A dual-source multi-cable narrow spacing control system and method

Abstract

The present invention relates to the field of marine geological surveys, and provides a dual-source multi-cable narrow spacing control system and method, which are used to solve the problem that the facets of seismic data acquisition are difficult to reduce. The dual-source multi-cable narrow spacing control system provided by the present invention includes dual seismic sources, tow cables, and a frame, wherein the frame is connected to a seismic ship, and the tow cables are connected to the seismic ship; there are no less than 2 tow cables, and a dual seismic source is arranged between any two adjacent seismic sources; the tow cables are connected by spacing ropes, and the spacing ropes are connected to the middle of the tow cables, and one end of the tow cables is connected to the seismic ship; the frame includes an extension rope and an extension arm, and the extension arm and the extension rope are connected to the seismic ship; the extension rope is connected to the middle of the outermost tow cable. The size of the facet can be reduced as much as possible, while maintaining the spacing between the tow cables stable, and the multi-cable spacing defense range is within ±5%, which provides the possibility of improving the lateral resolution of seismic data acquisition.

Description

Technical Field

[0001] The present invention relates to the field of marine geological survey, and in particular to a dual-source multi-cable narrow spacing control system and method. Background Art

[0002] According to seismic exploration theory, the lateral sampling interval (also called the trace spacing, the same below) determines the lateral resolution. From the sampling theorem, it can be seen that once the lateral continuous signal is discretely sampled, an irrecoverable frequency domain range will be generated. The relevant information of the frequency band area cannot be fully restored, and the information of the frequency band area will become new information in another frequency domain after sampling, which is spatial pseudo-frequency. It can be seen that for a specific research object, to ensure that it is not distorted, it must rely on the sampling interval, the bandwidth of the signal itself, and the energy of the high-frequency information outside the signal band. If the lateral sampling can ensure that the irrecoverable frequency band area is outside the signal bandwidth and the interference energy outside the signal band is very small, the signal can be completely restored.

[0003] Although the lateral sampling of seismic signals has satisfied the sampling theorem, there is still weak aliasing information. Since the interference energy outside the limited bandwidth of seismic signals is generally small, the imaging accuracy of seismic profiles depends on the trace spacing itself and the underground structure and exploration accuracy. Therefore, efforts should be made to avoid the spatial aliasing of signals within the effective frequency band so that the effective signal will not be distorted. Yilmaz conducted an in-depth analysis of the spatial aliasing problem, pointing out that the generation of spatial aliasing is related to the formation dip, regional velocity and trace spacing, and gave the following specific calculation formula:

[0004]

[0005] In the formula, It is the highest frequency that does not produce spatial aliasing in the horizontal direction; is the regional velocity, is the track spacing, It is clear that the smaller the track spacing is, the higher the maximum effective frequency that can be recorded laterally is, and the more beneficial it is to improve the lateral resolution.

[0006] In three-dimensional seismic area observation, in order to fully cover the detection area, the work area is generally "discretized" on the plane, that is, the continuous work area is divided into a large number of grid "surface elements". When collecting signals, the "coverage times" are calculated by the number of reflected signals falling in each "surface element". Under certain observation system parameter conditions, the minimum size of the surface element is certain. If the surface element is smaller than the minimum size, the problem of "missing detection" will occur.

[0007] In conventional offshore 3D seismic exploration, the airgun source spacing is 50 meters and the towline spacing is 100 meters. The distance between the two receiving signal towlines is 12.5 meters, that is, the spacing is 12.5 meters, so the minimum longitudinal bin size is 6.25 meters; the lateral distance between the towlines is 100 meters, and according to the bin size calculation formula, the minimum lateral bin size is 25 meters. In the 3D seismic exploration conducted in this way, the minimum underground reflection bin is 6.25×25 meters (longitudinal bin size×lateral bin size).

