Study On Structural Damage Assessment And Control Measures For FPSO Subjected To Oil & Gas Deflagration Hazard

Exploration and exploitation of offshore oil & gas resource is an important energy development strategy in China.With the vigorous development of offshore oil & gas industry in China,FPSO is more and more widely used in oil & gas production in the Bohai Sea and the South Sea because of its great advantage in economics and technology.During working,FPSO will encounter great risk caused by complex craft system,tight arrangement of equipment and hostile working conditions.Among the most serious accidents of FPSO,fire and explosion caused by oil & gas leak can bring equipment damage,hull scrap and huge casualties,but also the environmental disaster.Based on the 2012 State Administration of Work Safety(SAWS)Key Control Technology Projects for Work Safety Major Accidents “Risk management and emergency technology for deepwater drilling in the South China Sea”,the study on quantitative assessment of fire and explosion risk and risk control strategy is conducted to improve control ability of risk and efficiency of operation of FPSO.1.Analysis of oil & gas leakage,fire and explosion accident of FPSOBy investigating offshore accidents report of UK Health and Safety Executive,offshore oil & gas leakage risk in UK North Sea Continental Shelf work zone is presented,including risk resource,leakage type,leakage cause,et al.And the frequency of three type of oil & gas leakage(minor,significant,major)of FPSO in work zone is analyzed.By constructing four computing models,the frequency of fire and explosion caused by oil & gas leakage is calculated,which will roughly help to judge the criticality of oil & gas leakage and deflagration risk of FPSO.2.Analysis of FPSO structural response exposed to oil & gas explosive loadA CFD-based model to predict the diffusion behavior and distribution law of oil & gas is developed and the hazardous area of gas under the leakage condition of crude oil treatment system is identified based on the simulation result.TNT equivalent of combustible gas cloud is identified according to TNT equivalent method,and by establishing numerical simulation model,the propagation process of explosion shock wave and change of its propagation path caused by equipment is analyzed based on blast simulation soft AUTODYN.Moreover,structural dynamic response process and elastic-plastic state distribution of equipment in each module under explosive load is present.The influence of oil & gas leak aperture on deflagration risk is analyzed in details.3.Assessment on FPSO structural damage under oil & gas fireIn order to investigate the variation trend and influence scope of flame temperature and thermal radiation in each module when fire accident happens to crude oil treatment system,numerical simulation model of oil & gas combustion is proposed based on FLUENT.By combining FLUENT with thermal analysis module in WORKBENCH,the distribution of structural temperature is analyzed under fire.To make assessment on equipment damage,a thermal-structural coupling model is established to analyze thermal deformation and stress distribution of structure.Furthermore,the influence of wind speed,leak rate on flame development,fire load and structural damage is analyzed by setting different leakage situation and environmental conditions.4.Study on control strategy for FPSO subjected to oil & gas leakage and burning explosion accidentTo ensure the safety and efficiency of the FPSO,it is essential to carry out the study on control strategy for oil & gas burning explosion risk based on safety barrier theory.The Bow-tie model of oil & gas fire and explosion risk is put forward to analyze the cause and consequence of accident.In addition,the safety barrier is established to prevent and control oil & gas burning explosion accident,which will decrease FPSO risk.By establishing safety barrier failure analysis model,failure mode of safety barrier is analyzed,which describes occurrence and development of oil & gas burning explosion accident.It provides theoretical direction for oil & gas burning explosion accident prevention and control.