GB2463239A

GB2463239A - Subsea parking device

Info

Publication number: GB2463239A
Application number: GB0816034A
Authority: GB
Inventors: Paul Roberts
Original assignee: Viper Subsea Ltd
Current assignee: Viper Subsea Ltd
Priority date: 2008-09-03
Filing date: 2008-09-03
Publication date: 2010-03-10
Anticipated expiration: 2028-09-03
Also published as: GB2463239B; GB0816034D0

Abstract

A subsea parking device comprises a support 30 carrying at least one parking formation 40, the support 30 being shaped so as to permit it to be lowered over a subsea distribution unit 12 so as to locate the parking formation 40 adjacent a connector and/or stabplate receiving portion 14 of the subsea distribution unit 12. The parking device is preferably open topped to allow the subsea distribution unit 12 to be lifted through the opening. The support 30 may also include a sacrificial anode so that the device provides cathodic protection for the connectors and/or stabplates.

Description

Subsea Parking Device This invention relates to a parking device for use in subsea applications, to permit the temporary anchorage and protection of the connectors associated with cables and/or hoses whilst the devices to which the connectors are usually mounted are removed for service and/or replacement.

It is commonplace in the field of subsea oil, natural gas or other fluid extraction to use control equipment to control the flow of fluids from subsea wells. Often, the control equipment is located at the seabed. The control equipment is connected to surface or other remotely located equipment via an umbilical comprising a plurality of cables and/or hoses, a subsea distribution unit being provided at the subsea end of the umbilical to distribute hydraulic, chemical and/or electrical power to the control equipment, and to permit the transmission of control signals between the surface or other remotely located equipment and the subsea control equipment. The distribution unit is typically located at the seabed, for example being located upon a foundation structure provided on the seabed.

Depending upon the layout of the subsea system, the subsea distribution unit may take a range of forms, for example it may comprise an hydraulic distribution unit, a chemical distribution unit, an electrical distribution unit, an electro-hydraulic distribution unit or a subsea control module. The functionality of two or more such units may be incorporated into a single unit.

The hoses of the umbilical are typically connected to the subsea distribution unit by connectors in the form of multiway couplings known as stabplates. Cables of the umbilical are connected to the subsea distribution unit by means of subsea mateable electrical connectors. Flying leads are provided to permit the onward transmission of hydraulic, chemical and/or electrical power and/or signals between the subsea distribution unit and the control equipment. The flying leads may comprise single or bundled hoses and/or electrical cables, and are connected to the subsea distribution unit using similar stabplates and/or electrical connectors to those of the umbilical.

Usually, the subsea distribution unit is located upon a subsea foundation structure which supports the subsea distribution unit above the sea bed silt in the desired location If the subsea distribution unit needs to be removed for servicing, maintenance or replacement, the various stabplates and connectors need to be disconnected therefrom. The stabplates and connectors which have been disconnected from the subsea distribution unit cannot simply be left to rest upon the sea bed, but rather must be supported above the sea bed silt. Also, internal components of the connectors may require protection from the conosive effects of the surrounding sea water.

It is known to incorporate a series of parking formations into the foundation structure to which the connectors and/or stab plates can be connected when disconnected from the subsea distribution unit to protect the connectors and/or stabplates from such corrosion and avoid having to allow them to lie upon the seabed. Such permanent provision of parking formations is inefficient as, for the majority of the time, they are not in use. The expense of providing a large number of parking formations, most of which are out of use at any given time is inefficient.

Further, it is often necessary to provide the parking formations with covers or caps to protect against the ingress of sea bed silt or other debris, corrosion or calcareous growth during the extended periods when they are not in use. Also, the parking formations need to be installed from the outset, when all other major equipment is being installed, which can have an adverse effect on cash flow.

Another known technique is to use temporary parking formations which are lowered into position only when required, the formations being provided upon a structure which can be lowered into position close to the subsea distribution unit to be removed. When the seabed is suitable, the temporary structure may be free standing. Alternatively, parking formations may be lowered onto the foundation structure and secured in position using a simple pin or socket connection arrangement.

In all of the arrangements described hereinbefore, the connection features of the parking formations are usually located closer to the seabed than the conesponding features of the subsea distribution unit, and this can lead to difficulties in properly securing the stabplates and/or connectors thereto.

It is an object of the invention to provide a subsea parking device in which the above mentioned disadvantages are overcome or are of reduced effect.

According to the present invention there is provided a subsea parking device comprising a support carrying at least one parking formation, the support being shaped so as to permit it to be lowered over a subsea distribution unit so as to locate the parking formation adjacent, preferably at substantially the same height above the seabed as, a connector and/or stabplate receiving portion of the subsea distribution unit.

