A method and system for seismic data frequency protection imaging in a fiber optic well
By employing a linear observation system and a multi-step processing method in well seismic data acquisition and processing, the problem of reduced frequency of far-offset data in well seismic imaging was solved, frequency-protected imaging was achieved, and the imaging effect in complex tectonic areas was improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- OPTICAL SCI & TECH (CHENGDU) LTD
- Filing Date
- 2022-06-15
- Publication Date
- 2026-04-17
AI Technical Summary
The data fidelity of well-drilled seismic imaging in complex geological regions is a problem, especially the reduced frequency of data at long offsets, which leads to unreliable imaging.
A linear observation system was used to acquire seismic data in wells. The data was processed through multiple steps, including data screening, preprocessing, corridor stacking, imaging processing, pseudo-acoustic inversion, and bandpass filtering. In particular, frequency-preserving imaging processing was performed on the data with long offset distances.
It improves the imaging frequency fidelity of well-drilled seismic data, especially the quality of seismic data far from the wellhead, and is suitable for well-side geological structure research and stratigraphic lithology analysis in complex geological areas.
Smart Images
Figure CN115079267B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of geophysical exploration, and specifically relates to a well-drilled seismic data processing technology. Background Technology
[0002] In recent years, with the rise of downhole seismic technology, multi-excitation point downhole seismic projects have been designed and acquired in many regions both domestically and internationally, some of which are located in complex structural areas. With advancements in fiber optic downhole technology and downhole seismic data processing methods, downhole seismic technology has achieved certain successes in parameter estimation and reservoir characterization, such as in the Nanpu Depression and Raoyang Depression in the Bohai Bay region. It is well known that downhole seismic observation has certain advantages in understanding complex structural conditions near wells. However, imaging technology in complex structural areas has always been a challenge in downhole seismic data processing, especially in the field of complex structures, where imaging methods are not reliable enough. One of the most important problems is the data fidelity issue in the downhole seismic imaging calculation process, namely, the severe stretching and distortion of far-offset data. Summary of the Invention
[0003] To address the aforementioned technical problems, this invention proposes a frequency-preserving imaging method and system for seismic data in fiber optic wells, yielding frequency-preserving imaging results.
[0004] The technical solution adopted in this invention is: a method for frequency-protected imaging of seismic data in fiber optic wells, comprising:
[0005] S1. A linear observation system is used for seismic data acquisition in wells;
[0006] S2. Process the well seismic data collected in step S1 to obtain the processed seismic data near the wellhead and the processed seismic data of all points in the well, which are respectively recorded as the first processed data and the second processed data.
[0007] S3. Extract a certain data from the first processed data, remove the data retained at the beginning of the track, and obtain the pure track data;
[0008] S4. Treat the single-channel pure data as acoustic wave data and perform inversion processing on the second processed data to obtain the pseudo-acoustic wave inversion processed data.
[0009] S5. Bandpass filtering and boundary removal are performed on the data after pseudo-acoustic wave inversion processing to obtain frequency-preserving imaging results.
[0010] The beneficial effects of this invention: This invention addresses the problem of reduced frequency in long-offset vertical seismic data by proposing a fiber optic well-based seismic data frequency-protected imaging method, thus solving the problem of reduced imaging frequency at long offsets. It is widely applicable to various well-based seismic imaging processing fields. Attached Figure Description
[0011] Figure 1 This is a schematic diagram of the observation system in this embodiment.
[0012] Figure 2 This describes the method implementation process and system in this embodiment.
[0013] Figure 3 This is the inversion data curve proposed in this embodiment.
[0014] Figure 4 This is the imaging profile before inversion processing in this embodiment.
[0015] Figure 5 This is the imaging profile after inversion processing in this embodiment. Detailed Implementation
[0016] This invention addresses the problem of reduced frequency in long-distance vertical seismic data by proposing a frequency-preserving imaging method for fiber optic well-hole seismic data. The method comprises several steps, including multi-excitation-point well-hole seismic data acquisition, well-hole seismic data processing, pseudo-acoustic inversion processing, and frequency-preserving imaging processing. These steps are described in detail below with reference to the accompanying drawings.
