阅读说明：本技术 一种双源多缆窄间距控制系统及方法 (Double-source multi-cable narrow-spacing control system and method ) 是由 韦成龙 赵庆献 杨册 黄宁 于 2019-08-20 设计创作，主要内容包括：本发明涉及海洋地质调查领域,提供一种双源多缆窄间距控制系统及方法,用于解决地震数据采集的面元难以缩小的问题。本发明提供的一种双源多缆窄间距控制系统,包括双震源、拖缆、框架,所述框架同地震船连接,所述拖缆同地震船连接；所述拖缆不少于2条,所述任两根相邻的震源之间设置有双震源；所述拖缆之间通过间距绳连接,所述间距绳同拖缆的中部连接所述拖缆的一端同地震船连接；所述框架包括扩展绳、扩展臂,所述扩展臂、扩展绳同地震船连接；所述扩展绳同最外侧的拖缆的中部连接。可以尽可能的缩小面元的尺寸,同时维持托兰之间的间距稳定,多缆间距辩护范围在±5%以内,为提高地震数据采集的横向分辨率提供了可能。(The invention relates to the field of marine geological survey, and provides a double-source multi-cable narrow-spacing control system and method, which are used for solving the problem that the surface elements for seismic data acquisition are difficult to shrink. The invention provides a double-source multi-cable narrow-spacing control system which comprises double sources, a towing cable and a frame, wherein the frame is connected with a seismic vessel, and the towing cable is connected with the seismic vessel; the number of the towlines is not less than 2, and double seismic sources are arranged between any two adjacent seismic sources; the towing cables are connected through spacing ropes, and the spacing ropes are connected with the middle parts of the towing cables and one ends of the towing cables connected with the seismic vessels; the frame comprises an expansion rope and an expansion arm, and the expansion arm and the expansion rope are connected with the seismic ship; the expansion rope is connected with the middle part of the streamer on the outermost side. The size of a surface element can be reduced as much as possible, the stable spacing between the tolans is maintained, the multi-cable spacing discrimination range is within +/-5%, and the possibility is provided for improving the transverse resolution of seismic data acquisition.)

1. A double-source multi-cable narrow-spacing control system is characterized by comprising double sources, a towing cable and a frame, wherein the frame is connected with a seismic vessel, and the towing cable is connected with the seismic vessel; the number of the towlines is not less than 2, and double seismic sources are arranged between any two adjacent seismic sources; the towing cables are connected through spacing ropes, and the spacing ropes are connected with the middle parts of the towing cables and one ends of the towing cables connected with the seismic vessels; the frame comprises expansion ropes and expansion arms, the expansion arms and the expansion ropes are connected with the seismic ship, at least two expansion ropes are arranged on two sides of the ship body respectively, and at least two expansion arms are arranged on two sides of the ship body respectively; the expansion rope is connected with the middle part of the streamer on the outermost side.

2. The dual-source multi-cable narrow spacing control system according to claim 1, wherein said dual seismic sources comprise two sources, a first source and a second source, said two sources are connected by a support rod, said sources are connected with a seismic vessel by a pulse cable; the dual sources are disposed between the spacing ropes and the seismic vessel.

3. A dual source multiple cable narrow spacing control system according to claim 2, wherein said first and second transmission sources are symmetrically disposed along the midship axis.

4. The dual-source multi-cable narrow spacing control system as claimed in claim 1, wherein the junction of the towline and the spacing rope is provided with a bending preventer, a front lead is formed between the junction of the towline and the seismic vessel and the bending preventer, the towline is formed with a test cable from the bending preventer along the direction away from the seismic vessel, and the towline comprises the front lead and the test cable; the outer diameter of the front lead is 46 +/-2 mm.

5. A dual source multi-cable narrow spacing control system according to claim 1, wherein the two most outer concordant heads in said streamers are connected by a concordant pull cord; the expansion rope is connected with the towing rope through the anti-folding device.

