The Study On NGH Formation Prediction And Control Equipment Of The Gate Valve At Shale Gas Wellhead

The gate valve is one of the most important parts of wellhead equipment which are used on gas production.When it works,NGH(natural gas hydrate)may form on the inner wall,which may cause failure in opening and closing of the gate and may lead to accidents.The essay aims at the natural gas produced in the Lower Silurian Song Kan Formation Well Anye 1 of north Guizhou and studies the prediction of NGH formation.Then,flow field characteristics analysis of FLS gate valve has been done and a kind of NGH-restrain equipment has been designed.Eventually,NGH will not form on the inner wall of the valve.The essay establishes the inner fluid model of FLS gate valve by measuring.It confirms the numerical calculation method by repeating the simulation results of others and analyses the flow field inside the valve under two different conditions.Then,NGH formation prediction has been done using the method of maximum temperature difference.The well is in a location where its lowest temperature can reach-10?,which can be used as the ambient temperature for simulation.A series of simulations have been performed with a step of 5 ?,aiming to study how ambient temperature affects the formation of NGH.It shows that when the gate valve,with free water inside,is not heated or insulated and the ambient temperature is at-10?,NGH or ice will form.Based on the NGH prediction,the essay chooses the temperature-increasing scheme to restrain the formation of NGH and calculates the minimum energy it needs to eradicate NGH.Then,a heating scheme has been made and the armored heating device has been designed.At last,given that the NGH-restrain equipment is installed outside the surface of the gate valve,the essay analyses the thermal condition of the valve.It analyses the temperature increasement on the inner wall of the valve under different powers and thus analyses the inner flow field of the valve under two working conditions again.Eventually we have the conclusion: when the gate valve is at the lowest ambient temperature and there exists free water,the NGH-restrain equipment can eradicate NGH and ice.Meanwhile,we have efficiency curves under different powers and two working conditions.Therefore,we confirm the minimum power of NGH-restrain equipment.