A method for separation of multi-source mixed seismic wave fields based on first-arrival wave field constraints

Abstract

The present invention provides a multi-source mixed seismic wavefield separation method based on first-arrival wavefield constraints, which first constructs a seismic wave first-arrival wavefield; then mixes seismic first-arrival wavefield values ​​to obtain mixed first-arrival wavefield values; finally, embeds the mixed first-arrival wavefield values ​​into a conventional wavefield separation method, performs multi-source wavefield separation, and obtains a target separated wavefield record. The multi-source mixed seismic wavefield separation method of the present invention can effectively reduce the separation signal-to-noise ratio and improve the fidelity of the separation result by pre-attenuating the first-arrival wavefield with strong energy during the wavefield separation process.

Description

Technical Field

[0001] The invention belongs to the technical field of geophysical exploration, relates to a multi-source mixed seismic exploration technology, and specifically relates to a multi-source mixed seismic wave field separation method based on first arrival wave field constraints. Background Art

[0002] Seismic data acquisition is the most expensive part of seismic exploration. In recent years, a new and efficient acquisition method has emerged - multi-source hybrid seismic exploration technology. Multi-source hybrid seismic exploration technology has been favored by the industry because it can improve the efficiency of seismic data acquisition operations, increase the spatial sampling rate of the source and azimuth information. The essential difference between multi-source hybrid seismic exploration and traditional seismic exploration is that multi-source hybrid seismic exploration allows mutual interference between sources, and all sources can be "freely" excited in the work area, that is, the detector can receive the temporal aliasing signals of the sources on other survey lines while receiving the source signal on the current survey line. Due to the above differences, multi-source hybrid seismic exploration can greatly save acquisition time and cost compared with traditional seismic exploration technology.

[0003] Although multi-source hybrid seismic exploration technology has many advantages, due to the existence of the hybrid matrix, the first arrival wave with strong energy characteristics greatly affects the separation signal-to-noise ratio. Generally, the first arrival wave is a wave field with strong energy in the seismic record, and due to the response of the hybrid matrix in multi-source hybrid seismic exploration, the first arrival wave will be mixed with other wave fields, which seriously affects the quality of wave field separation. Therefore, based on the wave field characteristics of the first arrival wave, it is an urgent problem to study the high-fidelity wave field separation method suitable for multi-source hybrid seismic exploration.

[0004] At present, there are two main types of traditional multi-source mixed seismic wave field separation methods:

[0005] The first type of method is the filtering separation method, which includes the following steps: first, pseudo-separation of the multi-source mixed seismic wave field is performed; then, the pseudo-separated data is transferred to the non-common shot domain, and the filtering method is used to attenuate the multi-source mixed noise; finally, the non-common shot domain data is transferred to the common shot domain.

[0006] The second type of method is the inversion separation method. The steps of the inversion separation method include: first, converting the separation of the multi-source mixed seismic wave field into an inversion form for finding the extreme value of the cost function; then adding constraints in the inversion solution process; finally, extracting the unmixed single-shot record by solving the inverse problem cost function with constraints.

[0007] The defects of the above two types of existing methods are: the influence of the first arrival wave is not considered. Since the energy of the first arrival wave is large, it seriously affects the separation signal-to-noise ratio, and further affects the fidelity of the separation result. Summary of the invention

[0008] In view of the defects and shortcomings of the prior art, the purpose of the present invention is to provide a multi-source mixed seismic wavefield separation method based on first-arrival wavefield constraints, so as to solve the technical problem that the fidelity of the separation results of the multi-source mixed seismic wavefield separation method in the prior art needs to be further improved.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0010] A multi-source mixed seismic wavefield separation method, the method first constructs a seismic wave first arrival wavefield; then mixes the seismic first arrival wavefield to obtain a mixed first arrival wavefield value; finally, embeds the mixed first arrival wavefield into a conventional wavefield separation method, performs multi-source wavefield separation, and obtains a target separated wavefield record.

