In the mid-to-late stages of coalbed methane field development,to maintain extraction rates and control decline rates,pipeline network operating pressures are gradually reduced each year.Combi-ning Beck's flow pattern boundary method,the flow patterns in coalbed methane production pipelines are categorized and the influencing factors of their evolution are analyzed.In the development and evolution of two-phase flow in coalbed methane pipelines,mist flow,annular flow,laminar flow,wave flow,and slug flow appear successively.Factors affecting pattern development include cooling,merging,capturing,superposition,gravity,and special pipe sections.Additionally,due to changes in relative velocity or the cutoff effect,the phase with high liquid holdup will also transform into the phase with low liquid holdup.Studying the evolution process of gas-liquid two-phase flow helps in systematically analyzing the causes of liquid accumulation and in taking scientific countermeasures.To improve pipeline operating efficiency in winter and reduce coalbed methane development operating costs,further research is necessary to deeply analyze various influencing factors of two-phase flow evolution and explore intervention measures,provi-ding a basis for optimized pipeline design.
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