A joint wavefield separation method for optical fiber and geophone downhole seismic data

Abstract

The present invention discloses a method for jointly separating wavefields of optical fiber and geophone downhole seismic data, belonging to the field of geophysics. Aiming at the problem that the existing simultaneously collected optical fiber and geophone downhole seismic data cannot be processed simultaneously, a method for jointly separating wavefields of optical fiber and geophone downhole seismic data is proposed. The present invention gives full play to the advantages of the downhole seismic data collected by the optical fiber and the geophone, performs consistency correction of the depth, time difference and amplitude of the optical fiber data based on the geophone data, and increases the number of channels of the geophone processing data according to the depth sampling density of the optical fiber data, thereby realizing the true fusion of the data collected by the two instruments, and effectively improving the reliability of the downhole seismic data processing.

Description

Technical Field

[0001] The present invention belongs to the field of geophysics, and in particular relates to a seismic data processing technology in geophysical exploration wells. Background Art

[0002] In recent years, distributed optical fiber sensing (DAS) technology has gradually matured. Among them, fiber-optic vertical seismic profiling (DAS-VSP) has become an important means of acquiring seismic data in wells due to its advantages of full well section, high density, high efficiency, high temperature resistance, high pressure resistance, and low cost. DAS-VSP technology can provide high-precision reservoir parameters, improve the ability to describe the oil reservoir around the well in detail, and has the ability to dynamically monitor oil and gas reservoirs. In many exploration areas at home and abroad, a large amount of fiber-optic and geophone well seismic data have been collected simultaneously. Through comparative analysis and experience summary, it is known that fiber-optic VSP data has the following advantages and disadvantages compared with geophone data: (1) The quality of fiber-optic VSP data after preprocessing is comparable to that of conventional geophone data, and the wave field characteristics of the effective signal are similar, with good correspondence in time, waveform, amplitude, phase, etc., and consistent frequency characteristics in space and time; (2) Compared with conventional geophone data, fiber-optic data has weaker surface multiple waves, higher coverage and resolution, and rich low-frequency effective signal information. (3) In the acquisition method where the optical fiber is freely suspended in the casing, the quality of the original data is relatively low due to the lack of support. Noise suppression processing is required to improve the signal-to-noise ratio of the optical fiber data. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention proposes a method and system for joint wavefield separation of optical fiber and geophone downhole seismic data.

[0004] The technical solution adopted by the present invention is: a method for joint wavefield separation of optical fiber and geophone well seismic data, comprising:

[0005] S1. Collecting seismic data in a well through an optical fiber and a geophone, recording the seismic data in the well collected by the optical fiber as first original data, and recording the seismic data in the well collected by the geophone as second original data;

[0006] S2. Remove abnormal data from the first original data and the second original data to obtain filtered first data and filtered second data;

[0007] S3, performing time resampling processing on the filtered first data and the filtered second data to make the time sampling rates of the two data the same, thereby obtaining first preprocessed data and second preprocessed data;

[0008] S4, performing correction processing on the first preprocessed data and the second preprocessed data, specifically including sequentially performing polarity consistency correction processing, depth consistency correction processing, time difference consistency static correction processing, and amplitude consistency correction processing on the first preprocessed data and the second preprocessed data, and finally obtaining first corrected data and second corrected data;

[0009] S5. According to the depth sampling density of the first correction processing data, the second correction processing data is subjected to channel increase and amplitude weighted distribution processing;

[0010] S6, combining the second corrected data processed in step S5 with the first corrected data obtained in step S4 to obtain combined data;

[0011] S7. Perform multi-channel velocity filtering on the spliced data to obtain final wavefield separation data.

[0012] The beneficial effects of the present invention are as follows: the present invention is directed to simultaneously collected optical fiber and geophone downhole seismic data, and proposes a joint wave field separation method for optical fiber and geophone downhole seismic data, which brings into play the respective advantages of the two types of data and improves the reliability of downhole seismic data; specifically: the depth, time difference, and amplitude consistency of the optical fiber data are corrected based on the geophone data, and the number of channels of the geophone processing data is increased according to the depth sampling density of the optical fiber data, thereby realizing the true fusion of the data collected by the two instruments. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Flow chart of the method of the present invention.

[0014] Figure 2 This is the original data of the optical fiber in this embodiment.

