Patent ID: 6012873
Filing Date: 2000-01-11
Classification: B63B,E02D

Abstract:
A mobile deep water offshore oil platform with a retractable anchoring system to secure the platform at a drilling site in a body of water, the platform comprising:a column-shaped buoyant leg structure with a first end and a second end, the length of the buoyant leg structure being greater than the diameter of the buoyant leg structure;a work deck coupled to said first end of said buoyant leg structure;a gravity base containing at least one ballast compartment for ballasting and deballasting said gravity base;a plurality of tethers coupling said buoyant leg structure to said gravity base;a hoist to lower and retract said tethers, said hoist located on the first end of said buoyant leg structure and capable of lowering the attached gravity base to the bottom of the body of water; anda ballast compartment in said buoyant leg structure to control the tension of said tethers after said gravity base is lowered to the bottom of the body of water;wherein in the assembled platform, the ballast distribution of said buoyant leg structure is selected so that the center of gravity of the platform is below the center of buoyancy and the tether tension is selected to improve the response of the platform to the excitational loads of wind, waves and currents.