气井积液机理和临界气速预测新模型

井筒积液是气井生产过程中面临的问题之一，积液会导致气井产量降低，严重情况下甚至造成气井停产。准确预测气井临界携液气相流速可以及时采取措施以预防积液的发生。对比最小压力梯度模型、液滴模型和液膜模型并分析积液实验的结果表明，液膜反向是气井积液的主要原因。根据液膜在不同气速范围内速度分布规律，将液膜与管壁剪切应力为0对应的气速作为气井积液临界气速。基于环雾流型并考虑到管径、液相流速、气芯中液滴夹带等因素的影响，构建了适用于垂直气井积液预测的零剪切应力模型。利用实验数据和现场数据对新模型及已有的积液预测模型进行对比验证，以模型预测结果正确率和预测误差为评价指标。结果显示，新模型的预测效果优于其他模型，基于零剪切应力的新模型能够较准确地预测气井积液。

Mechanism of gas well liquid loading and a new model for predicting critical gas velocity

Wellbore liquid loading is one of the problems faced in the production process of gas wells. Liquid loading will cause the yield of gas wells to decrease, and even cause the off production of gas wells in severe cases. Accurately predicting the critical liquid-carrying gas flow rate of a gas well can help producers take timely measures to prevent the occurrence of liquid loading. Through comparing the minimum pressure gradient model, droplet model and liquid film model, and analyzing the results of the liquid loading experiment, it is indicated that the reverse movement of liquid film is the main reason for gas well liquid loading. According to the velocity profile of the liquid film in different ranges of gas velocity, this paper defines the gas superficial velocity corresponding to the zero shear stress between liquid film and pipe wall as the critical gas velocity of gas well liquid loading. Based on the annular mist flow pattern and taking into account the influence of such factors as pipe diameter, liquid flow rate and also droplet entrainment in the gas core, this study develops a zero shear stress model suitable for predicting the liquid loading of vertical gas wells. The new model and the existing prediction models of liquid loading are compared and verified by experimental data and field data; and the prediction accuracy and error of the model are used as evaluation indicators. The results show that the prediction agreement of the new model is better than other models, and the new model based on zero shear stress can predict the gas well liquid loading more accurately.