A method and system for VSP source wavelet consistency correction

Abstract

The application provides a VSP source wave consistent correction method and system, and belongs to the field of seismic data processing. The method first extracts a VSP record of a same well excited by different sources, then obtains a ground transmission function by using the extracted source wave and the VSP record, and finally obtains a VSP record after the wave consistent correction by using the source wave and the ground transmission function. The application is simple to operate, only needs to use the VSP record itself, does not need to use auxiliary data such as a source monitoring wave, is easy to realize, has stable effect, and has high popularization value.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of seismic data processing, and particularly relates to a VSP seismic source wave consistency correction method and system. BACKGROUND

[0002] In seismic data processing, VSP data collection of a well is seldom completed at one seismic source point. Even if it is completed at one seismic source point, the consistency of the collected wave is affected due to the change of the in-well excitation environment during the use of the well or the change of the surface compaction degree of the seismic source point. Especially, the consistency of the wave collected by the explosive seismic source is poorer, mainly including waveform inconsistency, first arrival time inconsistency and energy inconsistency.

[0003] The commonly used VSP seismic source wave consistency correction method mainly utilizes the cross-correlation of the seismic source wave and the standard wave to solve the shaping operator, and obtains the shaped wave profile by the convolution of the operator and the seismic source wave. The effect of this wave shaping method is greatly affected by the similarity of the seismic source wave and the standard wave: if the similarity is good, the energy of the wave before and after shaping is close to the energy of the unshaped wave; if the similarity is poor, the energy difference of the wave before and after shaping is large. In addition, the output energy of the wave shaping is affected by the operator length, white noise coefficient and other processing parameters in the processing.

[0004] Due to the change of the in-well excitation environment or the change of the surface compaction degree of the seismic source point, the consistency of the seismic source wave often appears in the VSP data collection of a well. SUMMARY

[0005] The purpose of the present application is to solve the problems existing in the prior art, and to provide a VSP seismic source wave consistency correction method and system, which can obtain the VSP record after the wave consistency correction only by using the VSP record itself.

[0006] The present application is achieved by the following technical solutions:

[0007] In a first aspect, the present application provides a VSP seismic source wave consistency correction method, which first extracts the seismic source wave of the VSP record excited by different seismic sources of the same well, then obtains the underground transmission function by using the extracted seismic source wave and the VSP record, and finally obtains the VSP record after the wave consistency correction by using the seismic source wave and the underground transmission function.

[0008] Preferably, the method comprises:

[0009] Step 1: dividing the VSP record into multiple data sets according to the seismic source points;

[0010] Step 2: extracting the seismic source wave of each data set;

[0011] Step three: obtain the subsurface transmission function by using the source wavelet and VSP record;

[0012] Step four: multiply the source wavelet with the subsurface transmission function to obtain the VSP record after the wavelet-consistent correction.

[0013] Preferably, the operation of step one comprises:

[0014] The VSP record is divided into multiple data sets according to the source points, and each source point corresponds to a data set;

[0015] The data sets are arranged from shallow to deep according to the receiving depth of the geophones.

[0016] Preferably, the operation of step two comprises:

[0017] The following processing is sequentially performed on each data set to extract the corresponding source wavelet:

[0018] The Fourier transform is sequentially performed on each trace in the data set to obtain the frequency spectrum of each trace;

[0019] The logarithm of the frequency spectrum of each trace is calculated to obtain the logarithmic spectrum of each trace;

[0020] The arithmetic mean of the logarithmic spectra of all traces is calculated to obtain the average logarithmic spectrum of the data set;

[0021] The average logarithmic spectrum is transformed into the time domain by inverse Fourier transform to obtain the source wavelet of the multi-trace averaged data set, which is the extracted source wavelet.

