CN117991347A

CN117991347A - Method and device for obtaining multiple waves in water layer in converted wave

Info

Publication number: CN117991347A
Application number: CN202410115159.1A
Authority: CN
Inventors: 宫云良; 孙雷鸣; 周秘; 常坤; 徐强; 鄢定华; 王旭谦; 张鹏; 肖莹; 李春雷; 李永超; 陈磅; 赵亮; 程耀; 陈文贵
Original assignee: China Oilfield Services Ltd
Current assignee: China Oilfield Services Ltd
Priority date: 2024-01-26
Filing date: 2024-01-26
Publication date: 2024-05-07

Abstract

The invention relates to a method and a device for acquiring water layer multiple in converted waves, wherein the method for acquiring the water layer multiple in the converted waves comprises the steps of establishing a sea water depth model according to sea water depth and acquiring seismic data; for any target shot point, taking the target shot point and the detection point as a shot-detection pair, and calculating a continuation value of wave field continuation between any intermediate shot point and the target shot point between the shot-detection pair; for any middle shot point between the shot and inspected pairs, calculating to obtain water layer multiple waves after being reflected by the middle shot point; and overlapping the water layer multiples corresponding to each middle shot point between the shot pairs to obtain the water layer multiples corresponding to the shot pairs. The acquisition method of the water layer multiple can obtain the water layer multiple at the shot point end by utilizing wave field continuation, thereby being capable of being used for suppressing the water layer multiple in the converted wave received by the wave detection point and improving the quality of converted wave imaging.

Description

Method and device for obtaining multiple waves in water layer in converted wave

Technical Field

The invention belongs to the technical field of marine seismic data processing, and particularly relates to a method and a device for acquiring multiple waves of a water layer in converted waves.

Background

Multiples are a prominent problem in marine seismic data processing, and can cover effective signals to form structural artifacts in offset imaging, so that multiple suppression is a very critical step in seismic data processing, and by suppressing the multiples, the speed analysis precision can be effectively improved, imaging artifacts are fewer, and the imaging quality of marine seismic data is greatly improved. The multiple technique has been developed for decades, and the longitudinal wave multiple attenuation technique has become more mature. Some of the techniques have been widely used in actual production, such as the predicted deconvolution technique, SRMR technique, and MWD technique, due to the advantages of fast calculation speed, high calculation efficiency, and good pressing effect.

Converted waves can be simply understood as longitudinal wave incidence and transverse wave emergence, the ray paths of the converted waves are different from those of the longitudinal wave fields, and the converted waves are geometrically asymmetric, so that the propagation rule of the transverse waves and the converted waves between the ground layers is far more complex than that of the longitudinal waves. The wave field of marine seismic longitudinal wave is known to contain a large number of water layer multiples and free surface multiples, and the converted wave also contains a large number of water layer multiples and free surface multiples, so that the multiples in the converted wave are mainly water layer multiples because the reflection coefficient of the sea surface is obviously stronger than any wave impedance interface including the sea bottom.

The presence of water layer multiples in the converted wave can severely impact the signal-to-noise ratio of the seismic data and can impact converted wave imaging, causing imaging artifacts. Therefore, the invention discloses a suppression method for water layer multiples in a converted wave field, which is necessary for improving the imaging quality of the converted wave.

Disclosure of Invention

The present invention has been made in view of the above problems, and provides a method and apparatus for acquiring water layer multiples in a converted wave, a computing device, and a computer storage medium, which overcome or at least partially solve the above problems.

According to a first aspect of the present invention, there is provided a method for acquiring multiples of a water layer in a converted wave, comprising:

establishing a sea water depth model according to sea water depth, collecting seismic data, and extracting the seismic data into a common detector gather according to a sorting mode of detectors and shots;

For any one target shot point, taking the target shot point and the detection point as an offset pair, and calculating a continuation value of wave field continuation between any one intermediate shot point and the target shot point between the offset pair according to the depth model and the seismic data;

Calculating water layer multiple waves after being reflected by the middle shot point according to the extension value between the middle shot point and the target shot point and the seismic data of the middle shot point in the common detection point gather for any middle shot point between the offset pairs;

and superposing the water layer multiples corresponding to each intermediate shot point between the offset pairs to obtain the water layer multiples corresponding to the offset pairs.

Further, for any one target shot, taking the target shot and the detection point as an offset pair, and calculating a continuation value of a wave field continuation between any one of the intermediate shot and the target shot between the offset pair according to the depth model and the seismic data further includes:

deriving a continuation operator of wave field continuation according to kirchhoff integral theorem under the pure longitudinal wave condition;

And calculating a continuation value of wave field continuation between any one of the middle shot points and the target shot point between the offset pairs according to the depth model, the seismic data and the continuation operator.

