US Patent 7413384 Floating offshore drilling/producing structure

A deep draft semi submersible structure wherein the semi-submersible has a center of gravity below its center of buoyancy and the structure is a floating vessel with at least three vertically oriented buoyant columns. Each of the vertically oriented buoyant columns have at least one ballasted compartment and the columns are spaced apart at a sufficient distance to reduce vortex induced vibration amplitude. There are at least two connecting structural sealed trusses connected to the columns below sea level, they are positioned to minimize hydrodynamic wave action on the trusses and to transfer shear loads between the columns while remaining transparent to wave and ocean current motion.