Method for eliminating fitting suppression multiples based on amplitude frequency difference

Abstract

The invention provides a method for rejecting fitting suppressed multiples based on amplitude frequency difference. The rejecting method comprises the steps of S1, acquiring seismic data needing to be subjected to multiple suppression; s2, identifying near-channel multiples by using the amplitude and the change of the amplitudes with different frequencies along with the offset distance; s3, suppressing near-channel multiples by using amplitude frequency characteristic differences and a rejection fitting method; and S4, eliminating the seismic data after fitting and suppressing the multiples by using the frequency amplitude difference. The method for effectively suppressing the near-offset multiple waves is formed by using the amplitude frequency characteristic difference of primary reflected waves and the multiple waves, and a primary wave protection technology and a near-channel multiple wave priority identification and elimination technology are used in the implementation process, so that the purpose of removing the near-offset multiple waves in an amplitude-preserving manner is achieved.

Description

Technical Field

[0001] The present invention relates to the field of geophysical processing technology, and in particular to a method for eliminating, fitting and suppressing multiple waves based on amplitude-frequency differences. Background Art

[0002] In recent decades, many methods for suppressing multiple waves have been developed and great progress has been made, but each suppression method is targeted at a certain type of multiple waves, and the results are not perfect. They all suppress the propagation of multiple waves according to an ideal model.

[0003] Suppression methods based on the periodicity of multiple waves, such as predictive deconvolution, include deconvolution in the τ-p domain and time domain. The deconvolution method has a good effect on suppressing short-period multiple waves such as rumble waves near the shallow seabed, but it is not suitable for predictive deconvolution in the entire work area for sea areas with large changes from shallow water to deep water.

[0004] The suppression method of distinguishing effective waves and multiple waves based on the residual time difference of the gather is represented by the velocity filtering method, such as the Radon transform method, FK filtering, etc. This type of method has a good effect on suppressing medium and long period multiple waves in medium and long distance channels, but the suppression of multiple waves in near channels is relatively poor, and this type of method has high requirements on the accuracy of velocity.

[0005] The SRME method for free surface multiple waves includes the wave field extrapolation model driven method based on seabed data and the pure data driven feedback method and scattering method. The former requires an accurate seabed model as prior information, and then simulates the multiple wave model, and then adaptively subtracts the original data. Its limitation is that the seabed model is not easy to obtain accurately.

[0006] The near-channel multiple waves have strong amplitude and high frequency, and the time difference between the multiple waves and the effective reflected waves is small. The currently used multiple wave suppression methods cannot effectively remove them. Summary of the invention

[0007] In view of the above problems, the present invention is proposed to provide a method for suppressing multiple waves based on amplitude-frequency difference elimination fitting, which overcomes the above problems or at least partially solves the above problems.

[0008] According to one aspect of the present invention, a method for eliminating and fitting multiple waves based on amplitude-frequency difference is provided, and the elimination method comprises:

[0009] Step S1: Acquire seismic data that requires multiple wave suppression;

[0010] Step S2: using the amplitude and the amplitude of different frequencies changing with the offset to identify the near-track multiple waves;

[0011] Step S3: using the amplitude-frequency characteristic difference to suppress the near-channel multiple waves by using the elimination fitting method;

[0012] Step S4: using frequency amplitude difference to eliminate fitting and suppress multiple waves of seismic data.

[0013] Optionally, the step S1: acquiring seismic data requiring multiple wave suppression specifically includes: acquiring common imaging point pre-stack gather data requiring multiple wave suppression.

[0014] Optionally, the step S2: identifying near-track multiple waves by using the amplitude and the amplitude of different frequencies changing with the offset specifically includes:

[0015] In order to express the relationship between elasticity and reflection parameters, formula (1) is obtained:

[0016]

[0017] Where: V P is the longitudinal wave velocity; V S is the shear wave velocity; ρ is the rock density; α is the incident angle; R is the reflection coefficient, which is expressed in the following formula (2):

[0018]

[0019] Optionally, the step S2 is simplified to a parabolic equation, as shown in formula (3), which expresses the amplitude change;

[0020] y≈R+Wx+Vx 2 (3)

[0021] Taking the derivative of the above formula, we get (4):

[0022] y′≈W+2Vx(4)

[0023] Formula (4) shows that the amplitude change in seismic data is related to the offset distance.

[0024] Optionally, the step S2: identifying near-track multiple waves by using the amplitude and the amplitude of different frequencies changing with the offset specifically includes:

[0025] The amplitude change of seismic data is related to the offset distance and the change is gentle, indicating that the reflection signal is effective;

[0026] If an extreme value appears, it indicates that the reflection signal is invalid.

