Simulation Of Natural Gas Pipeline And Analysis Of Flowing Assurance

With the increase of demand for energy,the production of natural gas is increasing year by year.In the process of natural gas processing,there're three kind of fluids in the pipeline: gas,oil and water.Under certain conditions of pressure and temperature,the natural gas and water can form hydrate which will probably block up the pipeline.Besides,due to the twophase flow in the pipe,slug flow will appear in many operating conditions and it will affect the normal operation of downstream facilities.Therefore,the natural gas pipeline hydrate prevention and slug control is important.The focus of this paper is listed as follows:Two-phase pipeline steady flow calculation model is established based on the pressure calculation relation and temperature calculation relation.The pressure relative errors of OLGA calculation results and steady state model results is 0.33% ~ 8.35%.The temperature relative errors of OLGA calculation results and steady state model results is 2.64% ~ 12.33%.The natural gas pipeline hydrate prediction model is set up base on the graphical hydrate predicting method.The prediction model can accurately predict the possible existence of the hydrate in the pipeline and calculate the hydrate formation position.The hydrate inhibitor injection rate calculation model is established.The methanol vapor-liquid equilibrium constant chart and natural gas saturated water content chart is converted to formulations so that they can be used for programming.By assuming a homogeneous flow in the pipe,a transient temperature model is established based on energy conservation principle.With the help of characteristics method,the partial differential equations of the temperature model is solved and the fluid temperature calculation relation is derived.A temperature calculation program of shutdown condition is written based on the relations.By comparison,the OLGA results and program results is very close.The OLGA software is used to simulate several slug control methods.According to the simulation results,gas lift method can control the slugs when the gas injection rate is high,the choking method can prevent slugs when the valve opening is very small and it will increase the pipe pressure.A combination of gas lift method and choking method can prevent slugs with low gas injection rate and it will not cause pressure increase in the pipeline.