A subsea riser comprising a rigid riser pipe 10 suspended from a surface support 14 as a catenary extending from the surface support through a sagbend 18 to a seabed touch-down point 20. The riser is attached to the surface support by hang-off interface 26 and a subsea buoy 36 is positioned on the riser above the sagbend, the buoy being attached to the riser by attachment interface 38. The hang-off and attachment interfaces allow rotation of the riser relative to the surface support and buoy respectively about at least two horizontal axes. The attachment interface may allow rotation about a central axis of the riser also. The buoy may be attached only to the riser and be slidable along the riser, limited by stopper formations 48. The buoy may comprise a buoyant body (54, fig. 3) spaced radially from and extending continuously around the riser, potentially in a toroidal shape. The attachment interface may have a part-spherical inner ball (50, fig. 3) fixed to the riser and contained in a complimentary socket (52, fig. 3) in the buoyant body. A pliant spool may extend between the surface support and the upper end of the riser pipe.
Subsea Risers
2021-09-29
Patent
Elektronische Ressource
Englisch