Abstract: A cantilevered jack-up rig having a support for supporting the free ends of the rig's cantilever beams when said beams are extended over a platform to be serviced by the rig, thereby maximizing the lateral reach of the rig and increasing the load capacity at the maximized reach. The support is positioned between the top of the platform and the bottoms of the extended cantilever beams. The top of the support is provided with a motion block to facilitate lateral and rotational motion of the extended cantilever beams relative to the support.

Abstract: The semi-submersible platform comprises a submersible lower hull including a plurality of spaced-apart hull segments. A wave-transparent stabilizing superstructure extends from the lower hull. An upper hull is supported by the superstructure. A wellhead system is suspended from the platform. A catenary mooring system moors the platform to the seabed, and plurality of risers connect the individual wellheads on the platform to the wellbores in the seabed.

Abstract: The mobile marine drilling structure is of the submersible type for operation in ice-covered waters. The structure comprises a base for placing the structure on the sea bed, a hull extends from the base, and a deck is supported by the hull. The deck is located above the water line for conducting drilling operations. The hull has an internal frame assembly including ballast tanks, and external wall sections at different inclinations to the horizontal to engage and break up the moving ice masses encroaching on the hull. These external wall sections include a plurality of matching polygonal, frusto-pyramidal, apex-up and apex-down walls extending above the base, and two transitional wall sections to provide two inflection points to the hull.

Abstract: The method involves erecting a very large-diameter column from a plurality of buoyant columnar members at a selected site in a body of sea water. Each columnar member is floated erect to the site. The first or lowermost columnar member is pulled down and fully submerged to a predetermined depth over the site. The second columnar member is then positioned directly over the lowermost member. The lowermost member is allowed to move up and lift the second member out of the water. The two columnar members are securely interconnected to each other in a watertight fashion. The partial column is then pulled down to a fully submerged condition and the third columnar member is positioned directly over the second member. The partial column is allowed to move up and lift the third member out of the water. A secure watertight connection is made between the third columnar member and the second columnar member.