A method and device for suppressing surface roll interference by using phase correction

Abstract

To better eliminate surface roll interference and recover valid seismic signals, the present invention proposes a method and apparatus for suppressing surface roll interference using phase correction. The method includes inverting the phase differences of surface roll interference from different seismic traces and filtering the seismic recordings using an optimal phase matching filter to eliminate the phase differences. This method eliminates the influence of velocity dispersion on surface roll interference suppression, maximally eliminating surface roll interference and improving the signal-to-noise ratio of seismic recordings.

Description

Technical Field

[0001] The present invention belongs to the technical field of exploration geophysics, and in particular relates to a method and device for suppressing surface wave interference by utilizing phase correction. Background Art

[0002] Actual seismic data contains various types of noise interference. Based on their spatial coherence, noise interference is generally classified into two categories: random noise and regular noise. Surface rolls are the most common regular noise, characterized by low frequency, low velocity, and dispersion. Surface rolls have strong amplitudes, often containing energy several or even dozens of times greater than the effective signal. Surface roll interference severely contaminates the effective reflection signal from the subsurface, significantly reducing the signal-to-noise ratio and imaging accuracy of seismic data.

[0003] Currently, there are various methods for suppressing surface roll interference. Among them, FK filtering and dispersion simulation filtering are the two most widely used in industry. The basic concept of FK filtering for surface roll suppression is based on the difference in frequency and apparent velocity between surface roll interference and seismic signals. Compared to the effective reflection signal, the frequency and velocity of surface roll interference are lower, and the two are somewhat separable in the frequency-wavenumber domain. Therefore, based on this difference in frequency and velocity, a fan-shaped filter is designed in the FK domain and applied to the seismic record to achieve surface roll suppression and signal recovery. However, unlike other regular interferences, surface roll interference exhibits velocity dispersion. This dispersion leads to non-stationary characteristics of surface roll interference, which severely reduces the practical effectiveness of FK filtering. To eliminate the impact of velocity dispersion on surface roll suppression, a surface roll suppression method based on dispersion simulation has been developed. The basic concept is to first estimate the surface roll dispersion curve using frequency-wavenumber conversion, frequency decomposition, and Radon transform. Then, phase correction is performed on the surface roll interference based on the dispersion curve to reduce the non-stationary characteristics of the surface roll interference. On this basis, coherent filtering is performed on the dispersion-corrected seismic data to recover the seismic signals that were submerged by surface waves. In areas with large variations in surface conditions, accurately estimating dispersion curves is extremely difficult, and the accuracy of dispersion curve estimation seriously affects the effectiveness of suppressing surface wave interference. Summary of the Invention

[0004] The embodiments of the present application provide a method and apparatus for suppressing surface roll interference by using phase correction, which directly inverts the phase difference of surface roll interference of different seismic traces from seismic data, thereby improving the recognition capability and attenuation accuracy of surface roll interference.

[0005] Suppose there is seismic data d(x,t) containing surface wave interference. Select a seismic record as the standard channel c(t). Calculate the phase matching filter h(t) between the other seismic channels d(t) and the standard channel. The matrix form of the filter target functional is expressed as

[0006]

[0007] Where D is the Toeplitz matrix composed of seismic traces d(t), h is the vector composed of filters h(t), c is the vector composed of standard traces c(t), and λ is the regularization coefficient. represents the l2 norm, A(ω) is the amplitude spectrum of the filter h(t), and

[0008]

[0009] Where H r (ω) and H i (ω) are the real and imaginary parts of the Fourier transform of the phase filter h(t). Since equation (2) contains a square root operation, it is difficult to directly use equation (1) to solve the filter h(t). Therefore, we rewrite equation (1) as

[0010]

[0011] The above formula consists of two terms, the first one is called the error term, and the second one is called the constraint term. Among them, h is the Toeplitz matrix composed of the filter h(t), and F is the Fourier transform matrix.