[0011] The present invention also has the following technical features:

[0012] The method specifically comprises the following steps:

[0013] Step 1: construct the seismic wave first arrival wave field;

[0014] Step 1.1, obtain the parameters required for wave field propagation;

[0015] Step 1.2, obtain the first arrival wave field value W f ;

[0016] According to the parameters required for wave field propagation obtained in step 1.1, the first arrival wave field value W is obtained using the seismic wave equation f ;

[0017] Step 2: Mix the seismic first arrival wave field values ​​to obtain the mixed first arrival wave field value W f ′;

[0018] Step 3: perform multi-source wavefield separation;

[0019] Step 3.1, obtain the wave field value W 0 ′;

[0020] According to the original multi-source mixed wave field value W′ and the mixed first arrival wave field value W obtained in step 2 f ′, calculate and obtain the wave field value W 0 ′;

[0021] Step 3.2, obtain the output separated wave field value W 02 ′;

[0022] Obtain the wave field value W using step 3.1 0 ′ as input, and obtain the first separation wave field value W 01 ′; the first separation wave field value W 01 ′ and the previous separation wave field value W 0ZSubstitute ′ into formula III to obtain the output separated wave field value W 02 '; The formula III is:

[0023] W 02 ′=W 01 ′+W 0Z ' Formula III;

[0024] Where:

[0025] W 02 ′ represents the output separated wave field value;

[0026] W 01 ′ represents the primary separation wave field value;

[0027] W 0Z ′ represents the previous separated wave field value;

[0028] Step 3.3, obtain the mixed separation wave field value W 03 ′;

[0029] According to Formula IV, the output separation wave field value W obtained in step 3.2 is 02 ′ to mix and obtain the mixed separation wave field value W 03 '; The formula IV is:

[0030] W 03 ′=W 02 ′×B Formula IV;

[0031] Where:

[0032] W 03 ′ represents the mixed separation wave field value;

[0033] B represents the mixing matrix deconstruction function;

[0034] Step 3.4, obtaining target separation wave field records;

[0035] According to the wave field value W 0 ′ and step 3.3 to obtain the mixed separation wave field value W 03 ′, calculate and obtain the mixed residual value W d '; judge according to the preset number of cycles, if it is less than the preset number of cycles, it is judged as "yes", and then the mixed residual value W d ' is substituted into step 3.2 to perform a new round of iteration; if it is equal to the preset number of cycles, it is judged as "no", and then the separated wavefield value output for the last time in step 3.2 is recorded as the target separated wavefield.

[0036] Specifically, the step 2 includes:

[0037] Step 2.1, establish the mixing matrix deconstruction function B;

[0038] Step 2.2, obtaining the mixed first arrival wave field value;

[0039] The mixing matrix deconstruction function B constructed by step 2.1 and the first arrival wave field value W obtained in step 1.2 f , use formula II to calculate and obtain the mixed first arrival wave field value W f '; The formula II is:

[0040] W f ′=W f ×B Formula II;

[0041] Where:

[0042] W f ′ represents the mixed first arrival wave field value;

[0043] W f represents the first arrival wave field value;

[0044] B represents the mixing matrix deconstruction function.

[0045] Optionally, the step 3.4 is:

[0046] According to the wave field value W 0 ′ and step 3.3 to obtain the mixed separation wave field value W 03 ′, calculate and obtain the mixed residual value W d ′; judge according to the preset residual value. If the mixed residual value W d ′ is greater than the preset residual value, it is judged as “yes”, and then the mixed residual value W d ′ is substituted into step 3.2 and a new round of iteration is performed; if the mixed residual value W d ′ is less than the preset residual value, it is judged as “No”, and then the separated wavefield value output for the last time in step 3.2 is recorded as the target separated wavefield.

[0047] Specifically and optionally, in step 1.1, the parameters required for wave field propagation include a propagation velocity v of the wave field propagation formation;

[0048] In step 1.2, a simplified form of the seismic wave equation is shown in Formula I:

[0049]

[0050] Where:

[0051] W represents the wave field value at time t corresponding to a certain position of the seismic wave;

[0052] t represents the propagation time of seismic waves in the wave field propagation strata;

[0053] v represents the propagation velocity of the wave field propagation stratum;

[0054] x represents the horizontal coordinate value of seismic wave propagation;

[0055] z represents the vertical coordinate value of seismic wave propagation.

[0056] Substitute the propagation velocity v of the wave field propagation formation obtained in step 1.1 into the above formula I to obtain the first arrival wave field value W f .