Further, the deriving the continuation operator of the wave field continuation according to kirchhoff integration theorem under the pure longitudinal wave condition further includes:

According to kirchhoff integration theorem under the pure longitudinal wave condition, representing the pressure field of any target point in a closed curved surface as the sum of two items, wherein the first item is related to the pressure on the closed curved surface, and the second item is related to the particle motion speed on the closed curved surface;

The second term is equal to 0 through an intermediate function, so that a first expression of the pressure field at any point in the closed curved surface and the pressure on the closed curved surface can be obtained;

the closed curved surface is formed by utilizing a plane and an infinity interface, the first expression is converted into a second expression on the premise that disturbance of the infinity interface does not reach the target point, and in the second expression, the pressure field of any point in the closed curved surface is related to the pressures on the plane and the closed curved surface;

And obtaining a continuation operator of wave field continuation according to the second expression.

Further, for any one of the intermediate shots between the offset pairs, according to the continuation value between the intermediate shot and the target shot and the seismic data of the intermediate shot in the common-detection-point gather, the calculating method obtains a water layer multiple after being reflected by the intermediate shot specifically includes:

And for any intermediate shot point between the offset pairs, calculating to obtain the water layer multiple after being reflected by the intermediate shot point according to the fact that the water layer multiple after being reflected by the intermediate shot point is equal to the product of the extension value between the intermediate shot point and the target shot point and the seismic data of the intermediate shot point in the common-detection-point gather.

Further, after acquiring the seismic data, the method further comprises: interpolation processing is carried out on the seismic data, so that the interval between two adjacent data points is smaller than or equal to a preset maximum sampling interval which is one half of the minimum wavelength of the seismic waves;

the seismic data are extracted into a common detector gather according to a detector and shot sorting mode, and the method comprises the following steps: and extracting the seismic data after interpolation processing into a common detector gather according to a detector and shot sorting mode.

Further, after calculating the water layer multiple reflected by the intermediate shot point according to the continuation value between the intermediate shot point and the target shot point and the seismic data of the intermediate shot point in the common-detection point trace set for any one of the intermediate shot points between the offset pairs, the method further comprises: filtering the water layer multiple;

The water layer multiples corresponding to each middle shot point between the offset pairs are overlapped, and the water layer multiples corresponding to the offset pairs are obtained specifically as follows: and overlapping the water layer multiples obtained after the filtering treatment to obtain the corresponding water layer multiple of the offset pair.

According to a second invention of the present invention, there is provided an acquisition apparatus of a water layer multiple in a converted wave, comprising:

The data acquisition and sea water depth model building module is used for building a sea water depth model according to sea water depth, acquiring seismic data and extracting the seismic data into a common detector gather according to a sorting mode of detectors and shots;

The first calculation module is used for calculating a continuation value of wave field continuation between any intermediate shot point and the target shot point between any target shot point according to the depth model and the seismic data by taking the target shot point and the detection point as an offset pair;

the second calculation module is used for calculating water layer multiple waves after being reflected by the middle shot point according to the extension value between the middle shot point and the target shot point and the seismic data of the middle shot point in the common-detection-point gather for any one of the middle shot points between the shot point pairs;

And the water layer multiple acquisition module is used for superposing the water layer multiple corresponding to each middle shot point between the offset pairs to obtain the water layer multiple corresponding to the offset pairs.

According to a third aspect of the present invention there is provided a computing device comprising: the device comprises a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface complete communication with each other through the communication bus;

The memory is used for storing at least one executable instruction, and the executable instruction enables the processor to execute the operation corresponding to the method for acquiring the water layer multiple in the converted wave.

According to a fourth aspect of the present invention, there is provided a computer storage medium having stored therein at least one executable instruction for causing a processor to perform operations corresponding to the method of acquiring multiples of a water layer in a converted wave as set forth in any one of the above.

According to the technical scheme, the method and the device for acquiring the multiple waves of the water layer in the converted wave have the following beneficial effects:

the method for acquiring the water layer multiples in the converted wave can acquire the water layer multiples at the shot point end by utilizing wave field prolongation, so that the method can be used for suppressing the water layer multiples in the converted wave received by the wave detection point and improving the quality of converted wave imaging.

The foregoing description is only an overview of the present invention, and is intended to be implemented in accordance with the teachings of the present invention in order that the same may be more clearly understood and to make the same and other objects, features and advantages of the present invention more readily apparent.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to designate like parts throughout the figures. In the drawings:

fig. 1 is a diagram showing propagation paths of reflected longitudinal waves and converted waves after incidence of the longitudinal waves;

FIG. 2 is a graph showing propagation paths of a plurality of waves in a water layer after incidence of a longitudinal wave;

FIG. 3 is a graph of propagation paths of converted waves and shot point end water layer multiple waves;

FIG. 4 is a flowchart of a method for acquiring water layer multiples in a converted wave according to an embodiment of the present invention;

FIG. 5 shows a schematic view of a closed curved surface constructed in accordance with an embodiment of the present invention;

FIG. 6 is a flow chart of a method for obtaining and suppressing multiples of a water layer in a converted wave according to an embodiment of the present invention;

FIG. 7 is a schematic diagram of an apparatus for acquiring multiples of a water layer in a converted wave according to an embodiment of the present invention;

FIG. 8 is a graph showing the spectrum of the converted wave before and after the water layer multiples are suppressed;

FIG. 9 is a graph showing a comparison of superimposed cross sections before and after the water layer multiples are suppressed when the distance between the shot point and the cable where the detector point is located is a first distance;

