Submerged buoyant offshore drilling and production tower and apparatus and method for installing same

摘要

A submerged tubular tower (10) (see Fig. 1) is connected at its lower end (15) to an ocean floor (11) at a site where at least one subsea hydrocarbon well is to be drilled. A riser duct (22) (see Fig. 5) for each well to be drilled extends from an upwardly accessible connection point (20) at the upper end (14) of the tower to the lower end of the tower. The tower is positively buoyant to stand erect in an unguyed manner. The upper end (18) of the tower is located a substantial distance above the ocean floor at a depth sufficiently small to enable wells to be drilled through the riser ducts, through equipment (19) landed on the top of the tower, using floating drilling equipment (12) designed for use in substantially shallower water depths.