KR101845965B1 - Method for correction of swell of seismic survey data - Google Patents

Abstract

The present invention relates to a swell correction method for seismic exploration data, which corrects distortions or errors in analysis of a seismic stack section, caused by a swell effect, occurring during performance of high-resolution seismic exploration for exploration of submarine geological features. The method includes: obtaining a seismic stack section by seismic exploration; obtaining a submarine location and extracting a submarine signal from the stack section by picking; flattening the extracted submarine signal; generating a reference reflection signal using a correlation; extracting lag values of traces by correlating the reference reflection signal and the traces; removing a swell effect by adding the extracted lag values to the trace signals, respectively; and restoring a stack section in which the swell is corrected. A stack section having a higher level of resolution can be obtained by removing distortions or alterations in analysis of the stack section caused by a swell effect occurring during performance of high-resolution seismic exploration.

Description

METHOD FOR CORRECTION OF SWELL OF SEISMIC SURVEY DATA BACKGROUND OF THE INVENTION [0001]

The present invention relates to a method for correcting waviness of seismic waves, and more particularly, to a method for correcting distortions or errors in the analysis of a cross-section due to the influence of waviness occurring when performing a high resolution seismic survey for exploration of an underwater geological structure The present invention relates to a method for correcting waviness of seismic data.

Oceanic seismic surveys are being carried out for the purpose of finding underwater resources such as oil, natural gas, gas hydrate, and investigating bedrock for marine construction such as submarine pipelines, cable laying, submarine tunnels, seabed storage facilities, and bridges . It is aimed at grasping the geological structure in the case of high resolution seismic exploration aimed at engineering such as marine civil engineering and construction such as submarine pipelines and cables, submarine tunnels, seabed storage facilities, and bridges.

High resolution seismic surveys require precise surveying so that the resolution of the survey data is within 1m. However, seawater always influences survey data by swells or waves generated by currents and wind, and it is not easy to precisely grasp the stratigraphic structure in the seismic section. The effect of the waviness on the section of the elastic wave is expressed by the sea bottom surface of the gear wheel. This phenomenon affects the whole section of the elastic wave, and the continuity of the ground layer is deteriorated.

A typical high resolution seismic data acquisition system is composed of a seismic source generator such as a small air gun, sparker, boomer, and a single channel or an 8-channel and 24-channel And a receiver of a multi-channel streamer of the present invention. Or Chirp Sub-Bottom Profiler (hereinafter referred to as "Chirp SBP"). Because these explorations are aimed at grasping the deep geological structure, it is possible to acquire high resolution seismic data with high resolution, though the penetration depth is low by utilizing a relatively high frequency. When the sound source is a small air gun, the frequency bands are 100 - 350 Hz, the sparker is 600 - 900 Hz, the boomer is 1000 - 2000 Hz, and the Chirp SBP is 2000 - 7000 Hz.

The higher the frequency of an acoustic wave source, the higher the vertical resolution, but the more sensitive it is to the effects of the waves and the waves. And because the depth of water creates a narrower blasting interval in the deep sea, this also affects the effects of swells and waves in the exploration data. Therefore, it can be said that the higher resolution seismic data are affected by the waves and waves.

For example, if we perform seismic surveys on four north-south lines of main lines and two east-west lines of auxiliary lines, a total of eight intersections occur. Since each intersection passes through the same point, the round-trip attention should be the same. However, there is a difference in the reciprocal distance between the north and south directions due to wind, algae, and current direction depending on the south-north direction or the north-south direction. Therefore, there is a difference in reciprocal attention at each intersection point. This phenomenon occurs when the intersection points become large, and when the isopach map or the time structure map is produced. In addition, since the wavelength is shorter as the acoustic wave source is higher in frequency, this crossing error is more apparent in high resolution seismic data.

Therefore, in order to obtain a high-resolution seismic wave data, a correction method of a wavenge having an improved accuracy is required.

