Marchenko multiple elimination method for tracking wave impedance interface

Abstract

This invention discloses a Marchenko multiple suppression method for tracking wave impedance interfaces, belonging to the field of seismic data processing technology. The method includes the following steps: S1, obtaining wave impedance inversion results across the entire depth domain based on surface observation seismic data and the background velocity field; S2, extracting the location information of strong wave impedance interfaces and identifying several key locations between these interfaces; S3, using a Bezier curve smoothing method to obtain the spatial location of the focal point that maximizes the penetration of the strong wave impedance interface; S4, determining the ascending and descending Green's functions for the spatial location of the focal point; S5, predicting interlayer multiples using seismic interferometry; and S6, obtaining the seismic shot gather for suppressing interlayer multiples through adaptive matched filtering. This invention does not require a precise velocity model, relying only on a macroscopic velocity model, and can obtain deep-domain strong wave impedance geological information, accurately predicting and suppressing interlayer multiples by combining wave impedance information.

Description

Technical Field

[0001] This invention belongs to the field of seismic data processing technology, specifically relating to a Marchenko multiple suppression method for tracking wave impedance interfaces. Background Technology

[0002] In the field of seismic data processing, seismic multiples can be classified into free-surface multiples and interlayer multiples based on their reflection horizon. Multiples are generated by changes in the velocity and density of the subsurface medium, which reduces the signal-to-noise ratio of seismic data and degrades imaging quality, severely impacting deep and ultra-deep oil and gas exploration (such as complex target areas in western China) and offshore oil and gas exploration. Currently, methods for suppressing free-surface multiples are relatively mature. However, interlayer multiples have a more complex generation mechanism, poor periodicity, weak energy, and often intersect with primary waves. This makes the identification and elimination of interlayer multiples extremely difficult, and suppressing interlayer multiples in areas with complex subsurface structures remains a global challenge.

[0003] Currently, the methods for suppressing interlayer multiples in the industry can be mainly divided into filtering methods and wave equation methods. Filtering methods utilize the periodicity and separability of primary and multiple waves to suppress them. When the assumptions are met, filtering methods can effectively suppress or eliminate multiples with low computational cost and high efficiency. However, for seismic data from areas with complex underground structures, multiples and primary waves are very similar in energy and velocity, and their dynamic correction time differences are generally small. Filtering methods based on geometric seismic differences are difficult to effectively suppress multiples and may even severely damage primary waves. Wave equation methods require the separation of specific components in the shot data or have high requirements for model accuracy. They involve a lot of prior information and are difficult to apply to complex seismic data without obvious reflection axes.

[0004] In recent years, a new inter-layer multiple prediction method based on Marchenko theory has been developed internationally. The Marchenko method avoids direct manipulation of shot data and only requires a coarse background velocity model. It has high adaptability to seismic data in complex regions, and can effectively suppress inter-layer multiples when combined with adaptive subtraction.

[0005] Interlayer multiples are generated by multiple reflections between two or more subsurface interfaces. Among them, because the reflection coefficient of the strong impedance interface is larger, the amplitude of the seismic wave propagating between the strong impedance interfaces is relatively large. Multiple reflections between the strong impedance interfaces are the main reason for the generation of interlayer multiples.

[0006] In the interlayer multiple suppression method based on Marchenko's self-focusing theory, the spatial location of the focal point is crucial. To predict as many and as complete as possible of interlayer multiples, the focal point must pass through the ray paths of most interlayer multiples. Therefore, the focal point should be located inside a strong impedance stratum or between two strong impedance interfaces.

[0007] Problem 1: In actual seismic data processing, the strong wave impedance interface underground is unknown, making it difficult to determine the optimal sinking depth of the focal point. Existing methods have arbitrariness and randomness in the selection of focal point depth.

[0008] Existing problem 2: Currently, the industry only considers horizontal placement when selecting focal points, without taking into account the tilt or curvature of underground strata. However, underground structures often feature tilted structures, and when strata are tilted, horizontally placed focal points will pass through the tilted strata. Theoretically, only when the focal point selection interface fits the curved or folded strata to the greatest extent can the most complete interlayer multiples be predicted; otherwise, some interlayer multiples will not be effectively predicted. Summary of the Invention

[0009] To address the problem that existing Marchenko theory does not consider the selection of the spatial location of the focal point, and that the location distribution of the focal point greatly affects the prediction results of interlayer multiples, this invention proposes a Marchenko multiple suppression method based on the tracking wave impedance interface.

