Risk Assessment And Control Strategy For FPSO Subjected To Oil&Gas Leakage And Chain Effects

After making a general survey of the development of global economy and energyresources, it becomes obvious that offshore oil&gas resource has been the most importantpillar industry for maintaining a steady and rapid economic growth, and exploiting activitieshas been encouraged and accelerated around the world. The development tendency ofoffshore resource exploitation is observed obviously, i.e. offshore platforms are movinggradually from shallow water to deep sea, and marginal oil fields have been brought to theforefront. To meet such needs, FPSOs (Floating Production Storage and Offloading Units)emerge and grow quickly because of its great advantages in economics and technology.FPSOs which have multiple complex process systems with abundant flammable andexplosive substances, narrow space, and hostile environment are exposed to huge potentialfire and explosion risk which would result from leakage incidents of oil&gas. The platformand workers would suffer great loss once such accidents happened. Given the high risk ofFPSOs’ operation, based on the independent innovation scientific research project of ChinaUniversity of Petroleum (East China),‘Research on Risk Control Technology and ApplicationFoundation for Deepwater Oil&Gas Exploration in South China Sea’(09CX05008A), thepaper is aimed to introduce our research on risk assessment and control strategy for FPSOsubjected to oil&gas leakage and subsequent chain effects, which can provide theoreticalfoundation and technical support for improving the ability of risk control and management aswell as the quality of emergency rescue for FPSO in operation.The latest research results and development of study on the risk of various offshorestructures (including FPSOs) affected by leakage, fire and explosion incidents of oil&gas aresurveyed extensively across the world, and the development trend and future of study on therisk of ocean engineering is summarized. It becomes obvious that the CFD-based numericalsimulation technology represented by FLUENT software has become a significant researchmethod for study on the fire and explosion risk of offshore platforms. Considering theparticularity of FPSO, the hazardous factors which include combustible substance, oxygensource, ignition source, equipments and process systems are identified systematically. Riskassessment models of fire and explosion accidents for FPSO in full life-circle and operationphase are established based on Analytic Hierarchy Process and Fuzzy Evaluation Theory. Theresults show that the risk level of FPSO in full life-circle and operation phase are both incritical state with a bias to safer state. And it is important to note that storage system, crude oil treatment system and flare stack system of FPSO in operation phase have higher risk leveland need significant attention. According to the actual operating conditions, the leak rate ofgas with different hole diameters is calculated based on appropriate leak source model. Then,A CFD-based model which has been proved to be useful in predicting the diffusion behaviorand distribution law of gas is developed, and the hazardous area of gas under the leakageconditions of crude oil treatment system and flare stack system is identified based on thesimulation result, and the hazardous division on FPSO topside is confirmed. Furthermore, theinfluence of wind direction, wind speed, and leak rate on the diffusion behavior of gas isanalyzed in details. In order to investigate the variation trend and influence scope ofdeflagration overpressure, flame temperature and thermal radiation when gas explosionincident happens to crude oil treatment system and flare stack system, another CFD-basedmodel is proposed based on the above results. The minimum safety radius for workers inemergency evacuation and fire fighting is suggested. At last, the safety protection system ofFPSO which include fire fighting system, emergency escape system, fire&gas monitorsystem, and emergency shutdown system is discussed systematically with the goal of accidentprevention and risk control. The present study is helpful for mastering the overall risksituation of FPSO in operation, and it is of great value in academic research and engineeringapplication.