气井井筒条件下单液滴动力学特征及其携带临界气流速

准确认识气井井筒条件环状流场中单液滴的动力学特征和正确计算液滴携带临界气流速是气井连续携液机理研究的重要内容之一。为深入研究气井井筒高温高压条件下液滴的动力学特征，首先建立了气流场中单液滴动力学特征的数值模型及求解方法，采用流体体积函数法(VOF)模拟液滴表面结构，利用直接数值模拟方法(DNS)模拟液滴周围气流场，开发了单液滴动力学特征数值模拟求解器。以气井压力温度为模拟条件，通过逐渐增加气流速而增加韦伯数，模拟得到了液滴椭球度随韦伯数增加而减小、曳力系数随韦伯数增加而增加的规律，和液滴破碎的临界韦伯数为12的认识；基于数值模拟结果和力平衡原理推导了单液滴携带临界气流速预测新模型，新模型中的综合系数为3.31，与李闽椭球模型的综合系数为2.5比较接近。利用公开文献数据对现有单液滴模型进行的适应性评价表明，在低液量(1 m3/d)气井条件下，井筒液滴稀疏、液滴相互作用弱，新模型和李闽椭球模型具有较高的准确性。

Dynamic behavior of single drop and critical single drop carrying gas flow rate under the well condition of gas well

One of the important study contents on the continuous liquid carrying mechanism of gas well is to accurately understand the dynamic behaviors of single drop in the annular flow under the well conditions of gas well and correctly calculate the critical drop carrying gas flow rate. In order to deeply research the dynamic behaviors of drop under the high temperature and high pressure conditions in the well of gas well, this paper firstly established a numerical model of dynamic behavior of single drop in the gas flow field and its solution method. In addition, a numerical simulation solver of dynamic behavior of single drop was developed by using the volume of fluid method (VOF) to simulate the surface structure of drop and the direct numerical simulation method (DNS) to simulate the gas flow field around the drop. Then, taking the pressure and temperature of gas well as the simulation condition, simulation was carried out by increasing the gas flow rate gradually to increase the Weber number. It is shown that the drop ellipsoidity decreases and the drag coefficient increases with the increase of Weber number, and the critical Weber number of drop breakup is 12. Finally, a new model for the prediction of critical single drop carrying gas flow rate was deduced based on numerical simulation results and force balance principle. The composite coefficient of this new model is 3.31, which is closer to that of Li Min’s ellipsoid model, i.e., 2.5. The adaptability evaluation on existing single drop models by using published literatures and data indicates that under the gas well condition of low liquid rate (1 m3/d), the drops in the well are scattered and interact weakly and the new model and the Li Min’s ellipsoid model have higher accuracy.