[0012]

[0013] Where N is the length of the filter h(t). Equation (3) is solved iteratively using a gradient optimization algorithm. We use the solution of the unconstrained objective functional as the initial value h0 of the filter h(t), that is,

[0014]

[0015] The target functional (3) is a nonlinear function of h. It is difficult to solve h directly. Therefore, we use an iterative method to solve equation (4). j Calculate the constraints At this time, the independent variable in the constraint term of equation (3) only contains h, and it is a linear function of h. Equation (3) can be rewritten as:

[0016]

[0017] in, The derivative of the target functional with respect to h is

[0018]

[0019] Setting the derivative equal to zero, we can obtain the solution h for the j+1th iteration. j+1 ,have

[0020]

[0021] Equation (7) is iterated to obtain the optimal phase-matched filter h(t). This filter is used to perform convolution filtering on the seismic record d(t), thereby eliminating the phase differences between different seismic traces due to velocity dispersion noise. After eliminating the phase differences between different seismic traces, the seismic record is then subjected to FK filtering, which can better suppress surface roll interference and recover seismic signals that are submerged by surface rolls.

[0022] The embodiment of the present application provides a method for suppressing surface roll interference by using phase correction, including:

[0023] The phase difference of surface wave interference of different seismic channels is inverted; the seismic records are filtered using the optimal phase matching filter to eliminate the phase difference of surface wave interference of different seismic channels.

[0024] The inversion of the phase difference of surface wave interference of different seismic channels includes: reading the time-space domain seismic data d(x,t), performing frequency wavenumber analysis on the seismic data, and obtaining the maximum velocity v0 and the highest frequency f0 of the surface wave interference.

[0025] The inversion of the phase difference of surface wave interference between different seismic traces includes: for each seismic trace d(t) in the seismic data, establishing a target functional about the optimal phase matching filter h(t):

[0026]

[0027] The above formula consists of two terms, the first term is called the error term, and the second term is called the constraint term, where: is the Toeplitz matrix composed of the filter h(t), and F is the Fourier transform matrix.

[0028] The initial value h0(t) of the optimal phase matching filter h(t) is calculated using the following equation:

[0029]

[0030] Here, the optimal phase-matched filter h(t) is calculated using an iterative inversion algorithm using the following equation:

[0031] h j+1 is the solution of the j+1th iteration.

[0032] Among them, using the optimal phase matching filter to filter the seismic record to eliminate the phase difference of surface wave interference in different seismic channels includes: using the optimal phase matching filter h(t) to phase filter the time-space domain seismic data d(x, t) to obtain the seismic record e(x, t); performing FK filtering on the seismic record e(x, t) to obtain surface wave interference g(x, t); subtracting the surface wave interference g(x, t) from the seismic record e(x, t) to obtain intermediate seismic data q(x, t).

[0033] Among them, using the best phase matching filter to filter the seismic record to eliminate the phase difference of the surface wave interference of different seismic channels also includes: using the inverse filter estimation method to calculate the inverse operator h corresponding to the best matching filter h(t) -1 (t), the inverse operator h -1 (t) acts on the intermediate seismic data q(x,t) to obtain the seismic data after surface wave suppression.

[0034] Wherein, the method of suppressing surface roll interference by using phase correction further includes: outputting seismic data after surface roll suppression.

[0035] The present application also provides a device for suppressing surface roll interference using phase correction, comprising:

[0036] The inversion unit is used to invert the phase difference of surface wave interference of different seismic channels; the elimination unit is used to filter the seismic records using the optimal phase matching filter to eliminate the phase difference of surface wave interference of different seismic channels.

[0037] The method and device for suppressing surface roll interference by using phase correction in the embodiments of the present application have the following beneficial effects:

[0038] This application does not need to calculate the dispersion curve of surface wave interference. It uses the optimal phase matching method to invert the phase difference of surface wave interference in different seismic channels, thereby eliminating the influence of velocity dispersion on the surface wave interference suppression effect, eliminating surface wave interference to the greatest extent, and improving the signal-to-noise ratio of seismic records. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a flow chart of a method for suppressing surface roll interference by using phase correction according to an embodiment of the present application;

[0040] Figure 2 This is the common shot point seismic data of an eastern oil field;

[0041] Figure 3 This is the seismic data after surface wave suppression using conventional FK filtering;

[0042] Figure 4 For seismic data after application of the present invention;

[0043] Figure 5 This is the common shot point seismic data of an oil field in western China;

[0044] Figure 6 This is the seismic data after surface wave suppression using conventional FK filtering;

[0045] Figure 7 For seismic data after application of the present invention;

[0046] Figure 8 Schematic diagram of the structure of a device for suppressing surface roll interference using phase correction according to an embodiment of the present application. DETAILED DESCRIPTION

[0047] The present application will be further described below with reference to the accompanying drawings and embodiments.

