A semisubmersible trimaran for use in an afloat sea base is disclosed. The trimaran has an upper deck structure 12 supported on a longitudinal center hull 26 and column-stabilized, longitudinal outrigger pontoons 28. The center hull 26 and pontoon columns 38 and 40 have a reduced waterplane area for minimizing motion during operations. The trimaran has a transit draft 37 for deployment at full waterplane area, and an operating draft 36 with a reduced waterplane area for damping motion. The vesse...

A large semisubmersible building is made up of a submerged section installed underwater, an intermediate section consisting of a plurality of column structures erected on the submerged section at specified intervals, and an above-water section built upon the intermediate section so that it is always situated above water. The submerged section is made larger than the above-water section. Because of this construction, the large semisubmersible building remain stable and stationary at a specified d...

A tendon installation for anchoring a semisubmersible platform to a sea bed foundation, wherein said tendons are tensioned by the updrift of the platform. The tendons are prefabricated in dimensions adapted to the depth of the sea bed foundation, expected tension load and in order to be substantially weightless in water. The tendons are connected in groups at each of their ends at a distance corresponding to the distance between anchoring points in the foundation and the platform respectively. T...

Improvements to a ring pontoon semisubmersible vessel. The centerlines of the corner columns ar displaced with respect to the axial centerlines of the forward and aft portions of the ring pontoon. Additionally, the centerlines of the corner columns may be displaced with respect to the axial centerlines of the starboard and port portions of the ring pontoon. The superstructure deck may be supported by radial braces extending from the ring pontoon to locations on the superstructure deck which are ...

A tendon installation for anchoring a semisubmersible platform to a sea bed foundation, wherein said tendons are tensioned by the updrift of the platform. The tendons are prefabricated in dimensions adpated to the depth of the sea bed foundation, expected tension load and in order to be substantially weightless in water. The tendons are connected in groups at each of their ends at a distance corresponding to the distance between anchoring points in the foundation and the platform respectively. T...

The derrick barge comprises a pair of laterally spaced elongated hulls having a plurality of upstanding columns spaced therealong supporting a working platform and a heavy duty derrick or crane in spaced relation above the hulls. The hulls bouyantly support the vessel including its deck load in the floating condition with the hulls having freeboard. The hulls have ballast compartments to submerge the hulls and portions of the stabilizing columns to a distance of approximately one-half the effect...

A semisubmersible, loading, mooring and storage (LMS) facility for handling petroleum products at offshore locations. The LMS facility is comprised of a submerged storage section and a central tower section. The submerged storage section is comprised of a plurality of dual crude/water tanks, each of which has a flexible diaphragm therein to prevent any contact between the crude and the water. The central tower section contains crude only tanks through which the LMS facility is loaded and offload...

The vessel comprises a pair of laterally spaced elongated hulls having a plurality of upstanding columns spaced along outboard portions of the hulls. In the preferred form, a central column supports a working platform in spaced relation above the hulls. The hulls buoyantly support the vessel in a low draft condition with the hulls having freeboard. The hulls and outboard columns have ballast compartments for ballasting and deballasting the vessel to respectively submerge the hulls, outboard colu...

A drilling tender (2) has a pair of laterally spaced buoyant hulls (4) with ballast chambers to permit the hulls to be moved between a submerged condition and a surface floating condition. Each hull (4) supports a row of columns (8). The columns (8) support a working platform (10) including a main deck (12) and a pipe rack deck (30) above the main deck (12). A bow deck (48) above a forward portion of the pipe rack deck (30) has mounted on a corner portion thereof a main heavy duty crane (50). Th...

A central pontoon semisubmersible floating platform for use in offshore applications has a hull configuration including vertical support columns, a central pontoon structure disposed inboard of the columns at a lower end thereof, and a deck structure supported at an upper end of the columns. The vertical columns and pontoon structure are constructed substantially of flat plate. The vertical columns are adjoined to the outer periphery of the central pontoon and have a transverse cross sectional s...