Korean Patent No. 10-1544829 (entitled: Width Influence and Cross Correction Method of High Resolution Seismic Data Using Multi Beam Echo Sounding Data)

SUMMARY OF THE INVENTION It is an object of the present invention to solve the problems of the prior art described above, and it is an object of the present invention to provide a method and apparatus for analyzing seismic waves, The present invention provides a method for correcting a waviness of seismic survey data.

In order to accomplish the above-mentioned object, a waveness correction method of seismic wave-

A step of acquiring a cross-section of the polymer by exploring an undersurface of an acoustic wave;

Obtaining a position of the bottom surface through picking from the cross-section of the cross-section and extracting a bottom surface signal;

Smoothing the extracted bottom surface signal;

Generating a reference reflection signal using cross-correlation;

Performing a cross-correlation between the reference reflection signal and each trace to extract a lag value for each trace;

Adding the extracted delay value to each trace signal to eliminate the influence of the swell; And

And restoring the corrected cross-section of the polymerization.

The process of acquiring the bottom surface position and extracting the bottom surface signal

Dividing the time representing the y-axis in the acoustic wave cross-section by a sampling interval to remove dt;

Picking up a seismic section of the seabed surface to smoothen and extracting a reflected signal;

An allocation step of setting a window of a predetermined size from an elastic wave sectional view of the sea floor and allocating an average of amplitude values in the set window to the center of the window;

And a moving step of moving the generated window by one sample in the x axis (trace axis) direction

The allocating step and the moving step may be repeatedly performed as many times as the sampling number corresponding to the number of x-axes.

The window may be configured to set a size of 100 to 150 samples.

The step of smoothing the bottom surface signal

Subtracting the depth of the bottom surface from the B reflection signal among the bottom surface signals constituted by the A reflection signal and the B reflection signal;

Adding a predetermined number of samples to the resultant value to flatten the reference alignment depth (y-axis); And

And extracting, as a file, a lag value subtracted from the B reflection signal for each of the traces.

Wherein the step of generating the reference reflection signal comprises:

a first cross-correlation step of cross-correlating the n-th trace and the n + 1 trace and stacking the two traces when the correlation coefficient is the highest;

A second cross-correlation step of cross-correlating the polymerized trace with an (n + 2) -th trace to polymerize when the correlation coefficient is highest;

Repeating the first cross-correlation step and the second cross-correlation step to cross-correlate and polymerize all traces; And

And generating a reference signal by dividing the result of the iterative step by the number of total traces.

(Where n represents a natural number value from 1 to 10301, repeating the process of 10301 cross-correlation and polymerization).

와

의 상호상관(

)은 아래의 식으로 표현하도록 구성될 수 있다. The cross-correlation indicates that the product of two signals is represented as a function of the displacement, while moving one signal from two different signals,

Wow

Cross-correlation of

) Can be configured to be expressed by the following equation.

은 지연(lag)값을 의미하며,

는 최대 지연(lag)값을 의미함)(Here, the above-mentioned correlation coefficient has a value of the correlation coefficient between -1 and 1

Means a lag value,

Means the maximum lag value)

The step of restoring the sheared,

Adding the depth of the seabed surface in the elastic wave cross-section where the swell influence is removed;

Subtracting the result value added by the depth by the predetermined number of samples; And

and restoring dt by multiplying the time representing the y-axis by the sampling interval.

