Abstract:
A method of installing a cable between a topside location of an underwater well installation and an underwater location of the installation is provided. The method comprises inserting an end of the cable into a passageway between the locations and using a fluid passed along the passageway to displace the cable along the passageway so that it extends between the locations.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    Embodiments of the present invention relate to installing a cable in an underwater well installation. 
         [0003]    2. Description of the Prior Art 
         [0004]    In subsea hydrocarbon well installations, umbilicals transmit power and fluid from a surface platform to a subsea fluid production facility. They typically have redundant or spare conduits for chemical and hydraulic control lines within them, originally intended for back-up purposes. 
         [0005]    Over time, the insulation around the copper cores of electrical cables in the umbilical may degrade, for example through water ingress or chemical degradation. The cores themselves may also degrade, typically through corrosion. Such degradation may result in a reduction in the electrical capacity of the cores so that inadequate power is available to the well installation which is then unable to function adequately. An alternative possibility is to update the well installation with additional facilities requiring additional power which is not available with the existing power distribution system. Currently, the only solution to these problems is to replace the umbilical, which is very expensive, although an alternative solution is taught in UK Patent Application No. 0921858.7. 
         [0006]    U.S. Pat. No. 5,871,052 relates to downhole tool deployment techniques using mud pumping techniques and U.S. Pat. No. 5,967,816 relates to a female wet connector for use in such techniques. 
       SUMMARY OF THE INVENTION 
       [0007]    According to one embodiment of the present invention, there is provided a method of installing a cable between a topside location of an underwater well installation and an underwater location of the installation, the method comprising inserting an end of the cable into a passageway between the locations and using a fluid passed along the passageway to displace the cable along the passageway so that it extends between said locations. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  shows schematically the topside end of a subsea hydrocarbon well installation; 
           [0009]      FIG. 2  shows schematically the subsea end of the installation; 
           [0010]      FIG. 3  is a detailed view of part of what is shown in  FIG. 1 ; 
           [0011]      FIG. 4  is a detailed view of part of what is shown in  FIG. 2 ; and 
           [0012]      FIG. 5  shows schematically an alternative to what is shown in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    In the following embodiments, an insulated cable is “pumped down” a spare, back-up or in-use chemical or hydraulic control line conduit. The cable may have one, two (for a return path) or more cores and can be used to transmit electric power and/or data to and/or from a subsea production facility. A fibre-optic cable could also be in the cable to provide a replacement, or additional, communication link. The embodiments allow additional electric power and/or communications capability to a “Brownfield” site, or provide for additional electrical and/or communication facilities to an updated fluid production facility. 
         [0014]    Referring first to  FIG. 1 , at the surface of a subsea hydrocarbon well installation, a multiplicity of gas and/or fluid and/or chemical supply conduits  1 ,  2  and  3  (three shown as an example only) and power and/or communication cables (not shown) within an umbilical  4  are terminated with connectors  5 . The connectors  5  are coupled with connectors  6  via respective ones of upper ducts  8 , which may be rigid ducts. Connectors  6  themselves mate with respective ones of connectors  61  at a topside umbilical termination unit (TUTU)  7 . 
         [0015]    Conduit  3  (which could, for example, be a spare or unused conduit in the umbilical  4 ) is chosen to receive a “pumped down” replacement or supplemental cable  9 . For the chosen conduit  3 , the respective duct  8  forms part of a “side-entry” sub-assembly  10 , which includes an arrangement  11  at duct  8  of conduit  3  that allows the cable  9  to enter but not fluid to escape. Fluid (either the normal fluid for conduit  3  or a special inert fluid if conduit  3  is a spare or unused conduit) is then pumped down the conduit  3  from the duct  8  of sub-assembly  10  in the direction of arrow  12 , towards a subsea facility, to carry cable  9  with it. A swab cup  13  is placed towards the end of cable  9  to help in this process. The cable  9  could comprise at least one electrical conductor for power and/or communications or it could comprise at least one fibre optic line for communication purposes or it could comprise at least one electrical conductor for power and/or communications and at least one fibre optic line. The cable  9  is terminated with a wet mateable connector  14  suitable for the function or functions of cable  9 . The swab cup  13  may be omitted if connector  14  is itself sufficient to assist in the “pumping down” of cable  9 . 
         [0016]    It should be noted that the sub-assembly  10  (which also comprises the rest of the ducts  8  and all the connectors  6 ) is effectively an extension of the umbilical  4  and its connectors  5  (which would otherwise mate with connectors  6 ) and is installed for the purpose of providing a side entry for inserting a cable, typically to extend the life of a “Brownfield” well. It should also be noted that the umbilical  4  in the Figures is not to scale and is exaggerated in size compared to the sub-assembly  10  and TUTU  7 . 
