Offshore oil storage structure with submergence shell

Claim 1

An offshore structure floatable to a site for positioning on the floor of a body of water comprising: a roof shell enclosing a volume therebelow, said roof shell having a peripheral ballasting ring which provides a substantial righting moment against significant tipping of the structure while the ballasting ring is at least partly above water level; means to remove air from beneath the roof shell and means to supply the same with liquid in submerging the structure; a submergence shell joined at its bottom to the roof shell and extending upwardly spaced away from the roof shell thereby defining a material well between the submergence shell and the roof shell; the upper part of said material well being provided with at least one opening permitting direct communication between the interior space of the material well and the exterior thereof; said material well being so positioned as to be completely submergEd when said structure is positioned on the floor of said body of water; a plurality of spaced apart upright partitions dividing the material well into compartments; means to supply ballasting material to the material well; at least one hollow vessel joined to the roof shell, said hollow vessel being of such size that the buoyancy of the vessel will statically float the roof shell above the floor of a body of water partly or fully submerged at least with all air removed from beneath the roof shell and with the material well full of material; and means to supply material to the hollow vessel.