Floating Production Mooring Turret
First introduced in the 1970’s, Floating Production Storage and Offloading (FPSO) vessels offered a solution to developing stranded oil reservoirs in locations where it would be uneconomic to install fixed platforms and pipeline facilities. Given the remote location of the Foinaven field to the East of Orkney, BP elected to install an FPSO to develop the oil reserves there.
A key component of an FPSO vessel is the turret which is anchored to the sea bed by mooring chains and connected via flexible risers to subsea wellhead structures. The design of the vessel / turret structural and pipework connections allows the vessel to pivot around a fixed vertical axis to accommodate prevailing wind and current whist transferring fluids between the subsea facilities and the vessel.
In November 1994 the Yard was awarded a contract to build the Foinaven upper and lower turret steelwork structures weighing 655Tonnes and 590 Tonnes respectively. To enable installation into the FPSO vessel, the turret was built in two sections, namely the larger upper collar (which also provided the winch deck), and lower cylindrical section.
Fabrication proved challenging, the complex structure with extensive stiffening resulted in 120 compartments and involved over 30 kilometres of welding, much of the work in areas of restricted access. The design required that a well-planned build and weld sequence be adopted to control shrinkage and distortion. The satisfactory conclusion of the project in meeting this new type of construction and tight schedule was a testament to the fabrication team, for which the yard received recognition letters from BP and Foinaven Development Team. Loadout of the Turret structures took place on 28 May 1995 with sail away on the 8th June to the Ferrol shipyard in Spain where the FPSO was under construction.
BP suspended production from the Foinaven oil field in 2021 and the FPSO has now been removed.