[0010] The technical solution of this invention is: a Marchenko multiple suppression method for tracking wave impedance interfaces, comprising the following steps:

[0011] S1. Based on surface observation seismic data and background velocity field, the wave impedance inversion results of the entire depth domain are obtained;

[0012] S2. Based on the wave impedance inversion results of the entire depth domain, take the wave impedance energy abrupt change interface as the dividing interface, extract the location information of the strong wave impedance interface, and pick out several key locations between the strong wave impedance interfaces.

[0013] S3. Based on several key locations between the strong wave impedance interfaces, the spatial location of the focal point that maximizes the penetration of the strong wave impedance interface is obtained using the Bezier curve smoothing method.

[0014] S4. Determine the ascending and descending Green's functions for the spatial location of the focal point;

[0015] S5. Based on the ascending and descending Green's functions of the focal point's spatial location, obtain the interlayer multiple waves;

[0016] S6. Based on the inter-layer multiple waves, obtain the seismic shot gather for suppressing the inter-layer multiple waves.

[0017] Furthermore, in S1, based on surface observation seismic data and background velocity field, the uplink and downlink Green's functions of all grids are calculated. Based on the energy of the uplink and downlink Green's functions, the wave impedance inversion results of the entire depth domain are obtained.

[0018] Furthermore, in S1, the energy of the Green's function The expression is:

[0019] ;

[0020] in, This represents any non-zero wave field value in the Green's function. This indicates the number of non-zero wave field values ​​in the Green's function. The type of energy norm is generally taken as... That is, to make the Green's function The norm is used as the wave impedance value.

[0021] Furthermore, in S3, the method for smoothing Bézier curves is as follows:

[0022] ;

[0023] in, This represents the value at any position on the curve. Represents the weight parameters. This indicates the first key point for segment selection. This indicates the second key point in the segment selection. This indicates the third key point in the segment selection. This indicates the fourth key point in the segment selection.

[0024] Furthermore, in S4, surface-observed seismic data and background velocity field are used as inputs, and strong wave impedance interface location information is used as spatial constraints to obtain the upward and downward Green's functions of the focal point spatial location.

[0025] Furthermore, S5 includes the following sub-steps:

[0026] S51. Remove the direct wave component of the descending Green's function at the spatial location of the focal point;

[0027] S52. Sorting and extracting the common focal point gathers of the downlink Green's function with the direct wave component removed, sorting and extracting the common shot gathers of the uplink Green's function, and obtaining interlayer multiples through seismic interferometry.

[0028] Furthermore, in S52, the confocal gather of the descending Green's function of the direct wave component is removed so that the wave field of the zeroth scattering is extracted.

[0029] Furthermore, in S52, both the ascending Green's function and the descending Green's function that extracts and removes the direct wave component are wave fields with first-order scattering or higher.

[0030] Furthermore, in S52, the expression for interlayer multiples is:

[0031] ;

[0032] in, Indicated by As the epicenter and with The interlayer multiple waves received by the detector Indicates the receiving time of the Green's function. This represents the downlink Green's function after removing the direct wave. Represents the complete upward Green's function. Represents the density function, Indicates the range of spatial integration.

[0033] Furthermore, in S6, if there are more than two strong wave impedance interfaces, the process returns to S3 and performs adaptive subtraction layer by layer until all inter-layer multiples associated with the strata are suppressed, resulting in a seismic shot gather with suppressed inter-layer multiples.

[0034] The beneficial effects of this invention are:

[0035] (1) This invention provides a wave impedance inversion method based on Marchenko theory to obtain the spatial distribution of strong wave impedance interface, which provides prior information for the selection of focal point location and also provides additional geological information.

[0036] (2) The present invention uses the spatial distribution of strong wave impedance interface as prior information, and can predict as many and as complete interlayer multiples as possible without increasing the amount of computation.

[0037] (3) Based on the wave impedance inversion information, if there are multiple strong wave impedance interfaces, the focal point layer can be set multiple times to predict the interlayer multiples generated by strata at different depths. The interlayer multiples generated by different strata can be suppressed one by one by combining adaptive subtraction in multiple rounds.