[0057] Specifically and optionally, in step 1.1, the parameters required for wave field propagation include the longitudinal wave velocity v of the wave field propagation formation. p The shear wave velocity v of the wave field propagation formation s ;

[0058] In step 1.2, a simplified form of the seismic wave equation is shown in Formula V:

[0059]

[0060] Where:

[0061] u represents the horizontal component of the seismic wave field;

[0062] w represents the vertical component of the seismic wave field;

[0063] t represents the propagation time of seismic waves in the wave field propagation strata;

[0064] v p Indicates the P-wave velocity of the formation in which the wave field propagates;

[0065] v s Indicates the shear wave velocity of the formation in which the wave field propagates;

[0066] x represents the horizontal coordinate value of seismic wave propagation;

[0067] z represents the vertical coordinate value of seismic wave propagation.

[0068] The P-wave velocity v of the wave field propagating the formation obtained in step 1.1 p and the shear wave velocity v s , substituted into the above formula V, and the first arrival wave field value W is obtained f .

[0069] Compared with the prior art, the present invention has the following beneficial technical effects:

[0070] The present invention proposes for the first time to pre-build a first arrival wave model in the multi-source mixed wave field separation process, then embed it into the traditional multi-source mixed wave field separation process, and finally obtain an unmixed seismic wave field record through iterative calculation separation. The multi-source mixed seismic wave field separation method of the present invention can effectively reduce the separation signal-to-noise ratio and improve the fidelity of the separation result by pre-attenuating the first arrival wave field with strong energy in the wave field separation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 It is a flowchart of the multi-source mixed seismic wave field separation method based on the first arrival wave field constraint.

[0072] Figure 2 These are the data for simulating multi-source mixed earthquakes in Example 1 and the comparative example.

[0073] Figure 3 It is the unmixed original shot gather in Example 1 and the comparative example.

[0074] Figure 4 This is the mixed residual distribution diagram in Example 1.

[0075] Figure 5 This is the separation result in Example 1.

[0076] Figure 6 This is the mixed residual distribution diagram in the comparative example.

[0077] Figure 7 This is the separation result in the comparative example.

[0078] The technical solution of the present invention is further described below in conjunction with embodiments. DETAILED DESCRIPTION

[0079] In the present invention:

[0080] The conventional wavefield separation method refers to the filtering separation method known in the prior art.

[0081] Unless otherwise specified, the units of all physical quantities are units commonly used in the art, and only the numerical parts of the physical quantities are used in the formulas of the present invention.

[0082] It should be noted that all the devices used in the present invention, unless otherwise specified, are devices known in the art.

[0083] In accordance with the above technical scheme, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical scheme of this application fall within the protection scope of the present invention.

[0084] Embodiment 1:

[0085] This embodiment provides a multi-source mixed seismic wave field separation method based on first arrival wave field constraints. Figure 1 As shown, the method specifically comprises the following steps:

[0086] Step 1: construct the seismic wave first arrival wave field;

[0087] Step 1.1, obtain the parameters required for wave field propagation;

[0088] The parameters required for wave field propagation in the formation where the geophone and the earthquake source are located are collected and acquired. The parameters required for wave field propagation include the propagation velocity v of the formation where the wave field propagates.

[0089] Step 1.2, obtain the first arrival wave field value;

[0090] Based on the position relationship between the source and the detector, the source excitation and the detector reception parameters, and the parameters required for wave field propagation obtained in step 1.1, the seismic wave equation is used to obtain the first-arrival wave field value. The first-arrival wave field includes the direct wave field and the refracted wave field.

[0091] As a specific solution of this embodiment, in step 1.2, a simplified form of the seismic wave equation is shown in Formula I:

[0092]

[0093] Where:

[0094] W represents the wave field value at time t corresponding to a certain position of the seismic wave;

[0095] t represents the propagation time of seismic waves in the wave field propagation strata;

[0096] v represents the propagation velocity of the wave field propagation stratum;

[0097] x represents the horizontal coordinate value of seismic wave propagation;

[0098] z represents the vertical coordinate value of seismic wave propagation.

[0099] Substitute the propagation velocity v of the wave field propagation formation obtained in step 1.1 into the above formula I to obtain the first arrival wave field value W f .

[0100] Step 2: Mixing the earthquake first arrival wave field;

[0101] Step 2.1, establish the mixing matrix deconstruction function B;

[0102] According to the actual acquisition requirements, a mixing matrix deconstruction function B is established. The mixing matrix deconstruction function B is composed of the seismic wave sources involved in the mixing and the phase encoding corresponding to the seismic wave sources. The mixing matrix deconstruction function B is constructed and obtained using a conventional mixing matrix function establishment method.