[0008] In the seismic exploration of natural gas hydrates in the sea, the hydrates in the development zone are often distributed in the form of scattered, patchy, faulted and thin layers, and there are very few thick layers with very good continuity. The distribution forms of natural gas hydrates in the sea are diverse, and the ore bodies vary in size and are scattered. Due to the conventional three-dimensional seismic exploration combination system, the minimum size of the underground reflection surface element can only reach 6.25×25 meters, which cannot meet the requirements of the lateral and vertical resolution of the seismic exploration of natural gas hydrates in the sea. With the requirements of fine detection of targets, the distance between seismic sources and cables needs to be greatly reduced to achieve the goal of improving the lateral resolution.

[0009] In conventional offshore 3D seismic exploration, the distance between two seismic sources is generally 50 meters, and each seismic source is composed of multiple sub-arrays; the cable spacing is 100 meters. The method of controlling the distance between the two seismic sources is to tie a fixed-width rope between each sub-array and use an expansion rope to expand it outward, so that the distance is finally kept within a certain range, and the distance variation is generally ±10%, that is, the distance varies between 45-55 meters; the method of controlling the distance between multiple cables is to connect them through a fixed-width rope, and use an expander to drag them outward on the outside, so that the lateral distance between the cables is kept within a certain range, and the distance variation is generally ±10%, that is, the distance varies between 90-110 meters.

[0010] As the spacing decreases, the range of spacing changes also needs to be reduced. For example, when the source spacing is reduced to 3.2 meters and the cable spacing is reduced to 6.4 meters, the lateral size of the smallest underground reflection surface element is 1.6 meters. If the spacing change requirement of ±10% is followed, the source spacing range is 2.88-3.52 meters, and the cable spacing range is 5.76-7.04 meters. As the surface element size becomes smaller, the change in spacing will cause the reflection signal falling on the surface element to be very uneven, affecting the subsequent processing of the signal and creating an illusion.

[0011] In order to more accurately control the source spacing and cable spacing and further reduce the spacing variation to within ±5%, a dual-source multi-cable narrow spacing control technology is considered. Summary of the invention

[0012] The technical problem solved by the present invention is to solve the problem that the facet of seismic data acquisition is difficult to reduce, and to provide a dual-source multi-cable narrow spacing control system and method.

[0013] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0014] A dual-source multi-cable narrow spacing control system comprises dual seismic sources, towlines and a frame, wherein the frame is connected to a seismic vessel, and the towlines are connected to the seismic vessel; there are no less than two towlines, and a dual seismic source is arranged between any two adjacent seismic sources; the towlines are connected by spacing ropes, and the spacing ropes are connected to the middle of the towlines, and one end of the towlines is connected to the seismic vessel; the frame comprises an extension rope and an extension arm, and the extension arm and the extension rope are connected to the seismic vessel, and there are at least two extension ropes, which are respectively arranged on both sides of the hull, and there are at least two extension arms, which are respectively arranged on both sides of the hull; the extension rope is connected to the middle of the outermost towline.

[0015] Twin sources send out seismic waves, and the framework is used to control the position and spacing of the streamers.

[0016] The size of the facet can be reduced as much as possible while maintaining the spacing between the tollands stable. The multi-cable spacing defense range is within ±5%, which makes it possible to improve the lateral resolution of seismic data acquisition.

[0017] Preferably, the dual seismic source comprises two transmitting sources, namely a first transmitting source and a second transmitting source, the two transmitting sources are connected by a support rod, and the transmitting source is connected to the seismic ship by an impulse cable; the dual seismic source is arranged between the spacing rope and the seismic ship. The support rod can ensure relative stability between the two seismic sources.

[0018] Preferably, the first and second transmitting sources are symmetrically arranged along the ship's mid-axis. The transmitting sources are symmetrical along the ship's mid-axis, which can effectively improve the coverage of the source, and most of the streamers can receive the returned data.

