described in detail in the method embodiment and will not be repeated here.

Claims

1. A seismic oil and gas detection method, characterized in that: The steps include: 1) Obtain common center point gather data; 2) extracting a plurality of azimuth common center point gather data in different azimuth ranges from the common center point gather data according to preset different azimuth ranges; 3) Obtain the AVO characteristic curves of the common center point gathers at each azimuth; 4) Carry out pairwise cross-correlation calculation on the AVO characteristic curves of all azimuth common center point gathers, and select reference gathers; The AVO characteristic curve of the reference gather has the lowest correlation with the AVO characteristic curves of other azimuth common center point gathers; 5) obtaining difference common center point gather data according to the reference gather and other azimuth common center point gather data; The difference common center point gather data is calculated according to the following formula: Among them, Y(IL,CL,off,i) is the difference common center point gather data, M is the number of azimuth ranges, X(IL,CL,off,Azi O ,i) is the reference gather, X(IL,CL,off,Azi k ,i) is the azimuth common center point gather of the kth azimuth range, k = 0, 1…M; 6) Obtaining the gradient attribute and intercept attribute of the difference common center point gather data, and performing oil and gas detection according to the gradient attribute and intercept attribute.

2. The seismic oil and gas detection method according to claim 1, characterized in that: In step 2), each azimuth angle range covers 0 to 180 degrees without overlapping each other.

3. The seismic oil and gas detection method according to claim 2, characterized in that: The number of the azimuth angle ranges is 3 to 5.

4. The seismic oil and gas detection method according to claim 1, characterized in that: In step 3), the AVO characteristic curves of the common center point gathers at each azimuth angle are obtained based on the change of the amplitude at the top of the reservoir segment with the offset distance.

5. The seismic oil and gas detection method according to claim 1, characterized in that: In step 6), the gradient attribute and the intercept attribute are multiplied together to form a detection data volume for oil and gas detection.

6. A seismic oil and gas detection system, characterized in that: The method comprises a processor, wherein the processor executes instructions for implementing the seismic oil and gas detection method according to any one of claims 1 to 5.

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