A surface wave suppression method

Abstract

The application relates to a surface wave suppression method. The surface wave suppression method comprises the following steps: 1) collecting original shot record in field acquisition; 2) performing surface wave suppression on the original shot record obtained in step 1) according to a cross-arrangement domain cone filtering method to obtain an initial surface wave suppressed shot record; 3) subtracting the initial surface wave suppressed shot record obtained in step 2) from the original shot record collected in step 1) to obtain a surface wave shot record containing effective signals; 4) separating effective signals from the surface wave shot record containing effective signals in step 3); and 5) summing the effective signals obtained in step 4) and the initial surface wave suppressed shot record obtained in step 2) to obtain a final shot record which is completely preserved in effective signals and is suppressed in surface waves. The application fully suppresses surface waves while fully preserving effective signals, so that the effective signals are not damaged.

Description

TECHNICAL FIELD

[0001] The present application relates to a surface wave suppression method, belonging to the field of seismic data processing in seismic exploration. BACKGROUND

[0002] Suppressing noise and highlighting effective signal are very key links in the work of seismic data processing. The noise in the seismic data collected in the field can be divided into random noise and regular noise, wherein the regular noise has certain regularity in time or space, has certain frequency band width and apparent velocity. Among the regular noise, the surface wave noise is the most common one, which is the noise generated by the seismic acquisition excitation and propagating along the near-surface layer, and has the characteristics of large energy (the surface wave energy is generally several times or even several dozens of times of the effective signal energy), low frequency and slow attenuation, which greatly reduces the signal-to-noise ratio of the seismic data. Therefore, the suppression of the surface wave noise becomes one of the important work in the seismic data processing.

[0003] In recent years, in order to effectively suppress the surface wave noise, many methods have been proposed by domestic and foreign scholars, which can be divided into two categories. The first category is to use the amplitude characteristics of the surface wave, and to use the regional anomaly processing on the single shot record. The second category is to use the frequency and spatial characteristics of the surface wave, and to use the cone-shaped filtering method in the cross-arrangement domain. Since the first category method does not completely suppress the surface wave, part of the surface wave will be left, therefore, at present, the second category method is applied more in the production practice, which can comprehensively suppress the surface wave, but since the frequency band of the surface wave overlaps with the low frequency component of the effective signal, in the process of suppressing the surface wave, the effective signal will also be damaged, resulting in that the effective signal cannot be fully preserved. SUMMARY

[0004] The purpose of the present application is to provide a surface wave suppression method, so as to solve the technical problem that the effective signal will be damaged when the frequency and spatial characteristics of the surface wave are used to suppress the surface wave in the prior art.

[0005] In the present application, the surface wave suppression method adopts the following technical scheme:

[0006] The surface wave suppression method comprises the following steps:

[0007] 1) Collecting the original shot record collected in the field;

[0008] 2) Suppressing the surface wave according to the cone-shaped filtering method in the cross-arrangement domain for the original shot record obtained in step 1), to obtain the initial shot record after the surface wave suppression;

[0009] 3) Subtracting the initial shot record after the surface wave suppression obtained in step 2) from the original shot record collected in step 1), to obtain the shot record containing the effective signal and the surface wave noise;

[0010] 4) Separating the effective signal and the surface wave noise record from the shot record containing the effective signal and the surface wave noise in step 3).

[0011] 5) Summing the effective signal obtained in step 4) and the initial surface wave suppressed shot record obtained in step 2), obtaining the final shot record which fully retains the effective signal and suppresses the surface wave.

[0012] The beneficial effect is that the effective signal is fully retained while the surface wave is completely suppressed, and the effective signal is not damaged. The surface wave suppression method has strong practicability, and can be popularized and applied in 3D seismic data collected on land and at sea.

[0013] As a further improvement, if the surface of the field has a large elevation difference, the shot record in step 1) needs to eliminate the surface elevation difference.

[0014] As a further improvement, in step 1), the shot record is processed by static correction.

