气举举升效率与井筒流态影响关系研究

RELATION STUDY BETWEEN ARTIFICIAL LIFT EFFICIENCY AND BOREHOLE FLOW STATE

目前，很多气田都存在气水同产的问题，其中多数气井都受到储层压力过低和井底积液双重因素的影响，这个问题在低渗透深层气井开发中显得尤为突出。随着气井开采年限的增加，地层能量衰减，气体流动速度不断下降，在井筒中会经历多种流态变化，其中段塞流向环雾流转换的过程中会经历一种中间流态——过渡流。通过可靠的实验证明过渡流是一种极不稳定的流动状态，严重影响气举工艺的携液效率，了解并能准确预测过渡流态的发生，可以对优化气举排液设计提供有效帮助。此外，通过对现场及实验室数据的分析，总结了一套预测过渡流发生的简单方法。该方法利用井口实际注入气体流速随深度变化曲线与Turner模型计算的临界携液速度随深度变化曲线为主要依据，依靠两条线的关系判断过渡流发生的可能性。现场实例验证该方法可以有效判断过渡流发生的时间，由此可以及时制定或改变相应的措施予以避免。

At present, the problem of gas-water coproduction is common in most gasfield and many gas wells are influenced by both low reservoir pressure and bottom-hole liquid loading, especially in the development of deep low-permeability gas wells. With the increase of exploitation age, producing energy and gas flow velocity are keep- ing dropping. Many flow states are changed in well bores. Among them, in the course of transferring from plug flow to circular fog flow, a kind of medium flow state can exist--transitional flow. In fact, by means of reliable experi- ment, the above flow is proven to be a kind of extreme instable flow state and it seriously influences liquid-carrying efficiency of gas lift technology. Understanding and accurate prediction of the state occurrence can do effective favor to optimize liquid delivery design. In addition, with the help of field test and laboratory data analyses, this paper summarizes a set of simple method of forecasting transitional flow. Through adopting the change curves of actual in- flow gas velocity with depth at well head and critical liquid-carrying velocity with depth calculated by Turner model, the method makes use of the relation of above two curves and judges the possibility of transitional flow occurring. Case study proves that the above method can effectively determine the occurrence time of transitional flow and then make or change corresponding measurements to avoid it.