Seismic data low-frequency compensation method, system, equipment and medium

Abstract

The invention discloses a seismic data low-frequency compensation method, system and device and a medium, and the method comprises the steps: S1, constructing an expected wavelet frequency spectrum according to a frequency spectrum range of to-be-compensated seismic data and an effective low-frequency signal range, and enabling a constructed objective function to be s.tJ = 0; in the formula, f is an expected wavelet and is a modal coefficient, and ui is a modal component; s2, carrying out wavelet extraction on the seismic data to be compensated, and carrying out variational mode decomposition on the extracted wavelet; s3, compensating the modal coefficient of the low-order modal component according to the target function, and reconstructing the compensated modal coefficient and the decomposed modal coefficient into a new wavelet; and S4, performing convolution processing based on the reconstructed wavelets and the original data to obtain seismic data after low-frequency compensation. According to the method, the low-frequency band energy compensation degree can be quantified, after low-frequency compensation is carried out on the seismic data, the frequency spectrum noise is low, no sudden change condition exists, and the method is suitable for being applied and popularized in practice.

Description

Technical Field

[0001] This invention relates to seismic data processing for oil and gas exploration and development, specifically a method, system, equipment, and medium for low-frequency compensation of seismic data. Background Technology

[0002] Low-frequency information from seismic data plays a crucial role in oil and gas reservoir exploration and development. This is especially true for deep and ultra-deep seismic exploration targets, where the importance of low-frequency information is even more pronounced. On one hand, as the propagation path of seismic waves lengthens, high-frequency information attenuates dramatically, making deep structural imaging highly dependent on low-frequency information. On the other hand, seismic inversion relies on the vertical resolution of well logging data and the lateral resolution of seismic data. If low-frequency information from seismic data is missing, the results of seismic inversion and reservoir prediction will be unreliable, and false reflection information may appear on the profile.

[0003] In recent years, with the continuous deepening of seismic exploration, the low-frequency information of controlled source data acquired during field seismic acquisition has been greatly expanded. However, when a large amount of old data is repeatedly processed, or when new and old data are processed in contiguous blocks, how to achieve good lateral frequency consistency when the low-frequency information of multiple data blocks differs greatly is an urgent problem to be solved.

[0004] There has been considerable research on low-frequency compensation technology for seismic data in recent years. For example, Chinese invention patent CN105093329B discloses an automatic compensation method and device for low-frequency information of seismic data, specifically disclosing a method for estimating the amplitude spectrum of wavelets using the amplitude spectrum of seismic data, and obtaining the frequency response curve of the compensation operator through amplitude spectrum calculation in the frequency range to be compensated for low-frequency compensation. However, this method, because it uses amplitude spectrum calculation for low-frequency compensation, does not consider the effective low-frequency range, resulting in strong low-frequency noise after compensation. Furthermore, it does not consider the shape of the spectrum after compensation, leading to an overly strong ground spectrum and jumps in the amplitude spectrum.

[0005] For example, Chinese invention patent CN112666609B discloses a method and apparatus for low-frequency compensation of seismic data based on sparse envelopes. It constructs a Ricker matching wavelet dictionary to sparsely decompose seismic data into matching wavelet sets. This method is based on a dictionary learning algorithm, which has limited efficiency in practical production. Summary of the Invention

[0006] To address the aforementioned shortcomings in the existing technology, this invention aims to provide a method, system, device, and medium for low-frequency compensation of seismic data, thereby improving the quality of seismic exploration and interpretation.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for low-frequency compensation of seismic data, the method comprising:

[0008] S1. Construct the desired wavelet spectrum based on the spectral range of the seismic data to be compensated and the effective low-frequency signal range. The objective function for this construction is: s.tJ = 0;

[0009] In the formula, f is the desired wavelet. U represents the modal coefficients. i Modal components;

[0010] S2. Extract wavelets from the seismic data to be compensated, and perform variational mode decomposition on the extracted wavelets;

[0011] S3. Compensate the modal coefficients of the low-order modal components according to the objective function, and reconstruct the compensated modal coefficients and the decomposed modal coefficients into a new wavelet;

[0012] S4. Based on the reconstructed wavelet and the original data, convolution processing is performed to obtain low-frequency compensated seismic data.