[0015] As a further improvement, the original shot record in step 1) is a 3D shot record.

[0016] As a further improvement, the original shot record is obtained by field blasting collection.

[0017] The above preferred technical solutions can be used alone, and two or more solutions can be combined in combination, and the technical solutions formed by combination are not specifically described here, and are included in the description of the patent. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a flowchart of the surface wave suppression method of the present application;

[0019] Figure 2 is a single shot record after static correction processing and elimination of surface elevation difference of the present application;

[0020] Figure 3 is a single shot record after surface wave suppression by the conventional cross-arrangement domain cone filtering method of the present application;

[0021] Figure 4 is a surface wave record containing effective signal of the present application;

[0022] Figure 5 is Figure 4 the surface wave noise record separated out in the present application;

[0023] Figure 6 is Figure 4 the effective signal record separated out in the present application;

[0024] Figure 7 is a single shot record after final surface wave suppression of the present application;

[0025] Figure 8 is a stack profile after grouping and stacking of the shot gather record after suppressing the surface wave by the surface wave suppression method in the prior art;

[0026] Figure 9 is a stack profile after grouping and stacking of the shot gather record after suppressing the surface wave by the surface wave suppression method in the present application;

[0027] Figure 10 is a schematic diagram of the positions of the geological points and the A detector and the B detector;

[0028] Figure 11 is a schematic diagram of the time difference when the A detector and the B detector detect;

[0029] Figure 12 is a diagram of the main influence area of the surface wave;

[0030] Figure 13 is a schematic diagram of the positions of the geological points and a row of detectors;

[0031] Figure 14 is a diagram of the corresponding relationship between the i point of the kth trace and the j point of the first trace. DETAILED DESCRIPTION

[0032] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application is further described in detail below in combination with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application, that is, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. The components of the embodiments of the present application described and shown in the accompanying drawings can be arranged and designed in different configurations.

[0033] Therefore, the detailed description of the embodiments of the present application provided in the accompanying drawings below is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0034] It should be noted that the terms "first" and "second" and the like in the specific embodiments of the present application can only be used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variants thereof appearing in the present application are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. The statement "including a…" appearing in the present application does not exclude the presence of additional identical elements in the process, method, article or device including the element, without more limitations.

[0035] In the description of the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting" appearing in the present application should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection; it can be direct connection, or indirect connection through intermediate medium, or internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0036] In the description of the present application, unless otherwise explicitly specified and limited, the term "provided with" appearing in the present application should be understood broadly, for example, the object "provided with" can be part of the body, or arranged separately from the body and connected to the body, and the connection can be detachable connection or non-detachable connection. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0037] The present application will be further described in detail below in combination with embodiments.

[0038] Embodiment 1 of the surface wave suppression method in the present application:

[0039] In this embodiment, the overall flow of the surface wave suppression method is as shown in Figure 1 The implementation steps of the method are specifically introduced below taking the three-dimensional seismic data collected in the mountainous area of Sichuan Basin as an example:

[0040] Step 1, data preparation of seismic data, specifically: collect the three-dimensional original shot record collected in the Shuangmiaochang area of Sichuan Basin, the sampling rate of the data body is ΔT=2ms, the trace interval is ΔX=25m, the data body has been processed by static correction to eliminate the elevation difference of surface relief. A shot record in the above data body is shown in Figure 2 The values of sampling rate and trace interval can be changed as needed.

[0041] The signal of the shot number l, trace number k, main survey line x, contact line y, and sampling point i of the original shot gather record is set as S(l, k, x, y, i);

[0042] The superimposed acceleration field of the Shuangmiaochang area in the Sichuan Basin is collected, and the velocity of the shot number l, trace number k, main survey line x, contact line y, and sampling point i of the superimposed acceleration field is set as V(l, k, x, y, i).

[0043] Step 2, the original shot gather record obtained in step 1 is subjected to surface wave suppression according to the conventional cross-arrangement domain conical filter method to obtain an initial surface wave suppression shot gather record T(l, k, x, y, i), as shown in Figure 3 .

