EVALUATION OF LOW FREQUENCY MOTIONS OF A TURRET MOORED FPSO SYSTEM AND THEIR INFLUENCE ON HULL GIRDER LOADS

摘要

Floating oil production, storage and off-loading systems (FPSOs) are one of the most viable offshore oil production facilities for the development of deep or ultra deep water marginal and small fields in remote locations and have been utilized in almost every part of the world. The accurate prediction of the low frequency motions of FPSOs is essential for safe design of mooring and riser systems. On the other hand as the water depth increases the mooring and riser line loads effect the hull girder loading. The increase in hull girder loads depends on the mooring system pre-tension forces, which increase with water depth. This paper describes a time-domain procedure to evaluate the low frequency motions of a turret FPSO and the increase in hull girder loads i.e. bending moments and shear forces due to low frequency motions which in turn determine the maximum mooring system loads. Finally, the results of parametric studies showing the variations in low frequency motions and hull girder loads as the mooring line stiffness varies are presented.