Therefore, the method of compensating the waviness of the seismic waveguide of the present invention can eliminate the distortion or distortion occurring in the analysis of the cross-section due to the influence of the waviness generated when the high resolution seismic wave survey is performed for exploring the geological structure of the seabed It is possible to obtain a polymerized cross-section with high resolution.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flowchart showing a process of correcting a waveness of an acoustic wave survey data according to an embodiment of the present invention; FIG.
2 is a view showing an example of a polymerization cross-section obtained by seismic exploration according to an embodiment of the present invention;
3 is a flowchart illustrating a process of acquiring the bottom surface position of FIG. 1 and extracting a bottom surface signal according to an embodiment of the present invention.
4 is a graph illustrating a state in which a reflection signal is picked according to an embodiment of the present invention.
FIG. 5 is a flowchart illustrating a process of smoothing a bottom surface signal of FIG. 1 according to an embodiment of the present invention. FIG.
6 is a graph showing a state in which a reflection signal is smoothed according to an embodiment of the present invention.
7 is a flowchart illustrating a process of generating a reference reflection signal according to an embodiment of the present invention.
8 is a diagram illustrating a reference reflected signal in accordance with an embodiment of the present invention.
FIG. 9 is a flowchart illustrating a process of restoring the original data of FIG. 1 according to an exemplary embodiment of the present invention; FIG.
10 is a diagram illustrating a signal reconstruction by cross-correlating a seismic section of a seabed that is smoothed with a reference signal according to an embodiment of the present invention.
11 is a view showing a comparison of elastic wave sections before and after removing the influence of a wavenge according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings showing embodiments of the present invention.

1 is a flowchart illustrating a process of correcting a waviness of an acoustic wave survey data according to an embodiment of the present invention.

Referring to FIG. 1, first, in step S202, an acoustic wave is surveyed to obtain a cross-section.

2 is a view showing an example of a cross-section obtained by seismic waves according to an embodiment of the present invention.

Referring to FIG. 2, a Seg-Y (Society of Exploration Geophysicists-Y) file acquired after performing a high-resolution seismic exploration is required. That is, the x-axis and the y-axis of the Seg-Y file showing the cross-section of the polymer represent the number of received traces and the y-axis represents the reflected signal recorded according to time (time). In the figure, the horizontal axis represents the number of traces, and in the embodiment of the present invention, 19303 pieces are shown. The vertical axis represents the number of samples, and in the embodiment of the present invention, 801 samples are sampled.

In step S204, the submarine surface position is obtained by picking from the cross section of the polymerization and the bottom surface signal is extracted. The step S204 will be described in more detail with reference to the flowchart of FIG. 3 which will be described later.

In step S206, the extracted bottom surface signal is smoothed. Step S206 will be described in more detail with reference to FIG. 5, which will be described later.

In step S208, a reference reflection signal is generated using cross-correlation. Cross-correlation and stacking of the trace-specific signals produces a reference reflection signal that is a signal representative of the impedance of the seabed.

The process of generating the reflex reflection signal in step S208 will be described in more detail with reference to FIG. 7 which will be described later.

)이 최대가 될 때의

값을 의미한다. In step S210, the reference reflection signal is cross-correlated with each trace to extract a lag value for each trace. The delay value extracted from the present invention is obtained by extracting a moving displacement value when a cross-correlation is performed while moving one signal from two different signals. That is, in Equation 1 described below,

) Is the maximum

Lt; / RTI >

The delay value extracted in step S212 is added to each trace signal to remove the influence of the swell.

In step S214, the corrected cross-section is restored. The process of restoring the corrected cross-section in which the waviness is corrected in step S206 will be described in more detail with reference to FIG. 9 described later.

3 is a flowchart illustrating a process of acquiring the bottom surface position of FIG. 1 and extracting a bottom surface signal according to an embodiment of the present invention.

Referring to FIG. 3, in step S302, dt is removed to convert the y-axis time into a sample number, not a time, in the elastic wave section. The specific procedure for removing dt is to divide the time representing the y-axis by the sampling interval to eliminate dt. After removing dt, 801 samples are output on the y-axis. A sample unit is referred to as a depth having an interval of 1 for the sake of convenience.

In step S304, the elastic wave section of the bottom surface is picked and smoothed to extract a reflection signal. In step S304, the reflected signal can be extracted by picking and picking using promax software.

