Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
  • H04B10/27—Arrangements for networking
  • H04B10/272—Star-type networks or tree-type networks

Definitions

• This invention relates to apparatus for providing communication between wells and a platform in a hydrocarbon extraction system.
• platform is intended to include all types of hydrocarbon collection facilities, such as offshore oil and gas installations, ships and other sea vessels, as well as land based oil and gas installations.
• wells is intended to include both subsea and subterranean oil and gas wells.
• optical communications apparatus on the vessel and similar apparatus associated with each well via optical fibres included in an umbilical.
• An optical fibre is provided for each well, to permit independent communication between the respective wells and the vessel.
• the umbilical also provides all other essential services between the vessel and the wells, the inclusion of optical fibres for communication increases the cost and complexity of the umbilical.
• the invention provides communications apparatus arranged to provide communication between a plurality of locations, one of which comprises a platform and the others of which comprise wells, the apparatus comprising a plurality of optical communication units associated with respective locations, each unit comprising an optical transmitter and an optical receiver connected in duplex operation, the apparatus further comprising at least one optical amplifier and an optical fibre arrangement in communication with the units, the fibre arrangement including a common optical fibre for the units.
• an optical amplifier permits the communications system to work in conjunction with a single common optical fibre; the amplifier compensates for losses which would be encountered with providing communications to a number of separate locations via a common fibre.
• the umbilical need only accommodate one optical fibre.
• optical transmitter is intended to include any type of optoelectronic device capable of generating an optical signal representing an electrical signal.
• optical receiver is intended to any type of optoelectronic device capable of generating an electrical signal representing a light signal.
• optical is intended to include radiation at the infra-red and ultra violet ends of the spectrum, as well as visible light.
• the invention allows multiplex communications between a platform and wells to be carried out.
• the multiplexing may be either in the frequency domain or in the time domain, or in a combination of both.
• Figure 1 is a schematic drawing of a subsea well system
• FIG. 2 is a schematic diagram of a communications system constructed according to a
• FIG. 3 is a schematic diagram of a communications system constructed according to a second embodiment of the invention.
• Figure 4 is a schematic diagram of a communications system constructed according to a third embodiment of the invention.
• Figure 5 is a schematic diagram of a communications system constructed according to a fourth embodiment of the invention.
• FIG. 1 illustrates a subsea well system, comprising a plurality of wells, the heads 1, 2, 3 of which are shown in this drawing.
• a sea vessel 4 is in communication with the well heads 1 to 3 by means of a so-called umbilical 5.
• the umbilical carries a variety of feeds, including electrical power and signals, hydraulic power and fibre optic cables, and is thus an expensive and bulky item.
• the umbilical terminates at a subsea manifold system 6, located on or near the seabed in proximity to the well heads 1 to 3.
• a multiservice connector 7 provides the interface between the umbilical 5 and the subsea manifold 6.
• the multi-service connector 7 is a both complex and expensive item as it has to operate reliably at considerable sea depths.
• Equipment on the vessel 4 needs to communicate with equipment located in the wells, and vice versa, and to this end a communication system is provided, such as that illustrated in Figure 2.
• the box indicated generally by the reference numeral 8 is intended to represent equipment located on the vessel 4. Similar equipment is shown in boxes 9, 10 and 1 1 in this drawing, and these are intended to represent equipment associated with the well heads 1 to 3 respectively. Some equipment is included in the manifold system 6, and this equipment is shown in the box indicated generally by the reference numeral 12.
• Each of the boxes 8 to 1 1 includes an optical communications unit comprising an optical transmitter 13-16, arranged to produce a modulated light signal representative of an electrical quantity, and an optical receiver 17-20 arranged to detect optical signals and generate corresponding electrical signals.
• the transmitter and receiver of each of the units 8 to 11 is connected via respective duplexers 21-24.
• Each duplexer 21-24 ensures that light emerging from the transmitter is dii cted into an optical fibre emerging from the unit, and not back into the receiver. Similarly, the duplexer also ensures that incoming light signals are directed to the leceiver only. In practice, however, it has been found that there is usually leakage of light into the unwanted direction.