[0027] Optionally, the step S2 specifically includes:

[0028] The multiple amplitudes are calculated within a sliding window and are larger than the average amplitude value;

[0029] The event axis of the effective reflection wave in a common imaging point gather within a suitable sliding window is relatively flat, and the amplitude changes evenly;

[0030] The phase axes of multiple waves are discontinuous or the amplitudes have extreme values.

[0031] Optionally, the method for identifying near-track multiple waves in step S2 further includes: identifying near-track multiple waves by using the change of amplitudes of different frequencies along with the offset distance.

[0032] Optionally, the step S3: using the amplitude-frequency characteristic difference to suppress near-channel multiple waves by using a elimination fitting method specifically includes:

[0033] The amplitude of effective reflection signal is regular, while the amplitude of multiple waves is quite different. The amplitude difference is used to identify multiple waves.

[0034] For effective reflected waves, the amplitude is expressed by the parabolic equation

[0035] A=P+Qx 2 (5)

[0036] Where A is the amplitude, P is the amplitude of the normally incident longitudinal wave, X is the offset, and Q can be called the parabola curvature.

[0037] Optionally, the step S3: using the amplitude-frequency characteristic difference to suppress near-channel multiple waves by using a elimination fitting method specifically includes:

[0038] The propagation path of multiple waves changes, the amplitude does not satisfy the AVO law, and the waveform deviates from the effective reflection wave parabola;

[0039] In data processing, points with deviations greater than the threshold are eliminated to suppress multiple waves.

[0040] Optionally, the step S3: using the amplitude-frequency characteristic difference to suppress near-channel multiple waves by using a elimination fitting method specifically includes:

[0041] The least squares algorithm is used to fit the P and Q values ​​to obtain the effective reflection wave parabola;

[0042] Then calculate the P and Q values ​​through multiple iterations until the elimination percentage is equal to the preset value;

[0043] Finally, the seismic data after suppressing multiple waves is output.

[0044] The present invention provides a method for suppressing multiple waves by eliminating fitting based on amplitude-frequency difference, and the elimination method includes: step S1: obtaining seismic data that needs to suppress multiple waves; step S2: identifying near-channel multiple waves by using amplitude and amplitude of different frequencies with offset; step S3: suppressing near-channel multiple waves by eliminating fitting method by using amplitude-frequency characteristic difference; step S4: eliminating seismic data after multiple waves are suppressed by fitting by using frequency-amplitude difference. By using the amplitude-frequency characteristic difference between the primary reflection wave and the multiple waves, a method for effectively suppressing near-offset multiple waves is formed, and in the implementation process, the primary wave protection technology and near-channel multiple wave priority identification and elimination technology are used to achieve the purpose of removing near-offset multiple waves with amplitude preservation.

[0045] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0047] Figure 1 A flow chart of a method for suppressing multiple waves based on amplitude-frequency difference elimination and fitting provided in an embodiment of the present invention;

[0048] Figure 2 A gather having close-offset multiple waves in an embodiment of the present invention;

[0049] Figure 3 The application effect of the gather after using amplitude-frequency difference elimination fitting to suppress multiple waves in the embodiment of the present invention;

[0050] Figure 4 is a gather with close-offset multiple waves in an embodiment of the present invention;

[0051] Figure 5 This is the application effect of the gather after eliminating the multiple waves suppressed by the fitting method in the embodiment of the present invention. DETAILED DESCRIPTION

[0052] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0053] The terms "comprises" and "having" and any variations thereof in the description embodiments, claims and drawings of the present invention are intended to cover non-exclusive inclusions, for example, including a series of steps or units.

[0054] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0055] A method for eliminating and fitting multiple waves based on amplitude-frequency difference suppression, the method comprising:

[0056] Step S1: inputting seismic data that needs to be subjected to multiple wave suppression;

[0057] Step S2: using the amplitude and the amplitude of different frequencies changing with the offset to identify the near-track multiple waves;

[0058] Step S3: using the amplitude-frequency characteristic difference to suppress the near-channel multiple waves by using the elimination fitting method;

[0059] Step S4: outputting seismic data after multiple waves are suppressed by fitting by frequency amplitude difference elimination;

[0060] In step S1, the pre-stack gather data of the common imaging point that needs to be subjected to multiple wave suppression is input.

[0061] In step S2, the change of amplitude with offset is used to identify the near-track multiple waves, and the change of amplitude with offset specifically includes:

[0062] In order to express the relationship between elasticity and reflection parameters, formula (1) is obtained:

[0063]

[0064] Where: V P is the longitudinal wave velocity; V S is the shear wave velocity; ρ is the rock density; α is the incident angle; R is the reflection coefficient, assuming the following formula (2):

[0065]

[0066] In step S2, R(a) can be simplified into a parabolic equation, as shown in formula (3), which can express the amplitude change more intuitively.

