Numerical Simulation Of Fluid Accumulation And Pigging In Wet Gas Pipelines With Hilly-Terrain Pipeline

During the long-term operation of the undulating wet natural gas gathering and transportation pipeline,the amount of liquid accumulation in the pipeline has accumulated over a period of time and has an upward trend with the increase of the transmission distance,and gradually accumulates in the low-lying places along the pipeline.There is a serious liquid accumulation problem in the pipeline.It will cause many problems such as reduced pipeline transportation efficiency and aggravated corrosion in the pipeline.Therefore,it is necessary for this paper to carry out research on the law of fluid accumulation in the undulating wet gas pipeline and the characteristics of the pigging process.In order to solve the problems related to liquid accumulation in the wet gas pipeline,this paper analyzes the two-fluid model,based on the basic differential equations,and uses the OLGA software to establish simulation models of the vapor-liquid two-phase flow accumulation and pigging in the wet gas pipeline.According to the single-factor control variable method,the change law of the fluid accumulation in the pipeline under different influencing factors is studied,and the degree of influence of each influencing factor on the fluid accumulation is deeply analyzed through the orthogonal experiment design.The results show that: The degree of influence of the volume is as follows: pipe diameter,inlet gas volume,gas mass liquid content,outlet pressure,and pipe inlet temperature.Using OLGA software to perform real-time dynamic simulation on the three pre-purge schemes initially determined,and found that the three schemes can reduce the amount of liquid accumulation in the pipe,but scheme 3 first reduces the pipeline outlet pressure and then increases the pipeline air volume after purging The amount of remaining fluid in the pipe after operation is the least.In Turner's research on the method of predicting the critical flow velocity in vertical gas wells,the dip angle in the topographic undulating pipeline is introduced,the force analysis of the droplets in the pipe is carried out,and the calculation formula of the critical flow velocity without liquid accumulation in the topographic undulating pipeline is derived,and OLGA is adopted.The software verifies the accuracy of the calculation formula and simulates the distribution of liquid accumulation in the pipe under each set of flow rates,thereby verifying the accuracy of the critical flow rate calculation formula,and can provide a theoretical basis for the control of liquid accumulation during the on-site operation of the topographic undulating wet gas pipeline.Real-time dynamic simulation of the pigging process under different pigging capacity and bypass pig bypass rate,and detailed analysis of pig speed,special point pressure of the pipeline,liquid discharge volume at the outlet of the pipeline,etc.during the pigging process The parameter changes,determine the best pigging parameters,in order to achieve the purpose of reducing the risk of pigging operations.Use MATALB software to compile the BWRS equation and pipeline transmission efficiency program to calculate the pipeline gas transmission efficiency,combine the upstream and downstream pressure drop of the pipeline as the basis for pigging,explore the best pigging cycle,and ensure the safety and efficiency of the existing wet gas gathering and transportation pipeline system Operation and provide experience guidance for the optimized operation of similar newly-built wet gas gathering and transportation pipelines in the future.