GB2378758A

GB2378758A - Seismic cable with guiding means for outer armouring elements

Info

Publication number: GB2378758A
Application number: GB0220582A
Authority: GB
Inventors: Anton Marius Knudsen; Joern Wardeberg
Original assignee: Nexans SA
Current assignee: Nexans SA
Priority date: 1998-06-19
Filing date: 1999-06-18
Publication date: 2003-02-19
Anticipated expiration: 2019-06-18
Also published as: GB0220582D0; GB2378758B

Abstract

A seismic cable includes a number of electrical, and possibly optical, power and signal conductors (6-9 figure 1) which positioned centrally and are surrounded by a polymeric sheath (10,11 figure 1) and by a protective outer armouring (12 figure 1). The conductors are arranged to be connected, via sleeve means 18 (see also figures 3, 4), to a number of seismic sensor devices arranged (see 24 figure 5) at intervals along the cable. The protective armouring is preferably stranded about the cable, with the armouring elements, such as wires, being distributed by guiding means 25 (see also figure 3).

Description

A SEISMIC CABLE The present invention relates to seismic cables in general and in particular to seabed laid seismic cables.

Such cables are arranged to be installed in arrays to cover a certain area on the seabed. The seismic cables are designed to detect sound wave signals reflected from subsea oil and gas reservoirs when air guns are detonated in the sea.

The seismic cables include a number of sensor devices which are powered from a surface vessel. The array of seabed seismic cables may also include electronic units for signal processing. The cables therefore also include power conductors for the electronic units and for the sensors, as well as signal conductors for interconnections and transmitting processed signals detected by the sensors to the vessel.

According to a first aspect of the present invention, there is provided a seismic cable including a number of elongate power and signal conductors which are arranged to be interconnected with a number of seismic sensor devices arranged at intervals along the cable outside a polymeric sheath surrounding the conductors, the cable having guiding means on its outer surface for distributing the wires of a protective armouring.

According to a second aspect of the present invention, there is provided a method for manufacturing a seismic cable including a number of elongate power and signal conductors to be interconnected with a number of seismic sensor devices arranged at intervals along the cable, a polymeric sheath surrounding the conductors and a protecting outer armouring, the elements being bundled or stranded with another and surrounded by a sheath,

comprising the steps of removing the sheath along the cable at intervals proposed for the arrangement of the sensor devices, replacing the removed sheath with sleeves having through-holes in the walls of the said sleeves, taking the conductors to be connected with the sensor devices out of the sleeves before the armouring of the cable, and stranding of armouring elements around the polymeric sheath as well as around the sleeves using guiding means on the outer surface of the cable to guide that stranding.

The present invention provides an improved seabed laid seismic cable which can be manufactured in long lengths, which is suitable for installation on the seabed and which can be connected in arrays.

An example of the present invention will now be described in detail with reference to the accompanying drawings, in which: Figure 1 schematically illustrates a cross-section of a cable; Figure 2 illustrates a cross-section of the same cable where a sleeve surrounds the cable core; Figure 3 illustrates a side view of the said sleeve integrated in the cable corresponding to Figure 2; Figure 4 illustrates a side view of the sleeve arranged on the seismic cable, partially in section; and Figures 5 and 6 illustrate the seismic cable with a housing for the sensor elements outside the cable armouring.

In Figure 1-which is not drawn to scale-the sensor cable 1 corresponding to the invention includes power and signal conductors 5 (electrical and/or optical). These conductors 5, which may include pairs 6, quads 7 or other conductor elements 8 and 9, may be

- In accordance with the invention the sensor elements are to be installed outside of the armouring 12. Therefore, this armouring-at the location of the sleeve 15-is covered by a housing 23 (Figures 5,6) within which the sensor devices 24 are integrated. The electrical/optical elements 19 inside the cable core are guided through the outlet 18 of the sleeve 15 and interconnected with the sensor elements 24 inside the housing 23. The housing 23 and the sleeve 15 are interlockable by, for example, screw means 25, and known sealing means 27 (Figure 3) between the individual parts to be connected may be used to avoid any water penetration.