[0019] Preferably, an anti-bend device is provided at the connection between the towline and the spacing rope, a leading wire is formed between the connection between the towline and the seismic ship and the anti-bend device, and the towline forms a test cable from the anti-bend device in a direction away from the seismic ship, and the towline includes a leading wire and a test cable; the outer diameter of the leading wire is 46±2mm. The anti-bend device can effectively prevent the towline from bending, and at the same time, the anti-bend device can stabilize the position of the towline and the distance between the towlines, and together with the extension rope and the extension arm, ensure that the position of the towline on the ship is relatively stable.

[0020] Preferably, the two outermost strands of the tow cable are connected to the head mark through a head mark pull rope, and the expansion rope is connected to the tow cable through an anti-bend device. The head mark pull rope fixes the head mark.

[0021] Preferably, the expansion rope, spacing rope and head mark pull rope are made of SK78 fiber rope; the water absorption rate of the SK78 fiber rope in seawater is 0, the specific gravity is 0.98, the melting point is 144-152 degrees Celsius, and the maximum working temperature is 65 degrees Celsius. The use of SK78 fiber makes the weight of the towline smaller, which can reduce resistance and improve the underwater stability of the towline.

[0022] Preferably, a pulley is provided on the expansion arm, one end of the expansion rope is connected to the seismic ship, the other end of the expansion rope is connected to the middle of the outermost towline, and the expansion rope passes through the pulley of the expansion arm. The expansion rope passes through the pulley of the expansion arm, so that during the dynamic movement of the ship, although the frame has a slight deformation, the whole is still stable.

[0023] Preferably, the tail end of the test cable is provided with a tail mark, and the test cable between the anti-bend device and the tail mark is provided with a compass bird, a CMX and a transverse rudder bird; the compass bird is provided with a depth-fixing device, the transverse rudder bird is provided with an acoustic ranging device, a transverse rudder blade and a motor; the tail mark is provided with a motor and a rudder propeller. The rudder blades of the tail mark and the transverse rudder bird can obtain a certain thrust from the water flow, thereby realizing the adjustment of the spacing between the tow cables.

[0024] Preferably, the header is provided with a relative GPS positioning device; the transmitting source is provided with a relative GPS positioning device and CTX.

[0025] A dual-source multi-source narrow spacing control method is provided, wherein the dual seismic sources are set at a position 25-35m away from the stern, the spacing between the left and right transmitting sources is adjusted to 2.5-3.5m through a support rod, the depth of the towline is obtained through a compass bird, the spacing of the towline is obtained through multiple transverse rudder birds on the towline, and the transverse rudder birds and the tail marker are controlled according to the spacing and depth, specifically including:

[0026] S11. Adjust the lateral rudder blades of the lateral rudder bird to generate lateral thrust to control the lateral deviation of the towline through the lateral rudder bird;

[0027] S12. Adjust the rudder propeller of the stern marker to generate lateral thrust to ensure the stability of the tow cable spacing.

[0028] Compared with the prior art, the present invention has the following beneficial effects: the size of the facet can be reduced as much as possible, while maintaining the spacing between the tollands stable, and the multi-cable spacing defense range is within ±5%, which makes it possible to improve the lateral resolution of seismic data acquisition.

[0029] The spacing between the seismic sources can be reduced to 3.125m, and the spacing between the streamers can be reduced to about 6.4m (both with a fluctuation of 10%). BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 This is a schematic structural diagram of the first embodiment of the dual-source multi-cable narrow spacing control system of the present application;

[0032] Figure 2 This is a schematic structural diagram of a second embodiment of a dual-source multi-cable narrow spacing control system of the present application;

[0033] Figure 3 This is the circuit connection block diagram of the dual-source multi-cable narrow spacing control system of this application. DETAILED DESCRIPTION

[0034] The following embodiments are provided to further illustrate the present invention, but are not intended to limit the present invention.