[0015] Figure 3 is the original data of the detector in this embodiment.

[0016] Figure 4 Schematic diagram of weighted processing of optical fiber and detector data in this embodiment.

[0017] Figure 5 This is the wave field separation processing result in the calculation diagram of this embodiment. DETAILED DESCRIPTION

[0018] To facilitate those skilled in the art to understand the technical content of the present invention, the present invention is further explained below with reference to the accompanying drawings.

[0019] The present invention aims at simultaneously collecting optical fiber and geophone borehole seismic data, and proposes a combined wave field separation method for optical fiber and geophone borehole seismic data, which gives full play to the advantages of both types of data and improves the reliability of borehole seismic data. Figure 1 As shown, the process specifically includes several steps such as data preparation, data preprocessing, data consistency correction processing, and weighted joint wavefield separation processing, which will be described in detail below with reference to the accompanying drawings.

[0020] 1) Data preparation:

[0021] Select the optical fiber and geophone well seismic data collected simultaneously, record the optical fiber well seismic data as the first original data, and record the geophone well seismic data as the second original data. Figure 2 、 Figure 3 shown.

[0022] The simultaneous acquisition refers to acquiring both optical fiber well seismic data and geophone well seismic data in the same operating well. The two types of data can be acquired at once using a composite electrical (optical) cable or separately.

[0023] The optical fiber and geophone well seismic data mentioned above refer to the vertical component data collected by the two observation methods.

[0024] Optionally, the depth sampling density of the optical fiber data is greater than the sampling density of the detector data, and may be a multiple relationship or a non-multiple relationship, and the recorded depth segments may be the same or different.

[0025] 2) Data preprocessing:

[0026] The first original data and the second original data in step 1) are preprocessed, specifically including data screening and time resampling processing, to obtain first preprocessed data and second preprocessed data.

[0027] (1) Data screening and processing: The abnormal data in the first raw data and the second raw data are removed respectively by comparing the data collection class report, including bad track removal, same-depth data optimization, etc. The first data screening data and the second data screening data are obtained.

[0028] The data collection class report refers to a detailed record of on-site seismic data collection information during the seismic data collection process, usually including the number, coordinates, elevation, recording time, etc. of the excitation point and the receiving point; the data collection class report is a well-known technology in this field.

[0029] The bad track removal and same-depth data optimization are conventional processing procedures, the main purpose of which is to remove abnormal and repeated data information, which can be achieved using existing software.

[0030] (2) Time resampling processing: Time resampling processing is performed on the first data screening data and the second data screening data in the above step to make the time sampling rates of the two the same, thereby obtaining first preprocessed data and second preprocessed data.

[0031] Optional, the time sampling rate is generally 0.5ms, 1ms, 2ms, which can be selected according to actual application needs. When processing individual ultra-high frequency data (main frequency greater than 100hz), it can be less than 0.5ms, but due to the high frequency and formation resolution of in-well seismic data, this selection should not be greater than 2ms.

[0032] In particular, the time sampling rates of the original fiber-optic well seismic data are currently different, and data interpolation calculations are required during the time resampling process. Generally, linear interpolation calculations can be used. When the data volume is extremely large, natural neighbor or nearest neighbor interpolation methods can also be used to save data processing time.

[0033] 3) Data consistency correction processing:

[0034] The first preprocessed data and the second preprocessed data obtained in step 2) are corrected, specifically including polarity consistency correction processing, depth consistency correction processing, time difference consistency static correction processing, and amplitude consistency correction processing, to obtain first corrected processing data and second corrected processing data.

[0035] The consistency correction processing steps have strict sequence requirements and cannot be changed or adjusted.

[0036] (1) Polarity consistency correction processing: The first pre-processed data and the second pre-processed data obtained in step 2) are corrected according to the SEG standard. Specifically, the downlink wave is corrected to the positive polarity zero phase to obtain the first polarity correction data and the second polarity correction data.

[0037] The positive polarity zero phase refers to that the wavelet characteristics of the first arrival seismic wave in the well meet the seismic data characteristics of positive polarity, zero phase, and first arrival position with a negative jump.

[0038] (2) Depth consistency correction: The first polarity correction data and the second polarity correction data from the previous step are compared. If there is a difference in depth, the optical fiber data is corrected based on the detector data. The corrected data is recorded as the first depth correction data, and the unchanged second polarity correction data is recorded as the second depth correction data. The detector data here refers to the second polarity correction data.