[0038] (4) The inter-layer multiples predicted by this invention have accurate travel time and phase, and can effectively suppress inter-layer multiples when combined with adaptive subtraction.

[0039] (5) This invention does not require an accurate velocity model, but can be realized by relying solely on a macroscopic velocity model. It is also highly robust to the errors of the velocity model, and can still accurately predict interlayer multiple waves even if there are certain velocity errors. Attached Figure Description

[0040] Figure 1A flowchart of the Marchenko multiple wave suppression method for tracking wave impedance interfaces;

[0041] Figure 2 (a) is a schematic diagram of the Green's function component ray of the descending Green's function;

[0042] Figure 2 (b) is a schematic diagram of the Green's function component rays of the upward Green's function;

[0043] Figure 3 A schematic diagram of interlayer multiple wave rays predicted by seismic interferometry theory;

[0044] Figure 4 (a) is a schematic diagram of the velocity model;

[0045] Figure 4 (b) is a schematic diagram of the density model;

[0046] Figure 5 (a) is a schematic diagram of the wave impedance inversion result of the downlink Green's function energy;

[0047] Figure 5 (b) is a schematic diagram of the wave impedance inversion result of the upward Green's function energy;

[0048] Figure 6 (a) is a schematic diagram of seismic shot data compared with forward modeling of shot records;

[0049] Figure 6 (b) is a schematic diagram of inter-layer multiples predicted by conventional methods;

[0050] Figure 7 (a) is a schematic diagram of the predicted interlayer multiples when the focal point is located in the second layer;

[0051] Figure 7 (b) is a schematic diagram of the predicted interlayer multiples when the focal point is located in the third layer;

[0052] Figure 7 (c) is a schematic diagram of the predicted interlayer multiples when the focal point is located in the fourth layer. Detailed Implementation

[0053] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0054] like Figure 1 As shown, this invention provides a Marchenko multiple suppression method for tracking wave impedance interfaces, comprising the following steps:

[0055] S1. Based on surface observation seismic data and background velocity field, the wave impedance inversion results of the entire depth domain are obtained;

[0056] S2. Based on the wave impedance inversion results of the entire depth domain, take the wave impedance energy abrupt change interface as the dividing interface, extract the location information of the strong wave impedance interface, and pick out several key locations between the strong wave impedance interfaces.

[0057] S3. Based on several key locations between the strong wave impedance interfaces, the spatial location of the focal point that maximizes the penetration of the strong wave impedance interface is obtained using the Bezier curve smoothing method.

[0058] S4. Determine the ascending and descending Green's functions for the spatial location of the focal point;

[0059] S5. Based on the ascending and descending Green's functions of the focal point's spatial location, obtain the interlayer multiple waves;

[0060] S6. Based on the inter-layer multiple waves, obtain the seismic shot gather for suppressing the inter-layer multiple waves.

[0061] This invention proposes a Marchenko multiple suppression method based on tracing wave impedance interfaces. By calculating the up and down Green's function energies corresponding to all spatial locations, it identifies strong wave impedance abrupt change interfaces. The spatial information of strong wave impedance constrains the selection of the focal point location, overcoming the theoretical limitation of conventional methods that blindly select focal points horizontally. This ensures that the focal point penetrates the interior of strong wave impedance strata to the greatest extent possible, or lies between two strong wave impedance interfaces. This allows for the prediction of as many and as complete inter-layer multiples as possible, combined with adaptive phase decompression to suppress inter-layer multiple artifacts. Furthermore, based on wave impedance inversion information, if multiple strong wave impedance interfaces exist, the focal point layer can be set multiple times to predict inter-layer multiples generated by strata at different depths. Multiple rounds of adaptive phase subtraction can then be used to successively suppress inter-layer multiple artifacts generated by different strata.

[0062] In this embodiment of the invention, in S1, based on the surface observation seismic data and the background velocity field, the uplink Green's function and downlink Green's function of all grids are calculated, and based on the energy of the uplink Green's function and the energy of the downlink Green's function, the wave impedance inversion result of the entire depth domain is obtained.

