Installation of subsea pipelines
AssigneeSubsea 7 (US) LLC
InventorsKarthik Mohan, Ilkay Darilmaz, Khalid Mateen
Life of this patent
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Abstract
A method of installing a subsea pipeline supports at least one elongate pipe stalk at the surface of the sea at a first, relatively shallow-water location by virtue of buoyancy added to the pipe stalk. The pipe stalk is then towed at the surface to a second location that is in deeper water. There, with the pipe stalk supported between leading and trailing towing vessels, at least some of the added buoyancy is removed. This causes the pipe stalk to hang with catenary curvature beneath the surface between the vessels. The catenary-curved pipe stalk hanging between the vessels is then towed to a third location for subsea installation, which may involve upending the pipe stalk before landing a lower end portion of it on the seabed.
Claims16
A method of installing a subsea pipeline comprises:
- at a first location, supporting at least one elongate pipe stalk at a surface of a sea by virtue of buoyancy added to the at least one pipe stalk;
- towing the at least one pipe stalk at the surface to a second location that is in deeper water than the first location;
- removing at least some of the added buoyancy so that the at least one pipe stalk hangs with catenary curvature beneath the surface between leading and trailing towing vessels, wherein the at least some of the added buoyancy is removed progressively from a central portion of the at least one pipe stalk before longitudinally outer regions of the at least one pipe stalk that are outboard of the inner region, so that the central portion of the at least one pipe stalk is submerged to a greater depth beneath the surface than end portions of the at least one pipe stalk and the at least one pipe stalk is substantially symmetrical about a plane disposed at a longitudinally central position between the towing vessels;
- and
- wherein the at least some of the added buoyancy is removed from the central portion and the longitudinally outer regions of the at least one pipe stalk while the at least one pipe stalk is supported between the towing vessels at the second location;
- and
- after removing the at least some of the added buoyancy from the central portion and the longitudinally outer regions of the at least one pipe stalk so that the at least one pipe stalk hangs with catenary curvature beneath the surface between the towing vessels, towing the at least one pipe stalk hanging with catenary curvature between the towing vessels to a third location for subsea installation.
Dependencies are inferred from the claim text.