Patent ID: 7963241

Claim:
(Currently amended A mobile column-stabilized floating offshore platform structure, comprising: at least four spaced apart buoyant main vertical columns enclosed at top and bottom ends capable of being ballasted and de-ballasted defining four opposed sides of the platform structure; lower lateral truss members formed of cross-braced tubular members secured horizontally between lower ends of adjacent said main vertical columns and interconnecting lower ends of said main vertical columns together in spaced apart relation on four sides of said platform structure to provide a pin connection that transfers axial and shear forces between said main columns; a buoyant deck mount structure secured to an upper end of said spaced apart main vertical columns for receiving and supporting a deck, said deck mount structure having generally rectangular sides formed of metal plate defining a hollow interior, said deck mount structure providing a moment connection that transfers moment as well as axial and shear forces between said main columns; cylindrical vertical columns each telescopically mounted in a respective said main vertical column and passing slidably through a bottom end of the respective said vertical column; a buoyant generally rectangular ring keel tank secured to a bottom end of said cylindrical vertical columns formed of metal plate defining a hollow interior compartment capable of being ballasted and de-ballasted and having a central moon pool opening; wherein said keel tank is selectively retractable and extensible relative to said main vertical columns between a retracted transport mode and an extended operating mode, and is capable of tensioning riser and vertical moorings, self floatation, and optional oil storage; and the weight and buoyancy of said main columns and said keel tank is adjustable to raise or lower the center of gravity (C.G.) of the entire mass of the structure with respect to its center of buoyancy (C.B.) according to ballast and variable or fixed loads including deck payloads, to stabilize the structure, and to compensate for different operational, environmental, survival and installation stages of the structure.