• communication is made between the optical communications units 9 to 1 1 associated with the wells and the unit 8 associated with the platform by means of a fibre optic arrangement which includes a common optical fibre 25.
• the common fibre extends from the unit 8 on the platform to the subsea manifold 6. Inside the manifold 6, the common fibre 25 encounters a series of optical splitters 26 to 28. Taking the case of a time multiplexed system, the splitters are arranged to direct a portion of light transmitted through the fibre into optical fibres 29, 30, 31 associated with the units 9, 10 and 1 1 respectively.
• partially silvered mirrors may be employed as splitters.
• Bragg gratings may instead be used.
• each of the units 9 to 1 1 only receives a portion of the light transmitted from the optical transmitter 13 located in the unit 8. Normally, this reduction in optical power would be prohibitive.
• optical amplifiers 32, 33 and 34 are provided in order to amplify the light signal immediately before it is received by the respective optical receiver 14, 15, 16. The insertion of an optical amplifier effectively increases the sensitivity of each receiver.
• the splitters are chosen so that substantially the same proportion of the initially transmitted light is directed to each receiver.
• identical splitters are likely to be used for cost reasons, with the result that the receivers receive different light levels.
• the light is split according to frequency, so that almost all of the light at a particular frequency can be directed to the appropriate receiver.
• Information relating to the wells is relayed to the transmitters 18, 19 and 20 for communication in different time periods, or at different frequencies, to the platform.
• Optical signals transmitted by transmitter 18 emerge from the duplexer 22 and travel along fibre 29. The signals are then directed into the common fibre 25 by means of the splitter 26, for transmission to the receiver 17 located in the unit 8.
• light signals from transmitter 19 emerge from the duplexer 23 and travel through fibre 30 and splitter 27. Here they are redirected into fibre 25', for transmission to the unit 8 via the splitter 26 and common fibre 25.
• light signals from transmitter 20 are directed to the receiver 17 by means of the duplexer 24, fibre 31, splitter 28, fibre 25", splitter 27, fibre 25', splitter 26 and common fibre 25.
• an optical amplifier is also provided in the unit 8, in order to amplify the incoming light signal immediately before it is received by the optical receiver 17.
• FIG. 3 An alternative arrangement of the invention is shown in Figure 3.
• the optical amplifiers 32, 33 and 34 have been omitted, but instead there is a second optical amplifier 36 located in the unit 8.
• the optical amplifier is inserted in the path of the optical transmitter 13, and serves to amplify the outgoing light signal from the platform, in order to compensate for losses caused by the splitters 26, 27, 28 and the duplexers 22, 23, 24.
• the advantage of this configuration is that there is generally more electrical power available at the platform end of the system than at the well heads or down hole.
• FIG. 4 A further alternative embodiment of the invention is illustrated in Figure 4.
• the fibre optic arrangement is arranged in a tree-like configuration. Light is transmitted from the unit 8 into the common optical fibre 25. At the first splitter 37, which is encountered in the manifold, the light signal is split into two equal portions.
• the light signals emerging from the two branches of the splitter are, in turn, input to two subsequent splitters 38, 39 via respective optical fibres 40, 41. These splitters also split the light into two equal portions which find their way into the optical units 9, 10, 11
• the light signals are then directed by the duplexers 22, 23, 24, 47 into optical amplifiers 32, 33, 34 and 48 respectively for reception by the receivers 14, 15, 16, 49.
• Figure 5 illustrates an alternative arrangement of the apparatus of Figure 4, in which the optical amplifiers 32, 33, 34, 48 associated with the units 9, 10, 1 1 and 42 are omitted. Instead, a second optical amplifier 36 is included in the unit 8 on the platform, just as in the Figure 3 embodiment of the invention.
• the invention enables data communication to be carried out via a single fibre optic cable in the umbilical, thus reducing the complexity of the umbilical and the connector to the subsea manifold. The result is a substantial reduction in the cost of the umbilical and the connector, as well as reduced testing time.

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• Engineering & Computer Science (AREA)
• Computing Systems (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Optical Communication System (AREA)

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• 2000
  • 2000-04-20 GB GB0009661A patent/GB2361597A/en not_active Withdrawn
• 2001
  • 2001-02-26 WO PCT/GB2001/000812 patent/WO2001081725A1/en not_active Application Discontinuation
  • 2001-02-26 EP EP01906010A patent/EP1200710A1/en not_active Withdrawn
  • 2001-02-26 AU AU33968/01A patent/AU3396801A/en not_active Abandoned
  • 2001-12-19 NO NO20016250A patent/NO20016250L/no not_active Application Discontinuation

Non-Patent Citations (1)

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