[0063] In this embodiment of the invention, in S1, the energy of the Green's function... The expression is:

[0064] ;

[0065] in, This represents any non-zero wave field value in the Green's function. This indicates the number of non-zero wave field values ​​in the Green's function. The type of energy norm is generally taken as... That is, the L2 norm of the Green's function is taken as the energy of the focal point. By calculating the uplink and downlink Green's function energies in the entire model space, the wave impedance information of the entire depth domain can be obtained.

[0066] Using surface-observed seismic data and background velocity models as input, and based on Marchenko self-focusing theory, the uplink and downlink Green functions of all grids in the model (or in the case of thinning) are calculated, and the L2 norm of the Green function is used as the energy of the grid point to obtain the wave impedance inversion results of the entire depth domain.

[0067] In the wave impedance inversion stage of Marchenko self-focusing theory, it is necessary to calculate the Green's function energy of the entire grid (or in the case of thinning).

[0068] In this embodiment of the invention, in step S3, based on the picked-up strong wave impedance interface position, the spatial position of the focal point that maximizes the penetration of the strong wave impedance interface is calculated using a Bezier curve smoothing method (or other curve smoothing methods). Comprehensive analysis of the uplink and downlink Green's function energy information can provide prior information for subsequently setting the focal point position.

[0069] The wave impedance information based on the energy inversion of the Green's function according to Marchenko theory can roughly reflect the morphology of the underground strong wave impedance interface. At the location of structural morphology changes, several key focal points can be selected. This invention adopts a piecewise third-order Bézier curve fitting formula.

[0070] The method for smoothing Bézier curves is as follows:

[0071] ;

[0072] in, This represents the value at any position on the curve. Represents the weight parameters. This indicates the first key point for segment selection. This indicates the second key point in the segment selection. This indicates the third key point in the segment selection. This indicates the fourth key point in the segment selection.

[0073] The essence of Bézier curves is weighted interpolation. Each control point is assigned a varying weight, and the curve is the weighted sum of all control points. By using a Bézier curve smoothing algorithm, the focal point layer that is located to the maximum extent between the strong wave impedance interfaces is obtained.

[0074] In this embodiment of the invention, in S4, surface observation seismic data and background velocity field are used as inputs, and strong wave impedance interface location information is used as spatial constraints to obtain the upward Green function and downward Green function of the focal point spatial location.

[0075] In this embodiment of the invention, S5 includes the following sub-steps:

[0076] S51. Remove the direct wave component of the descending Green's function at the spatial location of the focal point;

[0077] S52. Sorting and extracting the common focal point gathers of the downlink Green's function with the direct wave component removed, sorting and extracting the common shot gathers of the uplink Green's function, and obtaining interlayer multiples through seismic interferometry.

[0078] Several up-going and down-going Green's functions are reconstructed at the selected focal point. The Marchenko self-focusing theory method for predicting inter-layer multiples involves convolving the down-going Green's function (with the direct wave removed) with the complete up-going Green's function to predict inter-layer multiples.

[0079] In this embodiment of the invention, in S52, after removing the cofocal point gather of the downlink Green's function of the direct wave component, the wave field of the zeroth scattering is extracted.

[0080] In this embodiment of the invention, in S52, both the upward Green function and the downward Green function for extracting and removing the direct wave component are wave fields with first-order scattering or higher.

[0081] In this embodiment of the invention, in S52, the expression for interlayer multiples is:

[0082] ;

[0083] in, Indicated by As the epicenter and with The interlayer multiple waves received by the detector Indicates the receiving time of the Green's function. This represents the downlink Green's function after removing the direct wave. Represents the complete upward Green's function. Represents the density function, Indicates the range of spatial integration.

[0084] In this embodiment of the invention, if there are more than two strong wave impedance interfaces in S6, the process returns to S3 and performs adaptive subtraction layer by layer until all inter-layer multiples related to the strata are suppressed, thus obtaining a seismic shot gather that suppresses inter-layer multiples.