Such an anangement is advantageous in that it can be lowered into position only when removal of the subsea distribution unit is to take place, thus avoiding the cost of having to permanently install a number of parking plates. Further, the requirement to provide covers or caps for the parking plate is unnecessary. Also, as the parking formation is located, in use, adjacent the connector and/or stabplate receiving portion of the subsea distribution unit, connection of the connector and/or stabplate to the parking formation after disconnection from the subsea distribution unit is a relatively simple task, compared to the situation where the parking formation is located at a level closer to the seabed. Minimal relocation or disruption of the associated hoses and/or cables is required.

Preferably, the foundation structure upon which the subsea distribution unit is located is provided with a plurality of locating pins receivable within corresponding locating recesses or formations provided in the support, for example in the legs thereof. A latch mechanism may be provided to permit securing of the support in position.

The parking formation is preferably angled relative to the adjacent stabplate and/or connector receiving portion of the associated subsea distribution unit, again to minimise disruption to cables and/or hoses.

The support preferably includes at least one grab rail or the like.

The support is designed to be of open topped form so that, once the hoses and/or cables have been disconnected from the subsea distribution unit, the unit can be lifted through the open top of the support. The support is preferably of ramped form, adjacent the open top thereof, so as to act as a funnel, guiding a subsea distribution unit being lowered into position to the conect location.

The invention will further be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an illustration of a subsea distribution unit mounted upon a typical foundation structure incorporating permanently located parking formations; and Figure 2 is a view similar to Figure 1, but illustrating the use of a subsea parking device in accordance with one embodiment of the invention.

Referring to Figure 1 there is illustrated a typical subsea distribution unit installation which comprises a subsea foundation structure 10 permanently installed in position on the seabed. The foundation structure 10 is designed to permit a subsea distribution unit (SDU) 12 to be secured thereto and, for this purpose, includes mounting formations (not shown) cooperable with corresponding formations provided on the SDU 12 to locate and secure the SDU 12 in position. The SDU 12 includes a number of connectors 14 to which stabplates or other connectors 16 provided on hoses and/or cables 18 can be connected. Some of the hoses and/or cables 18 may form part of an umbilical whereby the SDU 12 is connected to surface or other remotely located equipment. Other of the hoses and/or cables 18 may comprise flying leads connected to other subsea located control equipment.

The nature of the hoses and/or cables 18 will depend upon their function and the nature of the SDU 12 and the subsea located control equipment. For example, the SDU 12 may comprise a hydraulic distribution unit, in which case the hoses 18 associated thereby would comprise hydraulic hoses. Alternatively, the SDU 12 may comprise a chemical distribution unit in which case the hoses 18 will be of appropriate design to carry the chemical(s). In a further alternative, the SDU 12 may comprise an electrical distribution unit in which case the cables 18 will comprise electrical cables. Other possibilities are for the SDU 12 to comprise an electro-hydraulic distribution unit or a subsea control module. It will further be appreciated that combinations are possible, in that where hydraulic and/or chemical supply hoses are provided, there may also be a need to provide electrical power cables or cables for transmitting signals to or from the subsea equipment.

The foundation structure 10 includes a support region 20 upon which the SDU 12 is mounted, and the sides of the support region 20 are provided with parking formations 22 of design similar to the connectors 14 so as to permit the stabplates or connectors 16 to be securely fastened thereto, when desired. The nature of the formations 22 is such as to provide a location to which the stabplates or connectors 16 can be secured, not to provide an electrical connection or hydraulic or chemical flow path from the associated hoses or cables 18.

Iii use, if it is determined that the SDU 12 needs to be removed for servicing and/or replacement, the stabplates or connectors 16 are disconnected from the connectors 14 and are secured to the associated formations 22, thereby avoiding having to leave them resting upon the seabed silt, and reducing the risk of contamination and of corrosion. Once this operation has been completed, the SDU 12 can be released from the foundation structure 10 and removed.

As outlined hereinbefore, the permanent provision of the parking formations 22 has adverse cost implications. Further, it is often required to provide covers or caps for the formations 22, when not in use, to reduce or avoid contamination, corrosion or the occunence of calcareous growth. The provision of such covers or caps has additional cost implications.

Figure 2 illustrates an arrangement in accordance with one embodiment of the invention. In the arrangement of Figure 2, an SDU 12 is secured to a foundation structure 10, in a manner similar to that of Figure 1. However, rather than provide permanently installed parking formations 22 on the foundation structure 10, a subsea parking device 30 is use when it is desired to remove the SDU 12.