[0103] Step 2.2, obtaining the mixed first arrival wave field value;

[0104] The mixing matrix deconstruction function B constructed by step 2.1 and the first arrival wave field value W obtained in step 1 f , use formula II to calculate and obtain the mixed first arrival wave field value W f ′.

[0105] W f ′=W f ×B Formula II;

[0106] Where:

[0107] W f ′ represents the mixed first arrival wave field value;

[0108] W f represents the first arrival wave field value;

[0109] B represents the mixing matrix deconstruction function B;

[0110] × represents the product of matrices or vectors, and it generally acts directly on the source.

[0111] Step 3: perform multi-source wavefield separation;

[0112] Step 3.1, obtain the wave field value W 0 ′;

[0113] Input the original multi-source mixed wave field value W′ and the mixed first arrival wave field value W obtained in step 2 f ′, the mixed first arrival wave field value W f ′ is correlated with the input of the original multi-source mixed wave field value W′ to calculate and obtain the wave field value W 0 ′; the original multi-source mixed wave field value W′ refers to the directly collected mixed shot gather data.

[0114] Step 3.2, obtain the output separated wave field value W 02 ′;

[0115] Obtain the wave field value W using step 3.1 0 ′ is used as input, and the conventional transform domain filtering or inversion separation method is used to obtain the first separation wave field value W 01 ′; According to formula III, the first separation wave field value W 01 ′ and the previous separation wave field value W 0Z 'Superposition of the separated wave field value W as output02 ′; It should be noted that if it is the first iteration, the previous separation wave field value W 0Z ’ is assigned a zero value.

[0116] W 02 ′=W 01 ′+W 0Z ' Formula III;

[0117] Where:

[0118] W 02 ′ represents the output separated wave field value;

[0119] W 01 ′ represents the primary separation wave field value;

[0120] W 0Z ′ represents the previous separated wave field value.

[0121] Step 3.3, obtain the mixed separation wave field value W 03 ′;

[0122] The output separation wave field value W obtained in step 3.2 02 ′, according to formula IV, the output separation wave field value W 02 ′ Mix according to the mixing matrix deconstruction function B to obtain the mixed separation wave field value W 03 ', the formula IV is:

[0123] W 03 ′=W 02 ′×B Formula IV;

[0124] Where:

[0125] W 03 ′ represents the mixed separation wave field value.

[0126] Step 3.4, obtaining target separation wave field records;

[0127] According to the wave field value W 0 ′ and step 3.3 to obtain the mixed separation wave field value W 03 ′, calculate and obtain the mixed residual value W d '; judge according to the preset number of cycles, if it is less than the preset number of cycles, it is judged as "yes", and then the mixed residual value W d ' is substituted into step 3.2 to perform a new round of iteration; if it is equal to the preset number of cycles, it is judged as "no", and then the separated wavefield value output for the last time in step 3.2 is recorded as the target separated wavefield.

[0128] In this embodiment, a simulated multi-source mixed earthquake is constructed, and the wave field separation method of the multi-source mixed earthquake based on the first arrival wave field constraint in the embodiment is used to separate the wave field of the simulated multi-source mixed earthquake. The results are as follows:

[0129] The data for simulating multi-source mixed earthquakes are as follows Figure 2 As shown, Figure 2 Only two mixed shot collections are shown in Figure 1, each of which contains two single-shot records; the unmixed original shot collections are shown in Figure 1. Figure 3 As shown. Mixed residual value W d The distribution of ′ is as follows Figure 4 As shown; the distribution of the target separation wave field record, that is, the separation result is as follows Figure 5 shown.

[0130] Embodiment 2:

[0131] This embodiment provides a multi-source mixed seismic wave field separation method based on first arrival wave field constraint. The method is basically the same as that in Embodiment 1, except that:

[0132] In this embodiment, in step 1.1, the parameters required for wave field propagation include the longitudinal wave velocity v of the wave field propagation formation. p and the shear wave velocity v s .

[0133] In this embodiment, in step 1.2, a simplified form of the seismic wave equation is shown in Formula V:

[0134]

[0135] Where:

[0136] u represents the horizontal component of the seismic wave field;

[0137] w represents the vertical component of the seismic wave field;

[0138] t represents the propagation time of seismic waves in the wave field propagation strata;

[0139] v p Indicates the P-wave velocity of the formation in which the wave field propagates;

[0140] v s Indicates the shear wave velocity of the formation in which the wave field propagates;

[0141] x represents the horizontal coordinate value of seismic wave propagation;

[0142] z represents the vertical coordinate value of seismic wave propagation.