[0085] Marchenko theory can reconstruct the accurate Green's function between the subsurface virtual source and the surface receiver. When reconstructing the Green's function using the Marchenko method, a macroscopic smooth velocity model is needed, with the subsurface focal point as the source and the direct wave component from the shot record received by the surface geophone as the algorithm input to drive iteration. The Marchenko equation can be expressed as:

[0086] ;

[0087] ;

[0088] In the formula, and Let these represent the downlink Green's function and the downlink focusing function, respectively. and These represent the ascending Green's function and the ascending focusing function, respectively. This represents earthquake observation data. For example... Figure 2 (a) and Figure 2 As shown in (b), Figure 2 (a) is a schematic diagram of the Green's function component rays of the descending Green's function. Figure 2 (b) Schematic diagram of the Green's function component rays of the ascending Green's function. The descending Green's function defined in this invention is a wave field excited at the ground surface and propagating downwards to the focal point, and the ascending Green's function is a wave field excited at the ground surface and propagating upwards to the focal point.

[0089] When the strong impedance interface that generates interlayer multiples underground is irregular, and when the selected focal point cannot completely penetrate the strong impedance stratum, some focal points are below the strong impedance interface. Focal points not within the strong impedance stratum cannot construct interlayer multiples within that stratum.

[0090] like Figure 3 As shown, the downlink Green's function includes the direct wave represented by the red ray and the multiple reflected wave represented by the blue ray. When the direct wave of the downlink Green's function is removed, the wave field with zero scattering is extracted. The remaining downlink Green's function and the complete uplink Green's function are both wave fields with one scattering or higher. The interlayer multiples constructed by their convolution are wave fields with two scatterings or higher. In other words, this method can directly predict all orders of interlayer multiples passing through the focal point.

[0091] Based on the theoretical framework of Marchenko's self-focusing theory for suppressing inter-layer multiples, this invention can predict more complete inter-layer multiples by placing the focal point between the strong impedance interfaces that cause inter-layer multiples, without changing the computational load.

[0092] In the Marchenko self-focusing theory method for predicting interlayer multiples, the ray path of the interlayer multiple must pass through the focal point. Therefore, in this method, the deepest scattering point of the interlayer multiple ray path must be deeper than the focal point. When the depth of the focal point is greater than the depth of a strong impedance interface, the interlayer multiples within that strong impedance stratum cannot be predicted.

[0093] Conventional Marchenko self-focusing theory simply selects a horizontal layer as the focal point, without considering the contact relationship between the selected focal point and the subsurface strata. When the selected focal point is located within a high impedance stratum, it can predict interlayer multiple reflections within that stratum. However, when the selected focal point is not located within a high impedance stratum, it is impossible to construct interlayer multiples formed by internal multiple scattering.

[0094] Meanwhile, when the focal point is selected below the strong wave impedance interface, the direct wave from the focal point to the surface detector is not the minimum arrival time of the focal point related to the multiple scattered wave. Some interlayer multiples formed between shallow strata will be cut off by the larger direct wave time window, thus cutting off useful information.

[0095] This invention proposes placing the focal point within or between strong impedance strata, which minimizes the direct wave travel time between the focal point and the surface geophone. This ensures a minimum cutoff window for calculating the Green's function, thus preserving the most effective information. When performing convolution and integration to predict interlayer multiples, more complete interlayer multiples are obtained. Without increasing the computational burden of solving the Marchenko equations, this invention maximizes the prediction of interlayer multiple reflections caused by strong impedance interfaces, which is more beneficial for subsequent adaptive matched filtering.

[0096] This invention uses the acoustic wave equation and, while maintaining both computational accuracy and efficiency, employs the finite difference forward modeling method to obtain seismic wave simulation results. The following is established: Figure 4 The velocity and density model shown is 48,000 meters long and 4,000 meters deep, with a model grid of 2.5*2.5. The third layer is a high-velocity, high-density layer with a folded tectonic structure, which causes a large difference in wave impedance between this layer and the surrounding rock, thus forming abundant interlayer multiples.

[0097] Following the land-based observation system, a total of 901 shots were fired, with a shot spacing of 40 meters. The lateral spatial position of the first shot was 6000 meters, and the lateral spatial position of the 901st shot was 42000 meters. The detectors moved with the shots, receiving signals at both ends, with a detector spacing of 20 meters. Each shot received 601 signals, and the detector offset was (-6000, 6000).