[0022] Preferably, the operation of step three comprises:

[0023] The following processing is sequentially performed on each data set and the source wavelet extracted from the data set to obtain the subsurface transmission function of the data set:

[0024] The Fourier transform is performed on the data set to obtain the frequency spectrum of the data set;

[0025] The Fourier transform is performed on the extracted source wavelet to obtain the frequency spectrum of the source wavelet;

[0026] The frequency spectrum of the data set is divided by the frequency spectrum of the source wavelet, and then inverse Fourier transform is performed to obtain the transmission function of the data set.

[0027] Preferably, the operation of step four comprises:

[0028] Each source wavelet is sequentially multiplied with each subsurface transmission function to obtain the VSP record after correction using the source wavelet.

[0029] Preferably, step four further comprises:

[0030] Compare each corrected VSP record, and take the VSP record with the best correction effect as the VSP record after the wavelet consistency correction.

[0031] In the second aspect of the present application, a VSP wavelet consistency correction system is provided, which is used to firstly extract the wavelet of the VSP record excited by different sources in the same well, then obtain the underground transmission function by using the extracted wavelet and the VSP record, and finally obtain the VSP record after the wavelet consistency correction by using the wavelet and the underground transmission function.

[0032] Preferably, the system comprises:

[0033] The distribution unit is used to divide the VSP record into multiple data sets according to the source points.

[0034] The extraction unit is connected with the classification unit and is used to extract the wavelet of each data set.

[0035] The underground transmission function acquisition unit is connected with the classification unit and the extraction unit respectively and is used to obtain the underground transmission function by using the wavelet and the VSP record.

[0036] The correction unit is connected with the extraction unit and the underground transmission function acquisition unit respectively and is used to fold the wavelet and the underground transmission function to obtain the VSP record after the wavelet consistency correction.

[0037] In the third aspect of the present application, a computer readable storage medium is provided, which stores at least one computer executable program, and the at least one program is executed by the computer to make the computer execute the steps in the VSP wavelet consistency correction method of the present application.

[0038] Compared with the prior art, the present application has the advantages that the present application is simple to operate, only needs to use the VSP record itself, does not need to use the auxiliary data such as the source monitoring wavelet, is easy to implement, has stable effect, and has high popularization value. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 The step block diagram of the method of the present application;

[0040] Figure 2 The original VSP data;

[0041] Figure 3 The extracted wavelet;

[0042] Figure 4 The underground transmission function;

[0043] Figure 5-1 The graph before the VSP wavelet correction;

[0044] Figure 5-2 VSP source wavelet corrected figure. DETAILED DESCRIPTION

[0045] The application will be described in further detail below with reference to the drawings:

[0046] For the inconsistency of the source wavelet caused by the change of the excitation environment of the well in use at the same source point, the application provides a VSP source wavelet consistency correction method, which firstly extracts the source wavelet of the VSP record excited by different sources of the same well, then obtains the underground transmission function by using the extracted source wavelet and the VSP record, and finally convolves the selected source wavelet with the underground transmission function to obtain the VSP record after the correction of the wavelet consistency.

[0047] As shown in Figure 1 , the method of the application comprises:

[0048] Step one: divide the VSP record into multiple data sets according to the source points;

[0049] Step two: extract the source wavelet of each data set;

[0050] Step three: obtain the underground transmission function by using the source wavelet and the VSP record;

[0051] Step four: convolve the source wavelet with the underground transmission function to obtain the VSP record after the correction of the wavelet consistency.

[0052] The implementation of the method of the application is as follows:

[0053] Example one:

[0054] The operation of step one comprises:

[0055] Divide the VSP record (i.e. the VSP original data) into multiple data sets, for example [D1 D2 D3], according to the source points, and each data set corresponds to a source point;

[0056] The data sets are arranged from shallow to deep according to the receiving depth of the geophones.

