CN112965193A

CN112965193A - Ocean seismic streamer based on DAS optical fiber

Info

Publication number: CN112965193A
Application number: CN202110159285.3A
Authority: CN
Inventors: 文鹏飞; 徐云霞; 孙琪真; 杨振; 刘斌; 薛花; 李延; 孟大江; 路允乾
Original assignee: Guangzhou Marine Geological Survey
Current assignee: Guangzhou Marine Geological Survey
Priority date: 2021-02-04
Filing date: 2021-02-04
Publication date: 2021-06-15

Abstract

The invention discloses a marine seismic streamer formed on the basis of DAS (distributed optical fiber system), which comprises a sheath, and a pull-in cable, a plurality of floats and a plurality of DAS optical fibers which are arranged in the sheath, wherein at least two pull-in cables are arranged in parallel in the axial direction of the sheath, the floats are arranged in the radial direction of the sheath, two ends of each float are respectively fixed on the two pull-in cables at two sides, each DAS optical fiber extends in parallel in the axial direction of the sheath, is positioned between the two pull-in cables and penetrates through the float, a sensitization structure is correspondingly arranged on each DAS optical fiber, the rest parts of the DAS optical fibers still keep straight lines, the sensitization structures on different DAS optical fibers are arranged in parallel at intervals and are staggered mutually, so that the sensitization structures on different DAS optical fibers are. The invention can realize the exploration of the small track spacing, and the DAS optical fiber is not pulled randomly to cause the snapping, thereby prolonging the service life of the marine seismic streamer.

Description

Ocean seismic streamer based on DAS optical fiber

Technical Field

The invention relates to the technical field of marine seismic streamer structures, in particular to a marine seismic streamer formed based on DAS optical fibers.

Background

Marine seismic streamers are used to receive seismic reflection signals and are one of the core devices of marine seismic exploration. The existing marine seismic streamer mainly uses a cable formed by piezoelectric detectors, namely a piezoelectric streamer, and the piezoelectric streamer is formed by connecting point type sensors (namely the detectors) in series. The distance between the individual receivers (i.e. the track pitch) is typically large, i.e. the track pitch is large, typically 12.5 meters or 6.25 meters. The size of the trace spacing is directly related to the resolution of the acquired seismic data, namely the quality of the acquired data, and the smaller the trace spacing, the larger the resolution of the seismic data, and vice versa. When the channel spacing needs to be further reduced, the existing marine seismic streamers are often unable to do so, and for respective reasons, the marine seismic streamers with the small channel spacing smaller than 3.125 meters are also limited in China abroad. Therefore, there is a need to propose streamers with smaller track spacing.

Distributed optical fiber acoustic wave sensing (DAS) is all-fiber signal collection, theoretically, DAS fibers formed by the DAS sensing can be extracted from collected data according to needs, so that the track distance can be small, and generally the track distance is within 1 meter. The track spacing can greatly improve the horizontal and vertical resolution of the detection of the reservoir where the resources such as hydrates and the like are located, and can be widely applied to oil and gas fields and shale gas development. In this regard, we propose a streamer based on DAS fiber to solve the problem of large inter-track spacing.

Disclosure of Invention

In view of the deficiencies of the prior art, it is an object of the present invention to provide a streamer configured based on DAS optical fibers that solves the problem of large trace spacing.

The technical scheme for realizing the purpose of the invention is as follows: a marine seismic streamer based on DAS optical fibers comprises a sheath, and a bearing cable, a plurality of floats and a plurality of DAS optical fibers which are arranged in the sheath, wherein at least two bearing cables are arranged in the sheath in a parallel extending mode along the axial direction of the sheath, the two bearing cables are respectively arranged on two sides of the sheath, the floats are arranged along the radial direction of the sheath, two ends of each float are respectively fixed on the two bearing cables on the two sides, the floats are distributed and arranged along the axial direction of the sheath at intervals, each DAS optical fiber extends in parallel along the axial direction of the sheath and is respectively positioned between the two bearing cables, the DAS optical fibers sequentially penetrate through each float in the sheath and are fixed on the float,

all be provided with the sensitization structure along DAS optic fibre axial direction interval on every DAS optic fibre, the sensitization structure obtains with certain angle winding through the relevant position on the DAS optic fibre, and the straight line still remains in the other positions of DAS optic fibre, and the parallel interval of each DAS optic fibre sets up and the sensitization structure on the different DAS optic fibres staggers each other to prevent that the sensitization structure on the different DAS optic fibres is on a straight line in the vertical direction.