[0098] Without considering regions with low data coverage at both ends, the uplink and downlink Green's function energies of all grid points in the horizontal spatial location from 6km to 42km of the model are calculated, and the wave impedance inversion results are obtained as follows: Figure 5 (a) and Figure 5 As shown in (b).

[0099] It can be observed that the wave impedance inversion results are in high agreement with the morphology of the model's structural interface. Furthermore, due to the close similarities in the fourth and fifth layers of the velocity and density models, the wave impedance difference between the two strata is small. Figure 5 In the wave impedance inversion results shown, the interface between the two strata is almost indistinguishable.

[0100] The ascending Green's function is the wave field excited at the Earth's surface and ascending to the focal point. When the focal point is above a strong impedance interface, the interface reflects most of the wave field energy, resulting in a stronger ascending Green's function at the focal point. Conversely, when the focal point is below the strong impedance interface, the interface also reflects most of the wave field energy and acts as a shield, causing the wave field energy passing through the interface and reflecting back to the focal point to decay rapidly. Figure 5 As shown in (b), with the strong wave impedance interface as the dividing line, the upward Green's function energy of the upper focal point is stronger, while the upward Green's function energy of the lower focal point decreases abruptly.

[0101] The descending Green's function represents a wave field excited at the Earth's surface and descending to the focal point. When there is no strong impedance interface above the focal point, the energy rebounding downwards from the interface above the focal point is very weak. Therefore, when the focal point is above a strong impedance interface, the Green's function energy is relatively small; when there is a strong impedance interface above the focal point, the energy rebounding downwards from the interface above the focal point is relatively strong. For example... Figure 5 As shown in (a), with the strong wave impedance interface as the dividing line, the downward Green's function energy at the upper focal point is weaker, while the downward Green's function energy at the lower focal point increases abruptly.

[0102] Therefore, the energy difference between the upward and downward Green's functions can reflect the difference in wave impedance of the underground strata.

[0103] In comprehensive analysis Figure 5 After obtaining the wave impedance inversion results shown, focus points are placed in accordance with the high wave impedance strata as shown in L1, L2 and L4. The L3 method is a conventional method to place the focus point horizontally and reconstruct the up and down Green's functions at the selected focus points.

[0104] Constructing a primary reflection wavefield passing through an underground virtual source point requires containing both its downlink direct wavefield and its primary uplink reflection wavefield. In other words, if the downlink Green's function direct wavefield or the primary reflection wavefield of the uplink Green's function is removed, it is impossible to construct a primary wavefield; only interlayer multiples of the corresponding strata can be constructed. Using shot data from a shot point 18 km laterally, and setting the focal point using a conventional horizontal method, the predicted interlayer multiples are as follows: Figure 6 As shown.

[0105] Figure 6(a) is the seismic single shot obtained from forward modeling. The five red arrows indicate the phase axes corresponding to the five strata, and the remaining phase axes are the inter-layer multiples. Figure 6 (b) Interlayer multiples predicted by conventional methods with the focal point layer placed horizontally, such as... Figure 5 (a) The focal point L3 is located at a depth of 2000 meters underground. It can be seen that interlayer multiples were not predicted at locations ① and ②. This is because the interlayer multiples at these locations are interlayer multiples between shallow strata above L3 and do not pass through the focal point at a depth of 2000 meters. The interlayer multiples predicted at location ③ are relatively... Figure 6 (a) The absence of a phase axis is due to the shallow strata causing interlayer multiples, making them unpredictable. At (④), the phase axis lacks the left-side reflection axis, with only the right half of the multiple data present. This is because the set focal point layer traverses the third and fourth strata. The interlayer multiples indicated by (④) are within the fourth stratum, but the left-side focal point is located within the third stratum, preventing the Green's function on that side from predicting interlayer multiples within the fourth stratum. In other words, the interlayer multiple information predicted using conventional methods is incomplete, hindering the adaptive subtraction method's ability to suppress interlayer multiples.

[0106] Figure 7 The figure shows the inter-layer multiple prediction results of the method of the present invention, wherein Figure 7 (a), (b), and (c) are respectively: Figure 5 The interlayer multiples predicted by focusing on high-impedance strata are shown in L1, L2, and L4. It can be observed that all interlayer multiples were correctly predicted. When the focusing layer is L1, the interlayer multiple shown in ① was correctly predicted; when the focusing layer is L2, the interlayer multiples shown in ② and ③ were correctly predicted; and when the focusing layer is L4, the interlayer multiples shown in ④ were correctly predicted, with no missing data on the left side. By successively combining the above interlayer multiple prediction results with the adaptive subtraction process, interlayer multiples caused by different strata in the seismic data can be suppressed to the greatest extent.

