WO2002041328A1

WO2002041328A1 - Improved downhole cable

Info

Publication number: WO2002041328A1
Application number: PCT/GB2001/004655
Authority: WO
Inventors: Andrew Richards
Original assignee: Expro North Sea Limited
Priority date: 2000-11-18
Filing date: 2001-10-17
Publication date: 2002-05-23
Also published as: AU2001295750A1; GB0028220D0

Abstract

A cable for use in remote sensing applications is disclosed which comprises in a preferred arrangement a first electrically conductive conduit (12), a second electrically conductive conduit (14) disposed within the first conduit (12), first signal carrying means (10) disposed within the second conduit (14) and second signal carrying means (18) disposed within the second conduit (14) parallel with said first signal carrying means (10), the second signal carrying means (18) comprising at least two electrical conductors. Other embodiments and aspects of the invention are disclosed.

Description

IMPROVED DOW HOLΞ CABLE

The present invention relates to a cable for supplying power particularly, but not exclusively, to a cable for, and method of, supplying power to components used for remote sensing in downhole wells. Remote sensing is increasingly being used in a number of applications, especially in the oil and gas production industry. Traditionally this has been carried out using an electronic sensor communicating via an electrical cable using industry standard or proprietary communication protocol. Increasingly, remote sensing is being undertaken using optical sensors with communication via an optical fibre. The remote location may be within a hostile environment, for example an oil/gas well or petrochemical process and may comprise high temperatures, high pressure, a hostile fluid environment or any combination of these. In order to protect the optical fibre or electrical signal conductor from the hostile environment the optical fibre or electrical signal conductor is often placed within one or two protective conduits. Furthermore, in arrangements such as these it is sometimes necessary to supply power to the sensing point to operate equipment at the remote location.

An object of the present invention is to obviate or mitigate at least one of the aforementioned problems. This is achieved by providing a cable for use in remote sensing applications, said cable comprising: an outer electrically conductive conduit of a first diameter, an inner electrically conductive conduit of a smaller diameter than the first diameter so that said inner conduit is disposed within said outer conduit; insulating means disposed between an inner surface of the outer conduit and an outer surface of the inner conduit; first signal carrying means disposed within said inner conduit for carrying a sensor signal; the inner conduit and outer conduit being electrically coupled so that electrical power is transmissible along said cable.

Preferably, a second signal carrying means is disposed within said inner conduit parallel with said first signal means for carrying monitoring or low power signals. Preferably, the first signal carrying means comprises a fibre optic conductor for conducting optical signals therealong.

Alternatively, the first signal carrying means comprises at least one electrical conductor.

Preferably, the second signal carrying means comprises at least two sheathed electrical conductors. Furthermore, the at least two sheathed electrical conductors are twisted. Conveniently, the outer electrically conductive conduit is the earth return for the electrical power.

Preferably, insulating means is a polymer. A method of providing an electrical power supply to a remote sensing location in a cable having a first electrically conductive conduit, a second electrically conductive conduit disposed within the first electrically conductive conduit and a signal carrying means disposed within the second electrically conductive conduit, said method comprising the steps of : supplying power between the first and second electrically conductive conduits, and monitoring signals by said signal carrying means . According to another aspect of the present invention there is provided a cable for use in remote sensing applications comprising : an outer electrically conductive conduit of a first diameter, an inner electrically conductive conduit of a smaller diameter than the first diameter so that said inner conduit is disposed within said outer conduit, insulating means disposed between an inner surface of the outer conduit and an outer surface of the inner conduit, first signal carrying means disposed within said inner ⁾ to l-¹ Π o σι o σ. o Π

embodiment of the present invention, and

Fig. 3 shows a view similar to Fig. 1 of a third embodiment of the present invention.

Reference is first made to Fig. 1 of the drawings which depicts a cable comprising an metal conductive conduit 12 of a first diameter within which is disposed an inner metal conduit 14 of a smaller diameter than the first diameter. The inner conduit 14 and outer conduit 12 are electrically coupled so that electrical power is transmissible along said cable. Insulating means 16 are disposed between the inner conduit 14 and outer conduit 12, the insulating means may be, for example Teflon (trademark) . A first signal carrying means 10, for example a fibre optic, is disposed within the inner metal conduit 14. This signal carrying means 10 communicates information from the remote sensing location. Ideally, the outer conduit 12 acts as an earth return for electrical power. It is noted that the inner conduit 14 and outer conduit 12 continue to act as protection for the signal carrying means 10 from the hostile environment .