6. The dual-source multi-cable narrow-spacing control system according to claim 1, wherein the expansion ropes, the spacing ropes and the head-marking pull ropes are SK78 fiber cables, the water absorption rate of the SK78 fiber cables in seawater is 0, the specific gravity of the SK78 fiber cables is 0.98, the melting point of the SK78 fiber cables is 144 ~ 152 ℃, and the highest working temperature of the SK78 fiber cables is 65 ℃.

7. The dual-source multi-cable narrow spacing control system of claim 1, wherein said extension arm is provided with a pulley, one end of said extension cable is connected to the seismic vessel, the other end of said extension cable is connected to the middle of the outermost streamer, and said extension cable passes through the pulley of the extension arm.

8. The dual-source multi-cable narrow spacing control system according to claim 1, wherein a tail marker is arranged at the tail end of the test cable, and a compass bird, a CMX and a transverse rudder bird are arranged on the test cable between the anti-bending device and the tail marker; the compass bird is provided with a depth setting device, and the transverse rudder bird is provided with an acoustic wave distance measuring device, a transverse rudder blade and a motor; the tail mark is provided with a motor and a steering oar.

9. A dual source multi-cable narrow spacing control system according to claim 1, wherein said header is provided with relative GPS positioning means; and a relative GPS positioning device and a CTX are arranged on the emission source.

10. A double-source multi-cable narrow-spacing control method is characterized in that double sources are arranged at a position 25m away from a stern 25 ~ 35m, the spacing between a left emission source and a right emission source is adjusted to be 2.5 ~ 3.5.5 m through a support rod, the depth of a streamer is acquired through a compass bird, the spacing between streamers is acquired through a plurality of transverse steering birds on the streamer, and the transverse steering birds and a tail marker are controlled according to the spacing and the depth, and specifically comprises the following steps:

s11, adjusting a transverse rudder blade of a transverse rudder bird to generate transverse thrust to control transverse deviation of a towing cable through the transverse rudder bird;

s12, adjusting a rudder propeller of the tail mark to generate lateral thrust and ensure the stability of the space between the towing cables.

Technical Field

The invention relates to the field of marine geological survey, in particular to a double-source multi-cable narrow-spacing control system and method.

Background

According to the theory of seismic exploration, the lateral resolution is determined by the lateral sampling interval (also called the trace pitch, the same below), and it is known from the sampling theorem that once a lateral continuous signal is discretely sampled, an unrecoverable frequency domain range is generated, the information of the frequency band region cannot be completely recovered, and the information of the frequency band region becomes new information of another frequency domain after being sampled, which is a spatial aliasing. Therefore, for a specific research object, the requirement for ensuring that the specific research object is not distorted necessarily depends on the sampling interval, the frequency bandwidth of the signal and the energy of high-frequency information outside the signal frequency band, and if the transverse sampling can ensure that an unrecoverable frequency band region is positioned outside the signal frequency band and the interference energy outside the signal frequency band is very small, the signal can be completely recovered.

Although the horizontal sampling of the seismic signals meets the sampling theorem, the alias information with weak energy still exists, because the interference energy outside the limited bandwidth of the seismic signals is generally very small, the imaging precision of a seismic section depends on the track spacing and the underground structure and exploration precision, therefore, the spatial alias existing in the signals in an effective frequency band is avoided, so that the effective signals are not distorted, the problem of the spatial alias is deeply analyzed by Elmazis, the generation of the spatial alias is related to the formation dip angle, the region velocity and the track spacing, and the following specific calculation formula is given:

f_max＝v/(4Δxsinθ)

in the formula (f)_maxThe highest frequency which does not generate spatial aliasing in the transverse direction; v is the zone velocity, Δ x is the track spacing, and θ is the formation dip. It can be seen that the smaller the track pitch, the higher the maximum effective frequency that can be recorded laterally, which is advantageous for the improvement of the lateral resolution.

In three-dimensional seismic area observation, in order to detect a work area in a full coverage manner, the work area is generally "discretized" on a plane, that is, a continuous work area is divided into a large number of grid "bins", and when signals are acquired, the number of "coverage times" is calculated according to the number of reflected signals falling in each "bin". Under certain observation system parameters, the minimum size of the bin is certain. Bin sizes smaller than the minimum size will cause a "missed measurement" problem.