[0057] Example two:

[0058] The operation of step two comprises:

[0059] Extract the corresponding source wavelet, for example [s1 s2 s3], from each data set in turn by using the multi-channel average method, and the specific operation is as follows:

[0060] Perform Fourier transform on each channel in the first data set D1 in turn to obtain the frequency spectrum of each channel;

[0061] Logarithm of the spectrum of each trace is taken to obtain the log spectrum of each trace;

[0062] Arithmetic mean of the log spectrum of all traces is calculated to obtain the average log spectrum of the data set;

[0063] Inverse Fourier transform is used to transform the average log spectrum to the time domain to obtain the source wavelet of the multi-trace averaged data set D1, i.e. the extracted source wavelet s1.

[0064] In the same way, the source wavelet s2 of the data set D2 and the source wavelet s3 of the data set D3 are extracted.

[0065] Example Three:

[0066] The operation of Step Three includes:

[0067] The subsurface transmission function of each data set is obtained by using each data set and the source wavelet extracted from the data set in turn, which is as follows:

[0068] The Fourier transform is performed on the first data set D1 to obtain the frequency spectrum FD1 of the data set, the Fourier transform is performed on the source wavelet s1 extracted from the first data set D1 to obtain the frequency spectrum Fs1 of the source wavelet, the frequency spectrum FD1 of the data set is divided by the frequency spectrum Fs1 of the source wavelet, and then inverse Fourier transform is performed to obtain the subsurface transmission function r1 of the data set D1; the number of the subsurface transmission functions is the same as the number of traces, for example, the data set D1 has 24 traces, and the subsurface transmission function r1 used has 24.

[0069] In the same way, the transmission function r2 of the data set D2 and the transmission function r3 of the data set D3 are obtained.

[0070] Example Four:

[0071] The operation of Step Four includes:

[0072] Each source wavelet is convolved with each subsurface transmission function in turn to obtain the VSP record corrected by using the source wavelet.

[0073] Specifically, the source wavelet s1 is convolved with each transmission function r1, r2 and r3 to obtain the VSP record [D1new D2new D3new] corrected by using the source wavelet s1, wherein D1new=s1*r1, D1new=s1*r2 and D1new=s1*r3, so that the VSP record corrected by using the same source wavelet is obtained.

[0074] Similarly, the VSP record corrected by using the source wavelet s2 is obtained by using the source wavelet s2 and each of the transmission functions r1, r2 and r3 for convolution, and the VSP record corrected by using the source wavelet s3 is obtained by using the source wavelet s3 and each of the transmission functions r1, r2 and r3 for convolution.

[0075] Step four further comprises:

[0076] The VSP record with the best correction effect is taken as the VSP record after the wavelet consistency correction by comparing each corrected VSP record.

[0077] In order to verify the effectiveness of the VSP source wavelet consistency correction method, the VSP seismic actual data is processed and verified. Figure 2 The original z-component data in the VSP record is taken as the VSP record, and the receiving channel number is 72 channels, wherein channels 1-24 are excited by the source 1, channels 24-48 are excited by the source 2, and channels 49-72 are excited by the source 3. Since the explosive excitation is used, the excitation environment changes after the well shooting excitation, the source wavelet changes, and the wavelet consistency at different depths in the same well is poor.

[0078] According to the three sources, the data is divided into three data sets according to channels 1-24, 24-48 and 49-72, and the source wavelets wavelet1, wavelet2 and wavelet3 of each data set are extracted, as shown in Figure 3 The VSP original record spectrum is divided by the source wavelet spectrum, and then inverse transformed to the time domain to obtain the underground transmission function, as shown in Figure 4 The source wavelets of channels 1-24, 25-48 and 49-72 are respectively convolved with the underground transmission function (72 channels) to obtain three VSP records after source wavelet correction. The correction effect of the three corrected VSP records is compared (the correction effect is judged by observing the continuity of the axis and the consistency of the wavelet, etc. to find the VSP record with the best correction effect as the VSP record after the wavelet consistency correction. The method for comparing the correction effect of the VSP record is well known in the art, and will not be described here again). It is found that the VSP record obtained by selecting the source wavelet of channels 1-24 for correction has the best correction effect, and therefore the corrected VSP record obtained by convolving the three underground transmission functions with the source wavelet extracted from channels 1-24 is taken as the final VSP record after the source wavelet correction. Figure 5-1 and Figure 5-2 The contrastive graphs before and after the source wavelet correction are shown in Figure 5-2 It can be seen from

[0079] The actual data processing test result shows that the method has the advantages of simple operation, good processing effect on actual data and popularization and application.

