Subject:A Study Of Gas-liquid Two-phase Flow Characteristics And Critical Liquid Carrying Model In Wellbore

In the late production period of natural gas wells,due to the gradual decrease of bottom hole pressure and the increase of water content,liquid loading often occurs,which will reduce the production of gas wells and even lead to production halt in severe cases.Therefore,it is necessary to accurately predict the critical liquid carrying velocity and pressure drop of the gas wells so as to take effective drainage measures and ensure the steady operation of gas well.Starting from the characteristics of gas-liquid two-phase flow in pipelines,through the stress analysis of liquid film and gas core in the wellbore,this paper establishes a prediction model of critical liquid carrying velocity for inclined gas wells,which based on liquid film reversal theory and considering the influence of droplet entrainment and wellbore inclination at the same time.The field data is used to compare the new model with other common models,and the results show that the prediction of this model is more accurate.In the meanwhile,in order to further increase the understanding of the critical liquid carrying velocity,this paper also analyzes the influencing factors combined with the model.The results show that the critical liquid carrying velocity of the gas well increases with the increase of the diameter of the wellbore,the temperature of the wellhead and the density of the liquid phase.The critical liquid carrying velocity of the gas well decreases with the increase of the pressure of the well head.The critical liquid carrying velocity of the gas well increases first and then decreases with the increase of the inclination of the wellbore.In addition,based on the annular-mist flow pattern and considering the influence of liquid drop entrainment,a pressure drop model for inclined gas well is also established in this paper,which starts with the conservation equation of momentum.The Beggs-Brill model is compared with the new model through the actual data and the results show that the prediction accuracy of the new model is better.In addition,various influencing factors of pressure gradient are further analyzed in this paper,and it is found that the pressure gradient in the wellbore increases with the increase of inclination angle,gas-liquid density and the superficial flow rate of liquid.The pressure gradient decreases with the increase of pipe diameter.It provides a theoretical reference for the actual production process.