Riser system connecting fixed subsea installations to floating surface unit, includes interconnected sub-surface buoys providing intermediate support

摘要

Each of the two immersed buoys (5) is associated with a riser (11) connected to one of the fixed subsea installations (2). Each has a flexible catenary pipe (10) to the surface. They are joined by a catenary restraint line (40). The restraint line is heavy and/or weighted. It is connected to the buoy through a fitting (17) beneath it, which prevents buoy rotation. The taught anchoring lines to each buoy are sensibly vertical and at right angles to the restraint line. The buoyancy of the buoy is variable; it comprises several components (22-24). The restraint line is connected at one end (20) of the buoy. This is opposite the other lateral end (21), where the riser is connected. The restraint line is connected to each immersed buoy at a location in the medial plane passing through the longitudinal axis of the buoy, perpendicular to a plane containing the restraint line.