FIG. 10 is a graph showing a comparison of superimposed cross sections before and after the water layer multiples are suppressed when the distance between the shot point and the cable where the detector point is located is a second distance;

FIG. 11 is a cross-sectional view of the water layer before and after the water layer multiple is suppressed when the distance between the shot point and the cable where the detector point is located is a third distance;

FIG. 12 is a superimposed autocorrelation plot of the water layer multiples before and after being suppressed when the distance between the shot and the cable where the geophone is located is a first distance;

FIG. 13 is a superimposed autocorrelation plot of the water layer multiples before and after being suppressed when the distance between the shot and the cable where the geophone is located is a second distance;

FIG. 14 is a superimposed autocorrelation plot of the water layer multiples before and after being suppressed when the distance between the shot and the cable where the geophone is located is a third distance;

FIG. 15 illustrates a schematic diagram of a computing device embodiment of the present invention.

Detailed Description

Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

Fig. 1 is a propagation path diagram of a reflected longitudinal wave and a converted wave after incidence of the longitudinal wave, wherein S represents a shot point, +.i represents a pressure detector, +.i represents a velocity detector, R1 and R2 represent reflection points, and it can be seen from fig. 1 that the reflected longitudinal wave P1 is received by the pressure detector after reflection of the incident longitudinal wave at the R1 reflection point, and the converted wave S2 is received by the velocity detector after reflection of the incident longitudinal wave at the R2 reflection point.

Fig. 2 is a graph of propagation paths of multiple waves of the water-end layer of the shot point after incidence of the longitudinal wave, wherein S represents the shot point, while d represents the velocity detector, R32 represents the reflection point, and as can be seen from fig. 2, the incident longitudinal wave is reflected once at the sea bottom and the sea surface, and then reflected by the reflection point R32 to obtain multiple waves S3 of the water-end layer of the shot point, which are received by the velocity detector.

Thus, as can be seen in conjunction with fig. 1 and 2: the shot point end water layer multiple S3 can be regarded as the wave field recorded by the receiver propagates through the sea water again through reflection, so that the water layer multiple in the converted wave can be predicted through wave field continuation. Again, as shown in fig. 3, the data received by the detectors R _j and R _i include converted waves and water layer multiples, where the converted waves are wave field data received by the detectors after the longitudinal wave sent by the shot point S _j is reflected by the stratum, and the shot point end water layer multiples are wave field data received by the detectors after the longitudinal wave sent by the shot point S _j is reflected by the seabed, the sea surface and the stratum, so that the wave field between the shot point S _j and the detector (shot point S _i and shot point S _i-1 in fig. 3) can be used to predict the water layer multiples of the shot point S _j in the converted waves by extending to the left.

Fig. 4 is a flowchart of a method for acquiring multiple waves in a water layer in a converted wave according to an embodiment of the present invention, where the method is applied to a computing device. The computing device includes: the device comprises a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface are communicated with each other through the communication bus; the memory is used for storing at least one executable instruction, and the executable instruction enables the processor to execute the operation corresponding to the water layer multiple acquisition method. As shown in fig. 4, the method comprises the steps of:

Step S100: establishing a sea water depth model according to sea water depth, collecting seismic data, and extracting the seismic data into a common detector gather according to a sorting mode of detectors and shots;

step S110: for any target shot point, taking the target shot point and the detection point as a shot-to-shot-detection pair, and calculating a continuation value of wave field continuation between any intermediate shot point between the shot-to-shot-detection pair and the target shot point according to the depth model and the seismic data;

Step S120: for any middle shot point between the shot-detection pairs, calculating to obtain water layer multiple waves after being reflected by the middle shot point according to the extension value between the middle shot point and the target shot point and the seismic data of the middle shot point in the common-detection-point gather;

step S130: and overlapping the water layer multiples corresponding to each middle shot point between the shot pairs to obtain the water layer multiples corresponding to the shot pairs.

The seismic data are specifically converted wave field data acquired by ocean bottom seismic, after the data are acquired, the converted wave field data of the ocean bottom seismic are required to be subjected to preprocessing such as secondary positioning, RT rotation, noise attenuation and the like, and then the seismic data are extracted into common detector point gathers according to a sorting mode of detector points and shot points; the prediction is mainly performed on the water body multiple waves at the seismic source end, and the wave field propagation distance between seismic sources can be conveniently calculated in the common-wave-detection-point gather, so that the prediction on the water body multiple waves at the seismic source end is more convenient; in addition, the process of multiple prediction needs to read out the related header information from the header information of the seismic data to participate in the calculation, so that the related header information needs to be placed in the seismic channel. The header information needed to be used mainly comprises: the cannon number and the detector number are used for judging the gather number of the input data; the shot water depth, the detector water depth, shot coordinates (corresponding to (x _i,y_i,z_i) and (x _j,y_j,z_j) in fig. 3) and the detector coordinates, which mainly calculate the wave field propagation distance between different guns in the common detector gather, thereby calculating the continuation operator of the source wave field continuation.

