A time-reversal method for borehole seismic imaging based on emission angle information

Abstract

The present invention discloses a time-reversal downhole seismic imaging method based on emergence angle information, which is applied to the field of seismic data processing and interpretation, and addresses the lack of a time-reversal downhole seismic imaging method based on emergence angle information in the prior art. The present invention utilizes a downhole seismic geophone to acquire three-component downhole seismic data, and performs horizontal component rotation, vertical component rotation, deconvolution, wave field separation, and data flattening processing. The invention utilizes radial component and vertical component data to obtain an emergence angle sequence. Based on the P component data, a root mean square velocity is calculated. Blank depth domain imaging data is generated and recorded as first imaging data. The root mean square velocity is used to convert second R component wave field data into depth domain data. The spatial position of each sample point in each trace is calculated based on a trigonometric function using the emergence angle sequence. The wave field amplitude data in the second R component is projected point by point and superimposed on the first imaging data to obtain final downhole seismic imaging data.

Description

Technical Field

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

[0002] In recent years, borehole seismic technology has developed rapidly and played an important role in the exploration and development of oil and gas resources. Imaging methods, as a key link in the processing of borehole seismic data, have also developed rapidly. However, compared with mature surface seismic imaging methods, there is still a long way to go. The main imaging methods currently include: traditional VSP-CDP mapping imaging method, ray-based Kirchhoff integral method similar to surface seismic data, and wave equation method based on wavefield continuation. Each method has certain applicability and limitations.

[0003] Among existing imaging methods, Wyatt et al. first proposed the concept of VSPCDP and provided a VSPCDP conversion formula. Each sample point in the VSP record is projected from the shot-detection pair (traveltime) domain to the reflection point position (depth) domain to obtain a borehole seismic imaging profile. Kirchhoff depth migration imaging is another widely used imaging method. These two most commonly used imaging methods determine the vast majority of borehole seismic imaging problems, while other methods such as one-way wave equations and full waveform inversion are also developing rapidly. Research indicates that no borehole seismic imaging method based on time inversion using exit angle information exists. Summary of the Invention

[0004] To solve the above technical problems, the present invention proposes a time-reversal method for wellbore seismic imaging based on emission angle information, which largely avoids the influence of the distance difference, elevation difference, static correction value, etc. of the excitation points during the acquisition process, and realizes wellside seismic imaging.

[0005] The technical solution provided by the present invention is: a time-reversed wellbore seismic imaging method based on emission angle information, comprising:

[0006] S1, acquiring three-component wellbore seismic data through existing wellbore seismic geophones;

[0007] S2. Processing the acquired three-component wellbore seismic data;

[0008] S3, calculating the emission angle sequence according to the result processed in step S2;

[0009] S4, establishing a velocity model according to the result processed in step S2;

[0010] S5. Produce blank depth domain imaging data;

[0011] S6. Based on the result after processing in step S2, the emission angle sequence in step S3, the velocity model in step S4 and the blank depth domain imaging data in step S5, the reflection point reverse regression stacking imaging is performed to obtain the final wellbore seismic imaging data.

[0012] The beneficial effects of the present invention are as follows: the present invention first uses three components to collect borehole seismic data, obtains the reflection wave field, root mean square velocity, and exit angle sequence, and reversely calculates the reflection point position based on the data to obtain borehole seismic imaging data; the method of the present invention largely avoids the influence of the excitation point distance difference, elevation difference, static correction amount, etc. on the imaging parameters during the acquisition process; the method of the present invention can obtain accurate imaging parameters, thereby achieving better imaging effects than those obtained by the prior art. The method of the present invention is very meaningful for actual data processing and expands the selection of borehole seismic imaging methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a flow chart of the solution of the present invention;

[0014] Figure 2 is the original well seismic time domain vertical component data;

[0015] Figure 3 is the first horizontal component data of the original well seismic time domain;

[0016] Figure 4 is the second horizontal component data of the original well seismic time domain;

[0017] Figure 5 This is the time domain data of the well seismic after the first arrival and leveling;

[0018] Figure 6 is the sequence of emission angles obtained by scanning with three-component data;

[0019] Figure 7 is the root mean square velocity used for migration imaging; the abscissa is time;

[0020] Figure 8 This is the time-reversed migration imaging result based on the exit angle information;

[0021] Figure 9 The time-reversed migration imaging result based on the exit angle information is used to remove the invalid imaging interval. DETAILED DESCRIPTION

[0022] 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.

