Hydrate Formation And Prevention Study Of Lifting Gas Pipeline Network

Nature gas hydrate is a kind of ice white crystals which can be formed above 0 ℃.Hydrate will form at high pressure or low temperature.Hydrate in gas pipeline may reduce the circulation area of pipeline,increase friction and decrease the capacity.If seriously,it may cause pipeline or valve clogging,affect the production efficiency.Pilot test of gas lifting will put into commission to get the technical experience of independent engineering for gas lifting in one oilfield.There will be five wells involved in pilot test.The source of lifting gas is raw gas.It is necessary to predict the hydrate formation conditions,and prevent the hydrate formation of pipeline network.Start with its structure,nucleation mechanism and influence factors,some widely used prediction methods are compared in different ways,include graphical method,relevant type method,thermodynamics,etc.In this paper,lifting gas pipeline network is simulated by HYSYS with PR equation of state to analyze hydrate formation condition and type at gas lifting wellhead injection pressure(10.1MPa).Heating natural gas,dehydration,inhibitor injection and some other methods to prevent hydrate formation are available.This paper outlines advantages,disadvantages,and prevention effects,application considerations of different prevention measures.After comprehensive analysis,TEG(triethylene glycol)dehydration is adopted as a primary measure,inhibitor injection is an auxiliary measure to avoid hydrate formation.TEG dehydration model is built and optimized on inlet gas temperature,number of tray,lean TEG concentration and circulation by HYSYS.Calculating methanol inhibitor and ethylene glycol inhibitor injection dosage and analyzing different calculation results of design handbook and HYSYS.Then,TEG dehydration and methanol inhibitor injection systems are designed,including absorb tower,separator,reboiler and methanol tank,etc.For gas lifting pipeline network,TEG dehydration and methanol injection can significantly avoid the hydrate formation and ensure the safety of pipeline network.