Offloading hydrocarbons from subsea fields
AssigneeSubsea 7 Norway AS
InventorsSigbjorn Daasvatn, Daniel Karunakaran
Life of this patent
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Abstract
A subsea hydrocarbon export system includes a riser tower having a riser column extending from a seabed location to a sub-surface buoy that supports the riser column in an upright orientation. A subsea connector is operable underwater to couple the riser column temporarily to a hose suspended from a surface shuttle tanker vessel for an export operation and to release the hose after the export operation.
Claims39
A subsea hydrocarbon export system, comprising:
- a riser tower having a column extending from a seabed location to a sub-surface buoy that supports the column in an upright orientation, wherein the column communicates with a subsea tank for storing hydrocarbon fluids and with a subsea processing system for processing hydrocarbon fluids;
- and
- a subsea connector that is operable underwater to couple the column temporarily to a hose suspended from a surface shuttle tanker vessel for an export operation and to release the hose after the export operation;
- wherein the subsea connector comprises an upwardly facing socket at an upper extremity of the column for receiving a plug connector of the hose;
- and
- wherein the buoy comprises one or more external tubes or sockets that open upwardly to receive at least one clump weight.
A method of exporting hydrocarbon fluids from a seabed location, the method comprising:
- sailing a shuttle tanker vessel to a surface export location above a column that extends from the seabed location and communicates with a subsea tank for storing the hydrocarbon fluids to a sub-surface buoy, wherein the buoy supports the column in an upright orientation, and wherein the buoy comprises one or more external tubes or sockets that open upwardly to receive at least one clump weight;
- suspending a hose from the vessel to reach the column;
- operating a subsea connector underwater to couple the hose temporarily to the column for an export operation by inserting a plug connector of the hose into an upwardly facing socket at an upper extremity of the column;
- during the export operation, causing hydrocarbon fluids to flow from the seabed location up the column and along the coupled hose to the vessel;
- and
- on completion of the export operation, releasing the hose from the column by removing the plug connector of the hose from the upwardly facing socket, lifting the hose to the vessel and sailing the vessel away from the surface export location.
A method of installing a subsea hydrocarbon export system, the method comprising:
- lowering a major lower section of a column into water beneath an installation vessel;
- suspending the lower section from the installation vessel;
- positioning a buoy and a minor upper section of the column over the suspended lower section;
- joining the upper section to the lower section to complete the column;
- adding ballast to the buoy by attaching one or more clump weights to the buoy, wherein attaching one or more clump weights to the buoy comprises inserting at least part of a clump weight into an upwardly extending external tube of socket on the buoy;
- lowering the buoy and the completed column into the water beneath the installation vessel to anchor a lower end of the column to a subsea facility comprising a subsea tank for storing hydrocarbon fluids at a seabed location, the buoy then being at a sub-surface location;
- and
- removing the added ballast from the buoy after anchoring the lower end of the column at the seabed location.
Dependencies are inferred from the claim text.