Step S100, a seawater depth model is established, namely, the depth of the shot water or the depth of sinking of each wave detection point measured in the field is read from seismic navigation data, abnormal seawater depth values are removed, and the seawater depth of the whole work area is obtained through interpolation of the water depth data, so that a seawater depth model is obtained; the depth model can be used for calculating the distance of the multiple propagation compared with the multiple propagation of the primary wave, and the prediction of the water layer multiple wave field obtained by the primary wave field continuation can be realized.

Wherein, for any target shot point, the step S110 uses the target shot point and the geophone as an offset pair, and the calculating the extension value of the wave field extension between any intermediate shot point between the offset pair and the target shot point according to the depth model and the seismic data further comprises:

And calculating a continuation value of wave field continuation between any one middle shot point and the target shot point between the shot-to-shot pairs according to the depth model, the seismic data and the continuation operator.

Wherein, deriving the continuation operator of wave field continuation according to kirchhoff integration theorem under pure longitudinal wave condition further comprises:

According to kirchhoff integration theorem under the pure longitudinal wave condition, representing the pressure field of any target point in the closed curved surface as the sum of two items, wherein the first item is related to the pressure on the closed curved surface, and the second item is related to the particle motion speed on the closed curved surface;

by utilizing a plane and an infinity interface to form a closed curved surface, under the premise that disturbance of the infinity interface does not reach a target point, converting a first expression into a second expression, wherein in the second expression, a pressure field at any point in the closed curved surface is related to the pressure on the plane and the closed curved surface;

Specifically, as shown in fig. 3, in submarine cable data, the multiple wave at the shot point end of the jth shot point is equivalent to the wave field after the jth shot point is started, and the wave field is reflected by the seabed and the sea surface at the ith shot point, reflected by the seabed stratum and finally received by the wave detector. Therefore, the wave field of the ith shot point can be reversely extended once in the sea water, and the multiple wave of the shot point end water layer of the jth shot point can be obtained.

The key of wave field extension is the construction of a extension formula among shots, and the wave field extension formula used in the embodiment is obtained by deriving from Kirchhoff integral theorem (Kirchhoff integral formula).

The Kirchhoff integral formula for the pure longitudinal case is as follows:

In the above formula, S is a closed curved surface, A is any target point in the curved surface, P is a pressure value on the closed curved surface S, r is a distance between the target point and any point on the curved surface S, v _n is a particle motion speed on the curved surface, k is a wave number, ω is an angular frequency, ρ ₀ is a density, j is an imaginary unit, and n is a direction vector Unit distance above. It can be seen that the first term is a sum of two terms, the first term being related to the pressure on the closed surface and the second term being related to the velocity of the particle motion on the closed surface.

From formula one, it can be seen that: given the pressure and particle motion velocity on the closed surface S, the pressure field P _A for any target point within the closed surface can be calculated. However, we often cannot obtain these two information simultaneously, so we want to determine their internal spatial wavefield using a single boundary condition on the surface, and to introduce an intermediate function H to make

By finding the appropriate intermediate function, one can make

Or cause

At this time, formula two may become:

When the formula is established, the velocity value v _n on the known S curved surface is expressed, and the wave field of any target point in the curved surface can be calculated; the pressure is pushed to the wavefield, and when the equation is established, the wavefield P on the surface of the surface S is known, and the wavefield P _A for any target point in the surface can be calculated. The solution formula of the wave field of any target point can be solved mainly by knowing the wave field P, namely, a solution of formula four needs to be found.

The fourth expression is a first expression of the pressure field at any point in the closed curved surface and the pressure on the closed curved surface. For a general curved surface, it is difficult to obtain an intermediate function satisfying the condition to establish the equation four, and in this embodiment, the closed curved surface S is formed by selecting a plane S ₁ and an infinity interface S ₂, and as shown in fig. 5, the equation five can be expressed as:

It is assumed that the pressure field of the upper half space (z < 0) is caused by the presence of a seismic source of the lower half space (z > 0). Since it is desirable to calculate the change in the pressure field at point A in the upper half space over a finite time interval t, where 0.ltoreq.t.ltoreq.t _max,t_max represents the maximum wavefield travel time set when the wavefield is calculated. A hemispherical surface with radius R ₀＝ct_max is taken as S ₂, where c is the wave field propagation velocity and R ₀ is the radius of the hemispherical surface. Within a finite time interval t, the disturbance propagated by S ₂ has not yet reached the target point A, so the second integral term of equation six is zero. Thus, the expression for 0.ltoreq.t.ltoreq.t _max,P_A may be translated into:

As can be seen from the seventh aspect: the pressure field at any point within the closed curve is related to the plane S ₁ and the pressure P on the closed curve. Again, there is one r=r' for equation four, which is found when equation four is established Bringing it into the seventh can give:

Also, since the following relation exists:

In the nine of which, Is vector/>The line and vector/>, between the intersection with plane S ₁ and target point AThe included angle between the straight lines can be further changed into a formula eight according to a formula nine:

The formula ten is a second expression, and it can be seen from the formula ten: the pressure field at any point within the closed curve is related to the plane S ₁ and the pressure P on the closed curve. The pressure field at any point can be synthesized by dipole seismic sources distributed on the plane, the intensity of the pressure field is the pressure value on the plane, the wave field value of any point in the space above the plane can be calculated by using the formula, and the wave field value of the plane can be extended outwards.