[0035] Example 1

[0036] See also Figure 1-Figure 3A dual-source multi-cable narrow spacing control system includes a dual seismic source 1, a streamer 2, and a frame, wherein the frame is connected to a seismic ship 4, and the streamer 2 is connected to the seismic ship 4; the streamers 2 are 4, and a dual seismic source 1 is arranged between the two adjacent streamers 2 in the middle; the streamers 2 are connected by a spacing rope 27, and the spacing rope 27 is connected to the middle of the streamer 2, and one end of the streamer 2 is connected to the seismic ship 4; the frame includes an extension rope 31 and an extension arm 32, and the extension arm 32 and the extension rope 31 are connected to the seismic ship, and at least two extension ropes 31 are arranged on both sides of the hull, and at least two extension arms 32 are arranged on both sides of the hull; the extension rope 31 is connected to the middle of the outermost streamer 2. The dual seismic source includes two transmitting sources, namely a first transmitting source 11 and a second transmitting source 12, and the two transmitting sources are connected by a support rod 13, and the transmitting source is connected to the seismic ship 4 by a pulse cable; the dual seismic source is arranged between the spacing rope 27 and the seismic ship 4. The first 11 and the second transmitting source 12 are symmetrically arranged along the ship's mid-axis. An anti-bending device 28 is provided at the connection between the towline 2 and the spacing rope 27. A leading wire 21 is formed between the connection between the towline 2 and the seismic ship 4 and the anti-bending device 28. The towline 2 forms a test cable 22 from the anti-bending device 28 in a direction away from the seismic ship 4. The towline includes a leading wire 21 and a test cable 22; the outer diameter of the leading wire 21 is 46±2mm. The two outermost wires of the towline 2 are connected to the head mark 26 through the head mark pull rope; the extension rope 31 is connected to the towline through the anti-bending device 28. The extension rope 31, the spacing rope 27, and the head mark pull rope are SK78 fiber cables; the water absorption rate of the SK78 fiber cable in seawater is 0, the specific gravity is 0.98, the melting point is 144~152 degrees Celsius, and the maximum working temperature is 65 degrees Celsius. The extension arm 32 is provided with a pulley 33, one end of the extension rope 31 is connected to the seismic ship 4, and the other end of the extension rope 31 is connected to the anti-bend device 28 in the middle of the outermost towline 2, and the extension rope 31 passes through the pulley 33 of the extension arm 32. The tail end of the test cable 22 is provided with a tail mark 25, and the test cable 22 between the anti-bend device 28 and the tail mark 25 is provided with a compass bird 23, CMX and a transverse rudder bird 24; the compass bird 23 is provided with a depth-fixing device, and the transverse rudder bird 24 is provided with an acoustic ranging device, a transverse rudder blade and a motor; the tail mark 25 is provided with a motor and a rudder propeller. The head mark 26 is provided with a relative GPS positioning device; the first transmitting source 11 and the second transmitting source 12 are provided with a relative GPS positioning device and CTX.

[0037] The dual seismic sources emit seismic waves, and the frame is used to control the position and spacing of the tow cables. The size of the facet can be reduced as much as possible, while maintaining the stable spacing between the tow cables. The multi-cable spacing defense range is within ±5%, which provides the possibility of improving the lateral resolution of seismic data acquisition. The support rod can ensure the relative stability between the two seismic sources. The transmitting source is symmetrical along the axis of the ship, which can effectively improve the coverage of the source, and most of the tow cables can receive the returned data. The anti-bend device can effectively prevent the tow cable from bending. At the same time, the anti-bend device can stabilize the position of the tow cable and the distance between the tow cables, and together with the extension rope and the extension arm, ensure that the position of the tow cable on the same ship is relatively stable. The head mark pull rope fixes the head mark. Using SK78 fiber, the weight of the tow cable is small, which can reduce resistance and improve the underwater stability of the tow cable. The extension rope passes through the pulley of the extension arm, so that during the dynamic movement of the ship, although the frame has a slight deformation, it is still stable as a whole. The rudder blades of the tail mark and the lateral rudder bird can obtain a certain thrust from the water flow, so as to adjust the spacing between the tow cables.

