Flow patterns of oil-water-gas three-phase downward flow and transition from bubble flow to slug flow

The accurate calculation of the flow characteristics of oil water gas mixed transportation is an important basis of pipeline design and safe and economic running. The flow patterns of oil water gas three phase flow are classified into bubble flow, slug flow and annular flow. The experimental results show that the phase transition of oil water mixture flow from the state of water in oil (W/O) to the state of oil in water (O/W) occurs at the water cut of 0.45. By analyzing the mechanism of bubble collision and coalescence, a method is presented to predict the flow pattern transition from bubble flow to slug flow of oil water gas three phase downward flow, the error between the result calculated by the method and the experimental data is 11%. Such transition takes place at the void fraction of 0.35. It is mainly influenced by superficial gas and liquid velocities, while the effect of water cut on it is a little.