Again, according to the second expression, a continuation operator G (s _i,s_j, ω) of the wave field continuation between shot s _i and shot s _j can be obtained, in particular,

Formula eleven is a continuation operator of wave field continuation, in formula eleven, r is a wave field propagation distance from the seismic wave excited by shot point s _j to shot point s _i after being reflected by the seabed and the sea surface, as shown by a dotted line in fig. 3, thusWherein H _w is the sea water depth, and k represents wave number; k=w/v _w, where ω represents angular frequency and v _w represents water velocity; j represents an imaginary unit; /(I)Note that the formula is calculated in the frequency domain.

After the extension operator is obtained, the sea water depth in the depth model and coordinates of the target shot point and the middle shot point are brought into the extension operator, and the extension value of wave field extension can be calculated. Setting the shot point s _j as a target shot point and r as a detection point, forming a shot-detection pair by s _j and r, and setting s _i as intermediate shot points, and calculating the extension value of wave field extension between any intermediate shot point between the shot-detection pair and the target shot point according to formula eleven.

Step S120, for any intermediate shot point between the offset pair, calculates, according to the extension value between the intermediate shot point and the target shot point and the seismic data of the intermediate shot point in the common-detection-point gather, a water layer multiple reflected by the intermediate shot point as follows:

and for any middle shot point between the offset pairs, calculating to obtain the water layer multiple after being reflected by the middle shot point according to the fact that the water layer multiple after being reflected by the middle shot point is equal to the product of the extension value between the middle shot point and the target shot point and the seismic data of the middle shot point in the common detection point gather.

Specifically, for the offset pair consisting of s _j and r, the extension operator between the middle shot point s _i and the target shot point s _j is denoted by G (s _i,s_j, ω), D (s _i, r, ω) is the converted wave field value of the middle shot point s _i received by the detector point r, and M (s _j,s_i, r, ω) is the water layer multiple after the target shot point s _j wave field is reflected by the middle shot point, then:

M(s_j,s_i,r,ω)＝G(s_i,s_j,ω)D(s_i，r，ω)

The water layer multiple wave after the wave field of the target shot point s _j is reflected by the middle shot point can be obtained through the above method.

Considering that there are many intermediate shots between the target shot s _j and the detector r, the primary wave becomes multiple after the reflection at the sea surface, so these points are the multiple downlink reflection points (DRP points) we need. And then, calculating a continuation value between each DRP point and the target shot point s _j, namely taking each DRP point as a connection point, and carrying out continuation on a received wave field of each DRP point in a water layer and finally receiving the wave field by a detector. This allows to obtain a set of multiple wave fields of different reflection points, i.e. different propagation paths, this set of wave fields being called a multiple contribution gather (Multiple Contribution Gather, MCG).

Step S130, overlapping the water layer multiples corresponding to each middle shot point between the offset pairs to obtain the corresponding water layer multiples of the offset pairs, namely overlapping each of the multiples in the multiple contribution channel set to finally obtain the water layer multiples M (S _j, r, omega) corresponding to the offset pairs S _j and r

In the above equation, Ω represents all intermediate shots between the offset pair s _j and r.

And replacing the target shot points to obtain water layer multiples M (s _j, r, omega) obtained after the earthquakes generated by the target shot points are reflected by all the multiple downlink reflection points when each shot point is taken as the target shot point.

Wherein, after the seismic data is acquired in step S100, the multiple acquisition method further includes: and carrying out interpolation processing on the seismic data, so that the interval between two adjacent data points is smaller than or equal to a preset maximum sampling interval, wherein the preset maximum sampling interval is one half of the minimum wavelength of the seismic waves.

In step S100, the seismic data is extracted into a common detector gather according to a sorting mode of detectors and shots, which is specifically: and extracting the seismic data after interpolation processing into a common detector gather according to a detector and shot sorting mode.

Specifically, a water layer multiple model in the converted wave can be obtained by selecting a proper aperture for superposition of multiple contribution gathers, but direct superposition often brings a plurality of aliasing, and aliasing is caused by the fact that acquired seismic data do not meet the sampling theorem and the part higher than or at the Nyquist frequency. In order to mitigate the interference of the aliasing on the multiple prediction, anti-aliasing processing is required.

Firstly, in submarine cable collection, the actual sampling interval is difficult to meet the ideal sampling interval requirement due to the limitation of collection cost, so that in order to avoid the generation of aliasing noise in the prediction process, interpolation processing is needed to be carried out on seismic data, and the interval between two adjacent data points is smaller than or equal to the preset maximum sampling interval. The preset maximum sampling interval is obtained by the following formula:

Where Δx is a preset maximum sampling interval for avoiding aliasing, v _min represents the propagation speed of the seismic wave in the water body, λ _min represents the wavelength of the seismic wave, and f _max represents the maximum frequency of the seismic wave.

In step S120, for any intermediate shot point between the offset pair, after calculating the water layer multiple reflected by the intermediate shot point according to the continuation value between the intermediate shot point and the target shot point and the seismic data of the intermediate shot point in the common-detection-point gather, the method further includes: and filtering the water layer multiple.