The principles of the invention which have been described in connection with marine seabed laid seismic cables, can also be used in connection with towed seismic cables and on shore seismic cables.

Claims

CLAIMS: 1. A seismic cable including a number of elongate power and signal conductors which are arranged to be interconnected with a number of seismic sensor devices arranged at intervals along the cable outside a polymeric sheath surrounding the conductors, the cable having guiding means on its outer surface for distributing the wires of a protective armouring.
2. A cable according to claim 1, in which the sensor devices are installed in a housing arranged at intervals along the cable outside the armouring.
3. A cable according to claim 1 or 2, in which the polymeric sheath is replaced at intervals along the cable by sleeves surrounding the elements and having outlets for those conductors to be interconnected with the sensor devices installed outside the armouring.
4. A cable according to any of the preceding claims, in which each sleeve consists of two interlockable halves having conical end portions.
5. A cable according to claim 3, in which the sleeves arranged inside the armouring are interconnectable with the corresponding housing arranged outside the armouring.
6. A cable according to claim 5, in which both the sleeve and the corresponding housing are provided with interlockable through-holes for the elements to be

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interconnected with the corresponding sensor devices in the housing.
7. A cable according to any preceding claim in which the guiding means are external studs for distributing the armouring wires on its outer surface.
8. A cable according to any one of claims 3 to 6 wherein the guiding means are external studs on the sleeves.
9. A method for manufacturing a seismic cable including a number of elongate power and signal conductors to be interconnected with a number of seismic sensor devices arranged at intervals along the cable, a polymeric sheath surrounding the conductors and a protecting outer armouring, the elements being bundled or stranded with another and surrounded by a sheath, comprising the steps of removing the sheath along the cable at intervals proposed for the arrangement of the sensor devices; replacing the removed sheath with sleeves having through-holes in the walls of the said sleeves; taking the conductors to be connected with the sensor devices out of the sleeves before the armouring of the cable ; and stranding of armouring elements around the polymeric sheath as well as around the sleeves using guiding means on the outer surface of the cable to guide that stranding.
10. A method according to claim 9, in which the conductors are SZ-stranded with one another.

10. A method according to claim 9, in which the conductors are SZ-stranded with one another.

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Amendments to the claims have been filed as follows CLAIMS:

1. A seismic cable including a number of elongate power and signal conductors which are arranged to be interconnected with a number of seismic sensor devices arranged at intervals along the cable outside a polymeric sheath surrounding the conductors, the cable having guiding means on its outer surface for distributing the wires of a protective armouring.

2. A cable according to claim 1, in which the sensor devices are installed in a housing arranged at intervals along the cable outside the armouring.

3. A cable according to claim 1 or 2, in which the polymeric sheath is replaced at intervals along the cable by sleeves surrounding the conductors and having outlets for those conductors to be interconnected with the sensor devices installed outside the armouring.

4. A cable according to any of the preceding claims, in which each sleeve consists of two interlockable halves having conical end portions.

5. A cable according to claim 3, in which the sleeves arranged inside the armouring are interconnect able with the corresponding housing arranged outside the armouring.

6. A cable according to claim 5, in which both the sleeve and the corresponding housing are provided with interlockable through-holes for the conductors to be

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interconnected with the corresponding sensor devices in the housing.

7. A cable according to any preceding claim in which the guiding means are external studs for distributing the armouring wires on its outer surface.

8. A cable according to any one of claims 3 to 6 wherein the guiding means are external studs on the sleeves.

9. A method for manufacturing a seismic cable including a number of elongate power and signal conductors to be interconnected with a number of seismic sensor devices arranged at intervals along the cable, a polymeric sheath surrounding the conductors and a protecting outer armouring, the conductors being bundled or stranded with another and surrounded by a sheath, comprising the steps of removing the sheath along the cable at intervals proposed for the arrangement of the sensor devices; replacing the removed sheath with sleeves having through-holes in the walls of the said sleeves; taking the conductors to be connected with the sensor devices out of the sleeves before the armouring of the cable; and stranding of armouring conductors around the polymeric sheath as well as around the sleeves using guiding means on the outer surface of the cable to guide that stranding.