Underwater cylindrical surface single-channel seismic exploration system and method

Abstract

The application relates to an underwater cylindrical wave single-channel seismic detection system and method, which comprises a cylindrical wave exciting device, a cylindrical wave receiving device and a processor. The cylindrical wave exciting device comprises a high-voltage charging and discharging unit and a high-voltage cable, and the cylindrical wave receiving device comprises an acquisition unit and a hydrophone cable. The high-voltage charging and discharging unit is connected with a power supply through a power cable, and the high-voltage cable is connected with the high-voltage charging and discharging unit. The hydrophone cable is connected with the acquisition unit through a communication cable, and the hydrophone cable comprises a plurality of hydrophones. The cylindrical wave is generated by a high-voltage cable sound source, the cylindrical wave has better directivity and focusing performance compared with the spherical diffusion wave of a traditional sound source, and through a suitable processing and imaging method, the quality of seismic data can be improved.

Description

Technical Field

[0001] This invention belongs to the field of marine geophysical exploration technology, and relates to an underwater cylindrical wave single-channel seismic detection system and method. Background Technology

[0002] Traditional single-channel marine seismic detection systems typically use sonar, spark, and boomer sources as sound sources. Sonar comes in various types, including Chrip, parametric array, and synthetic aperture sonar, which have good source directivity, but their dominant frequency is generally in the range of several thousand to tens of kilohertz. Due to the strong high-frequency absorption and attenuation effect of water and geological strata, their penetration depth is relatively shallow (around 10 meters). Spark and boomer sources, with dominant frequencies in the range of several hundred to several thousand kilohertz, can penetrate hundreds of meters of strata. However, these are point sources, generating spherically spreading sound waves underwater. Due to the diffusion effect, the source directivity is poor, leading to severe attenuation and interference of the seismic signal during propagation, thus reducing the quality and signal-to-noise ratio of the seismic data. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes an underwater cylindrical wave single-channel seismic detection system and method. The system utilizes a high-voltage cable acoustic source to generate cylindrical waves. Compared to the spherical diffused waves of traditional acoustic sources, cylindrical waves exhibit better directivity and focusing performance. Through appropriate processing and imaging methods, the quality of seismic data can be improved.

[0004] The technical solution of this invention to solve the above problems is: an underwater cylindrical wave single-channel seismic detection system, which is special in that:

[0005] Includes a cylindrical wave excitation device, a cylindrical wave receiving device, and a processor;

[0006] The cylindrical wave excitation device includes a high-voltage charging and discharging unit and a high-voltage cable, and the cylindrical wave receiving device includes a data acquisition unit and a hydrophone cable.

[0007] The high-voltage charging and discharging unit is connected to the power source via a power cable, and the high-voltage cable is connected to the high-voltage charging and discharging unit; the hydrophone cable is connected to the acquisition unit via a communication cable, and the hydrophone cable includes multiple hydrophones.

[0008] The high-voltage charging and discharging unit is used to boost and store the electrical energy provided by the power supply. The high-voltage cable is used to discharge and vibrate in water to generate cylindrical seismic waves. The hydrophone is used to receive seismic wave signals. The acquisition unit acquires and stores the signals from the hydrophone. The processor performs bandpass filtering and first-to-stable correction on the signals and superimposes the multi-channel signals to form a single-channel seismic profile. The obtained single-channel seismic profile is then post-processed. Finally, the processed profile is migrated using the cylindrical wave diffraction curve superposition method to form a migrated profile.

[0009] Furthermore, the aforementioned underwater cylindrical wave single-channel seismic detection system also includes a towing device. The high-voltage charging and discharging unit is connected to the towing device via a power cable, the length of which is 10-30 meters.

[0010] Furthermore, the length of the aforementioned high-voltage cable is 10 to 20 meters; the hydrophone cable includes eight hydrophones, with an adjacent hydrophone spacing of 0.25 meters and a length of 1.75 meters.

[0011] Furthermore, the hydrophone cable is installed parallel to the high-voltage cable, with the hydrophone cable located in the middle section of the high-voltage cable and at a vertical distance of 3-6 meters from the high-voltage cable.

[0012] Furthermore, the aforementioned acquisition unit includes an 8-channel 24-bit acquisition card.

[0013] In addition, this invention also proposes a detection method based on the above-mentioned underwater cylindrical wave single-channel seismic detection system, which is characterized by including the following steps:

[0014] 1) Set up a dragging device, a cylindrical wave excitation device and a cylindrical wave receiving device. The cylindrical wave excitation device periodically excites pulsed cylindrical seismic waves, and the cylindrical wave receiving device receives the seismic waves.