[0048] The following description provides multiple embodiments of the present invention. Different embodiments may be replaced or combined, and thus this application may be considered to include all possible combinations of the same and / or different embodiments described. Thus, if one embodiment includes features A, B, and C, and another embodiment includes features B and D, then this application should also be considered to include embodiments that include one or more of all other possible combinations of features A, B, C, and D, even though such embodiments may not be explicitly described in the following text.

[0049] Example 1

[0050] In order to better eliminate surface roll interference and restore effective seismic signals, this application proposes a surface roll interference suppression method based on phase correction, such as Figure 1 As shown, it includes: S1, inverting the phase difference of surface wave interference of different seismic channels; S2, filtering the seismic record with an optimal phase matching filter to eliminate the phase difference of surface wave interference of different seismic channels.

[0051] This application does not require calculation of dispersion curves, and directly inverts the phase differences of surface wave interferences of different seismic traces from seismic data, thereby improving the recognition capability and attenuation accuracy of surface wave interference.

[0052] Example 2

[0053] Velocity dispersion causes the non-stationary characteristics of surface-roll interference, rendering it no longer regular in the usual sense, but rather exhibiting spatial characteristics of "apparent" regular or "quasi-regular" interference. Velocity dispersion means that the propagation velocity of surface-roll interference is no longer a constant, but instead depends on a function of frequency. This frequency dependence of velocity causes phase differences in surface-roll interference between different seismic traces, severely reducing the effectiveness of the FK filter in suppressing surface-roll interference. Therefore, if we can estimate the phase differences between different seismic traces caused by velocity dispersion and eliminate these differences through phase filtering, we can effectively enhance the effectiveness of the FK filter in suppressing surface-roll interference.

[0054] Suppose there is seismic data d(x,t) containing surface wave interference. Select a seismic record as the standard channel c(t). Calculate the phase matching filter h(t) between the other seismic channels d(t) and the standard channel. The matrix form of the filter target functional is expressed as

[0055]

[0056] Where D is the Toeplitz matrix composed of seismic traces d(t), h is the vector composed of filters h(t), c is the vector composed of standard traces c(t), and λ is the regularization coefficient. represents the l2 norm, A(ω) is the amplitude spectrum of the filter h(t), and

[0057]

[0058] Where H r (ω) and H i (ω) are the real and imaginary parts of the Fourier transform of the phase filter h(t). Since equation (2) contains a square root operation, it is difficult to directly use equation (1) to solve the filter h(t). Therefore, we rewrite equation (1) as

[0059]

[0060] The above formula consists of two terms, the first term is called the error term, and the second term is called the constraint term. is the Toeplitz matrix composed of the filter h(t), F is the Fourier transform matrix, and

[0061]

[0062] Where N is the length of the filter h(t). Equation (3) is solved iteratively using a gradient optimization algorithm. We use the solution of the unconstrained objective functional as the initial value h0 of the filter h(t), that is,

[0063]

[0064] The target functional (3) is a nonlinear function of h. It is difficult to solve h directly. Therefore, we use an iterative method to solve equation (4). j Calculate the constraints At this time, the independent variable in the constraint term of equation (3) only contains h, and it is a linear function of h. Equation (3) can be rewritten as:

[0065]

[0066] in, The derivative of the target functional with respect to h is

[0067]

[0068] Setting the derivative equal to zero, we can obtain the solution h for the j+1th iteration. j+1 ,have

[0069]

[0070] Equation (7) is iterated to obtain the optimal phase-matched filter h(t). This filter is used to perform convolution filtering on the seismic record d(t), thereby eliminating the phase differences between different seismic traces due to velocity dispersion noise. After eliminating the phase differences between different seismic traces, the seismic record is then subjected to FK filtering, which can better suppress surface roll interference and recover seismic signals that are submerged by surface rolls.