[0023] like Figure 1As shown, the present invention first uses three components to collect well seismic data, obtains the reflection wave field, root mean square velocity, and exit angle sequence, and reversely calculates the reflection point position based on the data to obtain well seismic imaging data. The specific implementation method is as follows.

[0024] 1) Vertical seismic data acquisition

[0025] This data is collected using existing well seismic detectors to obtain three-component well seismic data, which is applicable to well conditions such as inclined wells and horizontal wells, as well as geological conditions such as inclined formations and complex structural formations. The well seismic detector is a three-component detector. Non-directional hydrophone detectors, grating detectors or distributed optical fiber methods are not suitable for implementation of this method. Figure 2-4 As shown, it includes vertical component data, first horizontal component data, and second horizontal component data. Figure 2 The horizontal axis is time, unit: ms; the vertical axis is depth, unit: m; Figure 3 The horizontal axis is time, unit: ms; the vertical axis is depth, unit: m; Figure 4 The horizontal axis is time, unit: ms; the vertical axis is depth, unit: m.

[0026] 2) Well seismic data processing

[0027] Downhole seismic data processing includes horizontal component rotation, vertical component rotation, deconvolution, wavefield separation, and data flattening. It does not include static corrections such as elevation correction and low-velocity zone correction. This step can be completed using existing commercial seismic processing software.

[0028] (1) Horizontal component rotation: using the two horizontal components of the three-component well seismic data acquired in step 1), polarization rotation processing is performed to obtain oriented horizontal component data.

[0029] (2) Vertical component rotation: Use the horizontal component data after orientation in the previous step and the vertical component data in the three-component well seismic data collected in step 1) to perform polarization rotation processing to obtain the P component wave field and the first R component wave field.

[0030] (3) Deconvolution, wavefield separation, and data dynamic correction are performed on the first R component wavefield in sequence to obtain the second R component wavefield, as shown in Figure 5 shown. Figure 5 The horizontal axis is time, unit: ms; the vertical axis is depth, unit: m.

[0031] 3) Calculation of the emission angle sequence

[0032] Using the radial component data from step 2) and the vertical component data from the three-component wellbore seismic data collected in step 1), a point-by-point exit angle scan is performed within a given scanning window. Specifically, within a single sampling window, the angles at the extreme values ​​of the radial and vertical component vectors are read and recorded as the exit angle for that scanning window. This is then slid sample by sample along the seismic trace to obtain an exit angle sequence.

[0033] The scanning time window is selected as the average wavelength time of the seismic data, which is generally 20-50ms.

[0034] There are certain abnormal values ​​in the resulting emission angle sequence, which need to be smoothed using the polynomial method.

[0035] The sequence of the exit angles of some seismic traces is as follows: Figure 6 shown. Figure 6 The horizontal coordinate is the angle, expressed as: o ; The vertical axis is depth, unit: m.

[0036] 4) Establish velocity model

[0037] Using the P component wave field in step 2), we pick up the first arrival time-depth relationship and calculate the root mean square velocity, as Figure 7 shown.

[0038] 5) Produce blank depth domain imaging data

[0039] The possible imaging range is estimated and blank depth domain imaging data is generated, which is recorded as the first imaging data. The maximum horizontal coordinate of the imaging range is 50% of the maximum excitation point offset distance, and the maximum vertical coordinate is 2 times the maximum acquisition well depth distance.

