Tension leg platform and method of instalation therefor

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. All components, except the deck, are installed by a drilling vessel without the need for specialist installation vessels and equipment. The tendons are arranged in groups offset from the hull body to resist platform overturning loadings, and to reduce the tendons pretension required to prevent platform pitch and roll motions. The wells are drilled prior to installation of the hull using a drilling vessel. After installation of the platform, all operations required on the wells are performed autonomously from the platform without the need for another drilling vessel or equipment.