[0013] As a limitation of the present invention, in step S1, the seismic data to be compensated is subjected to spectral analysis to determine the spectral range of the seismic data as f0~f1; and the seismic data to be compensated is subjected to low-pass scanning to determine the effective low-frequency signal of the seismic data as f2.

[0014] definition The amplitude value at the specified frequency is A1;

[0015] If f0 < f2, then define the amplitude A at frequency f2. f2 Let A1 define the amplitude A at frequency f0. f0 for

[0016] If f0 > f2, then define the amplitude A at frequency f2. f2 for Define the amplitude A at frequency f0. f0 It is A1.

[0017] As a further limitation of the present invention, in step S2, wavelet extraction is performed on the seismic data to be compensated using the second-order cumulant.

[0018] As a further limitation of the present invention, in step S2, when performing variational mode decomposition on the extracted wavelet, the number of modes is determined according to abs(f0-f1):

[0019] If abs(f0-f1)>10, then the number of mode decompositions is 6;

[0020] If abs(f0-f1) < 10, then the number of mode decompositions is 5.

[0021] As a further limitation of the present invention, in step S3, based on the objective function, according to the result of the wavelet variational mode decomposition in step S2, and the amplitude A at the frequency f0 defined in step S1... f0 Define the amplitude A at frequency f2. f2 For (f0,A) f0 ) and (f2,A f2 The modal coefficients of the low-order modal components to be compensated are obtained by fitting the data.

[0022] As a further limitation of the present invention, the compensated mode coefficients and the decomposed mode coefficients are subjected to variational mode decomposition inverse transform to obtain the reconstructed wavelet after low-frequency compensation.

[0023] The present invention also provides a system for low-frequency compensation of seismic data, which is used to implement the method for low-frequency compensation of seismic data as described above, comprising:

[0024] The desired wavelet spectrum construction module is used to perform spectral analysis on the seismic data to be compensated to determine the spectral range, perform low-pass scanning to determine the effective low-frequency signal range, construct the desired wavelet spectrum based on the spectral range and the effective low-frequency signal range, and construct the objective function.

[0025] The variational mode decomposition module is used to extract wavelets from the seismic data to be compensated and perform variational mode decomposition.

[0026] The wavelet reconstruction module is used to compensate the mode coefficients of the low-order mode components according to the objective function, and to reconstruct the compensated mode coefficients and the decomposed mode coefficients into a new wavelet;

[0027] The convolution processing module is used to convolve the reconstructed wavelet and the original data to obtain low-frequency compensated seismic data.

[0028] The present invention also provides an electronic device, including at least one processor and a memory communicatively connected to the processor; wherein the memory stores a computer program executable by the processor; and the processor executes the computer program to implement the method for low-frequency compensation of seismic data as described above.

[0029] The present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, is used to implement the method for low-frequency compensation of seismic data as described above.

[0030] By adopting the above-described technical solution, the beneficial effects achieved by this invention compared to the prior art are as follows:

[0031] The present invention differs from other low-frequency compensation methods in that: 1) it extracts wavelets from the seismic data to be compensated; 2) it performs variational mode decomposition on the wavelets and constructs an objective function based on the spectral range of the seismic data to be compensated and the effective low-frequency signal range for quantitative low-frequency compensation. The spectral noise after compensation by this invention is low and there are no abrupt changes, making it suitable for practical application.

[0032] Furthermore, this invention applies a second-order cumulant algorithm to extract wavelets from the seismic data to be compensated, and applies variational mode decomposition (VMD) to perform mode decomposition on the extracted wavelets. VMD has a rigorous mathematical theoretical foundation, extracts modes simultaneously within a fully variational framework, requires no prior information about the input signal, can adaptively decompose the signal into K modal components with different center frequencies, and is a non-stationary signal processing method that is also lossless and reversible.

