Study On Variation Law Of Gas-liquid Two-phase Transient Flow And Liquid Carrying In Inclined Pipeline With High Gas-liquid Ratio

With the development of oil and gas field production technology,directional well technology has gradually become mature.The number of inclined wells has increased significantly.In the process of liquid carrying in inclined gas wells,when the gas volume is not enough to carry the liquid out of the wellhead,there will be the problem of liquid accumulation,which will affect the production of gas wells or lead to shutdown.However,at present,the research on liquid carrying in gas wells at home and abroad is mainly aimed at vertical or horizontal wells,and the angle correction is usually applied to the calculation formula of liquid carrying in inclined gas wells.Therefore,it is necessary to study the critical liquid carrying in inclined gas wells.In addition,due to the limitation of experimental conditions,most of the research on fluid carrying in gas wells is under the condition of steady flow,but in the actual production process of gas wells,the gas-liquid two-phase flow belongs to multiphase transient flow,that is,the velocity of fluid in the wellbore changes continuously with time.Therefore,the application of the theory of fluid carrying in gas wells based on steady flow in actual production will have some limitations.Therefore,in this paper,gas-liquid two-phase transient flow experiments under different inclination angles are carried out,and combined with OLGA,the transient liquid holdup of inclined gas wells is simulated in real time,which provided a scientific basis for the actual production management of gas wells.(1)This paper investigates and analyzes the research status of gas-liquid two-phase transient flow and continuous liquid carrying in inclined gas wells at home and abroad,introduces and compares four kinds of liquid drop models(Turner model,Belfroid model,Li Li model and Yang Wenming model)and three kinds of liquid film models(Barnea model,Luo model and simplified model),and points out the limitations and unclear problems of current research on steady-state liquid carrying in gas wells.(2)The experiment of gas-liquid two-phase transient liquid carrying in inclined pipe was carried out by using the gas-liquid two-phase flow simulation experimental device.The water and air were used as the fluid medium.The transient flow pattern,droplet film distribution,pressure drop and critical gas velocity were obtained under different inclination conditions,and the results were processed and analyzed.In addition,Numerical simulation of gas-liquid two-phase transient flow in inclined pipes was carried out using OLGA software,which complements the flow law under the transient changes of liquid holdup and gas volume;(3)According to the experimental results of transparent glass tube,it can be seen that: the real manifold of transient flow in inclined tube is mainly transitional flow;in the inclined tube,the droplets cannot exist for a long time,and the liquid is mainly distributed around the tube wall in the form of a liquid film,which is mainly manifested as the thickness of the liquid film at the bottom of the tube is greater than the thickness of the liquid film at the top of the tube;(4)According to the results of experiment and OLGA simulation,the pressure drop of transient flow will fluctuate obviously,the closer to the initial time.The larger the fluctuation,the smaller the fluctuation of pressure drop;in addition,under the same liquid volume condition,with the increase of inclination angle,the transient critical liquid carrying gas velocity first increases and then decreases,and the maximum critical liquid carrying gas velocity appears when the inclination angle is 55 degrees,so 55 degrees is the most difficult angle to carry liquid.(5)In this paper,The pressure drop calculation model of inclined pipeline considering the transient flow characteristics of gas-liquid two-phase is established.Through the comparison and optimization of four commonly used droplet transport models and three different droplet transport models,the calculation model of critical liquid carrying gas velocity of inclined pipeline transient flow and the liquid film loading model are established.Combined with the experimental data,the new model is analyzed and evaluated.The accuracy of the modified model is high,and the calculation error is less than 10%.