Further, the certain angle is a 60 ° angle.

Further, the floaters are distributed and arranged at equal intervals along the axial direction of the sheath.

Further, the sensitization structures are arranged at equal intervals.

Furthermore, the sheath is filled with filler, and the filler is used for wrapping the DAS optical fiber, so that the streamer is provided with zero buoyancy while the DAS optical fiber sensor is protected.

Further, the filler is kerosene or polyurethane gel, or a mixture of kerosene and polyurethane gel.

Further, the sheath is made of rubber and the sheath is hollow.

Further, the floater is in a cylindrical or elliptic cylindrical structure with a hole on a cylinder body.

The invention has the beneficial effects that: the sensitivity enhancing structure is formed by winding and looping, the sensitivity enhancing structure can effectively improve the sensitivity and the signal to noise ratio of the DAS optical fiber, and the sensing of weak reflection signals can be effectively realized. The distance between two adjacent sensitization structures forms the inter-channel distance, and the sensitization structures can be made to be small (for example, less than 1 m), so that the marine seismic streamer of the embodiment can realize smaller inter-channel distance, namely, the exploration of the inter-channel distance can be realized. And the DAS optical fibers are not dragged randomly to cause the snapping, and the service life of the marine seismic streamer is prolonged.

Drawings

FIG. 1 is a schematic representation of a seismic streamer of the invention acquiring data;

fig. 2 is a schematic view of the DAS fiber passing through each float.

Detailed description of the preferred embodiments

The invention will be further described with reference to the accompanying drawings and specific embodiments:

as shown in fig. 1, the marine seismic streamer based on the DAS optical fibers comprises a sheath, and at least two stay cables, a plurality of floats and a plurality of DAS optical fibers which are arranged in the sheath, wherein the at least two stay cables are arranged in the sheath in a parallel extending manner along the axial direction of the sheath, and the two stay cables are respectively arranged on two sides of the sheath. The floater sets up along the radial direction of sheath, and the both ends of floater are fixed respectively on two of both sides hold the stay cable, and each floater along the axial interval distribution of sheath setting, preferably equal interval distribution. Each DAS optical fiber extends in parallel along the axial direction of the sheath and is positioned between the two tensile cables, and the DAS optical fibers sequentially penetrate through each floater in the sheath and are fixed on the floater. The floater is preferably in a cylindrical or elliptic cylindrical structure with a hole in the cylinder body, and is used for fixing the DAS optical fiber and preventing the dragged DAS optical fiber from being pulled apart. Fig. 2 is a schematic view of the DAS optical fiber passing through each float and being held by the float, thereby preventing the DAS optical fiber from being randomly dragged.

All be provided with the sensitization structure along DAS optic fibre axial direction interval on every DAS optic fibre, preferably equal interval sets up, and the sensitization structure is obtained with certain angle winding through the relevant position on DAS optic fibre, and certain angle is preferably 60 jiaos, promptly is 60 contained angles with the horizontal direction. The sensitization structure is formed after the DAS optical fiber surrounds a plurality of circles, and straight lines are still reserved at the rest parts of the DAS optical fiber. The DAS optical fibers are arranged in parallel at intervals, and the sensitization structures on different DAS optical fibers are staggered, so that the interval of sensitization data is smaller, and the data with smaller interval is obtained.

Form the sensitization structure through the mode of coiling lopping, the sensitivity and the SNR of DAS optic fibre can effectively be promoted to the sensitization structure, can effectively realize the response to weak reflection signal. The distance between two adjacent sensitization structures forms the track spacing, and the sensitization structures can be made to be small (for example, less than 1 m), so that the marine seismic streamer of the embodiment can realize the small track spacing, namely, the exploration of the small track spacing can be realized.