[0033] This invention determines the spectral range and effective low-frequency signal range by performing spectral analysis and low-pass scanning on the seismic data to be compensated. Based on the spectral range and effective low-frequency signal range, a desired wavelet is constructed, which can quantify the degree of energy compensation in the low-frequency band. Attached Figure Description

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0035] Figure 1 This is a flowchart illustrating a method for low-frequency compensation of seismic data according to an embodiment of the present invention.

[0036] Figure 2 This is a schematic diagram of the low-frequency compensation profile and the wavelet and spectrum extracted based on the second-order cumulant in an embodiment of the present invention; wherein, Figure 2 (a) is a schematic cross-section before low-frequency compensation. Figure 2 (b) shows the wavelet extracted from the profile (top) and the wavelet spectrum (bottom);

[0037] Figure 3 The wavelet and its decomposed modal components and spectrum are shown in the embodiments of the present invention; wherein, Figure 3 (a) is a seismic wavelet. Figure 3 (b) shows the decomposed mode 1 and its spectrum. Figure 3 (c) shows the decomposed mode 2 and its spectrum. Figure 3 (d) shows the decomposed mode 3 and its spectrum;

[0038] Figure 4 The images show the wavelet spectrum before low-frequency compensation (left) and the desired wavelet spectrum (right) in an embodiment of the present invention.

[0039] Figure 5 This is a schematic diagram comparing the cross-section before and after low-frequency compensation in an embodiment of the present invention; wherein, Figure 5 (a) is a schematic diagram of the gain profile before low-frequency compensation. Figure 5 (b) is a schematic diagram of the gain profile after low-frequency compensation;

[0040] Figure 6 This is a schematic diagram comparing the spectrum before and after low-frequency compensation in an embodiment of the present invention;

[0041] Figure 7 This is a comparison diagram of the 4Hz pure wave profile before and after low-frequency compensation in an embodiment of the present invention; wherein, Figure 7 (a) is a schematic diagram of the 4Hz pure wave profile before low-frequency compensation. Figure 7 (b) is a schematic diagram of the low-pass 4Hz pure wave profile after low-frequency compensation. Detailed Implementation

[0042] This embodiment uses the application of 3D seismic data processing in a certain area of ​​western China as an example to specifically illustrate the invention. This area mainly consists of desert and Gobi surface, with deep burial, lack of deep low-frequency information, and poor imaging of the bedrock bottom boundary.

[0043] This embodiment provides a method for low-frequency compensation of seismic data, such as... Figure 1 As shown, this method constructs an objective function for the desired wavelet spectrum based on the spectral range of the seismic data to be compensated and the effective low-frequency signal range. Simultaneously, it extracts wavelets from the seismic data to be compensated and performs variational mode decomposition on the extracted wavelets. Then, based on the constructed objective function, it compensates the mode coefficients of the low-order mode components, reconstructing a new wavelet from the decomposed mode coefficients and the compensated mode coefficients. Finally, it performs convolution processing based on the reconstructed wavelet and the original data to obtain the low-frequency compensated seismic data. The method specifically includes the following steps:

[0044] S1. Perform spectral analysis and low-pass scanning on the seismic data to be compensated to construct the desired wavelet spectrum.

[0045] Spectral analysis was performed on the seismic data to be compensated to determine the spectral range of the seismic data as f0 to f1; low-pass scanning was performed on the seismic data to determine the effective low-frequency signal of the seismic data as f2;

[0046] The desired wavelet spectrum is constructed based on the spectral range of the seismic data to be compensated and the effective low-frequency signal range. The objective function for this construction is:

[0047]

[0048] In the formula, f is the desired wavelet. U represents the modal coefficients. i These are modal components.

