This study explored flow patterns and void fraction prediction models for co-current upward liquid-gas two-phase flow in narrow annular spaces. Experiments on two-phase flow in both narrow and wide annular conduits were performed in a 4-inch (0.102 m) outside-diameter test section, with 3.5-inch (0.089 m) and 2-inch (0.051 m) inner pipes as representations of different annular geometries. Flow patterns and liquid holdup were recorded while flowing air and water upward through the test sections. The experimental results showed that the two-phase flow pattern maps in narrow annulus and wide annulus are with different major regime transition lines. A new drift-flux model for water-air two-phase flow in narrow annuli was developed using experimental data collected in this study. The new model was compared against previous models that were developed for wide annuli, and the results showed a better match in void fraction predictions for two-phase flow in narrow annuli with experimental data. The understanding of two-phase flow in narrow annuli is vital for real-time prediction of void fraction and annular pressure loss in wells with gas influx during casing/liner/slimhole drilling operations. An enhanced prediction can ensure delivery of safer wells with lower non-productive time and associated trouble encountered during well control operations.

本研究探索了在狭窄环形空间中并流向上的液-气两相流的流型和空隙率预测模型。在直径为4英寸（0.102 m）的试验段中，以3.5英寸（0.089 m）和2英寸（0.051 m）的内管为代表，进行了狭窄和宽环形管道中两相流动的实验不同的环形几何形状。当空气和水向上流过测试部分时，记录了流态和液体滞留率。实验结果表明，窄环带和宽环带的两相流型图具有不同的主态过渡线。利用在这项研究中收集的实验数据，开发了一种新的水-空气两相流在窄环形空间中的漂移-通量模型。将新模型与为宽环空开发的先前模型进行了比较，结果显示窄环空两相流的空隙率预测与实验数据更好地匹配。狭窄环空中两相流的理解对于实时预测套管/衬里/小孔钻进过程中有气体涌入的井中的空隙率和环形压力损失至关重要。增强的预测功能可以确保以更少的非生产时间交付更安全的井，并减少在井控制操作中遇到的相关麻烦。狭窄环空中两相流的理解对于实时预测套管/衬里/小孔钻进过程中有气体涌入的井中的空隙率和环形压力损失至关重要。增强的预测功能可以确保以更少的非生产时间交付更安全的井，并减少在井控制操作中遇到的相关麻烦。狭窄环空中两相流的理解对于实时预测套管/衬里/小孔钻进过程中有气体涌入的井中的空隙率和环形压力损失至关重要。增强的预测功能可以确保以更少的非生产时间交付更安全的井，并减少在井控制操作中遇到的相关麻烦。