[0017] 1) Seismic data acquisition in wells with multiple excitation points:
[0018] The design incorporates a linear observation system through observation wells, incorporating distributed optical fibers within the wells and using artificial seismic sources on the ground surface to generate seismic data from multiple excitation points.
[0019] The aforementioned linear observation system refers to an observation method in which the excitation points of the seismic source are distributed in a straight line on both sides of the observation well, and observation points are set up in the well. It is also known as the Walkaway-VSP observation system.
[0020] The aforementioned distributed optical fiber refers to a distributed optical fiber sensing device used for seismic data acquisition. In wells, this device records data with high density and good data consistency, making it suitable for the implementation of this invention.
[0021] Alternatively, artificial seismic sources can be selected from explosive sources, controllable sources, air gun sources, hammer sources, etc., and the excitation energy provided can be effectively recorded by optical fibers in the well.
[0022] 2) Well-drilled seismic data processing:
[0023] The multi-excitation point well seismic data obtained in step 1) are processed, including data screening and sorting, data preprocessing, corridor overlay and imaging processing, and imaging consistency processing, to obtain the near-wellhead point seismic data and the whole point well seismic data including the near-wellhead point, which are respectively denoted as the first processed data and the second processed data.
[0024] (1) Data screening and processing: The seismic data in the well with multiple excitation points obtained in step 1) are screened, and abnormal data are removed by referring to the data acquisition report, including bad passage removal and data of the same depth selection, to obtain the screened data.
[0025] (2) Data preprocessing: The filtered data obtained in the previous step is processed according to the process of amplitude compensation, wave field rotation, deconvolution, wave field separation, etc., to obtain preprocessed data with enhanced effective signals.
[0026] (3) Corridor overlay processing: In the preprocessed data obtained in the previous step, the seismic data near the wellhead is extracted, and after dynamic correction, near-wellhead removal and overlay processing, the corridor overlay processing data is obtained, which is recorded as the first processing data.
[0027] The near-wellhead seismic data refers to all seismic data within the zero offset range of the industry standard SYT 7450-2019, and its specific quantity is affected by both the working well depth and the distance between excitation points.
[0028] The corridor overlay processing data differs from conventional corridor overlay profiles. It is obtained by overlaying data from multiple excitation points near the wellhead, which has a certain statistical averaging effect and strong anti-anomaly capability.
[0029] (4) Imaging processing: The preprocessed data obtained in step (2) is processed by applying all excitation point seismic data, and then undergoing static correction, dynamic correction and imaging processing to obtain the processed imaging data.
[0030] The static correction of seismic activity in the well refers to eliminating data errors caused by undulating surfaces and changes in near-surface low-velocity strata. The ground motion correction in the well refers to uniformly correcting all data to two-way time data based on the seismic velocity in the well.
[0031] There are many options available for well-drilled seismic imaging methods. To ensure the reliability of this embodiment, more mature methods with better frequency preservation effects, such as VSP-CDP, Kochhoff migration, or inverse time-biased imaging, can be selected.
[0032] (5) Consistency correction processing: The imaging processing data obtained in step (4) is subjected to consistency correction processing based on the corridor overlay processing data obtained in step (3). Specifically, the polarity, depth, time difference and amplitude consistency of the two are checked. For the small differences that exist, consistency correction processing is performed to obtain the corrected imaging processing data, which is recorded as the second processing data.
[0033] 3) Pseudo-acoustic wave inversion processing
[0034] (1) Single-channel pure data extraction: From the first processed data obtained in step 2), extract one channel of data, remove the channel header, and retain only the data portion to obtain single-channel pure data, such as... Figure 3 As shown. Figure 3 The horizontal axis represents the number of channels, which is dimensionless, and the vertical axis represents time, expressed in milliseconds (ms).
[0035] (2) Pseudo-acoustic inversion processing: The single-channel pure data obtained in the previous step is used as acoustic data, and the second processed data obtained in step 2) is subjected to acoustic inversion processing to obtain the pseudo-acoustic inversion processed data.