[0080] The method is simple to operate, only needs to use VSP records, does not need to use auxiliary data such as shot monitor wavelet, is easy to realize, has stable effect, and has high popularization value.

[0081] The application further provides a VSP shot wavelet consistency correction system, which is used for firstly extracting a shot wavelet from VSP records excited by different shots in the same well, then obtaining a downhole transmission function by using the extracted shot wavelet and the VSP records, and finally obtaining VSP records after shot wavelet consistency correction by using the shot wavelet and the downhole transmission function.

[0082] The implementation of the system is as follows:

[0083] Example five:

[0084] The system comprises:

[0085] The diversity unit is used for dividing the VSP records into multiple data sets according to shot points;

[0086] The extraction unit is connected with the hierarchical unit and is used for extracting a shot wavelet of each data set;

[0087] The downhole transmission function acquisition unit is connected with the hierarchical unit and the extraction unit respectively and is used for obtaining a downhole transmission function by using the shot wavelet and the VSP records;

[0088] The correction unit is connected with the extraction unit and the downhole transmission function acquisition unit respectively and is used for performing convolution on the shot wavelet and the downhole transmission function to obtain VSP records after shot wavelet consistency correction.

[0089] Specifically, the diversity unit performs the following operations:

[0090] The VSP records are divided into multiple data sets according to shot points, and each shot point corresponds to a data set;

[0091] The data sets are arranged from shallow to deep according to the receiving depth of geophones.

[0092] The extraction unit performs the following operations:

[0093] The corresponding shot wavelet is extracted by sequentially performing the following processing on each data set:

[0094] The spectrum of each trace is obtained by sequentially performing Fourier transform on each trace in the data set.

[0095] logarithm of the spectrum of each trace is obtained;

[0096] the arithmetic mean of the logarithm spectra of all traces is calculated to obtain the average logarithm spectrum of the data set;

[0097] the average logarithm spectrum is transformed into the time domain by inverse Fourier transform to obtain the source wavelet of the multi-trace averaged data set, i.e., the extracted source wavelet.

[0098] The underground transmission function acquisition unit performs the following operations:

[0099] The following processing is sequentially performed on each data set and the source wavelet extracted from the data set to obtain the transmission function of the data set:

[0100] Fourier transform is performed on the data set to obtain the spectrum of the data set;

[0101] Fourier transform is performed on the source wavelet extracted from the data set to obtain the spectrum of the source wavelet;

[0102] The spectrum of the data set is divided by the spectrum of the source wavelet, and then inverse Fourier transform is performed to obtain the transmission function of the data set.

[0103] The correction unit performs the following operations:

[0104] Each source wavelet is sequentially multiplied by each underground transmission function to obtain the VSP record corrected using the source wavelet.

[0105] Specifically, the source wavelet s1 is multiplied by each transmission function r1, r2, and r3 to obtain the VSP record corrected using the source wavelet s1 [D1new, D2new, D3new], where D1new = s1*r1, D1new = s1*r2, and D1new = s1*r3. In this way, the VSP record corrected using the same source wavelet is obtained.

[0106] Similarly, the source wavelet s2 is multiplied by each transmission function r1, r2, and r3 to obtain the VSP record corrected using the source wavelet s2, and the source wavelet s3 is multiplied by each transmission function r1, r2, and r3 to obtain the VSP record corrected using the source wavelet s3.

[0107] The operation of the correction unit further includes:

[0108] The corrected VSP records are compared, and the VSP record with the best correction effect is taken as the VSP record after wavelet consistency correction.