Step S130, overlapping the water layer multiples corresponding to each middle shot point between the shot pairs, wherein the water layer multiples corresponding to the shot pairs are specifically: and overlapping the water layer multiples obtained after the filtering treatment to obtain the corresponding water layer multiple times of the offset pair.

Specifically, in the multiple contribution trace set, as the in-phase axis curvature is larger, the wavelengths of the seismic wavelets are longer, and their superposition causes an aliasing phenomenon, so that a filtering setting is required according to the in-phase axis slope. The specific anti-aliasing filter calculation formula is as follows:

In the above formula, Δt is the track interval, For slope operator, deltax is the actual seismic trace sampling interval and f is the anti-aliasing low-frequency filtering frequency. The low-pass filtering is performed according to the calculated frequency, so that the false frequency noise in the predicted multiple can be reduced.

And superposing the water layer multiples corresponding to each middle shot point between s _j and r by the offset in a certain aperture after filtering to obtain the water layer multiples corresponding to the offset pairs. And then replacing the target shot point s _j, repeating the steps, and calculating a water layer multiple model of a shot-detecting pair formed by each target shot point and the detection point, so that a converted wave shot point end water layer multiple model of a common detection point gather is formed.

Again, taking fig. 6 as an example, the following is true: in fig. 6, PS wave data is received converted wave data, that is, seismic data acquired in step S100, and the seismic data is processed to obtain a common detector gather, and at the same time, a depth model of the sea water is obtained by interpolation according to the depth of the sea water; the green's function in fig. 6, namely the continuation operator of the wavefield continuation constructed in the previous embodiment; in fig. 6, the nth shot is the target shot, the m shots are all shots between the nth shot and the demodulation point, so that a contribution gather of multiple of the nth shot can be obtained, the multiple of the shot end water layer of the nth shot can be obtained after superposition through anti-aliasing processing, and the nth shot is replaced by other shots, so that the multiple of the water layer corresponding to each shot can be obtained. And obtaining multiple wave waves corresponding to each shot point, and obtaining converted waves pressing multiple wave waves of the water layer through matching and subtracting.

Specifically, through the foregoing embodiment, the converted wave corresponding to each target shot and the water layer multiple after the waveform of the target shot is reflected by the middle shot can be obtained by calculation, so that the corresponding water layer multiple when the shot is taken as the target shot can be subtracted from the original converted wave field by frequency division and time division matching by utilizing the wave field of a certain shot received by the wave detection point, and finally the compression of the water layer multiple at the source end of the converted transverse wave is realized, and the transverse wave field without the water layer multiple is obtained.

Fig. 8 is a spectrum comparison chart of superimposed sections before and after the water layer multiples are suppressed, and it can be seen that the frequency band of the superimposed section after the water layer multiples are suppressed is slightly expanded, which illustrates that the suppression method of the embodiment better removes the water layer multiples in the converted wave field.

FIG. 9 is a graph showing a comparison of superimposed cross sections before and after the water layer multiples are suppressed when the distance between the shot point and the cable where the detector point is located is a first distance; FIG. 10 is a graph showing a comparison of superimposed cross sections before and after the water layer multiples are suppressed when the distance between the shot point and the cable where the detector point is located is a second distance; FIG. 11 is a cross-sectional view of the water layer before and after the water layer multiple is suppressed when the distance between the shot point and the cable where the detector point is located is a third distance; wherein the first distance is less than the second distance and the second distance is less than the third distance, and the aqueous layer is attenuated to some extent by the plurality of waves as can be seen in fig. 9-11.

FIG. 12 is a superimposed autocorrelation plot of the water layer multiples before and after being suppressed when the distance between the shot and the cable where the geophone is located is a first distance; FIG. 13 is a superimposed autocorrelation plot of the water layer multiples before and after being suppressed when the distance between the shot and the cable where the geophone is located is a second distance; FIG. 14 is a superimposed autocorrelation plot of the water layer multiples before and after being suppressed when the distance between the shot and the cable where the geophone is located is a third distance; the first distance is smaller than the second distance, the second distance is smaller than the third distance, and as can be seen from fig. 12-14, after the water layer multiple is pressed, the periodicity of the autocorrelation function is obviously weakened, which indicates that the water layer multiple is effectively pressed in the converted wave.

The embodiment of the invention also provides a device for acquiring the water layer multiple in the converted wave, as shown in fig. 7, which comprises a data acquisition and sea water depth model building module 200, a first computing module 210, a second computing module 220 and a water layer multiple acquiring module 230, in particular,

The data acquisition and sea water depth model building module 200 is used for building a sea water depth model according to sea water depth, acquiring seismic data, and extracting the seismic data into a common detector gather according to a detector and shot sorting mode;

for any one target shot, taking the target shot and the detection point as a shot-to-shot pair, the first calculation module 210 is used for calculating a continuation value of wave field continuation between any one middle shot and the target shot between the shot-to-shot pair according to the depth model and the seismic data;

For any intermediate shot point between the shot-detection pairs, the second calculation module 220 is configured to calculate, according to the extension value between the intermediate shot point and the target shot point and the seismic data of the intermediate shot point in the common-detection-point gather, a water layer multiple after being reflected by the intermediate shot point;

The water layer multiple acquisition module 230 is configured to superimpose water layer multiples corresponding to each middle shot point between the offset pairs, so as to obtain water layer multiples corresponding to the offset pairs.