The subsea parking device 30 comprises a support frame 32 comprising legs 34 depending from an upper, open part 36. The support frame 32 carries a plurality of parking plates 38, each of which is provided with a parking formation 40 similar to the parking formations 22. As shown in Figure 2, each parking plate 38 and associated parking formation 40 is located adjacent a corresponding one of the connectors 14 of the SDU 12, at substantially the same height above the seabed.

Further, each parking formation 40 is angled relative to the plane of the associated connector 14. As a result, the operation of disconnecting each stabplate or connector 16 from the associated connector 14 and securing it to the adjacent parking formation 40 is a relatively simple operation, requiring minimal movement of the stabplate or connector 16 or of the associated cable or hose 18.

The lower end of each leg 34 is provided with a recess or cavity (not shown) adapted to receive a corresponding projection 42 (see Figure 1) to allow the frame 32 to be positively located in position. A latch mechanism (not shown) may be provided to allow securing of the frame 32 in position if desired, thereby reducing the risk of it moving or being knocked out of position.

The upper part 36, as mentioned above, is of open form, thus the upper surface of the SDU 12 is exposed, permitting access to lifting fittings 12a provided thereon.

The size of the opening in the upper part 36 is designed so as to permit the SDU 12 to be lifted through the opening. The upper part 36 is conveniently manufactured from components of tapering shape, or is otherwise shaped to be of inwardly ramped or sloped form so that an SDU 12 being lowered into position is guided through the opening and into the correct position on the foundation structure 10.

Conveniently, grab rails 44 are fitted to the upper part 36 and/or legs 34 of the frame 32 to assist a diver or ROV in his work.

In use, when it is desired to remove the SDU 12, the parking device 30 is lowered into position and, if desired, is secured in position. A diver or remote operated vehicle then removes each stabplate or connector 16 from the associated connector 14 of the SDU 12, withdraws by a small distance, moves sideways, and secures the stabplate or connector 16 to the adjacent parking formation 40. As mentioned hereinbefore, the location of the parking formations 40 adjacent, at substantially the same height as, and angled relative to the associated connector 14 makes this operation relatively simple, requiring minimal disruption to the hoses or cables 18.

Where this operation is performed by an ROy, it may use the grabrails 44 to assist with this work. Likewise, the grabrails 44 may be used by a diver, if desired.

After disconnection and resecuring of the stabplates or connectors 16 in this manner, the SDU 12 can be released from the foundation structure 10 and lifted through the open upper part 36 of the frame 32. A replacement SDU 12 can subsequently be lowered into position and engagement of parts of the SDU 12 with the ramped surfaces of the frame 32 will assist in guiding the SDU 12 to its desired position ready for securing to the foundation structure 10 and for securing of the stabplates or connectors 16 thereto.

It will be appreciated that, by using the parking device of the present invention, the cost of having parking formations permanently installed can be avoided. The provision of covers or caps to reduce corrosion, contamination or calcareous growth can also be avoided. All of the required parking formations required for a particular operation are lowered and retrieved in a single operation, thereby simplifying the task. Another advantage is that the parking device can incorporate a sacrificial anode and thereby provide cathodic protection for the stabplates or connectors 16 connected thereto whilst disconnected from the SDU 12.

A wide range of modifications and alterations may be made to the embodiment or example of the described hereinbefore without departing from the scope of the invention.

Claims

CLAIMS1. A subsea parking device comprising a support carrying at least one parking formation, the support being shaped so as to permit it to be lowered over a subsea distribution unit so as to locate the parking formation adjacent a connector and/or stabplate receiving portion of the subsea distribution unit.
2. A device according to Claim 1, wherein the support is shaped so as to locate the parking formation at substantially the same height above the seabed as the adjacent connector and/or stabplate receiving portion of the subsea distribution unit.
3. A device according to Claim 1 or Claim 2, wherein the parking formation is angled relative to a plane containing the adjacent connector and/or stabplate receiving portion of the subsea distribution unit.
4. A device according to any of the preceding claims, wherein the foundation structure upon which the subsea distribution unit is located is provided with a plurality of locating formations cooperable with corresponding locating formations provided in the support.
5. A device according to Claim 4, further comprising a latch mechanism to permit securing of the support in position.
6. A device according to any of the preceding claims, wherein the support includes at least one grab rail or the like.
7. A device according to any of the preceding claims, wherein the support is designed to be of open topped form so that, once the hoses and/or cables have been disconnected from the subsea distribution unit, the unit can be lifted through the open top of the support.
8. A device according to Claim 7, wherein the support is of ramped or sloping form, adjacent the open top thereof, so as to guide a subsea distribution unit being lowered into position to the colTect location.
9. A device according to any of the preceding claims, wherein the support is provided with a sacrificial anode so that the device provides cathodic protection for connectors and/or stabplates connected thereto.