Patent ID: 6375391
Filing Date: 2002-04-23
Classification: B63B,E21B

Abstract:
A system for use in petroleum production at sea, with a guide frame for one or more risers on a semisubmersible production vessel, with one or more main buoyancy members arranged separately on at least one of said risers to carry the main part of the said riser's weight, each said riser arranged to separately carry a dry Christmas tree on top of said riser, near a main deck of the vessel, wherein:said main deck of said semisubmersible production vessel is disposed in a spaced-apart relation with respect to a submersible portion of said production vessel so as to form an generally open area at a splash zone between the sea surface and a bottom portion of said main deck, said guide frame comprises vertical main elements arranged to extend vertically downwards from the main deck, through a splash zone and through an upper, more wave- and current-influenced zone of the sea, said guide frame has horizontal guide plates comprising vertically open cells formed of a horizontally arranged framework of beams, with lateral stabilization devices for guiding said risers' and the said main buoyancy members' vertical movement relative to said guide frame and for restricting horizontal movement with respect to said guide frame, said guide plates are arranged in two or more levels on said guide frame; with one lower guide plate arranged in level with the lower ends of the vertical main elements, and one guide plate arranged to be positioned in a level just below or near the splash zone, and at least one said main buoyancy member is arranged for being held on one of said risers in level with, and guided by said lateral stabilization devices arranged in one or more guide plates arranged to be positioned below the upper, more wave- and current-influenced zone near the sea surface, and with the risers being essentially without buoyancy elements through the splash zone.