The data acquisition and sea water depth model building module 200 acquires seismic data, specifically, acquires submarine seismic converted wave field data, and extracts the seismic data into a common detector gather according to a detector and shot sorting mode after acquiring the data; the process of multiple prediction needs to read out the related header information from the header information of the seismic data to participate in the operation, so that the related header information needs to be placed in the seismic channel. The header information needed to be used mainly comprises: the cannon number and the detector number are used for judging the gather number of the input data; the shot water depth, the detector water depth, shot coordinates (corresponding to (x _i,y_i,z_i) and (x _j,y_j,z_j) in fig. 3) and the detector coordinates, which mainly calculate the wave field propagation distance between different guns in the common detector gather, thereby calculating the continuation operator of the source wave field continuation.

The data acquisition and sea water depth model building module 200 builds a sea water depth model, specifically, obtains the sea water depth of the whole work area through water depth data interpolation, and then obtains the sea water depth model.

The first calculation module 210 calculates a continuation value of a wavefield continuation between any one of the intermediate shots and the target shots between the offset pair from the depth model and the seismic data further comprising:

The first calculation module 210 derives a continuation operator of wave field continuation according to kirchhoff integration theorem under the pure longitudinal wave condition;

The first calculation module 210 calculates a continuation value of the wavefield continuation between any one of the intermediate shots and the target shot between the offset pair based on the depth model, the seismic data, and the continuation operator.

Wherein, the first calculation module 210 derives a continuation operator of the wave field continuation according to kirchhoff integration theorem under the pure longitudinal wave condition further includes:

The first calculation module 210 represents the pressure field of any one target point in the closed curved surface as the sum of two terms according to kirchhoff's integral theorem in the case of pure longitudinal waves, wherein the first term relates to the pressure on the closed curved surface and the second term relates to the particle motion velocity on the closed curved surface;

The first calculation module 210 makes the second term equal to 0 through an intermediate function, so as to obtain a first expression of the pressure field at any point in the closed curved surface and the pressure on the closed curved surface;

The first calculation module 210 converts the first expression into a second expression on the premise that disturbance of the infinity interface does not reach the target point by forming a closed curved surface by using the plane and the infinity interface, wherein the pressure field at any point in the closed curved surface is related to the pressures on the plane and the closed curved surface;

The first computation module 210 obtains a continuation operator of the wavefield continuation according to the second expression.

After obtaining the extension operator, the first calculation module 210 brings the seawater depth in the depth model and the coordinates of the target shot and the middle shot into the extension operator, so as to calculate the extension value of the wave field extension.

The second calculation module 220 calculates, according to the continuation value between the middle shot and the target shot and the seismic data of the middle shot in the common-detector gather, a water layer multiple reflected by the middle shot specifically as follows:

For any intermediate shot between the shot pairs, the second calculation module 220 calculates the water layer multiples after being reflected by the intermediate shot by using the water layer multiples after being reflected by the intermediate shot equal to the product of the extension between the intermediate shot and the target shot and the seismic data of the intermediate shot in the common detector gather.

The water layer multiple acquisition device further comprises an interpolation processing module, wherein the interpolation processing module is used for carrying out interpolation processing on the seismic data, so that the interval between two adjacent data points is smaller than or equal to a preset maximum sampling interval, and the preset maximum sampling interval is one half of the minimum wavelength of the seismic waves.

The data acquisition and sea water depth model building module 200 extracts the seismic data into a common detector gather according to the sorting mode of the detectors and shots, which is specifically as follows: the data acquisition and sea water depth model building module 200 extracts the seismic data after interpolation processing into a common geophone gather according to the sorting mode of the geophones and the shots.

The water layer multiple acquisition device further comprises a filtering processing module, and the filtering processing module carries out filtering processing on the water layer multiple.

The water layer multiple acquisition module 230 superimposes the water layer multiple corresponding to each middle shot point between the shot pairs, so as to obtain the water layer multiple corresponding to the shot pairs specifically as follows: the water layer multiple acquisition module 230 superimposes the water layer multiple obtained after the filtering process, and obtains a corresponding water layer multiple of offset pairs.

The acquisition device of the water layer multiples in the converted wave can acquire the water layer multiples at the shot point end by utilizing wave field continuation, so that the acquisition device can be used for suppressing the water layer multiples in the converted wave received by the wave detection point and improving the quality of converted wave imaging.

The embodiment of the invention provides a nonvolatile computer storage medium, which stores at least one executable instruction, and the computer executable instruction can execute the method for acquiring the water layer multiple in the converted wave in any method embodiment.

FIG. 15 illustrates a schematic diagram of one embodiment of a computing device, and embodiments of the invention are not limited to a particular implementation of a computing device.

As shown in fig. 15, the computing device may include: a processor 402, a communication interface (Communications Interface) 404, a memory 406, and a communication bus 408.

