Abstract: A disconnectable mooring system for offshore semi-submersible floating structures. A disconnectable buoy has a number of mooring lines which include a buoy chain between the mooring chain and the buoy. The mooring chain and the buoy chain are connected via a three way mooring connector, with the third connection configured to pull the mooring connector to a mooring point on the structure. In a first configuration the buoy is disconnected and supports the mooring chains for recovery at shallow depths to be pulled in. In a second configuration, the mooring lines are pulled in via the mooring connectors thereby providing a spread mooring to the structure with the buoy chain left as a catenary between the buoy and mooring point.

Abstract: A portable subsea storage tank for the storage of gas products under pressure or oil products consisting of pipeline sections in an array which can be coated in specialist coatings and recovered for inspection and re-use. A method of self-installing the subsea storage tank is also described.

Abstract: A floating structure in the form of a spar which from a base (12) includes a first ballast weight (16), an entrapped fluid compartment (18), an equipment compartment (20), a second ballast weight (22) and a topside (24) wherein, in use, the structure floats with the water line between the topside and the second ballast weight. The arrangement utilises vertical spacing between physical masses and entrapped fluid to increase the natural period in pitch and roll motions to provide high stability. Embodiments of entrapped fluid compartments are described. The floating structure finds application in hydrocarbon recovery in shallow water and offshore renewables.

Abstract: Apparatus and method for managing water or other ballast fluid in an underwater storage tank (14), used for storing fluids such as oil or CO2, where a dis-connectable inflatable bag (16) is coupled to the underwater storage tank to capture displaced ballast fluid from the underwater storage tank. A supply line (36) between the bag and tank provides a closed loop system. Embodiments are shown in which the tank is initially filled with fresh water and multiple dis-connectable inflatable bags are used.

Abstract: A system for improving the static and dynamic stability of an offshore floating structure in which outriggers having a unit with an inertial mass are supported from the structure to hold each unit at a radial distance from a centre of rotation of the offshore floating structure and be entirely submerged. Water may enter and exit a tank in a unit to statically adjust and dynamically control stability and dampen roll and pitch of the structure. The outriggers can be raised for tow. The outriggers ballast can be adjusted during tow, installation and in operation. The units can transport mooring lines. An embodiment of a hydrocarbon production or support facility is described with the dynamic flexible risers connected to a support structure of the system.

Abstract: A method for installing a subsea structure at a target installation site in an underwater location is disclosed. The method includes connecting at least one mooring line and at least one leading line to the structure, and towing the structure via the leading line from a deployment position to the target installation site, such that the structure moves both vertically and horizontally between the deployment position and the target installation site. The mooring line is anchored, e.g. to an anchoring device on the seabed, and can incorporate a ballast to apply a sinking force to the structure in proportion to the length of unsupported line. The mooring line and the leading line can together stabilise the structure as it descends to the installation site. The non-vertical installation allows accurate structure placement, e.g. in crowded fields, with less sensitivity to tidal or current forces.

Abstract: Apparatus and method for processing of production fluids from a subsea oil or gas well, in order to recover hydrocarbons from the well. In an embodiment, the apparatus is a column stabilised structure having an interconnected array of three columns, with the upper portion protruding above the surface of the sea. The apparatus described has processing facilities in a lower portion of a first column, power generation facilities in a lower portion of a second column and service and utilities in a lower portion of a third column. Further facilities equipment and storage tanks can be located in the columns.

Abstract: The invention relates to methods and apparatus for storing at least one chainon an offshore service vessel. The chain is stored in a carousel on the vessel which is driven to rotate while the chain is being loaded into the carousel.

Abstract: There is disclosed a variety of arrangements for laying of rigid pipe from reeled storage and/or on-board welding fabrication. Thirteen independent aspects of the invention are identified. In one particular arrangement (FIGS. 3a-3b), a tilting lay tower (106) having two travelling clamps (210, 220) is provided centrally on a pipelay vessel with a radius control arch (140) pivotable to receive rigid pipe from either port or starboard lay paths. A vertical axis reel or carousel (104) is provided, within an arrangement of curved take-off arms (130, 134) and a large radius curved wall (128). By these means, pipe can be loaded onto the carousel either clockwise or anti-clockwise, and can be supplied to the lay tower via the port or starboard lay path. Continuous rigid product fabricated by a selection of welding lines (112, 114, 116) at the port side can be guided around the large radius wall either for reeling onto the carousel or for direct feeding to the lay tower.

Abstract: There is disclosed a variety of arrangements for laying of rigid pipe from reeled storage and/or on-board welding fabrication. Thirteen independent aspects of the invention are identified. In one particular arrangement (FIGS. 3a-3b), a tilting lay tower (106) having two travelling clamps (210, 220) is provided centrally on a pipelay vessel with a radius control arch (140) pivotable to receive rigid pipe from either port or starboard lay paths. A vertical axis reel or carousel (104) is provided, within an arrangement of curved take-off arms (130, 134) and a large radius curved wall (128). By these means, pipe can be loaded onto the carousel either clockwise or anti-clockwise, and can be supplied to the lay tower via the port or starboard lay path. Continuous rigid product fabricated by a selection of welding lines (112, 114, 116) at the port side can be guided around the large radius wall either for reeling onto the carousel or for direct feeding to the lay tower.

Abstract: There is disclosed a variety of arrangements for laying of rigid pipe from reeled storage and/or on-board welding fabrication. Thirteen independent aspects of the invention are identified. In one particular arrangement (FIGS. 3a-3b), a tilting lay tower (106) having two travelling clamps (210, 220) is provided centrally on a pipelay vessel with a radius control arch (140) pivotable to receive rigid pipe from either port or starboard lay paths. A vertical axis reel or carousel (104) is provided, within an arrangement of curved take-off arms (130, 134) and a large radius curved wall (128). By these means, pipe can be loaded onto the carousel either clockwise or anti-clockwise, and can be supplied to the lay tower via the port or starboard lay path. Continuous rigid product fabricated by a selection of welding lines (112, 114, 116) at the port side can be guided around the large radius wall either for reeling onto the carousel or for direct feeding to the lay tower.