The Research Of Wet Natural Gas Pipeline Anti-jam Bypass Pigging Technology

In the undersea gas condensate pipeline,the gas and liquid are prone to slip and form rententate,which will reduce the effective area of the gas transmission.Also,the temperature is low and the pressure is high in the undersea gas condensate pipeline,and it is prone to form hydrate,which will block up the pipeline.In order to solve the problem and improve the efficiency of gas transmission,the pipeline can be cleaned with pig regularly.In the process of pigging with traditional pig,there will be liquid slug in the front of the pig,which will cause unstable operation.Especially in the riser,the velocity of pig increases,and the terminal trap receive large condensate instantly,which will bring impact damage to the trap.The anti-jam bypass pig can solve the problems effectively,so the research is very important.This paper summarizes the model of bypass pig motion and provides new design structure on the basis of study in bypass pig research and structure design at home and abroad.The bypass pig with certain bypass ratio can cut down the velocity of pig,reduce pipeline pressure fluctuations and control the gas-liquid flow pattern at the head of pig.At the same time,once the pig block up in the pipeline,the valve in the pig can move forward to stop up gas.The pressure between pig increases and the pig restarts.The heart of the anti-jam bypass pig depend on the preference of bypass ratio and the design of anti-jam valve.Combined with a subsea gas condensate pipeline in Nan Hai Liwan,The paper simulates different bypass ratio pigging process with OLGA simulation software,selects the best bypass ratio through the comparative study of pig velocity,pipeline pressure,terminal liquid slug flow,holdup and flow pattern.In order to ensure safe pigging condition,the paper determines the minimum amount of MEG to prevent the formation of hydrate by simulating the process of normal gas transmission,normal pigging,and pigging jam.In order to achieve the function of anti-jam for bypass pig,the pig is added valve element,and the spring is the key to realize the function of restart.The paper simulates the force of indoor pig with simulation software Fluent.It analyzes the valve force of pig with different bypass ratio in different pressure condition and summarizes the influence law of differential pressure between pig on the valve.The force of valve in the pig is tested in the indoor pipeline.The micro force sensors are arranged on the flow axial plane for the test.The bypass ratio,valve displacement,and gas flow rate is changed to realize the mutual authentication between experiment and Fluent numerical simulation.Also the valve force discipline influenced by bypass,valve displacement,gas flow rate is analyzed.Finally,the design method of spring is received and the integral design guideline of anti-jam bypass pig is formed.