[0038] Example 2

[0039] See also Figure 2 A dual-source multi-cable narrow spacing control system includes a dual seismic source 1, a streamer 2, and a frame, wherein the frame is connected to a seismic ship 4, and the streamer 2 is connected to the seismic ship 4; there are two streamers 2, and a dual seismic source 1 is arranged between the two adjacent streamers 2 in the middle; the streamers 2 are connected by a spacing rope 27, and the spacing rope 27 is connected to the middle part of the streamer 2, and one end of the streamer 2 is connected to the seismic ship 4; the frame includes an extension rope 31 and an extension arm 32, and the extension arm 32 and the extension rope 31 are connected to the seismic ship, the two extension ropes 31 are respectively arranged on both sides of the hull, and the at least two extension arms 32 are respectively arranged on both sides of the hull; the extension rope 31 is connected to the middle part of the outermost streamer 2.

[0040] Example 3

[0041] A dual-source multi-cable narrow spacing control method is provided, wherein the dual seismic sources are set at a position 25-35 m away from the stern, the spacing between the left and right transmitting sources is adjusted to 2.5-3.5 m through a support rod, the depth of the towline is obtained through a compass bird, the spacing of the towline is obtained through multiple lateral rudder birds on the towline, and the lateral rudder birds and the tail marker are controlled according to the spacing and depth, specifically including:

[0042] S11. Adjust the lateral rudder blades of the lateral rudder bird to generate lateral thrust to control the lateral deviation of the towline through the lateral rudder bird;

[0043] S12. Adjust the rudder propeller of the stern marker to generate lateral thrust to ensure the stability of the tow cable spacing.

[0044] Example 4

[0045] See also Figure 3 A dual-source multi-cable narrow spacing control method is provided. The dual sources are set at a distance of 25-35m from the stern. The spacing between the left and right transmitting sources is adjusted to 2.5-3.5m through the support rod. The depth of the towline is obtained by the compass bird. The spacing of the towline is obtained by multiple lateral rudder birds on the towline. The lateral rudder birds and the tail marker are controlled according to the spacing and depth. Specifically, it includes:

[0046] S11. Adjust the lateral rudder blades of the lateral rudder bird to generate lateral thrust to control the lateral deviation of the towline through the lateral rudder bird;

[0047] S12. Adjust the rudder propeller of the stern marker to generate lateral thrust to ensure the stability of the tow cable spacing.

[0048] The rudder propeller includes a rudder blade 253 and a first motor 254, and the first motor 254 is connected to the rudder blade 253; the first motor 254 drives the rudder blade 253 to rotate, and the rudder blade 253 can rotate at an angle of -15 to 15 degrees. The tail mark 25 is provided with a relative GPS positioning device and a first communication device 251, and the first communication device 251 is connected to the seismic ship 4. The rudder propeller also includes a first single-chip microcomputer, and the first communication device 251 is connected to the seismic ship 4. The relative GPS positioning device and the first single-chip microcomputer 252 are connected to the first communication device 251, and the first motor 254 is connected to the first single-chip microcomputer 252. The lateral bird includes an acoustic ranging device 241 and a lateral rudder propeller, and the lateral rudder propeller includes a second single-chip microcomputer 242, a second motor 243 and a lateral rudder blade 244. The acoustic ranging device 241 is connected to the second single-chip microcomputer 242, the second single-chip microcomputer 242 is connected to the second motor 243, the second motor 243 is connected to the lateral rudder blade 244, and the number of the lateral rudder blade 244 is not less than two. The lateral bird 3 also includes a second communication device 245, the second communication device 245 is connected to the seismic ship 4, and the second single-chip microcomputer 242 is connected to the second communication device 245. The compass bird includes a depth determination device 231 and a third communication device 232, and the third communication device 232 is connected to the seismic ship 4. The response value of the rotation of the rudder blade 253 is ≥0.4°.