[0015] 2) The signal from step 1) is bandpass filtered and first-to-stable correction is performed by the processor, and the multi-channel signals are superimposed to form a single-channel seismic profile;

[0016] 3) Post-process the single-channel seismic profiles obtained in step 2);

[0017] 4) The cross-section processed in step 3) is offset by the cylindrical wave diffraction curve superposition method to form an offset cross-section.

[0018] Further, in step 1) above, the high-voltage cable is 10 to 20 meters long and generates cylindrical seismic waves by discharging and vibrating in water; the high-voltage charging and discharging unit is connected to the high-voltage cable and is dragged 10-30 meters behind the towing device; the hydrophone cable consists of eight hydrophones with a spacing of 0.25 meters and a length of 1.75 meters; the acquisition unit simultaneously acquires and stores the signals from the eight hydrophones through an 8-channel 24-bit acquisition card; the hydrophone cable is dragged at the middle section of the high-voltage cable 2, at a vertical distance of 3-6 meters from the high-voltage cable.

[0019] Furthermore, in step 2) above, the bandpass filtering uses a trapezoidal filter to filter out high and low frequency interference in the signal, with a low cutoff frequency of 200 Hz and a high cutoff frequency of 6400 Hz; the first arrival static correction refers to correcting the signal time difference caused by surge and equipment attitude, specifically by first picking up the first arrival of 8 channels and calculating the average value, and then correcting the first arrival time of each channel to the average value time; the multi-channel superposition refers to superimposing the aforementioned 8 processed signals into 1 channel.

[0020] Furthermore, the post-processing in step 3) above refers to true amplitude recovery, channel equalization, predictive deconvolution, random noise suppression, and automatic gain control.

[0021] Furthermore, the cylindrical wave diffraction curve superposition migration process in step 4) above refers to migrating the phase axis of the post-stacked reflected wave to the correct spatial location. Specifically, for a point P (x0, t0) on the seismic profile, the time-distance curve of the cylindrical wave diffraction hyperbola with this point as its vertex is first calculated as follows: Where i represents the recording track participating in the offset stacking, and v is the propagation velocity of the cylindrical wave; then, the time t corresponding to all recording tracks is... i The amplitude values ​​are superimposed to obtain the amplitude value of point P after migration; finally, the amplitude values ​​of all positions on the seismic profile are calculated one by one after migration to obtain the migration profile.

[0022] Advantages of this invention:

[0023] This invention provides a single-channel underwater cylindrical wave seismic detection method. It utilizes a high-voltage cable to generate a cylindrical wave source. Compared to the spherical diffused waves of traditional sound sources, cylindrical waves exhibit better directivity and focusing performance. With appropriate processing and imaging methods, the quality of seismic data can be improved. Addressing the shortcomings and imperfections of existing technologies, this invention provides a single-channel underwater cylindrical wave seismic detection method that significantly improves the directivity and focusing of seismic signals compared to conventional methods, which is beneficial for imaging deep strata. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the single-channel seismic exploration method for cylindrical waves proposed in this invention.

[0025] Figure 2 This is a diagram showing the calculation of the hyperbola in the superposition method of cylindrical wave diffraction curves.

[0026] Among them, 1-high voltage charging and discharging unit, 2-high voltage cable, 3-acquisition unit, 4-hydrophone cable, 5-survey vessel, 6-communication cable, and 7-power cable. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0028] Example

[0029] This invention proposes an underwater cylindrical wave single-channel seismic detection system, comprising a cylindrical wave excitation device, a cylindrical wave receiving device, and a processor. See also... Figure 1 The cylindrical wave excitation device includes a high-voltage charging and discharging unit 1 and a high-voltage cable 2. The cylindrical wave receiving device includes a data acquisition unit 3 and a hydrophone cable 4. The high-voltage charging and discharging unit 1 is connected to a power source via a power cable, and the high-voltage cable 2 is connected to the high-voltage charging and discharging unit 1. The hydrophone cable 4 is connected to the data acquisition unit 3 via a communication cable 6, and the hydrophone cable 4 includes multiple hydrophones.

[0030] As a preferred embodiment of the present invention, the above-mentioned underwater cylindrical wave single-channel seismic detection system further includes a towing device, which is a survey vessel 5, powered by 220V ship power. The high-voltage charging and discharging unit 1 is connected to the survey vessel 5 via a power cable 7, and the high-voltage charging and discharging unit 1 is towed 10-30 meters behind the stern of the survey vessel.