[0040] 6) Reflection point reverse positioning and superposition imaging

[0041] The second R component wave field data in step 2) is converted into depth domain data using the root mean square velocity in step 4). The spatial position of each sample point in each trace is calculated based on trigonometric functions using the exit angle sequence in step 3). The wave field amplitude data in the second R component in step 2) is projected point by point and superimposed on the first imaging data in step 5) to obtain the second imaging data, i.e., the final wellbore seismic imaging data, as shown in FIG. Figure 8 and Figure 9 shown. Figure 7 The horizontal axis is speed, unit: m / s; the vertical axis is depth, unit: m. Figure 8 The horizontal coordinate is distance, unit: m; the vertical coordinate is depth, unit: m. Figure 9 The horizontal coordinate is distance, unit: m; the vertical coordinate is depth, unit: m.

[0042] 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 time-reversal method for borehole seismic imaging based on emission angle information, characterized in that: include: S1. Acquire three-component wellbore seismic data by using an existing wellbore seismic geophone; the three-component wellbore seismic data in step S1 includes vertical component data, first horizontal component data, and second horizontal component data; S2. Processing the acquired three-component wellbore seismic data; Step S2 specifically includes: S21, using the two horizontal component data of the three-component well seismic data acquired in step S1, performing polarization rotation processing to obtain oriented horizontal component data; S22, using the oriented horizontal component data obtained in step S21 and the vertical component data in the three-component well seismic data collected in step S1, performing polarization rotation processing to obtain a P component wave field and a first R component wave field; S23, performing deconvolution, wavefield separation, and data dynamic correction processing on the first R component wavefield in sequence to obtain a second R component wavefield; S3. Calculating an exit angle sequence based on the result processed in step S2. Step S3 specifically comprises: using the radial component in step S2 and the vertical component data in the three-component well seismic data acquired in step S1, and scanning the exit angle sample by sample point within a given scanning window, thereby obtaining an exit angle sequence. The exit angle of each scanning window is determined by reading the angle at the vector extreme value of the radial component and the vertical component within a single scanning window, and recording it as the exit angle of the scanning window; then sliding sample by sample point along the seismic trace to obtain the exit angle sequence. S4, establishing a velocity model according to the result processed in step S2; S5. Produce blank depth domain imaging data; S6. Based on the result after processing in step S2, the emission angle sequence in step S3, the velocity model in step S4 and the blank depth domain imaging data in step S5, the reflection point reverse regression stacking imaging is performed to obtain the final wellbore seismic imaging data.

2. The method for time-reversal wellbore seismic imaging based on exit angle information according to claim 1, characterized in that: The scanning time window is selected as the average wavelength time of the three-component well seismic data is 20-50ms.

3. The method for time-reversal wellbore seismic imaging based on exit angle information according to claim 2, characterized in that: The method also includes using a polynomial method to smooth the emission angle sequence.

4. The method for time-reversal wellbore seismic imaging based on exit angle information according to claim 3, characterized in that: Step S4 uses the P component wave field in step S2 to pick up the first arrival time-depth relationship and calculate the root mean square velocity.

5. The method for time-reversal wellbore seismic imaging based on exit angle information according to claim 4, characterized in that: Step S5 generates blank depth domain imaging data by estimating the possible imaging range, which is recorded as the first imaging data; the maximum horizontal coordinate of the imaging range is 50% of the maximum excitation point offset distance, and the maximum vertical coordinate is 2 times the maximum acquisition well depth distance.

6. The method for time-reversal wellbore seismic imaging based on exit angle information according to claim 5, characterized in that: Step S6 is specifically as follows: Converting the second R component wavefield data in step S2 into depth domain data using the root mean square velocity in step S4; Using the exit angle sequence in step S3, the spatial position of each sample point in each trace is calculated based on trigonometric functions. The wave field amplitude data in the second R component of step S2 is projected point by point and superimposed on the first imaging data of step S5 to obtain the second imaging data, i.e., the final wellbore seismic imaging data.

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