[0049] The compass bird, lateral rudder bird, tail marker and the like communicate with the seismic ship, and the movement of the lateral rudder bird and tail marker is controlled by the seismic ship.

[0050] The above detailed description is a specific description of the feasible embodiments of the present invention. The above embodiments are not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not deviate from the present invention should be included in the patent scope of this case.

Claims

1. A dual-source multi-cable narrow spacing control system, characterized in that: It includes dual seismic sources, towlines, and a frame, wherein the frame is connected to a seismic ship, and the towlines are connected to the seismic ship; there are at least two towlines; a dual seismic source is arranged between any two adjacent towlines; the towlines are connected by a spacing rope, the spacing rope is connected to the middle of the towline, and one end of the towline is connected to the seismic ship; the frame includes an extension rope and an extension arm, the extension arm and the extension rope are connected to the seismic ship, there are at least two extension ropes, which are respectively arranged on both sides of the hull, and there are at least two extension arms, which are respectively arranged on both sides of the hull; the extension rope is connected to the middle of the outermost towline; the dual seismic source is arranged between the spacing rope and the seismic ship; the first transmitting source and the second transmitting source in the dual seismic source are symmetrically arranged along the axis of the ship; the two transmitting sources are connected by a supporting rod, The transmitting source is connected to the seismic ship through a pulse cable; the tow cable includes a leading wire and a test cable; an anti-folding device is provided at the connection between the tow cable and the spacing rope; wherein, a leading wire is formed between the connection between the tow cable and the seismic ship and the anti-folding device, and the tow cable forms a test cable from the anti-folding device in a direction away from the seismic ship; the outer diameter of the leading wire is 46±2mm; the two outermost headers in the tow cable are connected by a header pull rope; the extension rope is connected to the tow cable through an anti-folding device; a pulley is provided on the extension arm, one end of the extension rope is connected to the seismic ship, and the other end of the extension rope is connected to the middle part of the outermost tow cable, and the extension rope passes through the pulley of the extension arm.

2. A dual-source multi-cable narrow spacing control system according to claim 1, characterized in that: The expansion rope, spacing rope and head mark pull rope are made of SK78 fiber cable; the water absorption rate of the SK78 fiber cable in seawater is 0, the specific gravity is 0.98, the melting point is 144~152 degrees Celsius, and the maximum working temperature is 65 degrees Celsius.

3. A dual-source multi-cable narrow spacing control system according to claim 1, characterized in that: A tail mark is provided at the tail end of the test cable, and a compass bird, CMX and a transverse rudder bird are provided on the test cable between the anti-folding device and the tail mark; the compass bird is provided with a depth setting device, and the transverse rudder bird is provided with an acoustic ranging device, a transverse rudder blade and a motor; the tail mark is provided with a motor and a rudder propeller.

4. A dual-source multi-cable narrow spacing control system according to claim 1, characterized in that: The header is provided with a relative GPS positioning device; the transmitting source is provided with a relative GPS positioning device and CTX.

5. A control method applied to the dual-source multi-cable narrow spacing control system according to any one of claims 1 to 4, characterized in that: The dual seismic sources are set at a distance of 25-35m from the stern. The spacing between the first and second sources is adjusted to 2.5-3.5m by the support rod. The depth of the streamer is obtained by the compass bird. The spacing between the streamers is obtained by the multiple lateral rudder birds on the streamer. The lateral rudder birds and the tail marker are controlled according to the spacing and depth of the streamers. Specifically, the following are included: S11. Adjust the lateral rudder blades of the lateral rudder bird to generate lateral thrust, and control the lateral deviation of the towline through the lateral rudder bird; S12. Adjust the rudder propeller of the stern marker to generate lateral thrust to ensure the stability of the tow cable spacing.

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