Wherein, the float not only can connect into a DAS optic fibre with many DAS optic fibres, but also plays the fixed action to DAS optic fibre, avoids dragging the optic fibre in-process and causes DAS optic fibre position change, and then influences data acquisition.

The DAS optical fiber has smaller tensile force due to the material, so that the two sides of the DAS optical fiber are respectively provided with one tensile cable, and the damage of the DAS optical fiber caused by overlarge tensile force in the dragging process can be effectively reduced.

The sheath is filled with filler, and the filler is used for wrapping the DAS optical fibers to prevent the DAS optical fibers from being pulled randomly to cause the DAS optical fibers to be pulled apart. Due to the action of the filler, the DAS is difficult to drag under normal conditions, so that the DAS is not easily broken and pulled out of the sheath, and the use stability of the whole marine seismic streamer is ensured. The filler not only protects the DAS optical fiber, but also can reduce noise in the dragging process and realize zero buoyancy.

The filling material is preferably kerosene or polyurethane gel or a mixture of kerosene and polyurethane gel, and the specific gravity of the filling material can be adjusted according to actual needs.

The sheath is made of rubber (namely the rubber in figures 1 and 2) and is hollow, namely a cavity structure is arranged in the sheath, the pull-up cable, the floater and the DAS optical fiber are all arranged in the cavity, and the pull-up cable is respectively arranged on the upper side wall and the lower side wall of the cavity.

The sensitization fiber in fig. 1 and 2 is referred to as DAS fiber.

The embodiments disclosed in this description are only an exemplification of the single-sided features of the invention, and the scope of protection of the invention is not limited to these embodiments, and any other functionally equivalent embodiments fall within the scope of the invention. It will be apparent to those skilled in the art that other various changes and modifications can be made based on the above-described technical solutions and concepts, and all such changes and modifications should fall within the scope of the present invention.

Claims

1. A marine seismic streamer based on DAS optical fibers is characterized by comprising a sheath, and a pull-in cable, a plurality of floats and a plurality of DAS optical fibers which are arranged in the sheath, wherein at least two pull-in cables are arranged in parallel in the axial direction of the sheath in an extending mode, the two pull-in cables are respectively arranged on two sides of the sheath, the floats are arranged in the radial direction of the sheath, two ends of each float are respectively fixed on the two pull-in cables on the two sides, the floats are distributed and arranged in an axially spaced mode along the sheath, each DAS optical fiber extends in parallel in the axial direction of the sheath and is located between the two pull-in cables, the DAS optical fibers sequentially penetrate through each float in the sheath and,

all be provided with the sensitization structure along DAS optic fibre axial direction interval on every DAS optic fibre, the sensitization structure obtains with certain angle winding through the relevant position on the DAS optic fibre, and the straight line still remains in the other positions of DAS optic fibre, and the parallel interval of each DAS optic fibre sets up and the sensitization structure on the different DAS optic fibre staggers each other to prevent that the sensitization structure on the different DAS optic fibre is on a straight line in the vertical direction.

2. The DAS fiber based streamer of claim 1, wherein the certain angle is a 60 ° angle.

3. The DAS optical fiber based streamer of claim 1, wherein each of the floats is disposed axially along the jacket at equal intervals.

4. The DAS optical fiber based streamer of claim 1, wherein the sensitising structures are equally spaced.

5. The DAS-based marine seismic streamer of claim 1, wherein the jacket is further filled with filler material that surrounds the DAS fibers to provide zero buoyancy to the streamer while protecting the DAS fiber sensors.

6. The DAS-based fiber optic streamer of claim 5, wherein the filler is kerosene or polyurethane gel, or a mixture of kerosene and polyurethane gel.

7. The DAS-fiber based streamer of claim 1, wherein the sheath is made of rubber and the sheath is hollow.

8. The DAS optical fiber-based streamer of claim 1, wherein the floats are of perforated cylindrical or elliptical cylindrical configuration.