In step S306, a window of a predetermined size is set from the acoustic wave cross-sectional view of the sea floor, and an average of the amplitude values in the set window is assigned to the center of the window. At this time, the size of the predetermined size window is set to about 100 to 150 samples.

In step S308, the window is shifted by one sample in the x-axis (trace axis) direction.

Steps S306 and S308 are repeatedly performed.

4 is a graph illustrating a state in which a reflection signal is picked according to an embodiment of the present invention.

Referring to FIG. 4, a yellow solid line A represents a reflection signal extracted by picking. (0 to 353) of the B reflection signal including the bottom surface are extracted for the efficiency of the above-mentioned cross correlation calculation (shortening the calculation time considering the computer performance).

5 is a flowchart illustrating a process of smoothing the bottom surface signal of FIG. 1 according to an embodiment of the present invention.

First, the bottom surface signal includes an A reflection signal and a B reflection signal.

In step S402, subtracting the depth of the bottom surface from the B reflection signal among the bottom surface signals extracted for each trace. Here, the depth of the sea floor is the position of the A reflection signal of the seabed bottom.

In step S404, the number of 100 samples is added and the reference alignment depth (y axis) is flattened to 100. The addition of 100 samples is intended to prevent the signal from being cut off because the value obtained by subtracting the reflection signal by the depth is aligned to 0 or less on the y-axis.

In step S406, smoothing is performed in step S404, and a lag value subtracted from the B reflection signal for each trace is extracted as a file.

6 is a graph showing a state in which a reflection signal is smoothed according to an embodiment of the present invention.

Referring to FIG. 6, a signal smoothed according to the flowchart of FIG. 5 is shown.

7 is a flowchart illustrating a process of generating a reference reflection signal according to an embodiment of the present invention.

Referring to FIG. 7, in step S502, the two traces are stacked when the n-th trace and the n + 1 trace cross-correlate with each other and the correlation coefficient is the highest.

와

의 상호상관(

)은 아래의 식으로 표현됨.

은 지연(lag)값을 의미하며,

는 최대 지연(lag)값을 의미한다. Cross correlation is a function indicating the degree of similarity between signals. It is a function of moving displacement of two signals while moving one signal from two different signals. signal

Wow

Cross-correlation of

) Is expressed by the following equation.

Means a lag value,

Means the maximum delay value.

In addition, the above-mentioned correlation coefficient is an index for measuring the correlation between two signals. The correlation coefficient has a value between -1 and 1, and the closer to 1, the more similar signals. That is, when the value of the cross-correlation is the largest, the correlation coefficient is the highest.

In step S504, the polymerized trace is cross-correlated with the (n + 2) -th trace and polymerized when the correlation coefficient is the highest.

Repeat steps S502 and S504 to repeat the steps of cross-correlation and polymerizing all the traces. Here, n represents a natural number value from 1 to 10301, and therefore the process of cross-correlation and polymerization of 10301 is repeated.

In step S506, the reference signal is generated by dividing the result obtained by repeating the above process by the total number of traces. As described above, the total number of traces is set to 19303.

8 is a diagram showing a reference reflection signal according to an embodiment of the present invention.

Referring to FIG. 8, a reference reflection signal representing the impedance of the undersurface is generated by performing cross-correlation and polymerization of each signal.

FIG. 9 is a flowchart illustrating a process of restoring the original data of FIG. 1 according to an exemplary embodiment of the present invention.

Referring to FIG. 9, in step S602, the depth of the seabed surface (the position of the A reflection signal on the bottomed seam)

In step S604, the resultant value added by the depth is subtracted by 100 samples.

In step S606, the sampling interval is multiplied by the time representing the y-axis to restore dt.

As a result, we can obtain a seismic section with no waviness effect. We obtain 19393 traces in the x axis and 801 in the y axis.

10 is a diagram illustrating a signal reconstruction by cross-correlating elastic wave sections of a submarine smoothed with a reference signal according to an embodiment of the present invention.

