Patent ID: 8733265

Claim:
A buoyant structure for petroleum drilling, production, storage and offloading, comprising: a. a hull symmetric about a vertical axis and having a circular platform and a vertical profile designed to extend below and above a sea surface simultaneously, the hull including: i. an upper vertical wall section; ii. an upper tapered wall section having a gentle inward slope; iii. a lower tapered wall section having a steep outward slope; and iv. a lower vertical wall section with the conical form of the hull being structurally efficient, offering a high payload and storage volume per ton of material used to build the hull; b. a planar horizontal keel of a lower hull diameter and a generally horizontal main deck; c. a plurality of fin-shaped appendages attached to a lower and outer portion of the lower vertical wall section of the hull; each fin-shaped section comprising: a plurality of fin sections separated from each other by gaps and the gaps adapted to accommodate catenary production risers and anchor lines on the exterior of hull without contact with the fin-shaped appendages; d. a low center of gravity (CG) located below its center of buoyancy (CB) thereby providing inherent stability with the low center of gravity (CG) enhancing a meta centric height of the buoyant structure resulting in a large righting movement; and e. ballasting in one or more ring-shaped lower compartments with a heavy slurry with the compartments forming a ring shape and located in outer-most portions of the lower vertical wall section providing the advantages of high density structural ballast with the ease and flexibility of removal by pumping the heavy slurry material creates large righting moments and increases the natural period of the structure to above the period of the most common waves, thereby limiting wave-induced acceleration in all degrees of freedom, and thereby further increasing the large righting movement.