[0031] The high-voltage charging and discharging unit 1 is used to boost and store the 220V ship power supply. The high-voltage cable 2 is used to generate cylindrical seismic waves through discharge vibration in water. The hydrophone is used to receive the seismic wave signals. The acquisition unit acquires and stores the signals from the hydrophone. The processor performs bandpass filtering and initial-to-static correction on the signals, and superimposes the multi-channel signals to form a single-channel seismic profile. The obtained single-channel seismic profile is then post-processed. Finally, the processed profile is subjected to cylindrical wave diffraction curve superposition migration processing to form a migrated profile. The cylindrical wave diffraction curve superposition migration processing refers to the migration of the phase axis of the reflected wave after superposition to the correct spatial position. Specifically, for a point P (x0, t0) on the seismic profile, the time-distance curve of the cylindrical wave diffraction hyperbola with this vertex is first calculated as follows: Where i represents the recording track participating in the offset stacking, and v is the propagation velocity of the cylindrical wave; then, the time t corresponding to all recording tracks is... i The amplitude values ​​are superimposed to obtain the amplitude value of point P after migration; finally, the amplitude values ​​of all positions on the seismic profile are calculated one by one after migration to obtain the migration profile.

[0032] In a preferred embodiment of the present invention, the length of the high-voltage cable 2 is 10 to 20 meters; the hydrophone cable 4 includes eight hydrophones, with an adjacent hydrophone spacing of 0.25 meters and an arrangement length of 1.75 meters.

[0033] In a preferred embodiment of the present invention, the hydrophone cable 4 is arranged parallel to the high-voltage cable 2, and the hydrophone cable 4 is located in the middle section of the high-voltage cable 2, at a vertical distance of 3-6 meters from the high-voltage cable 2. The acquisition unit includes an 8-channel 24-bit acquisition card, which simultaneously acquires and stores signals from 8 hydrophones.

[0034] This invention also proposes a detection method based on the above-mentioned underwater cylindrical wave single-channel seismic detection system, comprising the following steps:

[0035] 1) Set up a dragging device, a cylindrical wave excitation device and a cylindrical wave receiving device. The cylindrical wave excitation device periodically excites pulsed cylindrical seismic waves, and the cylindrical wave receiving device receives the seismic waves.

[0036] 2) The signal from step 1) is bandpass filtered and first-to-stable correction is performed by the processor, and the multi-channel signals are superimposed to form a single-channel seismic profile;

[0037] 3) Post-process the single-channel seismic profiles obtained in step 2);

[0038] 4) The cross-section processed in step 3) is offset by the cylindrical wave diffraction curve superposition method to form an offset cross-section.

[0039] In a preferred embodiment of the present invention, in step 1) above, the high-voltage cable 2 is 10 to 20 meters long and generates cylindrical seismic waves by discharging and vibrating in water; the high-voltage charging and discharging unit 1 is connected to the high-voltage cable 2 and is dragged 10-30 meters behind the towing device; the hydrophone cable 4 consists of eight hydrophones with a spacing of 0.25 meters and a length of 1.75 meters; the acquisition unit simultaneously acquires and stores the signals from the eight hydrophones through an 8-channel 24-bit acquisition card; the hydrophone cable 4 is dragged at the middle section of the high-voltage cable 2, at a vertical distance of 3-6 meters from the high-voltage cable 2.

[0040] In a preferred embodiment of the present invention, the bandpass filtering in step 2) above uses a trapezoidal filter to filter out high and low frequency interference in the signal, with a low cutoff frequency of 200 Hz and a high cutoff frequency of 6400 Hz; the first arrival static correction refers to correcting the signal time difference caused by surge and equipment attitude, specifically by first picking up the first arrival of 8 channels of signal and calculating the average value, and then correcting the first arrival time of each channel to the average value time; the multi-channel superposition refers to superimposing the aforementioned 8 processed signals into 1 channel.

[0041] As a preferred embodiment of the present invention, the post-processing in step 3) above refers to processes similar to true amplitude recovery, trace equalization, predictive deconvolution, random noise suppression, and automatic gain control in conventional single-channel seismic processing.

[0042] As a preferred embodiment of the present invention, see [link to previous document]. Figure 2 The cylindrical wave diffraction curve superposition migration process in step 4) above refers to the migration of the phase axis of the post-stacked reflected wave to the correct spatial location. Specifically, for a point P (x0, t0) on the seismic profile, the time-distance curve of the cylindrical wave diffraction hyperbola with this point as the vertex is first calculated as follows: Where i represents the recording track participating in the offset stacking, and v is the propagation velocity of the cylindrical wave; then, the time t corresponding to all recording tracks is... i The amplitude values ​​are superimposed to obtain the amplitude value of point P after migration; finally, the amplitude values ​​of all positions on the seismic profile are calculated one by one after migration to obtain the migration profile.

[0043] The above description is merely an embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related system fields, are similarly included within the scope of protection of the present invention.