[0036] 4) Frequency-preserving imaging processing
[0037] The data obtained in step 3) after pseudo-acoustic wave inversion processing is subjected to bandpass filtering and boundary removal to obtain frequency-preserving imaging results, which are the final results of this invention. The comparison results are as follows: Figure 4 , Figure 5 As shown. Figure 4 The horizontal axis represents channel count, which is dimensionless, and the vertical axis represents time, expressed in milliseconds. Figure 5 The horizontal axis represents the number of traces, which is dimensionless, and the vertical axis represents time, expressed in milliseconds (ms). A comparison shows that the imaging results obtained using the method of this invention have better frequency protection, especially the seismic data quality at both ends far from the wellhead is well preserved, which is highly beneficial for well-side geological structure research or stratigraphic lithology analysis.
[0038] The boundary removal process refers to the operation of removing abnormal data with low signal-to-noise ratio or severely stretched waveforms in accordance with the SYT 7450—2019 quality control standard, which generally requires human-computer interaction.
[0039] The bandpass filtering refers to the method of eliminating problems such as zero-point drift of seismic data during the inversion process. Therefore, its bandpass window should not be too narrow, and it is recommended to use [1 1.2 100 120].
[0040] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of the claims of the invention.
Claims
1. A method of seismic data frequency preserving imaging in a fiber optic well, characterized by, include: S1. A linear observation system is used for seismic data acquisition in wells; S2. Preprocess the well seismic data collected in step S1 to obtain the preprocessed seismic data near the wellhead and the preprocessed seismic data of all points including the wellhead, which are respectively denoted as the first processed data and the second processed data. Preprocessing specifically includes: (1) Data screening and processing; The well seismic data collected in step S1 is screened, and abnormal data is removed by referring to the data acquisition report to obtain the screened data; (2) Data preprocessing; The data after screening and processing in step (1) is processed according to the process of amplitude compensation, wave field rotation, deconvolution and wave field separation to obtain preprocessed data with enhanced effective signals; (3) Corridor overlay; In the preprocessed data obtained in step (2), the seismic data near the wellhead is extracted, and after dynamic correction, near-wellhead removal and overlay processing, the corridor overlay processing data is obtained and recorded as the first processing data; (4) Imaging processing; The preprocessed data obtained in step (2) are processed by applying all excitation point seismic data to perform static correction, dynamic correction and imaging processing of the well seismic data to obtain the imaging processed data. (5) Imaging consistency processing: The imaging processing data obtained in step (4) is subjected to consistency correction processing based on the corridor overlay processing data obtained in step (3) to obtain the corrected imaging processing data, which is recorded as the second processing data. S3. Extract a certain data from the first processed data, remove the data retained at the beginning of the track, and obtain the pure data of a single track; S4. Treat the single-channel pure data as acoustic wave data and perform inversion processing on the second processed data to obtain the pseudo-acoustic wave inversion processed data. S5. Bandpass filtering and boundary removal are performed on the data after pseudo-acoustic wave inversion processing to obtain frequency-preserving imaging results.
2. The method of claim 1, wherein, The linear observation system is an observation method in which the source excitation points are linearly distributed on both sides of the observation well, and observation points are set up in the well. By inserting distributed optical fibers in the observation well and using artificial sources on the ground surface for excitation, seismic data in the well with multiple excitation points can be collected.
3. The method of claim 2, wherein, Artificial seismic sources are one of the following: explosive seismic sources, controllable seismic sources, air gun seismic sources, and heavy hammer seismic sources.
4. The method for frequency protection imaging of seismic data in fiber optic wells according to claim 2, characterized in that, The near-wellhead point seismic data mentioned in step S2 is all seismic data within the zero offset range that meets the industry standard SYT 7450—2019.
5. The method of claim 2, wherein, Step S2, or well seismic static correction, refers to eliminating data errors caused by undulating surfaces and changes in near-surface low-velocity strata.
6. The method of claim 2, wherein, The wellbore ground motion correction refers to the unified correction of all data to two-way time data based on the wellbore seismic velocity.