SYSTEM WITH A GUIDE FRAME FOR PETROLEUM PRODUCTION RISERS; A GUIDE FRAME FOR RISERS; RISER BUOYANCY ELEMENTS AND A SEMI-SUBMERSIBLE PRODUCTION PLATFORM

摘要

The invention describes a systemwith a system for use in petroleum pro-duction at sea, with a guide frame (2)for one or more riser pipes (3), on asemisubmersible production vessel (1),with one or more main buoyancy mein-ber (4) arranged separately on at leastone riser (3) to carry the main part ofthe riser's (3) weight. Each riser (3) isarranged to separately carry a Christ-mas tree (6) on top, near the maindeck (10) of the vessel (1). The guideframe (2) comprises vertical main ele-ments (7) arranged to extend verticallydownwards from the deck (10), throughthe splash zone and through the upper,more wave- and current- influencedzone of the sea. The guide frame (2)has horizontal guide plates (20) com-prising vertically open cells formed ofa horizontally arranged framework (21)of beams (21'), with lateral stabiliza-tion devices (24) for guiding the riser's (3) and the main buoyancy member's (4) vertical relative movement and restricting the horizontalrelative movement with respect to the guide frame (2). The guide plates (20) are arranged in at least two levels on the guide frame (2);a lower guide plate (20) arranged in level with the lower ends of the vertical main elements' (7), and a guide plate (20) arranged in alevel just below or near the splash zone. At least one main buoyancy member (4)is arranged for being held on the riser (3) in levelwith, and guided by the lateral stabilization devices (24) arranged in one or more guide plates (20), below the upper, more wave- andcurrent-influenced zone near the sea surface, and with the risers (3) being essentially without buoyancy elements through the splash zone.for being less exposed to the water forces in the upper zone of the sea.