Developing a Turret Mooring System for Arctic FPSO units

Abstract The prospect of large oil and gas reserves in fields below Arctic waters hasdriven the design development of production solutions for these areas. Thispaper presents the development of an Arctic Turret Mooring System technologywhich facilitates year-round station keeping of floating offshore structures, like FPSOs in the Arctic environment. The Arctic turret mooring system candisconnect the mooring when the FPSO encounters extreme ice loads, which couldotherwise damage its hull or mooring system. When disconnected, a mooring riserbuoy supports the production risers and control umbilicals. The system isdesigned to quickly disconnect and re-connect the mooring riser buoy. Especially the fast re-connection will reduce the downtime to the productionsystem when disconnection is necessary. The Bluewater Arctic Turret is based on further development of existingBluewater know-how and designs of (quick) disconnectable Turret MooringSystems. However, in addition to existing designs, the Bluewater Arctic Turretuses a unique and patented design that allows the mooring riser buoy to bereleased from the turret, while being subject to the large (horizontal) mooringloads. In this design, the mooring riser buoy is released from the turret tosink below the FPSO hull, before the mooring system is disconnected from theturret. Following disconnection, the mooring riser buoy descends further to asafe equilibrium depth away from ice hazards. This allows the disconnected FPSOto sail from its production location and later return for reconnection andquickly resume production. The paper presents the unique Bluewater ArcticTurret Mooring concept, its design basis, the development process as well asconsideration to key aspects such as operational and safety issues.