 FIG. 11 is a view showing a comparison of elastic wave sections before and after removal of the influence of a wavenge according to an embodiment of the present invention. FIG.

Referring to Figs. 10 and 11, in particular, Fig. 11 (a) shows a section of the sea floor before correction and Fig. 11 (b) shows a section of the sea floor after correction. It can be seen that the distortion shown inside the yellow ellipse of FIG. 11 (a) is corrected in the case of FIG. 11 (b) to show a more natural section.

In other words, by correcting the influence of the waveness by the cross-correlation method of the present invention, a signal representative of the depth of the undersea surface and the impedance of the undersurface is extracted through cross-correlation, And the correction of the waveness effect is performed, so that the calculation time is fast and the wavenumber is accurately corrected.

In the meantime, the process of correcting the waviness of the seismic survey data according to the present invention using the cross section obtained after performing the seismic survey can be performed using a computer. The computer used in the present invention may be a general home computer, a work station, a super computer, or the like, depending on the amount of calculation.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. will be. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

Claims (7)

Seismic waves to obtain a cross-section of the polymer;
Extracting the undersea surface position and extracting the undersea signal from picking up the cross-section through picking;
Smoothing the extracted bottom surface signal;
Generating a reference reflection signal using cross-correlation of the signal for each trace;
Performing a cross-correlation between the reference reflection signal and each trace to extract a lag value for each trace;
Adding the extracted delay value to each trace signal to eliminate the influence of the swell; And
And recovering the corrected cross-section of the polymerization,
The process of acquiring the bottom surface position and extracting the bottom surface signal includes:
Dividing the time representing the y-axis in the acoustic wave cross-section by a sampling interval to remove dt;
Picking up a seismic section of the seabed surface to smoothen and extracting a reflected signal;
An allocation step of setting a window of a predetermined size from a seismic section of the sea floor and allocating an average of amplitude values within a set window to the center of the window; And
And a moving step of moving the generated window by one sample in the x axis direction (trace axis), and repeating the allocating step and the moving step. delete The apparatus of claim 1,
100 to 150 sample sizes. ≪ RTI ID = 0.0 > 8. < / RTI > 2. The method of claim 1, wherein smoothing the undersea signal comprises:
Subtracting the B reflection signal from the bottom surface signal including the A reflection signal and the B reflection signal by a depth of the bottom surface;
Adding a predetermined number of samples to flatten the reference alignment depth (y-axis); And
Extracting a lag value subtracted from the B reflection signal for each trace to a file; and correcting a waveness correction method of the seismic wave- 2. The method of claim 1, wherein generating the reference reflection signal comprises:
a first cross-correlation step of cross-correlating the n-th trace and the n + 1 trace and stacking the two traces when the correlation coefficient is the highest;
A second cross-correlation step of cross-correlating the polymerized trace with an (n + 2) -th trace to polymerize when the correlation coefficient is highest;
Repeating the first cross-correlation step and the second cross-correlation step to cross-correlate and polymerize all traces; And
And generating a reference signal by dividing the result of the iterative step by the number of total traces.
(Where n represents a natural number value from 1 to 10301, repeating the process of 10301 cross-correlation and polymerization). 6. The method of claim 5,
Indicates that a product of two signals is represented as a function of moving displacement while moving one signal from two different signals,

Wow

Cross-correlation of

) ≪ / RTI > is expressed as: < RTI ID = 0.0 >

(Here, the above-mentioned correlation coefficient has a value of the correlation coefficient between -1 and 1

Means a lag value,

Means the maximum lag value) 2. The method of claim 1, wherein restoring the wedge-
Adding the depth of the seabed surface in the elastic wave cross-section where the swell influence is removed;
Subtracting a result value added by the depth by a predetermined number of samples; And
and multiplying the sampling interval by a time representing a y-axis to reconstruct dt.

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