Research Of Annulus Pressure Risk Assessment Technology Of Offshore Gas Well

Sustained casing pressure of offshore production wells has become a major security hidden danger at national level which has seriously threatened the productive safety.The causes of offshore gas wells annulus pressure and gas leakage ways were analyzed combining with production practice.Gas diffusion rules and the influence range of fire and explosion accident caused by leakage of annulus pressure gas wells were studied,which have important production practice significance in evaluating risk level of annulus pressure,putting forward reasonable control measures and improving the ability of accident prevention.The following main research contents are completed:(1)According to different annulus pressure situations,the cause of each annulus pressure was discovered based on qualitative and quantitative analysis with FTA.The risk level was divided and relevant control measures were proposed.Meanwhile,leakage routes of gas wells were analyzed and corresponding risks were explained.(2)Wellhead's leakage model of offshore gas well was established.Leakage and combustion status of production gas well's wellhead were simulated by taking production and environment conditions of LD22-1 gas well into consideration.The impact of different wind directions,different wind speeds,different leakage rates on leakage and combustion were explored.The relationship between concentration distribution of leakage gas,concentration distribution of combustion product and wind direction,wind speed,leakage rate were respectively presented,and the temperature distribution status was also demonstrated,which provide the basis for quantitative assessment of the accident consequences.(3)The fire and explosion risk level was determined and casualties zone was divided by evaluating LD22-1 offshore production gas wells with Dow fire and explosion index evaluation method.The relevant prevention control measures were brought forward.(4)The annulus pressure risk assessment software of offshore gas well was developed.The qualitative and quantitative analysis,risk level evaluation of the accident and outputting the evaluation reports were realized,which provide the technical support for evaluating the risk of annulus pressure wells in production practice..