Risk Analysis Of FPSO Offloading System

FPSO has been widely used in shallow, deep water and marginal oil and gas field development. Oil and gas resources usually are transported to shore by shuttle tankers. There exists collision, hawser fracture, broken oil hose leaks, oil spills and fires / explosions and other risks during the process of offloading, which endanger the safety of the personnel, environment and marine equipments. Therefore, the study of the risk of the offloading system appears to be very necessary and urgent.Firstly, the risk of offloading berthing and hose are assessed, pointing out various factors which affect risk. Appropriate measures can be taken accordingly to reduce the risk.By analyzing the collision incidents; the risk root of collision is identified to be fish-tailing and excessive surging.Finite element models of FPSO and shuttle tanker are created to calculate hydrodynamic parameters of the two bodies by Hydrostar, and then import these parameters into mooring analysis software. In allusion to the three typical and dangerous loading conditions during tandem offloading, as well as wind change and different combinations of wind, wave and current, a lot of simulation calculation of the two bodies'relative motion is done in time-domain, and introduce extreme value theory; and study different methods of estimation of parameters, Then the extreme value theory is used to predict the occurrence probability of fish-tailing and surging, and analyze the impact of different loading, combinations of wind ,wave and current, wind change and the use of tugs to the fish-tailing and excessive surging,and some protective measures are put forward. Better effect is obtainedBased on the weakest failure modes theory, the broken cable risk analysis of hawser and mooring system is classified into several orthogonal weakest failure modes. Then make use of the software calculation results to calculate respectively and classified them as series system to calculate reliability,combining with the advanced first order-second moment method. The correlation of multi-failure modes of double cable are solved and the weakest failure mode are find by use of probability grid evaluation technique, in the end the reliability in offloading operations using double cables is analyzed based on the former calculation result. Finally a set of analysis method universally used for broken cable risk analysis is suggested.