[0067] y≈R+Wx+Vx 2 (3)

[0068] Taking the derivative of the above formula, we get (4):

[0069] y′≈W+2Vx(4)

[0070] Formula (4) shows that the amplitude change in seismic data is related to the offset distance.

[0071] In step S2, identifying the near-path residual multiple waves specifically includes:

[0072] The amplitude change of seismic data is related to the offset distance and changes gently. If an extreme value appears, it indicates that it is not a valid reflection signal. This is the key to identifying near-track multiple waves.

[0073] In step S2, the previous law of finding multiple waves mainly depends on periodicity and time difference, and the most obvious feature is that the amplitude change is easy to be ignored. In this method, the amplitude of multiple waves is calculated in a sliding window, which is larger than the average amplitude value; the phase axis of the effective reflection wave in the common imaging point gather in a suitable sliding window is relatively flat, and the amplitude changes evenly; while the phase axis of the multiple waves is discontinuous or the amplitude has an extreme value.

[0074] In step S2, similar to using amplitude differences to identify near-offset multiples, near-track multiples can also be identified by using the change in amplitude of different frequencies with offset.

[0075] In step S3, the frequency amplitude difference is used to suppress the near-channel multiple waves by adopting the elimination fitting method, and the elimination fitting method specifically includes:

[0076] The amplitude of the effective reflection signal is regular, while the amplitude of the multiple waves varies greatly, so the amplitude difference is used to identify the multiple waves. For the effective reflection wave, the amplitude is expressed by the parabola equation

[0077] A=P+Qx 2 (5)

[0078] In formula (5), P represents the amplitude of the longitudinal wave, X represents the offset, A represents the amplitude, and Q represents the parabolic curvature.

[0079] In step S3, the change of the propagation path of the multiple waves, the amplitude does not meet the AVO law, and its waveform deviates from the effective reflection wave parabola. In data processing, these points with large deviations are eliminated to suppress the multiple waves.

[0080] In step S3, the amplitude-frequency difference is used to suppress the near-offset multiple waves by adopting a elimination fitting method. The implementation steps of the elimination fitting specifically include:

[0081] First, the least squares algorithm is used to fit the P and Q values ​​to obtain the effective reflection wave parabola; then the P and Q values ​​are calculated through multiple iterations until the elimination percentage is equal to the preset value; finally, the seismic data after suppressing multiple waves is output.

[0082] like Figure 1 As shown, a method for suppressing multiple waves by eliminating fitting using amplitude-frequency differences includes:

[0083] Step S1: inputting seismic data that needs to be subjected to multiple wave suppression;

[0084] Step S2: using the amplitude and the amplitude of different frequencies changing with the offset to identify the near-track multiple waves;

[0085] Step S3: using the amplitude-frequency characteristic difference to suppress the near-channel multiple waves by using the elimination fitting method;

[0086] Step S4: outputting seismic data after multiple waves are suppressed by fitting by frequency amplitude difference elimination;

[0087] In step S1, the pre-stack gather data of the common imaging point that needs to be subjected to multiple wave suppression is input.

[0088] Specific embodiment 1: Figure 2 is a gather with close-offset multiples; Figure 3 This is the application effect of the gather after the amplitude-frequency difference is eliminated and fitted to suppress multiple waves. Figure 3 It can be seen that the multiple wave suppression effect at close offset is good, and the effective wave is almost not damaged or lost. After removing the multiple waves, the signal-to-noise ratio of the weak reflection signal is significantly improved, and the wave group characteristics are also restored.

[0089] Specific embodiment 2: Figure 4 It is the gather of close-offset multiple waves; Figure 5 This is the application effect of the gather after eliminating the fitting method to suppress multiple waves. Figure 5 It can be seen that by utilizing the differences in amplitude and frequency characteristics between multiple waves and primary waves, the multiple waves at near offset are suppressed effectively, achieving the purpose of removing multiple waves at near offset with amplitude preservation.

[0090] Beneficial effects: The present invention provides a method for suppressing multiple waves by eliminating and fitting based on amplitude-frequency difference. The method utilizes the difference in amplitude-frequency characteristics between the primary reflected wave and the multiple waves to form a method for effectively suppressing the multiple waves at near offset. The method uses primary wave protection technology and near-channel multiple wave priority identification and elimination technology in the implementation process to achieve the purpose of removing the multiple waves at near offset with amplitude preservation.