With reference to Fig. 2 of the drawings, a second signal carrying means 18 is disposed within inner conduit 14 parallel with said first signal carrying means 10. The second signal carrying means 18 comprises at least two sheathed electrical conductors, they may be twisted together. Again, the inner conduit 14 and outer conduit 12 are electrically coupled so that power is transmissible along said cable. The second signal carrying means 18 acts as a monitoring system and can monitor the power being supplied across the inner conduit 14 and outer conduit 12.

With reference to Fig. 3 of the drawings, the at least two sheathed electrical conductors of second signal carrying means 18 are electrically coupled and transmit low electrical power to the remote location. In this embodiment, inner conduit 14 and outer conduit 12 can act as a monitoring system, in particular monitoring the power supplied across the second signal carrying means 18. Various modifications may be made to the embodiments hereinbefore described without departing from the scope of the invention. For example, the outer electrically conductive conduit 12 and inner electrically conductive conduit 14 may be made of a conductive polymer or a polymer with a conductive coating metal. Alternatively, for high power applications, the inner electrically conductive conduit 14 may be made of copper. Additionally, the inner electrically conductive conduit 14 may be coated with an insulator, for example Teflon.

Claims

1. A cable for use in remote sensing applications, said cable comprising: an outer electrically conductive conduit of a first diameter, an inner electrically conductive conduit of a smaller diameter than the first diameter so that said inner conduit is disposed within said outer conduit ; insulating means disposed between an inner surface of the outer conduit and an outer surface of the inner conduit ; first signal carrying means disposed within said inner conduit for carrying a sensor signal; the inner conduit and outer conduit being electrically coupled so that electrical power is transmissible along said cable.

2. The cable of claim 1, wherein a second signal carrying means is disposed within said inner conduit parallel with said first signal means for carrying monitoring or low power signals .

3. The cable of claim 1 or 2 , wherein the first signal carrying means comprises a fibre optic conductor for conducting optical signals therealong.

4. The cable of claim 1 or 2, wherein the first signal carrying means comprises at least one electrical conductor.

5. The cable of claim 2, 3 or 4, wherein the second signal carrying means comprises at least two sheathed electrical conductors.

6. The cable of claim 5, wherein the at least two sheathed electrical conductors are twisted.

7. The cable of any preceding claim, wherein the outer electrically conductive conduit is the earth return for the electrical power.

8. The cable of any preceding claim, wherein insulating means is a polymer.

9. A method of providing an electrical power supply to a remote sensing location in a cable having a first electrically conductive conduit, a second electrically- conductive conduit disposed within the first electrically conductive conduit and a signal carrying means disposed within the second electrically conductive conduit, said method comprising the steps of : supplying power between the first and second electrically conductive conduits, and monitoring signals by said signal carrying means .

10. A cable for use in remote sensing applications comprising : an outer electrically conductive conduit of a first diameter, an inner electrically conductive conduit of a smaller diameter than the first diameter so that said inner conduit is disposed within said outer conduit, insulating means disposed between an inner surface of the outer conduit and an outer surface of the inner conduit, first signal carrying means disposed within said inner conduit for carrying a sensor signal, second signal carrying means disposed within said inner conduit parallel with said first signal carrying means, the second signal carrying means comprising at least two electrical conductors wherein said second signal carrying means is coupled so that electrical power is transmissible along said second signal carrying means.

11. The cable of claim 10, wherein the outer electrically conductive conduit and inner electrically conductive conduit are arranged for carrying monitoring signals .

12. The cable of claim 10 or 11, wherein the first signal carrying means comprises a fibre optic conductor for conducting optical signals therealong.

13. The cable of claim 10 or 11, wherein the first signal carrying means comprises at least on electrical conductor.

14. The cable of any one of claims 10 to 13, wherein said insulating means is a polymer.

15. A method of providing an electrical power supply to H o Lπ