[0044] Step 3, the initial surface wave suppression shot gather record is subtracted from the original shot gather record obtained in step 1 to obtain a surface wave shot gather record M(l, k, x, y, i) containing effective signals, as shown in Figure 4 , and the calculation formula is as follows:

[0045] M(l, k, x, y, i) = S(l, k, x, y, i) - T(l, k, x, y, i).

[0046] Comparison Figure 2 and Figure 3 , after being subjected to surface wave suppression according to the conventional cross-arrangement domain conical filter method, the initial surface wave suppression shot gather record obtained is suppressed well, but as can be seen from Figure 4 , there is still part of the effective signal (as indicated by the arrow in Figure 4 ) in the surface wave record suppressed.

[0047] Step 4, the surface wave noise record M'(l, k, x, y, i) as shown in Figure 5 and the effective signal T'(l, k, x, y, i) as shown in Figure 6 are separated from the surface wave shot gather record M(l, k, x, y, i) containing effective signals obtained in step 3, and the specific steps are as follows:

[0048] 4.1, as shown in Figure 10 , the inverted triangle is the shot point, the remaining equilateral triangle is the geophone, and the circle is the geological point. The A geophone receives the seismic wave first, and the B geophone receives the seismic wave later. The performance on the earthquake is as shown in Figure 11 . Then the time difference between the A geophone and the B geophone can be approximately Δt = x 2 / (2*v 2 *to), which is a known formula, wherein x is the distance between the A geophone and the B geophone, and v is the velocity at to.

[0049] As Figure 12 shown, since the surface wave in the shot record is in the triangular area, the farther from the triangular area, the less affected by the surface wave. Therefore, the farthest is the first and last trace. As Figure 13 shown, assuming there are n traces, the middle trace is n / 2, less than n / 2 traces are taken as the first trace as the reference trace, and more than n / 2 traces are taken as the last trace as the reference trace.

[0050] Now take the record of less than n / 2 traces as an example to illustrate whether it is a surface wave or an effective signal. Assuming that the kth trace signal (1 < k ≤ n / 2) is to be distinguished, the ith sampling point is a surface wave or an effective signal, as Figure 14 shown, first find the signal from the same geological point as i on the first trace, then the signal from the same geological point as i on the first trace is j, and j needs to be calculated. That is, set M(l, 1, x, y, i) as the first trace; obtain the comparison signal M(l, 1, x, y, j) of the kth trace M(l, k, x, y, i) on the reference trace; wherein: ΔT is the sampling rate, ΔX is the trace spacing.

[0051] Here we need to use the h point of the middle trace, according to the principle of Figure 11 , the time difference between i and h is approximately Because i is a sampling point, and the calculated time may not be an integer, so rounding is needed, and the time when h receives the signal is i*ΔT-integer , that is, T0.

[0052] Then the time difference between J and i is: Then, rounding the above formula and adding i, the time when j receives the signal is Divide the above formula by ΔT to get the position of the sampling point j.

[0053] Similarly, for seismic traces greater than n / 2, select the last trace as the reference trace, and according to the above calculation principle, obtain the sampling point corresponding to the last trace of the point to be determined.

[0054] 4.2, when M(l, k, x, y, i) is greater than P x M(l, 1, x, y, j), it is judged as surface wave noise, recorded as M'(l, k, x, y, i), otherwise as effective signal T'(l, k, x, y, i), wherein, P ≥ 2.

[0055] 4.3, if there are still effective signals in the separated surface wave record, the value of P in step 4.2 is increased by a fixed value, and the fixed value is 1, and the surface wave noise and effective signal are distinguished again until no effective signal can be identified in the separated surface wave record. The main basis for the discrimination is to watch whether there are similar Figure 5If there is a hyperbolic curve characteristic in the signal, it indicates that the P value is not set correctly, and the P value needs to be further increased until no similar hyperbolic curve is observed. (It should be noted here that the effective signal is always a hyperbolic curve on the shot record)

[0056] Step 5: Sum the initial surface wave suppressed shot record obtained in step 2 and the effective signal obtained in step 4, as shown in the following formula to obtain the final surface wave suppressed single shot record F(l, k, x, y, i): Figure 7

[0057] F(l, k, x, y, i) = T(l, k, x, y, i) + T'(l, k, x, y, i).