In conventional marine three-dimensional seismic exploration, the distance between air gun seismic sources is 50 meters, and the distance between towing cables is 100 meters. Wherein the distance between two channels of the signal receiving streamer is 12.5 meters, namely the channel spacing is 12.5 meters, and the size of the longitudinal surface element is 6.25 meters at the minimum; the transverse distance between the streamers is 100 meters, and the transverse bin size is 25 meters at the minimum according to a bin size calculation formula. For the three-dimensional seismic survey thus conducted, the subsurface minimum reflection bin is 6.25 × 25 meters (longitudinal bin size × transverse bin size).

In sea natural gas hydrate seismic exploration, hydrate occurrence forms of development areas are often in a dispersion shape, a patch shape, a fault shape and a lamellar shape, few thick layers with very good continuity exist, sea natural gas hydrates have various occurrence forms, and ore bodies are different in size and exist in a dispersion manner. Due to the conventional three-dimensional seismic exploration combination system, the minimum size of the underground reflection surface element can only reach 6.25 multiplied by 25 meters, and the requirements of sea area natural gas hydrate seismic exploration on the transverse resolution and the longitudinal resolution cannot be met. With the requirement of fine target detection, the distance between the seismic sources and the distance between the cables need to be greatly reduced, so as to achieve the aim of improving the transverse resolution.

In conventional marine three-dimensional seismic exploration, the spacing between two seismic sources is generally 50 meters, and each seismic source consists of a plurality of sub-arrays; the cable spacing was 100 meters. The 2 seismic source spacing control methods are that fixed width ropes are tied between each subarray, the expansion ropes are used for outward expansion, and finally the spacing is kept in a certain range, the spacing change is generally +/-10%, namely the spacing is changed between 45 meters and 55 meters; the method for controlling the distance between the plurality of cables is characterized in that the cables are connected through a fixed-width rope, the outer side of the cables is dragged outwards by using an expander, the transverse distance between the cables is kept in a certain range, and the change of the distance is generally +/-10 percent, namely the distance is changed between 90 meters and 110 meters.

As the pitch is reduced, the range of variation of the pitch is also reduced. If the seismic source spacing is reduced to 3.2 meters and the cable spacing is reduced to 6.4 meters, the transverse dimension of the underground minimum reflection surface element is 1.6 meters, if the spacing change requirement is +/-10%, the variation range of the seismic source spacing is 2.88-3.52 meters, and the variation range of the cable spacing is 5.76-7.04 meters, and due to the fact that the surface element size is reduced and the spacing changes, the reflection signals falling in the surface element are very uneven, the subsequent processing of the signals is affected, and artifacts are caused.

In order to more accurately control the distance between the seismic sources and the distance between the cables and further reduce the change of the distance to be within +/-5 percent, a double-source multi-cable narrow-distance control technology is considered.

Disclosure of Invention

The invention provides a dual-source multi-cable narrow-spacing control system and method for solving the technical problem that the bin of seismic data acquisition is difficult to reduce.

In order to solve the technical problems, the technical scheme provided by the invention is as follows:

a dual-source multi-cable narrow-spacing control system comprises dual sources, a streamer and a frame, wherein the frame is connected with a seismic vessel, and the streamer is connected with the seismic vessel; the number of the towlines is not less than 2, and double seismic sources are arranged between any two adjacent seismic sources; the towing cables are connected through spacing ropes, and the spacing ropes are connected with the middle parts of the towing cables and one ends of the towing cables connected with the seismic vessels; the frame comprises expansion ropes and expansion arms, the expansion arms and the expansion ropes are connected with the seismic ship, at least two expansion ropes are arranged on two sides of the ship body respectively, and at least two expansion arms are arranged on two sides of the ship body respectively; the expansion rope is connected with the middle part of the streamer on the outermost side.

The dual sources emit seismic waves and the frame is used to control the position and spacing of the streamers.

The size of a surface element can be reduced as much as possible, the stable spacing between the tolans is maintained, the multi-cable spacing discrimination range is within +/-5%, and the possibility is provided for improving the transverse resolution of seismic data acquisition.