[0049] It should be noted that the definitions in this embodiment are as follows: The amplitude value at the specified frequency is A1;

[0050] If f0 < f2, then define the amplitude A at frequency f2. f2 Let A1 define the amplitude A at frequency f0. f0 for

[0051] If f0 > f2, then define the amplitude A at frequency f2. f2 for Define the amplitude A at frequency f0. f0 For A1, S2, perform wavelet extraction and variational mode decomposition on the seismic data to be compensated.

[0052] Wavelet extraction is performed using second-order cumulants on the seismic data to be compensated, such as... Figure 2 As shown, Figure 2 a is a schematic diagram of the cross-section of the area before low-frequency compensation. As can be seen from the diagram, the deep low-frequency signal is relatively weak. Figure 2 b is the wavelet (top) and wavelet spectrum (bottom) extracted from the profile. This figure shows that the wavelet spectrum has weak energy in the low-frequency range. Then, variational mode decomposition is performed on the extracted wavelet. The number of mode decompositions is determined based on abs(f0-f1):

[0053] If abs(f0-f1)>10, then the number of mode decompositions is 6;

[0054] If abs(f0-f1) < 10, then the number of mode decompositions is 5.

[0055] The result of variational mode decomposition in this embodiment is as follows: Figure 3 As shown, the wavelet is decomposed into a series of modal components of different orders.

[0056] S3. Compensate the modal coefficients of the lower-order modal components and perform wavelet reconstruction.

[0057] Based on the above objective function, the low-order mode components that need to be compensated are determined according to the result of the wavelet variational mode decomposition in step S2. Then, the amplitude A at the frequency f0 end is defined according to step S1. f0 Define the amplitude A at frequency f2. f2 For (f0,A) f0 ) and (f2,A f2 The fitting process is performed to obtain the modal coefficients of the low-order modal components that need to be compensated.

[0058] Extract the decomposed mode coefficients from the result of the variational mode decomposition of the wavelet in step S2, and perform an inverse variational mode decomposition transformation on them and the compensated mode coefficients to reconstruct a new wavelet.

[0059] A comparison between the reconstructed wavelet and its spectrum and the extracted wavelet and its spectrum. Figure 4 As shown in the figure, the low-frequency energy of the reconstructed wavelet is compensated (circled part).

[0060] S4. Based on the reconstructed wavelet and the original data, convolution processing is performed to obtain the final low-frequency compensated seismic data.

[0061] Depend on Figures 5 to 7 It can be seen that the deep low-frequency signal in the seismic data is enhanced, and the phase axis is more continuous. The spectrum shows an increase in amplitude at the low-frequency end; and the low-pass scan of the pure wave profile shows a significant enhancement of the effective low-frequency signal.

[0062] After processing the three-dimensional seismic data of this block using the low-frequency compensation method for seismic data provided in this embodiment, the imaging of the bedrock bottom boundary is improved, and the spatial distribution of the strata and the distribution of the bedrock in this block are clearer.

[0063] This embodiment also provides a system for low-frequency compensation of seismic data, used to implement the method for low-frequency compensation of seismic data as described above. The system includes a desired wavelet spectrum construction module, a variational mode decomposition module, a wavelet reconstruction module, and a convolution processing module.

[0064] Among them, the expected wavelet spectrum construction module is used to perform spectral analysis on the seismic data to be compensated to determine the spectral range, perform low-pass scanning to determine the effective low-frequency signal range, construct the expected wavelet spectrum based on the spectral range and the effective low-frequency signal range, and construct the corresponding objective function.

[0065] The variational mode decomposition module is used to extract wavelets from the seismic data to be compensated and perform variational mode decomposition.

[0066] The wavelet reconstruction module is used to compensate the mode coefficients of the low-order mode components according to the constructed objective function, and to reconstruct the compensated mode coefficients and the decomposed mode coefficients into a new wavelet;

[0067] The convolution processing module is used to convolve the reconstructed wavelet and the original data to obtain low-frequency compensated seismic data.

[0068] This embodiment also provides an electronic device, including at least one processor and a memory communicatively connected to the processor. The memory stores a computer program executable by the processor; when the processor executes the computer program, it implements the method for low-frequency compensation of seismic data as described above.

