Abstract: An apparatus and method for ballasting and de-ballasting a vessel having a hull with several watertight ballast compartments. In a first embodiment, a pressure tank is isolatably and fluidly coupled to a common sea chest, to the atmosphere, to ballast compartments via a distribution manifold, and to a source of compressed gas. The pressure tank is first vented and filled with water from the sea chest, then isolated. The filled tank is then coupled to a ballast tank and the source of compressed gas, which displaces water from the tank to the ballast compartment. In other embodiments, ballasting is by venting and flooding compartments using individual sea chests located within the ballast compartments or a firewater system. For de-ballasting, compressed gas displaces ballast water through overboard discharges, through the common sea chest via the pressure tank, or through individual sea chests located within the ballast compartments.

Abstract: A method and system for attaching a TLP to its tendons using pull-down lines to rapidly submerge the hull to installation draft while compensating for inherent hull instability during submergence and to provide motion arrest and aid in station keeping. The system includes tensioning devices mounted on the TLP, usually one for each tendon. Each tensioning device is equipped with a pull-down line which is connected to the corresponding tendon. The TLP hull is submerged to lock-off draft by applying tensions to the pull-down lines connected to the top of the tensions, or by a combination of applying tensions to the pull-down lines and ballasting the hull. As the tensioners take in pull-down line, the hull submerges, i.e. the draft increases.

Abstract: A method and system for attaching a TLP to its tendons using pull-down lines to rapidly submerge the hull to installation draft while compensating for inherent hull instability during submergence and to provide motion arrest and aid in station keeping. The system includes tensioning devices mounted on the TLP, usually one for each tendon. Each tensioning device is equipped with a pull-down line which is connected to the corresponding tendon. The TLP hull is submerged to lock-off draft by applying tensions to the pull-down lines connected to the top of the tensions, or by a combination of applying tensions to the pull-down lines and ballasting the hull. As the tensioners take in pull-down line, the hull submerges, i.e. the draft increases.

Abstract: A system and method for mating risers or umbilicals extending vertically or near vertically from the ocean floor to a floating offshore system such as a TLP or semi-submersible platform. The risers or umbilicals are suspended vertically above the vessel's keel and are supported laterally near the platform's keel by keel guides or riser receptacles positioned along the submerged perimeter of the vessel's hull, or within the hull by production riser slots disposed in the bottom of the hull. The keel guides or production riser slots each receive a keel joint assembly which laterally supports a riser or umbilical passing therein while providing a bearing surface for free vertical movement of the riser.

Abstract: A passive riser tensioner apparatus for tensioning riser pipes on floating platforms and tension leg platforms utilizes one or more elongate elastic tensioning elements connected at top and bottom ends to the upper end of a riser pipe that are capable of being axially stretched. Each tensioning element has a threaded length adjustment rod and tension preload nut at its top end which adjusts the axial length to produce a predetermined preload tension force in the tensioning element between its connection to the riser pipe. A riser support collar slidably received on the length adjustment rod and riser pipe upper end is configured to be supported on the deck of the platform and allow axial movement of the riser pipe. A tension locking nut on the length adjustment rod releasably engages the length adjustment rod with the riser support collar when it is supported on the deck.

Abstract: An offshore tension leg platform having a deck, a hull, and a plurality of elongate tendons securing the hull to an ocean floor foundation provides full well workover and production capabilities for autonomous operation and can be installed and operated in any water depth and sustains any environmental loading conditions. The hull supports well risers of well trees located below the water surface at an elevation in close proximity to the connections of the tendons to the hull. Alternatively the risers and trees may be supported above water by a deck or the trees may be located on the seabed. A workover platform supported by a perimeter trackway on the deck may be positioned over any of the well risers for workover operations. Liquid products may be exported from the platform via a pipeline or to a floating tanker. The hull is configured to minimize loadings in the tendons. All components are installed by a drilling vessel without the need for special installation vessels and equipment.

Abstract: A compact offshore tension leg platform having a deck, a hull, and a plurality of elongate tendons securing the hull to an ocean floor foundation provides full well workover and production capabilities for autonomous operation and can be installed and operated in any waterdepth and sustain any environmential loading conditions. The hull supports the well risers of well trees located below the water surface at an elevation in close proximity to the connections of the tendons to the hull. Alternatively the risers and trees may be supported by the deck. A well workover platform, supported by a circular perimeter trackway on the deck may be positioned over any of the well risers for workover operations. Liquid products may be exported from the platform via a seabed pipeline or to a floating tanker moored to a mobile offtake on the deck support column. The hull is configured to minimize loadings in the tendons.