Influence Of Viscosity On Pressure Drop Of Gas-liquid Two-phase Flow In Horizontal Tube

With the constant increase of world energy demand and the consumption of conventional crude oil deposits,high-viscosity crude oil has become one of the most important hydrocarbon energy sources in the future.To date,experimental studies,models and empirical formulas have focused on conventional low-viscosity crude oils,leading to large errors for many commercial gas-liquid two-phase flow simulation softwares at high viscosities.With the development of the oil industry,high viscosity crude oil is found and produced all over the world.Most existing multiphase flow models treat viscosity as an invariant.Changes in viscosity alter the physical properties of the liquid phase and can affect the relatively multi-phase flow properties,including the formation of droplets,the wave of the surface,the entrainment of the bubbles,and the mixing area of the slugs.The mixed flow of the lower Reynolds number oil phase and the higher Reynolds number gas phase may further lead to the formation of new flow patterns and the accompanying pressure drop changes.In summary,the in-depth study of the effect of viscosity on the pressure drop of the gas-liquid two-phase flow in horizontal pipes can solve important technical problems for oil production and is of great significance.In this paper,the analysis of the gas-liquid two-phase flow of horizontal tubes with high viscosity is carried out and the following conclusions have been carried out:Experiments and the progress of model research of gas-liquid two-phase flow conducted so far both domestic and abroad were investigated.The investigations found that the experimental research,models,and empirical formulas so far focused on low-viscosity conventional crude oils and high-viscosity gas-liquid two-phase flow was less focused.The current pressure drop model is summarized.Horizontal tube gas-liquid two-phase flow experiment with high viscosity is designed and carried out.The experiment was conducted in an plexiglass tube with an internal diameter of 60 mm and a length of 8 m.The basic parameters such as liquid viscosity,gas phase flow rate,liquid phase flow rate,pressure,pressure drop,liquid holdup,and temperature were measured.Three kinds of flow patterns were identified by the naked eye and the high-speed camera:laminar flow,annular flow,transitional flow between laminar flow and annular flow.Based on the experimental data obtained,according to different viscosities,the flow pattern maps are using gas-phase superficial velocity,liquid-phase superficial velocity as the coordinates.Through the flow pattern,the effect of liquid viscosity on the liquid holding rate and pressure drop was studied.It was concluded that the viscosity had little effect on the liquid holding rate and had a certain influence on the pressure drop.Comparison of experimental and theoretical results show that the Taitel&Dukle model has consider the effect of viscosity on flow pattern transitions too less.The flow transition boundary of three different viscosities obtained by the double-circle model is compared with the experimental data.The double-circle model has a good agreement with the flow pattern obtained from the experiment.Because of considering the effect of viscosity on the gas-liquid two-phase horizontal flow,Zhang-Sarica model and the steady-state model were chosen.Using two models to calculate pressure drop and liquid holdup on three different viscosities(1142 cp,740 cp and 518 cp).Results of the two models were compared with the data obtained in this experiment.It was found that the steady-state point model had better prediction effect on the liquid holding rate and pressure drop under high viscosity.