Apparatus and Method for Laying Down, Abandoning, and Recovering a Pipe on the Sea Floor
First Claim
1. A method of positioning on a sea floor, from a floating vessel, a last end portion of a pipe that is being laid on the sea floor, comprising the steps of:
- lowering the last end portion of the pipe from a first lowering/raising device on the vessel to a depth in the sea that is less than the depth of the sea floor;
transferring a load of the pipe to a second lowering/raising device on the vessel having a relatively lower capacity than the first lowering device; and
lowering the last end portion of the pipe from the lower capacity second lowering/raising device to the sea floor.
3 Assignments
0 Petitions
Accused Products
Abstract
Disclosed are a method and apparatus for laying down, abandoning and/or recovering a pipe on the sea floor. During lay-down and abandonment, the pipe is lowered by a high capacity winch to an intermediate depth, at which the loading exerted by the pipe has dropped to within the rated capacity of a low capacity winch, to which the loading is then transferred. The high capacity winch line is then recovered to the attendant vessel and the pipe lowered to the sea floor using the low capacity winch. Pipe recovery is essentially a reversal of the above procedure. In this way, the length of the line of the high capacity winch is considerably reduced, which reduces the winch size and hence cost.
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Citations
38 Claims
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1. A method of positioning on a sea floor, from a floating vessel, a last end portion of a pipe that is being laid on the sea floor, comprising the steps of:
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lowering the last end portion of the pipe from a first lowering/raising device on the vessel to a depth in the sea that is less than the depth of the sea floor;
transferring a load of the pipe to a second lowering/raising device on the vessel having a relatively lower capacity than the first lowering device; and
lowering the last end portion of the pipe from the lower capacity second lowering/raising device to the sea floor. - View Dependent Claims (2, 3, 4, 5, 6, 32)
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7. A method of recovering from a floating vessel a pipe lying on a sea floor, comprising the steps of:
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raising a last end portion of the pipe from the sea floor to a depth less than a depth of the sea floor, using a second lowering/raising device;
transferring a load of the pipe to a first lowering/raising device on the vessel having a higher capacity than the second lowering/raising device; and
raising the last end portion of the pipe to the vessel, using the higher capacity first lowering/raising device. - View Dependent Claims (8, 9, 10, 11, 33)
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12. Apparatus for recovering a pipe from or lowering a pipe towards a sea floor from a floating vessel, comprising:
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a first lowering/raising device configured to be mounted on the vessel;
a second lowering/raising device configured to be mounted on the vessel, the second lowering/raising device having a lower capacity than the first lowering/raising device; and
a connector body having thereon a first connector configured for releasable connection to a last end portion of the pipe, a second connector configured for releasable connection to the higher capacity first lowering/raising device, and a third connector configured for releasable connection to the lower capacity second lowering/raising device. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 34, 35, 36, 37)
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- 21. Apparatus according to claim 21, including respective friction devices configured to prevent the first, second, and third, pivotally mounted, connectors from hanging down under gravity in an uncontrolled manner, and wherein the arrangement being such that when the apparatus is under load, the loading overcomes pivotal friction forces of the friction devices and the connector body tilts to balance the loading.
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23. Apparatus for positioning on a sea floor, from a floating vessel, a last end portion of a pipe that is being laid on the sea floor, the apparatus comprising:
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a connector body;
a first connector on the connector body configured to releasably connect to a last end portion of the pipe;
a second connector on the connector body configured to releasably connect to a first lowering/raising device mounted on the vessel; and
a third connector on the connector body configured to releasably connect to a second lowering/raising device mounted on the floatable vessel, the second lowering/raising device having a lower capacity than the first lowering/raising device. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 38)
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Specification