Importance

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Abstract

A jacket tower structure for use in deep water which includes a plurality of tapering jacket sections adapted to be nested, each section including at least three jacket legs. The base and lower jacket sections include cylindrical legs interconnected by box section bracing, the upper jacket sections including cylindrical bracing. The box section bracing is connected to the legs by a unique joint for transmitting stresses to the legs. The box section bracing is floodable for equilizing hydrostatic pressure during and upon installations. Certain transverse box section bracing at ends of adjacent jacket sections include intermediate connection projections for welding during joining of adjacent jacket sections. The cylindrical legs include a plurality of water tight compartments of selected volume, each compartment having one or more check valves for admitting water into the compartments when external water pressure exceeds air pressurization of the compartments. A method of installing the jacket tower includes floating the tower, to the site, on two of the legs; rotating the tower about a longitudinal axis to submerge one leg while at least the other two are at water level and tilting the structure by flooding certain portions of the base and lower sections and continuing such tilting by automatically flooding the legs by preselected pressure conditions in the water tight compartments until the tower reaches a vertical position. Once vertical, the remaining compartments are flooded to settle the tower vertically on the sea floor.

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First Claim