[0109] The application further provides a computer readable storage medium, which stores at least one program executable by a computer, and the at least one program enables the computer to execute steps in the VSP seismic source wavelet consistency correction method when executed by the computer.

[0110] The technical scheme described above is only one embodiment of the application, and those skilled in the art can make various types of improvements or modifications on the basis of the disclosed principles, and the technical scheme described in the above specific embodiments is not limited. The above description is only preferred, and is not limited in meaning.

Claims

1. A method for VSP source wavelet consistency correction, characterized in that: The method first extracts source wavelets from VSP records excited by different sources in the same well, then obtains underground transmission functions by using the extracted source wavelets and the VSP records, and finally obtains VSP records after wavelet consistency correction by using the source wavelets and the underground transmission functions; The method comprises: Step 1: dividing the VSP records into multiple data sets according to source points; Step 2: extracting source wavelets of each data set; Step 3: obtaining underground transmission functions by using the source wavelets and the VSP records; Step 4: obtaining VSP records after wavelet consistency correction by convolving the source wavelets with the underground transmission functions; The operation of Step 4 comprises: Convolving each source wavelet with each underground transmission function in sequence to obtain VSP records after correction by using the source wavelet, and comparing the corrected VSP records to obtain the VSP record with the best correction effect as the VSP record after wavelet consistency correction.

2. The VSP source wavelet consistency correction method of claim 1, wherein: The operation of Step 1 comprises: Dividing the VSP records into multiple data sets according to source points, and each source point corresponds to a data set; The data sets are arranged from shallow to deep according to the receiving depths of geophones.

3. The VSP source wavelet consistency correction method of claim 1, wherein: The operation of Step 2 comprises: Processing each data set in sequence to extract the corresponding source wavelet: Performing Fourier transform on each trace in the data set to obtain the frequency spectrum of each trace; Taking the logarithm of the frequency spectrum of each trace to obtain the logarithmic spectrum of each trace; Calculating the arithmetic mean of the logarithmic spectra of all traces to obtain the average logarithmic spectrum of the data set; Converting the average logarithmic spectrum to the time domain by inverse Fourier transform to obtain the source wavelet of the data set after multi-trace averaging, which is the extracted source wavelet.

4. The VSP source wavelet consistency correction method of claim 1, wherein: The operation of Step 3 comprises: Processing each data set and the extracted source wavelet of the data set in sequence to obtain the underground transmission function of the data set: Performing Fourier transform on the data set to obtain the frequency spectrum of the data set; Performing Fourier transform on the extracted source wavelet to obtain the frequency spectrum of the source wavelet; Dividing the frequency spectrum of the data set by the frequency spectrum of the source wavelet, and then performing inverse Fourier transform to obtain the transmission function of the data set.

5. A VSP source wavelet consistency correction system based on the VSP source wavelet consistency correction method according to any one of claims 1-4, characterized in that: The system is used for first extracting source wavelets from VSP records excited by different sources in the same well, then obtaining underground transmission functions by using the extracted source wavelets and the VSP records, and finally obtaining VSP records after wavelet consistency correction by using the source wavelets and the underground transmission functions.

6. The VSP source wavelet consistency correction system of claim 5, wherein: The system comprises: A division unit for dividing the VSP records into multiple data sets according to source points; An extraction unit connected with the division unit and configured to extract source wavelets of each data set; An underground transmission function acquisition unit connected with the division unit and the extraction unit and configured to obtain underground transmission functions by using the source wavelets and the VSP records; A correction unit connected with the extraction unit and the underground transmission function acquisition unit and configured to obtain VSP records after wavelet consistency correction by convolving the source wavelets with the underground transmission functions.

7. A computer-readable storage medium, characterized in that: The computer readable storage medium stores at least one program executable by the computer, and the at least one program is executed by the computer to make the computer execute the steps in the VSP source wavelet consistency correction method in any one of claims 1-4.

Images