Preferably, the dual seismic sources comprise two emission sources, namely a first emission source and a second emission source, the two emission sources are connected through a support rod, and the emission sources are connected with the seismic ship through pulse cables; the dual sources are disposed between the spacing ropes and the seismic vessel. The support rods can ensure relative stability between the two seismic sources.

Preferably, said first and second emission sources are arranged symmetrically along the mid-ship axis. The emission source is symmetrical along the axis of the ship, so that the coverage range of the seismic source can be effectively improved, and most of the towlines can receive the returned data.

Preferably, the joint of the streamer and the spacing rope is provided with a folding preventer, a front lead is formed between the joint of the streamer and the seismic vessel and the folding preventer, the streamer forms a test cable along the direction away from the seismic vessel from the folding preventer, and the streamer comprises the front lead and the test cable; the outer diameter of the front lead is 46 +/-2 mm. Prevent rolling over the ware and can effectually avoid the towline to buckle, simultaneously, prevent rolling over the ware and can stabilize the position of towline and the distance between the towline, guarantee with extension rope and extension arm that the towline is with the position relatively stable of ship together.

Preferably, two same-head signs at the outermost side in the towlines are connected through a head sign pull rope; the expansion rope is connected with the towing rope through the anti-folding device. The head heading pull rope fixes the head heading.

Preferably, the expansion ropes, the spacing ropes and the head mark pull ropes adopt 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 ℃, and the highest working temperature is 65 ℃. With the SK78 fiber, the weight of the streamer is small, so that the resistance can be reduced, and the underwater stability of the streamer can be improved.

Preferably, the expansion arm is provided with a pulley, one end of the expansion rope is connected with the seismic vessel, the other end of the expansion rope is connected with the middle part of the streamer on the outermost side, and the expansion rope passes through the pulley of the expansion arm. The expansion rope passes through the pulleys of the expansion arms, so that the frame is stable as a whole although slightly deformed in the dynamic movement process of the ship.

Preferably, a tail marker is arranged at the tail end of the test cable, and a compass bird, a CMX and a transverse rudder bird are arranged on the test cable between the anti-bending device and the tail marker; the compass bird is provided with a depth setting device, and the transverse rudder bird is provided with an acoustic wave distance measuring device, a transverse rudder blade and a motor; the tail mark is provided with a motor and a steering oar. The rudder blades of the tail vane and the transverse rudder bird can obtain certain thrust from water flow, so that the adjustment of the distance between the towing cables is realized.

Preferably, the header is provided with relative GPS positioning means; and a relative GPS positioning device and a CTX are arranged on the emission source.

A double-source multi-source narrow-spacing control method comprises the steps that double sources are arranged at positions 25-35 m away from a stern, the spacing between a left emission source and a right emission source is adjusted to be 2.5-3.5 m through a support rod, the depth of a towing cable is obtained through a compass bird, the spacing between the towing cables is obtained through a plurality of transverse steering birds on the towing cable, and the transverse steering birds and a tail marker are controlled according to the spacing and the depth, and specifically comprises the following steps:

s11, adjusting a transverse rudder blade of a transverse rudder bird to generate transverse thrust to control transverse deviation of a towing cable through the transverse rudder bird;

s12, adjusting a rudder propeller of the tail mark to generate lateral thrust and ensure the stability of the space between the towing cables.

Compared with the prior art, the invention has the beneficial effects that: the size of a surface element can be reduced as much as possible, the stable spacing between the tolans is maintained, the multi-cable spacing discrimination range is within +/-5%, and the possibility is provided for improving the transverse resolution of seismic data acquisition.

The spacing of the seismic sources can be reduced to 3.125m and the streamer spacing can be reduced to about 6.4m (both with 10% fluctuation).

Drawings

Fig. 1 is a schematic diagram of a dual-source multi-cable narrow-spacing control system.

Fig. 2 is a partial schematic view of a dual source multi-cable narrow spacing control system.

Fig. 3 is a schematic connection diagram of the rudder paddle.

Detailed Description

The following examples are further illustrative of the present invention and are not intended to be limiting thereof.