Mooring System Design For FPSO In Ultra-deepwater

With the exhausted of near offshore oil and gas resources，deep or even ultra-deepwatersuch as South China Sea and West Africa is becoming the next hot spots in the next stage.Due to we have a huge demand for offshore oil and gas resources, development orparticipation with orther excited oil field in deepwater has became an important economicstrategy. Domestically,"Offshore Oil981” successful operations are leading to a newupsurge in the oil and gas development in the South China Sea. Overseas, the West Africanarea is one of the three hot spots around world, in which the biggest chinaese oil and gascompanies such as CNOOC, CNPC and SINOPEC have its target blocks. Therefore, it isnecessary to investigate the floating structures (such as FPSO, etc.) working in West Africanwaters and the South China Sea.Firstly, a typical deep-water FPSO working in West African is proposed for the study,then the influence of swell on hydrodynamic performances of FPSO in West Africa and itsmechanical mechanism were investigated, and the effect of mooring parameters onhydrodynamic performances of FPSO were investigated as well. Secondly, a typicaldeep-water single point moored FPSO working in the South China Sea is proposed for thelatter study, low frequency response of the FPSO was studied during the whole process ofgrowing of wind/wave/current, and then the methods to control the weight of mooringsystem and the influence of mooring parameters on hydrodynamic performances of FPSOwere investigated. Finally, a new hybrid mooring system is designed, and compared with thehybrid line system of “chain-rope-chain" and the hybrid line system of“chain-polyester-chain". The major works are shown as follow:1、The design of multi-point mooring arrangement of FPSO in West AfricanFirstly, the FPSO was subjected in swell only and wind-sea conditions separately, andthen the influence of such two environment conditions on hydrodynamic performances ofFPSO in West Africa and the internal mechanical mechanism were investigated. Then, theeffects of incident angle, amount, and length of the each cable on hydrodynamicperformance of FPSO in West Africa where swell exists together with wind-sea in differentdirection were investigated.2、The design of SPM arrangement of FPSO in the South China SeaFirstly, the whole process of wind/wave/current was divided into three stages(development, peak, and decay), low frequency extreme response of single point mooredFPSO in each stage and the internal mechanical mechanism were studied. For the problem of excessive weight of mooring system, three methods were proposed and some numericalexamples were carried out. Secondly, the effects of mooring system parameters, such aslength, amount, position of turret, and etc on hydrodynamic performance of FPSO in SouthChina Sea were investigated. And a set of reasonable mooring parameters were finallyproposed.3、Investigation the hydrodynamic performance of SPM FPSO with a new hybrid lineBased on traditional hybrid mooring line, a new hybrid mooring line and the method tocalculate the material properties were proposed, and then compare of the hydrodynamicperformance with new and traditional hybrid mooring system were undertaken.