GB1491684A - Offshore structure and a method of erecting such a structure - Google Patents

Abstract

1491684 Offshore structures SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ BV 27 Nov 1974 51371/74 Heading E1H An offshore structure is made in two units which are finally joined together at the offshore location, the parts being a base unit 2 having three legs 4 with internal buoyancy chambers portions 6 and pile guides at the lower ends of the legs 4 and female coupling parts 8 and a top unit 3 having three legs 10 with internal buoyancy chambers, a platform 12 and male coupling parts 13 for cooperation with the parts 8 to define chambers in which the two units are welded together. The base unit 2 is towed to the location upright, the internal buoyancy chambers the pontoons 6 and if necessary the bracing structure 5 are controllably ballasted to sink the base unit 2 to the seabed and the legs are fixed to the seabed by piling. The top unit 3 is then towed to the location upright or on its side in which case it is uprighted by flooding the buoyancy chambers in the legs 10 and is positioned over the sunken base unit 2. Lines 19 are attached to the base unit 2 by divers and tensioned by winches or the like on the top unit 3 to pull it down onto the unit 2 with respective male and female parts 13, 8 engaged. The parts 13, 8 define respective chambers which are rendered watertight by seals and are emptied to permit entry by welders who then weld the two units together.