Wherein: processor 402, communication interface 404, and memory 406 communicate with each other via communication bus 408. A communication interface 404 for communicating with network elements of other devices, such as clients or other servers. The processor 402 is configured to execute the program 410, and may specifically perform relevant steps in the embodiment of the method for acquiring multiple waves in a water layer in a converted wave of a computing device.

In particular, program 410 may include program code including computer-operating instructions.

The processor 402 may be a central processing unit CPU, or an Application-specific integrated Circuit ASIC (Application SPECIFIC INTEGRATED Circuit), or one or more integrated circuits configured to implement embodiments of the present invention.

Memory 406 for storing programs 410. Memory 406 may comprise high-speed RAM memory or may also include non-volatile memory (non-volatile memory), such as at least one disk memory.

The one or more processors included in the device for acquiring the water layer multiple in the converted wave can be the same type of processor, such as one or more CPUs; but may be different types of processors such as one or more CPUs and one or more ASICs; program 410 may be specifically configured to cause processor 402 to perform the method of acquiring water layer multiples in a converted wave in any of the method embodiments described above.

The algorithms or displays presented herein are not inherently related to any particular computer, virtual system, or other apparatus. Various general-purpose systems may also be used with the teachings herein. The required structure for a construction of such a system is apparent from the description above. In addition, embodiments of the present invention are not directed to any particular programming language. It will be appreciated that the teachings of the present invention described herein may be implemented in a variety of programming languages, and the above description of specific languages is provided for disclosure of enablement and best mode of the present invention.

In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

Similarly, it should be appreciated that in the above description of exemplary embodiments of the invention, various features of the embodiments of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. However, the disclosed method should not be construed as reflecting the intention that: i.e., the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

Those skilled in the art will appreciate that the modules in the apparatus of the embodiments may be adaptively changed and disposed in one or more apparatuses different from the embodiments. The modules or units or components of the embodiments may be combined into one module or unit or component and, furthermore, they may be divided into a plurality of sub-modules or sub-units or sub-components. Any combination of all features disclosed in this specification (including any accompanying claims, abstract and drawings), and all of the processes or units of any method or apparatus so disclosed, may be used in combination, except insofar as at least some of such features and/or processes or units are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise.

Furthermore, those skilled in the art will appreciate that while some embodiments herein include some features but not others included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the following claims, any of the claimed embodiments can be used in any combination.

Various component embodiments of the invention may be implemented in hardware, or in software modules running on one or more processors, or in a combination thereof. Those skilled in the art will appreciate that some or all of the functionality of some or all of the components according to embodiments of the present invention may be implemented in practice using a microprocessor or Digital Signal Processor (DSP). The present invention can also be implemented as an apparatus or device program (e.g., a computer program and a computer program product) for performing a portion or all of the methods described herein. Such a program embodying the present invention may be stored on a computer readable medium, or may have the form of one or more signals. Such signals may be downloaded from an internet website, provided on a carrier signal, or provided in any other form.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by one and the same item of hardware. The use of the words first, second, third, etc. do not denote any order. These words may be interpreted as names. The steps in the above embodiments should not be construed as limiting the order of execution unless specifically stated.

Claims

1. The method for acquiring the multiple waves of the water layer in the converted wave is characterized by comprising the following steps of:

2. The method of claim 1, wherein for any one target shot, using the target shot and the geophone as a shot pair, calculating a continuation value of a wavefield extension between any one of the intermediate shots and the target shot between the shot pair based on the depth model and the seismic data further comprises:

3. The method of claim 2, wherein deriving a continuation operator of the wavefield continuation according to kirchhoff integration theorem for pure longitudinal wave conditions further comprises:

4. The method of claim 1, wherein for any one of the intermediate shots between the offset pairs, calculating a water layer multiple after being reflected by the intermediate shot from a continuation value between the intermediate shot and a target shot and the seismic data of the intermediate shot in the common receiver gather is:

5. The method of claim 1, wherein after acquiring the seismic data, the method further comprises: interpolation processing is carried out on the seismic data, so that the interval between two adjacent data points is smaller than or equal to a preset maximum sampling interval which is one half of the minimum wavelength of the seismic waves;

6. The method of claim 1, wherein after calculating a water layer multiple after reflection from any one of the intermediate shots between the pair of shots from the continuation value between the intermediate shot and the target shot and the seismic data for the intermediate shot in the common bin gather, the method further comprises: and filtering the water layer multiple.

7. The method of claim 6, wherein the stacking the water layer multiples corresponding to each of the intermediate shots between the offset pairs results in the water layer multiples corresponding to the offset pairs being: and overlapping the water layer multiples obtained after the filtering treatment to obtain the corresponding water layer multiple of the offset pair.

8. A converted wave water layer multiple acquisition device, comprising:

9. A computing device, comprising: the device comprises a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface complete communication with each other through the communication bus;

the memory is configured to store at least one executable instruction, where the executable instruction causes the processor to perform the operation corresponding to the method for acquiring multiple waves in a water layer in a converted wave according to any one of claims 1 to 7.

10. A computer storage medium having stored therein at least one executable instruction for causing a processor to perform operations corresponding to the method of acquiring multiples of a water layer in a converted wave according to any one of claims 1to 7.