[0058] Application example: Figure 8 The stacked profile after grouping and stacking the shot record suppressed by the surface wave in the prior art surface wave suppression method, Figure 9 The stacked profile after grouping and stacking the shot record suppressed by the surface wave in the prior art surface wave suppression method, Figure 8 And Figure 9 It can be seen that the stacked profile after suppressing the surface wave according to the present application has strong energy (as shown in the box Figure 9 This is because the present application fully suppresses the surface wave while fully preserving the effective signal, ensuring that the effective signal is not damaged. The surface wave suppression method of the present application has strong practicability and can be widely applied to three-dimensional seismic data collected on land and at sea.

[0059] Embodiment 2 of the surface wave suppression method in the present application:

[0060] The difference between this embodiment and embodiment 1 is that in embodiment 1, if the effective signal still exists in the separated surface wave noise record, the value of P value increased each time is a fixed value. In this embodiment, the value of P value increased each time is a variable value, such as 1 for the first time, 2 for the second time, and 1 for the third time.

[0061] Embodiment 3 of the surface wave suppression method in the present application:

[0062] The difference between this embodiment and embodiment 1 is that in embodiment 1, if the effective signal still exists in the separated surface wave noise record, the value of P value increased each time is a fixed value, and the fixed value is 1. In this embodiment, based on the condition that the value of P value increased each time is a fixed value, the fixed value is 2. In other embodiments, the fixed value is 0.5 or 1.5.

[0063] Embodiment 4 of the surface wave suppression method in the present application:

[0064] ​The difference between this embodiment and embodiment 1 is that in embodiment 1, the original shot gather record collected in step 1) is a three-dimensional shot gather record. In this embodiment, the original shot gather record collected in step 1) is a two-dimensional shot gather record.

[0065] Embodiment 5 of the surface wave suppression method in the present application:

[0066] The difference between this embodiment and embodiment 1 is that in embodiment 1, the original shot gather record is collected from the field blasting. In this embodiment, the original shot gather record is a shot gather record that has been blasted and collected.

[0067] The above is only a preferred embodiment of the present application, and is not used to limit the present application. The patent protection scope of the present application is subject to the claims, and any equivalent structural changes made by using the content of the specification and drawings of the present application shall also be included in the protection scope of the present application.

Claims

1. A method of surface wave suppression, characterized by, The method comprises the following steps: 1) collecting original shot gather records collected in the field; 2) performing surface wave suppression on the original shot gather records obtained in step 1) according to a cross-arrangement domain cone filtering method to obtain initial surface wave suppressed shot gather records; 3) subtracting the initial surface wave suppressed shot gather records obtained in step 2) from the original shot gather records collected in step 1) to obtain surface wave shot gather records containing effective signals; 4) separating effective signals from the surface wave shot gather records containing effective signals in step 3); 5) summing the effective signals obtained in step 4) and the initial surface wave suppressed shot gather records obtained in step 2) to obtain final shot gather records which completely retain effective signals and are surface wave suppressed.

2. The method of surface wave suppression according to claim 1, wherein, If there is a large elevation difference on the ground surface in the field, the shot gather records in step 1) need to eliminate the surface elevation difference.

3. The method of surface wave suppression according to claim 1 or 2, characterized in that, In step 1), the shot gather records are processed through static correction.

4. The method of surface wave suppression according to claim 1 or 2, wherein, The original shot gather records in step 1) are three-dimensional shot gather records.

5. The method of surface wave suppression according to claim 1 or 2, wherein, The original shot gather records are collected through on-site blasting.

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