[0039] (3) Time difference consistency static correction processing: The first depth correction data and the second depth correction data in the previous step are subjected to time difference correction according to the statistical analysis results to obtain first time difference correction data and second time difference correction data.

[0040] The statistical analysis refers to obtaining the time difference of the first arrival of a series of data at the same depth position in two data, and obtaining a time difference value by using the median calculation method.

[0041] The time difference is generally a small difference in seismic wave travel time caused by differences in offset distance or excitation depth.

[0042] The correction process is an addition operation, that is, the two data are added sample by sample, and the optical fiber data is corrected for time difference using the detector data as the reference data. Here, the detector data is the second depth correction data, and the optical fiber data is the first depth correction data.

[0043] (4) Amplitude consistency correction processing: The first time difference correction data and the second time difference correction data in the previous step are amplitude corrected according to the statistical analysis results to obtain first correction processing data and second correction processing data.

[0044] The statistical analysis refers to obtaining a series amplitude ratio at the same depth position in two data and obtaining an amplitude ratio using a median calculation method.

[0045] The correction process is a multiplication operation, that is, the two data are multiplied sample by sample, and the fiber data is amplitude corrected using the detector data as the reference data. Here, the detector data is the second time difference correction data, and the fiber data is the first time difference correction data.

[0046] 4) Weighted joint wavefield separation processing:

[0047] The first corrected data and the second corrected data obtained in step 3) are subjected to joint wavefield separation processing, specifically weighted distribution processing, data splicing processing, and multi-channel velocity filtering processing, to obtain final wavefield separation data.

[0048] (1) Weighted distribution processing: According to the depth sampling density of the first correction processing data, the second correction processing data is increased in number and amplitude weighted distribution processing is performed. Specifically, new data with linear increment is added between two adjacent depth sampling points to obtain weighted distribution processing data.

[0049] The linear increase rule is that the position between two adjacent depth sampling points is set to 0, and the algorithm starts from position 0 and increases data to the two adjacent sampling points in equal proportion.

[0050] like Figure 2 As shown, this embodiment provides a specific implementation process of increasing data in equal proportion:

[0051] Define the first correction processing data depth sampling interval as a, the second correction processing data depth sampling interval as b, a is an integer multiple of b, and the element in the first correction processing data record data sequence is recorded as A i , then the elements in the second correction processing data record data sequence can be recorded as The second correction data is changed to B after adding elements i . Original adjacent elements and Added in the middle elements, becomes

[0052] (2) Data splicing: The weighted distribution data obtained in the previous step is deeply aligned with the first correction processing data in step 3) and the average value is calculated to obtain the spliced processing data.

[0053] The data depth correspondence refers to aligning seismic traces of the same depth. Since there are many seismic traces in the optical fiber data, data redundancy will occur, but these redundant seismic trace data will also be retained in the final spliced data.

[0054] The averaging calculation refers to a mathematical operation of adding two corresponding data and dividing by 2.

[0055] (3) Multi-channel velocity filtering: Perform multi-channel velocity filtering on the combined data in the previous step to obtain the final wave field separation data, such as Figure 5 shown.

[0056] The wavefield separation data mentioned above refers to the decomposition of different types of seismic wavefield information using existing data processing methods. Usually, one data is separated into two or more data containing different wavefields, and the required one of the data is retained. Its wavefield information is purer and has a higher signal-to-noise ratio, which is conducive to further data processing applications.

[0057] Optionally, multi-channel velocity filtering includes: median filtering, mean filtering and its derivative methods, as well as frequency-wavenumber (FK), singular value decomposition (SVD) filtering and its derivative methods, etc. According to actual data processing needs, one or more of them are selected for processing.

[0058] Those skilled in the art will appreciate that the embodiments described herein are intended to aid the reader in understanding the principles of the present invention, and it should be understood that the scope of the present invention is not limited to such specific descriptions and embodiments. Various modifications and variations are readily apparent to those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are intended to be included within the scope of the claims.

