Feedback on the Design and Operation of the Skarv FPSO Mooring System

Naciri, Mamoun (SBM Offshore) | Heimsnes, Tom Erik (AkerBP) | Newport, Andrew (SBM Offshore) | Mée, Romain le (SBM Offshore)

OnePetro 

AbstractThe Skarv field, located 210 km offshore Norway, has been developed by BP using a turret moored FPSO, with first oil production achieved in December 2012. This paper presents the station keeping philosophy adopted for the FPSO, and gives an overview of the turret system design, and the challenges involved. In addition, based on four years of offshore operation, feedback on the behaviour of the mooring system is reported and compared with the design assumptions. The turret mooring system is located at 1/3 of ship length aft of the forward perpendicular, which reduces its passive weathervaning characteristics, leading to the provision of a heading control system to optimize topside ventilation, minimize turret loads and improve vessel motions. The harsh environment of the Skarv field, together with survivability considerations for a black ship conditions when power for the heading control is lost, result in mooring loads in excess of 5000 tons. These loads are significantly higher than loads imposed on previous FPSO turret mooring systems.Operational experience from nearly four years will be compared to global performance as predicted during design stage through both analysis and model testing. Conclusions will be drawn about monitored global performance. Lessons learnt will be provided. Feedback from this frontier project will help the Industry tackle mooring system design in more and more challenging metocean conditions in the future.