초록 ▼

An improved semi-submersible unit for use in offshore operations which has a significantly reduced susceptability to heave motions in wave periods which are most likely to be encountered during practical operation conditions. The unit consists of a lower hull or hulls supporting vertical buoyant cai

An improved semi-submersible unit for use in offshore operations which has a significantly reduced susceptability to heave motions in wave periods which are most likely to be encountered during practical operation conditions. The unit consists of a lower hull or hulls supporting vertical buoyant caisson which also support an upper deck or platform which supports and is supported by a centrally disposed, large diameter buoyant caission which contributes a significant portion of the total water plane area of the vessel when it is submerged to its operational draft. The vessel may be configured for offshore drilling operations, diving support, and various other offshore support functions. When configured for the offshore drilling operation, the central column serves as buoyant chamber and as a primary storage chamber for tubular products which are associated with the drilling function. This clears the deck of the vessel for other operations and introduces a less hazardous method for handling tubulars than in previous designs. The central caisson has an interior annulus which is open both to the drill floor and the sea through which operations may be carried out. The improved semi-submersible vessel exhibits significantly less heave in operational wave conditions than existing semi-submersibles or similar water plane area and displacement.

대표청구항 ▼

An improved semi-submersible vessel for supporting drilling operations at sea, comprising: a platform having a drill center, the platform being supported by at least one submersible pontoon held in spaced relationship to the platform by a plurality of outside columns which provide the major structur

An improved semi-submersible vessel for supporting drilling operations at sea, comprising: a platform having a drill center, the platform being supported by at least one submersible pontoon held in spaced relationship to the platform by a plurality of outside columns which provide the major structural support for holding the pontoon and platform in spaced relationship, the water plane area of the outside columns at operational draft being at least as great as the water plane area of the columns immediately above the pontoons; and a central, buoyant caisson extending vertically downward from the work platform in surrounding relationship to the drill center to a point below the waterline level of the vessel when submerged to operating draft.