气井井筒气液两相环雾流压降计算新方法

气液两相环雾流是气井生产中最常见的流型之一，正确预测其井筒压降是气井节点系统分析、生产动态预测的重要基础。从环雾流气芯-液膜分相流结构出发，建立了环雾流压力梯度方程；其中持液率计算综合考虑了液膜及液滴的影响，通过引入Henstock & Hanratty无因次液膜厚度关系式，导出了液膜厚度计算显式方程，基于液滴沉降与液膜雾化的动态平衡，导出了适用于气井低液相雷诺数条件的液滴夹带率关系式；摩阻计算考虑了液膜与管壁的剪切应力，最终采用龙格库塔法迭代求解井筒压力。利用国内外91井次气井测压数据评价表明，新模型提高了凝析气井和产水气井井筒环雾流压降预测准确度，优于传统的均匀流模型和分相流模型，而且能够获得液滴夹带率、液膜厚度等特性参数，为油气田开发提供技术理论支持。

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.