Claims

1. A method for joint wavefield separation of optical fiber and geophone downhole seismic data, characterized in that: include: S1. Collecting seismic data in a well through an optical fiber and a geophone, recording the seismic data in the well collected by the optical fiber as first original data, and recording the seismic data in the well collected by the geophone as second original data; S2. Remove abnormal data from the first original data and the second original data to obtain filtered first data and filtered second data; S3, performing time resampling processing on the filtered first data and the filtered second data to make the time sampling rates of the two data the same, thereby obtaining first preprocessed data and second preprocessed data; S4, performing correction processing on the first preprocessed data and the second preprocessed data, specifically including sequentially performing polarity consistency correction processing, depth consistency correction processing, time difference consistency static correction processing, and amplitude consistency correction processing on the first preprocessed data and the second preprocessed data, and finally obtaining first corrected data and second corrected data; S5. According to the depth sampling density of the first correction processing data, the second correction processing data is subjected to channel increase and amplitude weighted distribution processing; S6, combining the second corrected data processed in step S5 with the first corrected data obtained in step S4 to obtain combined data; S7. Perform multi-channel velocity filtering on the spliced data to obtain final wavefield separation data.

2. The optical fiber and geophone downhole seismic data joint wave field separation method according to claim 1, characterized in that: The first original data and the second original data are collected at the same time.

3. The method for joint wavefield separation of optical fiber and geophone downhole seismic data according to claim 2, characterized in that: The polarity consistency correction processing described in step S4 is specifically: correcting the first preprocessed data and the second preprocessed data according to the SEG standard, specifically correcting the downlink wave to the positive polarity zero phase respectively to obtain the first polarity correction data and the second polarity correction data.

4. The method for joint wavefield separation of optical fiber and geophone downhole seismic data according to claim 3, characterized in that: The depth consistency correction processing described in step S4 is specifically as follows: comparing the first polarity correction data and the second polarity correction data. When there is a difference in depth, the first polarity correction data is corrected based on the second polarity correction data. The corrected first polarity correction data is recorded as the first depth correction data, and the unchanged second polarity correction data is recorded as the second depth correction data.

5. The method for joint wavefield separation of optical fiber and geophone downhole seismic data according to claim 4, characterized in that: The time difference consistency static correction process in step S4 is specifically: performing time difference correction on the first depth correction data and the second depth correction data according to the statistical analysis result to obtain the first time difference correction data and the second time difference correction data.

6. The optical fiber and geophone downhole seismic data joint wave field separation method according to claim 5, characterized in that: The implementation process of the time difference correction based on the statistical analysis results is as follows: calculating the time difference of the first arrival of the series at the same depth position in the first depth correction data and the second depth correction data, and obtaining a time difference value by using the median calculation method; performing time difference correction on the first depth correction data based on the second depth correction data, recording the first depth correction data after time difference correction as the first time difference correction data, and recording the unchanged second depth correction data as the second time difference correction data.

7. The optical fiber and geophone downhole seismic data joint wave field separation method according to claim 6, characterized in that: The amplitude consistency correction process in step S4 is specifically: performing amplitude correction on the first time difference correction data and the second time difference correction data according to the statistical analysis result to obtain first correction processing data and second correction processing data.

8. The optical fiber and geophone downhole seismic data joint wave field separation method according to claim 7, characterized in that: The implementation process of amplitude correction based on the statistical analysis results is as follows: obtain the series amplitude ratios of the same depth position in the first time difference correction data and the second time difference correction data, and obtain an amplitude ratio using the median calculation method; perform amplitude correction on the first time difference correction data using the second time difference correction data as the reference data, specifically: multiply the first time difference correction data and the second time difference correction data sample by sample, then record the amplitude-corrected first time difference correction data as the first correction processing data, and record the unchanged second time difference correction data as the second correction processing data.

9. The optical fiber and geophone downhole seismic data joint wave field separation method according to claim 8, characterized in that: Step S5 increases the number of channels of the second corrected data, specifically by adding linearly increasing new data between two adjacent depth sampling points; The linear increase is specifically as follows: the middle position of two adjacent depth sampling points is set as 0, and data is increased in equal proportion from the middle position 0 to the two adjacent sampling points respectively.

10. The optical fiber and geophone downhole seismic data joint wave field separation method according to claim 9, characterized in that: The data stitching in step S6 specifically includes: performing depth correspondence between the weighted distribution data and the first correction processing data and calculating an average value to obtain stitched processing data.

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