The Influence Of Liquid Viscosity On Slug Flow Characteristics Of Gas-liquid Two-phase Flow In Upward Inclined Pipe

Slug flow is widely existed in the fields of oil and gas exploration and mixed transportation,chemical industry and nuclear power generation.With the development and utilization of shale oil,it is necessary to study the gas-liquid two-phase flow with medium and high viscosity.Compared with the low viscosity liquid phase,the slug flow characteristics of medium and high viscosity oil are significantly different.Most of the existing slug flow pressure drop,slug frequency,liquid slug holdup and slug length model are developed on the basis of low viscosity oil.It is relatively accurate to predict the flow characteristics of slug flow under the condition of low viscosity liquid.As the liquid viscosity increases,the friction between the liquid phase and the pipe wall and the gas-liquid phase changes.These models have relatively large prediction errors.Therefore,this paper conducts experimental and theoretical research on the changes of liquid viscosity on the flow pattern characteristics,slug period,liquid plug length,liquid holdup and pressure drop of oil and gas two-phase slug flow in the upward inclined pipe.(1)White oil and air are used as experimental working fluids.The experiment of slug flow is carried out in the organic transparent pipe with a total length of 9.5m,differential pressure section of 8m and an inner diameter of 60 mm.The flow pattern is observed by high-speed camera,and pipe temperature,gas-liquid flow and pressure difference are collected synchronously,then the average liquid holdup was measured.(2)Barnea flow pattern has a great deviation in predicting the flow pattern of the gas-liquid two-phase flow with larger viscosity.The total pressure drop increases with the increase of pipe angle and decreases with the increase of apparent gas velocity.When the superficial gas velocity is small,the pressure drop decreases greatly.With the increase of gas velocity,the pressure drop decreases slowly.The average liquid holdup of slug flow increases with the increase of liquid viscosity and angle,and the gravity pressure drop also increases with the increase of viscosity and angle.When the inclination angle is 30° and the superficial gas velocity increases,the frictional pressure drop increases gradually;The phenomenon of negative frictional pressure drop appears when the inclination angle is 60°.(3)With the increase of apparent gas velocity,the liquid holdup of slug and frequency of slug decreases,and the length of liquid slug increases.With the increase of viscosity,the frequency of liquid slug increases,the length of slug decreases gradually;With the increase of angle,the length of liquid slug increases and the frequency of liquid slug decreases gradually;the comparison analysis of different models is carried out.Some different models are compared and analyzed.The Majeed(2018)model,the modified Yahaya model and zabaras model respectively improved the prediction accuracy of liquid slug holdup,liquid slug length and frequency.(4)Beggs Brill,DPI,Kaya and Zhang models are used to predict the pressure drop of slug flow.As the viscosity increases,the prediction effects of the four methods all become worse,but the results of Kaya model are relatively better;The prediction results of the four methods are compared and analyzed.The results show that the prediction results are worse with the increase of viscosity,but the results of B-B method are relatively good.A pressure drop prediction model suitable for different liquid viscosity conditions in upward inclined pipe is given by modifying Kaya model,and the accuracy of prediction is improved.