[0071] This application uses the following steps to perform multiple wave suppression:

[0072] (1) Read the time-space domain seismic data d(x,t), perform frequency wave number analysis on the seismic data, and obtain the maximum velocity v0 of surface wave interference and the highest frequency f0 of surface wave interference.

[0073] (2) From the time-space domain seismic data d(x,t), a seismic trace with stable surface wave interference is selected as the standard trace c(t).

[0074] (3) For each seismic trace d(t) in the seismic data, a target functional for the optimal phase matching filter h(t) is established as shown in equation (3).

[0075] (4) Use equation (4) to calculate the initial value h0(t) of the optimal phase matching filter h(t).

[0076] (5) Using the iterative inversion algorithm of equation (7), calculate the optimal phase matching filter h(t).

[0077] (6) Use the optimal phase matching filter h(t) to phase filter the time-space domain seismic data d(x,t) to obtain the seismic record e(x,t).

[0078] (7) Design a fan-shaped filter with a maximum speed of v0 and a maximum frequency of f0, perform FK filtering on the seismic record e(x, t), and obtain the surface wave interference g(x, t).

[0079] (8) Subtract the surface wave interference g(x,t) from the seismic record e(x,t) to obtain the intermediate seismic data q(x,t).

[0080] (9) Using the inverse filter estimation method, calculate the inverse operator h corresponding to the optimal phase matching filter h(t) -1 (t), and apply it to the intermediate seismic data q(x,t) to obtain the seismic data s(x,t) after surface wave suppression.

[0081] (10) Output the seismic data s(x, t) after surface wave suppression.

[0082] This application provides a method for suppressing surface-roll interference using phase correction. This method eliminates the need to calculate the dispersion curve of surface-roll interference. Instead, it uses an optimal phase matching method to invert the phase differences of surface-roll interference from different seismic traces. This method eliminates the effect of velocity dispersion on the suppression of surface-roll interference, maximally eliminating surface-roll interference and improving the signal-to-noise ratio of seismic recordings. In addition to surface-roll interference, this application can also be expanded to effectively suppress other non-stationary regular noise, such as multiple refraction.

[0083] Figure 2 This is the common shot point seismic data of an oil field in eastern my country. The "broom-shaped" surface wave noise in the seismic data has very high energy and drowns out the effective signals from the underground. Figure 3 It is the seismic data after surface roll suppression using conventional FK filtering. Although most of the surface roll interference has been effectively suppressed, the dispersion characteristics of the surface roll interference reduce the application effect of FK filtering. After filtering, the seismic data still retains a certain amount of surface roll interference energy. Figure 4 In the seismic data after the present invention is applied, the surface wave interference is more thoroughly suppressed, and the seismic signal contaminated by the surface wave interference is better restored.

[0084] Figure 5 This is the common shot point seismic data of an oil field in western my country. The surface wave interference frequency in this seismic data is relatively high, and there is a large overlap with the frequency components of the effective signal. Figure 6 These are seismic data obtained after surface wave suppression using conventional FK filtering. The dispersion characteristics of surface wave interference not only affect the surface wave suppression effect, but also some low-frequency energy that is close to the effective signal spatial trajectory appears in the seismic data after surface wave suppression. Figure 7 is the seismic data after the application of the present invention, and Figure 6 Compared with the conventional FK filtering method shown in FIG, the seismic data after filtering by the present invention presents clearer seismic signals.

[0085] This application uses an iterative inversion method to estimate the phase difference of surface wave interference in different seismic records caused by velocity dispersion, effectively eliminating the non-steady-state characteristics of surface wave interference caused by velocity dispersion, overcoming the influence of surface wave dispersion on FK filtering, improving the ability to suppress surface wave interference, and better restoring seismic signals submerged by surface wave interference.

[0086] like Figure 8 As shown, the present application also provides a device for suppressing surface wave interference using phase correction, including: an inversion unit 201, used to invert the phase difference of surface wave interference of different seismic channels; an elimination unit 202, used to filter the seismic record using an optimal phase matching filter to eliminate the phase difference of surface wave interference of different seismic channels.

