Dynamic Analysis Of FPSO Buoy Offloading System

Catenary Anchor Leg Mooring(CALM)is a widely used offshore mooring device in the world.Floating structures attached to it can have wind vane effect and reduce the impact of environmental loads effectively.At the same time,CALM can be used for oil transporting.In offshore oilfields,crude oil can be offloaded to shuttle tankers from FPSO and other floating production devices,which can avoid collision between oil tankers and floating production devices.It can also be used as offshore crude oil offloading terminal to transfer crude oil from tanker to land receiving terminal through CALM buoy to submarine pipeline.Compared with crude oil terminal,it has the advantages of low cost and strong adaptability.In this paper,a deep-water CALM buoy offloading system cooperated with FPSO is taken as the research object,and its mooring system is analyzed.The motion response of buoy and the tension response of mooring anchor cables are considered under extreme conditions and transportation conditions.On the basis of time domain analysis,parameter sensitivity analysis of other key components of the CALM buoy system is carried out.Firstly,a series of simplifications of buoys and tankers are made,and hydrodynamic model is established.The hydrodynamic analysis of buoys and tankers is carried out,and a series of parameters,such as amplitude motion response operator,are obtained.Then,in the time domain,the dynamic analysis of the whole buoy system and mooring anchor cable is carried out.According to the environmental characteristics of the target sea area,the a-hundred-year return period swell and a-hundred-year return wind wave and current are listed as the limit conditions.Operating conditions are set as main swell once a year and wind wave once a year.The breakage of an anchor chain under extreme conditions is also considered.On the basis of time domain analysis,parameter sensitivity analysis of other key components of the CALM buoy system is carried out.In the whole system,in addition to the buoy and its mooring system,the hawser which moored the shuttle tanker to the buoy and the oil hose which offloaded the oil from the FPSO to the buoy are also the key components.For the hawser,the effect of mooring hawser length on the system is investigated by length sensitivity analysis.For the oil hose,it focuses on the fatigue life,and it studies the factors that affect the fatigue life of the oil hose.It includes the contribution of different wave conditions to the fatigue damage of oil pipeline and so on.Based on parameter sensitivity analysis,the effects of related factors in the fatigue calculation of oil pipeline are obtained.