Study On Leakage Risk And Safety Protection Of Shale Gas Wellhead Equipment

In recent years,shale gas development efforts by leaps and bounds,but China's shale gas exploration and development is still in the initial stage,shale gas storage geological conditions are complex,and shale gas relative to other unconventional natural gas buried deeper,domestic shale gas extraction technology And equipment behind the shale gas leakage caused by the occurrence of shale gas leakage and the formation of flammable and explosive atmosphere of the explosive mixture,endangering the physical and equipment safety of the station.Therefore,in order to ensure the safe and efficient mining of shale gas,this paper uses numerical simulation and theoretical analysis to study the leakage mode,leakage probability,leakage and diffusion law,fire explosion risk and safety protection of shale gas production wellhead as follows:(1)This paper analyzes the causes of the leakage of the wellhead in the shale gas extraction.The Bayesian network(BN)analysis is used to determine the probability of the basic event of the shale gas wellhead leakage.Flange leakage probability> pipe leakage probability> oil / casing leakage probability,and the shale gas wellhead device leakage accident probability of the size of 2.3×10-5,diagnostic reasoning the impact of shale gas wellhead device leakage factors Carbon dioxide gas corrosion,sealing material aging,misuse of personnel and third-party human destruction and other factors than the other factors of sensitivity.(2)The three-dimensional model of shale gas wellhead leakage and diffusion based on real scene was established.Fluent was used to simulate the distribution of shale gas diffusion concentration under different parameters(wind speed,leakage,leakage location,terrain,hydrogen sulfide content)and its influence.The effect of wind speed exacerbates the spread of shale gas,making the high concentration of shale gas area decreases as wind speed increases.When the leak is exposed,the danger zone is larger than the leakage port,and the area of the suffocation area is larger in the horizontal direction.The existence of the mountain for the spread of shale gas in the atmosphere has a hindrance;the mountain will affect the original direction of wind speed,thus affecting the spread of shale gas.Sulfur-bearing shale gas due to the presence of heavy gas components,steady-state case of leakage and diffusion of sulfur less shale gas diffusion area smaller.(3)Determine the leaking area of shale gas in the shale gas extraction station,and divide the asphyxia and explosion area of shale gas leakage.When the leakage time is 5min,the dangerous area of shale gas is concentrated near the leak,and the area of asphyxia is larger than that of the explosion area.The risk range of shale gas leakage is 10m×8m×9m in the wind direction,the size of the explosion range of the gas leak is mainly 4m×5m×3m of the center of the leak.(4)The use of personal risk and social risk of shale gas leakage after the occurrence of fire and explosion risk level,when the leakage times of 5min,the fire and explosion safety distances were 22.6m and 455 m.The hazard of the explosion is far greater than the impact of the fire.When the leakage time is less than 5min,it is acceptable to have a fire risk caused by a fire distance of 20 m and beyond.And the explosion risk inside the station is unacceptable.Finally,the safety protection distance of the shale gas trap is analyzed,and the safety protection measures of the shale gas leakage accident are put forward.