[0087] In this application, the device embodiment for suppressing surface roll interference using phase correction is basically similar to the method embodiment for suppressing surface roll interference using phase correction. For relevant details, please refer to the introduction of the method embodiment for suppressing surface roll interference using phase correction.

[0088] An embodiment of the present application further provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, any one of the above-mentioned method steps for suppressing surface roll interference using phase correction is implemented.

[0089] An embodiment of the present invention further provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-described method steps for suppressing surface roll interference using phase correction. The computer-readable storage medium may include, but is not limited to, any type of disk, including a floppy disk, an optical disk, a DVD, a CD-ROM, a microdrive, a magneto-optical disk, a ROM, a RAM, an EPROM, an EEPROM, a DRAM, a VRAM, a flash memory device, a magnetic or optical card, a nanosystem (including a molecular memory IC), or any other type of medium or device suitable for storing instructions and / or data.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for suppressing surface roll interference using phase correction, characterized in that: include: Invert the phase difference of surface wave interference between different seismic traces; Filter the seismic records using the optimal phase matching filter to eliminate the phase differences of surface wave interference from different seismic traces; The inversion of the phase difference of surface wave interference between different seismic traces includes: , establish the optimal phase matching filter The target functional is: The above formula consists of two terms, the first term is called the error term, and the second term is called the constraint term, where: The optimal phase matching filter The Toeplitz matrix formed by is the Fourier transform matrix, By earthquake The Toeplitz matrix formed by The optimal phase matching filter The vector formed, By Standard Road The vector formed, is the regularization coefficient, represent norm; The optimal phase-matched filter is calculated using the following equation: Initial value of , ； The optimal phase-matched filter is calculated using the iterative inversion algorithm of the following equation: : , h j+1 is the solution of the j+1th iteration, .

2. The method for suppressing surface roll interference by using phase correction according to claim 1, characterized in that: Inversion of phase differences of surface wave interferences between different seismic traces also includes: reading time-space domain seismic data , perform frequency wave number analysis on seismic data and obtain the maximum velocity of surface wave interference The highest frequency of surface wave interference .

3. The method for suppressing surface roll interference by using phase correction according to claim 1 or 2, characterized in that: Filtering the seismic records using the best phase matching filter to eliminate the phase difference of surface wave interference from different seismic channels includes: using the best phase matching filter Seismic data in time and space Perform phase filtering to obtain earthquake records ; Earthquake records Perform FK filtering to obtain surface wave interference ; From the earthquake record Subtract surface wave interference , get the intermediate seismic data .

4. The method for suppressing surface roll interference by using phase correction according to claim 3, characterized in that: Filtering the seismic records with the best phase matching filter to eliminate the phase difference of surface wave interference from different seismic channels also includes: using the inverse filter estimation method to calculate the best phase matching filter The corresponding inverse operator , the inverse operator Acting on intermediate seismic data , get the seismic data after surface wave suppression .

5. The method for suppressing surface roll interference by using phase correction according to claim 1 or 2, characterized in that: The method of suppressing surface roll interference by using phase correction further includes: outputting seismic data after surface roll suppression.

6. A device for suppressing surface roll interference using phase correction, characterized in that: include: The inversion unit is used to invert the phase difference of surface wave interference between different seismic channels; the elimination unit is used to filter the seismic records using the optimal phase matching filter to eliminate the phase difference of surface wave interference between different seismic channels; Inversion of phase differences in surface wave interference from different seismic traces includes: For each seismic trace in the seismic data , establish the optimal phase matching filter The target functional is: The above formula consists of two terms, the first term is called the error term, and the second term is called the constraint term, where: The optimal phase matching filter The Toeplitz matrix formed by is the Fourier transform matrix, By earthquake The Toeplitz matrix formed by The optimal phase matching filter The vector formed, By Standard Road The vector formed, is the regularization coefficient, represent norm; The optimal phase-matched filter is calculated using the following equation: Initial value of , ； The optimal phase-matched filter is calculated using the iterative inversion algorithm of the following equation: : , h j+1 is the solution of the j+1th iteration, .

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