Coupled Analysis of FPSO and CALM Buoy Offloading System in West Africa

Abstract

FPSO and CALM (Catenary Anchor Leg Mooring) buoy offloading systems are being extensively employed in water field of West Africa. In this paper we did some research on the response of FPSO and CALM offloading systems under special environment conditions in West Africa. It is found that Swell dominate sea state has much larger effects on wave frequency motions of FPSO than responding results introduced by Wind Sea dominate sea state, and squall and current will introduce large horizontal motions of FPSO, such as surge and sway. As for CALM, swell and wind sea mainly affect its heave and roll motions, respectively. Due to its little wind area, CALM does not show great response to Squall which is the extreme environment condition for FPSO though. By comparing the results from OOL (Oil Offloading Line) dynamic analysis and quasi-static analysis, it could be that OOL dynamic effect has little influence on motions of FPSO. But it can bring large changes of responses of CALM because of its small water displacement which indicates coupled analysis of the whole system is necessary. Besides, investigations on OOL fatigue have also been done, and the results show that CALM motion plays an important role on fatigue damage and life of OOL under different sea states.