[0091] The present invention utilizes the differences in amplitude and frequency characteristics between multiple waves and primary waves to form a method for effectively suppressing near-offset multiple waves; in the implementation process of the present invention, primary wave protection technology and near-channel multiple wave priority identification and elimination technology are used to achieve the purpose of removing near-offset multiple waves with amplitude preservation.

[0092] The above specific implementation methods further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific implementation methods of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for eliminating and fitting multiple waves based on amplitude-frequency differences. It is characterized in that The elimination method includes: Step S1: Acquire seismic data that requires multiple wave suppression; Step S2: using the amplitude and the amplitude of different frequencies changing with the offset to identify the near-track multiple waves; Step S3: using the amplitude-frequency characteristic difference to suppress the near-channel multiple waves by using the elimination fitting method; Step S4: using frequency amplitude difference to eliminate fitting and suppress multiple waves of seismic data.

2. According to claim 1, a method for eliminating and fitting multiple waves based on amplitude-frequency difference, It is characterized in that The step S1: acquiring seismic data that needs to be subjected to multiple wave suppression specifically includes: acquiring pre-stack gather data of common imaging points that needs to be subjected to multiple wave suppression.

3. According to claim 1, a method for eliminating and fitting multiple waves based on amplitude-frequency difference, It is characterized in that The step S2: identifying near-track multiple waves by using the amplitude and the amplitude of different frequencies changing with the offset specifically includes: In order to express the relationship between elasticity and reflection parameters, formula (1) is obtained: Where: V P is the longitudinal wave velocity; V S is the shear wave velocity; ρ is the rock density; α is the incident angle; R is the reflection coefficient, which is expressed in the following formula (2):

4. The method for suppressing multiple waves by eliminating and fitting based on amplitude-frequency difference according to claim 3, It is characterized in that The step S2 is simplified to a parabolic equation, as shown in formula (3), which expresses the change of amplitude; y≈R+Wx+Vx 2 (3) Taking the derivative of the above formula, we get (4): y′≈W+2Vx(4) Formula (4) shows that the amplitude change in seismic data is related to the offset distance.

5. The method for suppressing multiple waves by eliminating and fitting based on amplitude-frequency difference according to claim 1, It is characterized in that The step S2: identifying near-track multiple waves by using the amplitude and the amplitude of different frequencies changing with the offset specifically includes: The amplitude change of seismic data is related to the offset distance and the change is gentle, indicating that the reflection signal is effective; If an extreme value appears, it indicates that the reflection signal is invalid.

6. The method for suppressing multiple waves by eliminating and fitting based on amplitude-frequency difference according to claim 1, It is characterized in that The step S2 specifically includes: The multiple amplitudes are calculated within a sliding window and are larger than the average amplitude value; The event axis of the effective reflection wave in a common imaging point gather within a suitable sliding window is relatively flat, and the amplitude changes evenly; The phase axes of multiple waves are discontinuous or the amplitudes have extreme values.

7. The method for suppressing multiple waves by eliminating and fitting based on amplitude-frequency difference according to claim 1, It is characterized in that The method for identifying near-track multiple waves in step S2 further includes: identifying near-track multiple waves by using the change of amplitudes of different frequencies along with the offset distance.

8. The method for suppressing multiple waves by eliminating and fitting based on amplitude-frequency difference according to claim 1, It is characterized in that The step S3: using the amplitude-frequency characteristic difference to suppress the near-channel multiple waves by using the elimination fitting method specifically includes: The amplitude of effective reflection signal is regular, while the amplitude of multiple waves is quite different. The amplitude difference is used to identify multiple waves. For effective reflected waves, the amplitude is expressed by the parabolic equation A=P+Qx 2 (5) Where A is the amplitude, P is the amplitude of the normally incident longitudinal wave, X is the offset, and Q can be called the parabola curvature.

9. The method for suppressing multiple waves by eliminating and fitting based on amplitude-frequency difference according to claim 1, It is characterized in that The step S3: using the amplitude-frequency characteristic difference to suppress the near-channel multiple waves by using the elimination fitting method specifically includes: The propagation path of multiple waves changes, the amplitude does not satisfy the AVO law, and the waveform deviates from the effective reflection wave parabola; In data processing, points with deviations greater than the threshold are eliminated to suppress multiple waves.

10. The method for suppressing multiple waves based on amplitude-frequency difference elimination and fitting according to claim 1, It is characterized in that The step S3: using the amplitude-frequency characteristic difference to suppress the near-channel multiple waves by using the elimination fitting method specifically includes: The least squares algorithm is used to fit the P and Q values ​​to obtain the effective reflection wave parabola; Then calculate the P and Q values ​​through multiple iterations until the elimination percentage is equal to the preset value; Finally, the seismic data after suppressing multiple waves is output.

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