Claims

1. An underwater cylindrical wave single-channel seismic detection system, characterized in that: Includes a cylindrical wave excitation device, a cylindrical wave receiving device, and a processor; The cylindrical wave excitation device includes a high-voltage charging and discharging unit (1) and a high-voltage cable (2), and the cylindrical wave receiving device includes a data acquisition unit (3) and a hydrophone cable (4). The high-voltage charging and discharging unit (1) is connected to the power source via a power cable, and the high-voltage cable (2) is connected to the high-voltage charging and discharging unit (1); the hydrophone cable (4) is connected to the acquisition unit (3) via a communication cable (6), and the hydrophone cable (4) includes multiple hydrophones; The high-voltage charging and discharging unit (1) is used to boost and store the electrical energy provided by the power supply. The high-voltage cable (2) is used to discharge and vibrate in water to generate cylindrical seismic waves. The hydrophone is used to receive seismic wave signals. The acquisition unit acquires and stores the signals from the hydrophone. The processor performs bandpass filtering and initial-to-static correction on the signals and superimposes the multi-channel signals to form a single-channel seismic profile. The obtained single-channel seismic profile is then post-processed. Finally, the processed profile is offset by the cylindrical wave diffraction curve superposition method to form an offset profile.

2. The underwater cylindrical wave single-channel seismic detection system according to claim 1, characterized in that: The underwater cylindrical wave single-channel seismic detection system also includes a towing device. The high-voltage charging and discharging unit (1) is connected to the towing device through a power cable (7), and the power cable (7) is 10-30 meters long.

3. The underwater cylindrical wave single-channel seismic detection system according to claim 2, characterized in that: The high-voltage cable (2) is 10 to 20 meters long; the hydrophone cable (4) includes eight hydrophones with an adjacent hydrophone spacing of 0.25 meters and a length of 1.75 meters.

4. The underwater cylindrical wave single-channel seismic detection system according to any one of claims 1-3, characterized in that: The hydrophone cable is set parallel to the high-voltage cable (2), and the hydrophone cable (4) is located in the middle of the high-voltage cable (2), with a vertical distance of 3-6 meters from the high-voltage cable (2).

5. The underwater cylindrical wave single-channel seismic detection system according to claim 4, characterized in that: The acquisition unit (3) includes an 8-channel 24-bit acquisition card.

6. The detection method based on the underwater cylindrical wave single-channel seismic detection system according to claim 1, characterized in that, Includes the following steps: 1) Set up a dragging device, a cylindrical wave excitation device and a cylindrical wave receiving device. The cylindrical wave excitation device periodically excites pulsed cylindrical seismic waves, and the cylindrical wave receiving device receives the seismic waves. 2) The signal from step 1) is bandpass filtered and first-to-static correction is performed on the processor, and the multi-channel signals are superimposed to form a single-channel seismic profile; 3) Post-process the single-channel seismic profiles obtained in step 2); 4) The cross-section processed in step 3) is offset by the cylindrical wave diffraction curve superposition method to form an offset cross-section.

7. The detection method according to claim 6, characterized in that: In step 1), the high-voltage cable (2) is 10 to 20 meters long and generates cylindrical seismic waves by discharging and vibrating in the water; the high-voltage charging and discharging unit (1) is connected to the high-voltage cable (2) and is dragged 10-30 meters behind the towing device; the hydrophone cable (4) consists of eight hydrophones with a spacing of 0.25 meters and a length of 1.75 meters; the acquisition unit acquires and stores the signals of the eight hydrophones simultaneously through an 8-channel 24-bit acquisition card; the hydrophone cable (4) is dragged in the middle of the high-voltage cable (2) at a vertical distance of 3-6 meters from the high-voltage cable (2).

8. The detection method according to claim 7, characterized in that: In step 2), the bandpass filtering uses a trapezoidal filter to filter out high and low frequency interference in the signal, with a low cutoff frequency of 200 Hz and a high cutoff frequency of 6400 Hz. The first arrival static correction refers to correcting the signal time difference caused by surge and equipment attitude. Specifically, it involves first picking up the first arrival times of the 8 channels and calculating the average value, and then correcting the first arrival times of each channel to the average value time. The multi-channel signal superposition refers to superimposing the aforementioned 8 processed signals into 1 channel.

9. The detection method according to claim 8, characterized in that: The post-processing in step 3) refers to true amplitude recovery, channel equalization, predictive deconvolution, random noise suppression, and automatic gain control.

10. The detection method according to claim 9, characterized in that: The cylindrical wave diffraction curve superposition method migration processing in step 4) refers to the migration of the phase axis of the post-stacked reflected wave to the correct spatial location, specifically: a point on the seismic profile. Location( First, calculate the time-distance curve of the cylindrical wave diffraction hyperbola with this vertex as follows: ,in, For the recording tracks that participate in offset stacking It is the propagation speed of cylindrical waves; then all recorded channels correspond to the time. The amplitude values ​​are summed to obtain the offset. The amplitude value of each point is calculated; finally, the amplitude value of the offset superposition of all positions on the seismic profile is calculated one by one to obtain the offset profile.

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