[0107] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A Marchenko multiple wave suppression method based on the tracking wave impedance interface, characterized in that, Includes the following steps: S1. Based on surface observation seismic data and background velocity field, the wave impedance inversion results of the entire depth domain are obtained; S2. Based on the wave impedance inversion results of the entire depth domain, take the wave impedance energy abrupt change interface as the dividing interface, extract the location information of the strong wave impedance interface, and pick out several key locations between the strong wave impedance interfaces. S3. Based on several key locations between the strong wave impedance interfaces, the spatial location of the focal point that maximizes the penetration of the strong wave impedance interface is obtained using the Bezier curve smoothing method. S4. Determine the ascending and descending Green's functions for the spatial location of the focal point; S5. Based on the ascending and descending Green's functions of the focal point's spatial location, obtain the interlayer multiple waves; S6. Based on the inter-layer multiple waves, obtain the seismic shot gather for suppressing the inter-layer multiple waves.

2. The Marchenko multiple suppression method for tracking wave impedance interfaces according to claim 1, characterized in that, In S1, based on surface observation seismic data and background velocity field, the uplink and downlink Green's functions of all grids are calculated, and the wave impedance inversion results of the entire depth domain are obtained based on the uplink and downlink Green's function energies.

3. The Marchenko multiple suppression method for tracking wave impedance interfaces according to claim 2, characterized in that, In S1, the energy of the Green's function The expression is: ； in, This represents any non-zero wave field value in the Green's function. This indicates the number of non-zero wave field values ​​in the Green's function. Indicates the type of energy norm.

4. The Marchenko multiple suppression method for tracking wave impedance interfaces according to claim 1, characterized in that, In S3, the method for smoothing the Bézier curve is as follows: ； in, This represents the value at any position on the curve. Represents the weight parameters. This indicates the first key point for segment selection. This indicates the second key point in the segment selection. This indicates the third key point in the segment selection. This indicates the fourth key point in the segment selection.

5. The Marchenko multiple suppression method for tracking wave impedance interfaces according to claim 1, characterized in that, In S4, surface observation seismic data and background velocity field are used as inputs, and strong wave impedance interface location information is used as spatial constraints to obtain the upward Green's function and downward Green's function of the focal point spatial location.

6. The Marchenko multiple suppression method for tracking wave impedance interfaces according to claim 1, characterized in that, S5 includes the following sub-steps: S51. Remove the direct wave component of the descending Green's function at the spatial location of the focal point; S52. Sorting and extracting the common focal point gathers of the downlink Green's function with the direct wave component removed, sorting and extracting the common shot gathers of the uplink Green's function, and obtaining interlayer multiples through seismic interferometry.

7. The Marchenko multiple suppression method for tracking wave impedance interfaces according to claim 6, characterized in that, In step S52, the cofocal point gather of the descending Green's function of the direct wave component is removed so that the wave field of the zeroth scattering is extracted.

8. The Marchenko multiple suppression method for tracking wave impedance interfaces according to claim 6, characterized in that, In S52, both the upward Green's function and the downward Green's function for extracting and removing the direct wave component are wave fields with first-order scattering or higher.

9. The Marchenko multiple suppression method for tracking wave impedance interfaces according to claim 6, characterized in that, In S52, the expression for interlayer multiples is: ； in, Indicated by As the epicenter and with The interlayer multiple waves received by the detector Indicates the receiving time of the Green's function. This represents the downlink Green's function after removing the direct wave. Represents the complete upward Green's function. Represents the density function, Indicates the range of spatial integration.

10. The Marchenko multiple suppression method for tracking wave impedance interfaces according to claim 1, characterized in that, In step S6, if there are more than two strong wave impedance interfaces, return to step S3 and perform adaptive subtraction layer by layer until all inter-layer multiples related to the strata are suppressed, and a seismic shot gather with suppressed inter-layer multiples is obtained.

Images