[0069] This embodiment also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the method for low-frequency compensation of seismic data as described above.

[0070] It should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions described in the above embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for low frequency compensation of seismic data, characterized in that, The method comprises: S1, constructing a desired wavelet spectrum according to a frequency spectrum range of the seismic data to be compensated and an effective low frequency signal range, and constructing a target function as: where f is the desired wavelet, are modal coefficients, u i are modal components; S2, wavelet extraction is performed on the seismic data to be compensated, and the extracted wavelet is subjected to variational mode decomposition; S3, the mode coefficients of the low-order mode components are compensated according to the target function, and the compensated mode coefficients and the decomposed mode coefficients are reconstructed into a new wavelet; S4, convolution processing is performed based on the reconstructed wavelet and the original data to obtain low-frequency compensated seismic data.

2. The method for low frequency compensation of seismic data of claim 1, wherein: In step S1, the spectrum of the seismic data to be compensated is analyzed to determine the spectrum range f0-f1, and low-pass scanning is performed on the seismic data to be compensated to determine the effective low-frequency signal f2; Definitions the amplitude value at the frequency is A1; If f0 < f2, define the amplitude A at the frequency f2 as A f2 A1, define the amplitude A at the frequency f0 as A f0 A1, define the amplitude A at the frequency f0 as A If f0 > f2, define the amplitude A at the frequency f2 as f2 A1 = A0 If f0 > f2, define the amplitude A at the frequency f2 as f0 A1 = A0 3. The method for low frequency compensation of seismic data of claim 2, wherein: In step S2, the second-order cumulant is used to extract the wavelet from the seismic data to be compensated.

4. The method for low frequency compensation of seismic data according to claim 2 or 3, characterized in that: In step S2, when the extracted wavelet is subjected to variational mode decomposition, the number of modes is determined according to abs(f0-f1): If abs(f0-f1)>10, the number of mode decompositions is 6; If abs(f0-f1)<10, the number of mode decompositions is 5.

5. The method for low frequency compensation of seismic data of claim 4, wherein: In step S3, based on the objective function, according to the result of the wavelet variational mode decomposition in step S2, and the amplitude A at the frequency f0 defined in step S1... f0 Define the amplitude A at frequency f2. f2 For (f0,A) f0 ) and (f2,A f2 The modal coefficients of the low-order modal components to be compensated are obtained by fitting the data.

6. The method for seismic data low frequency compensation of claim 5, wherein: The compensated mode coefficients and the decomposed mode coefficients are subjected to inverse transformation of variational mode decomposition to obtain the low-frequency compensated reconstructed wavelet.

7. A system for low frequency compensation of seismic data, characterized by: The system is used to implement the method for low-frequency compensation of seismic data according to any one of claims 1-6, and comprises: An expected wavelet spectrum construction module is configured to analyze the spectrum of the seismic data to be compensated to determine the spectrum range, perform low-pass scanning to determine the effective low-frequency signal range, construct the expected wavelet spectrum according to the spectrum range and the effective low-frequency signal range, and construct the target function; A variational mode decomposition module is configured to extract the wavelet from the seismic data to be compensated and perform variational mode decomposition; A wavelet reconstruction module is configured to compensate the mode coefficients of the low-order mode components according to the target function, and reconstruct the compensated mode coefficients and the decomposed mode coefficients into a new wavelet; A convolution processing module is configured to perform convolution processing on the reconstructed wavelet and the original data to obtain low-frequency compensated seismic data.

8. An electronic device, comprising: The computer readable storage medium stores a computer program, and the computer program is executed by a processor to implement the method for low-frequency compensation of seismic data according to any one of claims 1-6.

9. A computer-readable storage medium, characterized in that: The computer readable storage medium stores a computer program, and the computer program is executed by a processor to implement the method for low-frequency compensation of seismic data according to any one of claims 1-6.

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