         [0017]    Although in this embodiment spare or disused conduit  3  within the umbilical  4  is used, if the size of the cable  9  and its swab cup  13  and connector  14  are small enough compared with the diameter of the conduit  3 , then it could be a conduit which continues to be used for its normal function. Thus, pumping fluid down the conduit to transport the replacement or supplemental cable  9  may be part of normal operations or could be performed specifically for this task. 
         [0018]    As shown diagrammatically in  FIG. 2 , an exit sub-assembly  15  is placed between the subsea end of the umbilical  4  and a subsea umbilical termination unit (SUTU)  16 . The sub-assembly  15  comprises, for each of connectors  17  at the subsea ends of the conduits in the umbilical  4  except conduit  3  used for “pumping down” the cable, a lower duct  18  (which may be rigid) terminating in a connector  19  which mates with a respective connector  191  of the SUTU  16 . Also, the sub-assembly  15  comprises a lower duct  20  (which may be rigid) extending from the connector  17  of conduit  3  for expelling fluid from conduit  3  to the surrounding water and carrying at its lower end a wet mateable connector  21  providing connection to an external cable  22  to feed subsea devices such as at least one subsea control module (SCM). The wet mateable connector  21  allows fluid past it both before and after being mated with the connector  14 . 
         [0019]    The mode of operation for installing cable  9  in the conduit  3  within the umbilical  4  is as follows.  FIGS. 3 and 4  show details of the topside side-entry and subsea cable exit arrangements. Before the side entry sub-assembly  10  is installed between the umbilical  4  and the TUTU  7 , the cable  9  without swab cup  13  or the connector  14  is inserted through a sealing clamp  23  of arrangement  11  so that it protrudes through a connector port of the side-entry sub-assembly  10 . The swab cup  13  and the connector  14  are then assembled on the cable  9 . The clamp  23 , which is around a packer  24  for example of felt or a synthetic material, is then tightened sufficiently to allow sliding of the cable  9 , yet provide a good seal resulting from the saturation of the material comprising the packer  24  with grease injected via a grease point  25 . The sub-assembly  10  is then fitted between the umbilical  4  and the TUTU  7 . 
         [0020]    The subsea side-exit assembly  15  is installed by a remotely operated vehicle. With fluid flow through the conduit  3 , the cable  9  is “pumped down” and the connector  14  is aligned with the mating connector  21  by a centraliser  26  for guiding the cable  9  and connector  21 , located just above the connector  21  in the side-exit sub-assembly  15 . There could be at least one farther such centraliser above centraliser  26  in the passageway comprising duct  8 , conduit  3  and duct  20 . The connector  14  carries a cylinder of spring fingers which clamp it to a spigot  27  on the connector  21  to lock them together. The configuration of the side-exit sub-assembly  15  shown allows venting of the pumped down fluid to the sea or its recovery. Alternatively, it can be configured to connect to the SUTU  16  to allow continued use of the conduit  3  for fluid flow, as shown by  FIG. 5 . Other arrangements include the venting of the pumped down fluid during installation of the cable  9  and then closing the vent to allow continued use of the conduit for fluid flow. If multiple spare fluid conduits are free, then the side-exit assembly  15  can be configured to route the flow from the conduit carrying the cable  9  hack up another fluid conduit to the surface. This flow path may then be closed (during the wet mating of connector  14  with connector  21 ) to allow future use of the second fluid conduit. Thus, the side-exit assembly  15  provides electrical and/or optical break-outs from the wet mated connection to traditional jumpers for connection to an SCM or other device requiring power and/or communication. 
         [0021]    The side-entry and side-exit sub-assemblies may be for a single use or can be permanently in an installation or can be releasable and deployed for occasional operations. For example, the connector  14  could be latched and locked on to connector  21  and spigot  27  for a permanent installation or include the ability to de-latch it if the operator wants to remove it. De-latching could be achieved by applying tension from the topside, although an operator could just remove the subsea side exit assembly  15  and cut the cable  9 . 
         [0022]    In one embodiment of the present invention a supplemental or replacement cable may be “pumped up” from a subsea location to a topside location using production fluid. 
         [0023]    In a further embodiment of the present invention, a cable may be “pumped down” via a passageway which comprises a line separate from the umbilical and carrying a fluid, such as a chemical or water and/or gas injection line. 
         [0024]    Embodiments of the present invention enable the avoidance of replacing a degraded umbilical for power and/or communication. Embodiments of the present invention also enable an increase in the amount of power available at an installation through an additional cable (field expansion or new equipment). Embodiments of the present invention further enable a second communication path for additional equipment.