[0143] The P-wave velocity v of the wave field propagating the formation obtained in step 1.1 p and the shear wave velocity v s, substitute it into the formula Ⅰ described above to obtain the first arrival wave field value W f .

[0144] In this embodiment, step 3.4 is as follows:

[0145] According to the wave field value W 0 ′ and the mixed separation wave field value W 03 ′ obtained in step 3.3, calculate and obtain the mixed residual value W d ′; make a judgment according to the preset size of the residual value. If the mixed residual value W d ′ is greater than the preset residual value, judge it as "yes", and then substitute the mixed residual value W d ′ into step 3.2 for a new round of iteration; if the mixed residual value W d ′ is less than the preset residual value, judge it as "no", and then record the separated wave field value output last time in step 3.2 as the target separated wave field.

[0146] Comparative example:

[0147] This comparative example presents a traditional multi-source mixed seismic wave field separation method, which is a conventional filtering separation method known in the prior art.

[0148] In this comparative example, the traditional multi-source mixed seismic wave field separation method is used to separate the wave field of the simulated multi-source mixed earthquake in Example 1, and the results are as follows:

[0149] The distribution of the mixed residual value W d ′ is as shown in Figure 6 , and the separation result is as shown in Figure 7 .

[0150] It can be seen from the above embodiments and comparative examples that: compared with the comparative example, the mixed residual of the embodiment is smaller, indicating that the separation signal-to-noise ratio is lower. Therefore, by using the multi-source mixed seismic wave field separation method based on the first arrival wave field constraint of the present invention, the fidelity of the separation result is higher.

Claims

1. A method for separating multi-source mixed seismic wave fields. It is characterized in that The method first constructs the seismic wave first arrival wave field; then mixes the seismic first arrival wave field to obtain the mixed first arrival wave field value; finally, embeds the mixed first arrival wave field into the conventional wave field separation method to perform multi-source wave field separation to obtain the target separation wave field record; The method specifically comprises the following steps: Step 1: construct the seismic wave first arrival wave field; Step 1.1, obtain the parameters required for wave field propagation; Step 1.2, get the first arrival wave field value W f ; According to the parameters required for wave field propagation obtained in step 1.1, the first arrival wave field value is obtained using the seismic wave equation W f ; Step 2: Mix the seismic first arrival wave field values ​​to obtain the mixed first arrival wave field values W f ′; Step 2.1, establish the mixing matrix deconstruction function B ; Step 2.2, obtaining the mixed first arrival wave field value; The mixing matrix deconstruction function constructed by step 2.1 B , and the first arrival wave field value obtained in step 1.2 W f , use formula II to calculate and obtain the mixed first arrival wave field value W f '; The formula II is: W f ′= W f × B Formula II; Where: W f ′ represents the mixed first arrival wave field value; W f represents the first arrival wave field value; B represents the mixing matrix deconstruction function; Step 3: perform multi-source wavefield separation; Step 3.1, get the wave field value W 0 ′; According to the original multi-source mixed wave field value W ′ and the mixed first arrival wave field value obtained in step 2 W f ′, the mixed first arrival wave field value W f ′ and the original multi-source mixed wave field value W ′ is used as input for relevant attenuation, and the wave field value is calculated and obtained. W 0 '; Calculate and obtain the wave field value W 0 ′; Step 3.2, obtain the output separated wave field value W 02 ′; Step 3.3, obtain the mixed separation wave field value W 03 ′; Step 3.4, obtain the target separation wave field record.

2. The multi-source mixed seismic wave field separation method according to claim 1, Features: In step 1.1, the parameters required for wave field propagation include the propagation velocity of the wave field propagation formation ; In step 1.2, a simplified form of the seismic wave equation is shown in Formula I: Formula I; Where: W Indicates the time corresponding to a certain position of the seismic wave t The wave field value at ; It represents the propagation time of seismic waves in the strata propagating through the wave field; Indicates the propagation velocity of the wave field propagating through the formation; The horizontal coordinate value representing the propagation of seismic waves; The ordinate value representing the propagation of seismic waves; The propagation velocity of the wave field obtained in step 1.1 is Substituting into the above formula I, we can obtain the first arrival wave field value W f .

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