Mobile offshore drilling structure for the arctic

Abstract

A mobile platform structure, installation and method for use in arctic waters where the dominant environmental loading threats are posed by winter ice pressures and summer ice floes. The structure includes an ice load bearing, submergible substructure and a platform superstructure of approximately equal lateral dimensions. The substructure has a height approximately equal its depth of submergence when ballasted down onto the sea floor and includes a plurality of peripherally arranged, surface accessible spud guides. The spuds are laterally restrained by the spud guides in the top and bottom walls for transmission of lateral loads therebetween at respective vertically spaced apart fulcrum points and are vertically movable in the spud guides for penetration into high shear soils which may be overlaid by relatively low shear soils whereby the shear capacities of both soils combine with the frictional capacity of the structure/sea floor interface to provide high displacement resistance to lateral ice loads. Provision also is made for extracting the spuds for redeployment of the structure at another arctic installation site and for fixedly but releasably securing the spuds in an elevated position within the spud guides when not in use.