Abstract: A lateral mooring system for tendon-based platforms is disclosed, which provides reduced installation and/or operational cost associated with the installation and operation of an extended-base tension leg platform. The lateral mooring system includes a plurality of mooring lines that provide lateral support to the platform in mild metocean conditions, but may have application in more severe oceanic condition. A method for installing the system on the platform and a method for drilling wells on a offshore site.

Abstract: An offshore well platform is towed in an upright condition to a well site by the use of a temporary flotation device. The flotation device mounts to a portion of the platform and is partially submerged, increasing the ability and buoyancy of the platform. At the site, the engagement of the flotation device shifts to a deploying position. In the deploying position, the ballast of the platform is increased to cause it to more deeply submerge. The flotation device remains at least partially surrounding the platform and floating while the platform moves downwardly relative to it. This provides lateral support if needed to prevent heeling while being submerged. The flotation device is disengageable from the platform when the platform is fully submerged.

Abstract: An offshore well platform is towed in an upright condition to a well site by the use of a temporary flotation device. The flotation device mounts to a portion of the platform and is partially submerged, increasing the ability and buoyancy of the platform. At the site, the engagement of the flotation device shifts to a deploying position. In the deploying position, the ballast of the platform is increased to cause it to more deeply submerge. The flotation device remains at least partially surrounding the platform and floating while the platform moves downwardly relative to it. This provides lateral support if needed to prevent heeling while being submerged. The flotation device is disengageable from the platform when the platform is fully submerged.

Abstract: An extended-base tension leg substructure, an offshore platform supported on the substructure and a method for supporting an offshore platform on the substructure are disclosed, where the substructure includes a plurality of support columns disposed about a central axis of the substructure and interconnected by at least one pontoon. Each column comprises an above water and submerged portion. The substructure also includes a plurality of wings or arms radiating from the columns and/or the pontoons, each wing fixedly or removably securing at least one tendon extending from a wing to an anchor on the seabed. The substructure includes an open, wave transparent central zone for improved access to well-related equipment, conduits or the like and the wings minimize translational movement and rotational flex in the substructure reducing fatigue in the tendons and their connections.