New calculation method of gas-liquid two phase annular-mist flow pressure drop of wellbores in gas wells

Gas-liquid two phase annular-mist flow is one of the most common flow patterns in the production of gas wells and the important foundation of nodal system analysis and production performance prediction for the gas wells is correct prediction of the wellbore pressure drop.The pressure gradient equation for the annular-mist flow was established from the air core-liquid membrane separated phase flow structure of annular-mist flow.Therein, the contributions of liquid membranes and droplets were comprehensively considered in the liquid holdup calculation.By inducing Henstock & Hanratty dimensionless liquid membrane thickness relation formula, the explicit equation for the liquid membrane thickness calculation was derived.Based on the dynamic equilibrium of droplet settling and liquid membrane atomization, the droplet entrainment relation formula of low liquid phase Reynolds numbers applicable to gas wells was also derived.Besides, the shear stress of liquid membranes and tube walls was considered in the friction calculation and the wellbore pressure was finally solved by using Runge-Kutta iteration.The pressure test data evaluation for 91 gas wells at home and abroad shows that the new model has improved the prediction accuracy of the wellbore annular-mist flow pressure drop in the condensate gas wellsand water-yielding gas wells and is better than the traditional uniform phase flow model and divided phase flow model.Moreover, the characteristic parameters of droplet entrainment rate and liquid membrane thickness and etc.can also be obtained.