Numerical Simulation of Gas/Liquid Two-Phase Flow in a Large-Diameter Vertical Pipe

Accurate knowledge of flow behaviors of gas/water two-phase flow in pipeline is crucial to production optimization, production string selection, production logging interpretation, down-hole metering, and artificial lift design and modeling. In this study, two-dimensional simulation model of a large-diameter vertical pipe was established by using the software of FLUENT 19.0, which with 125 mm I.D., and 10 m long. Based on the verification of grid independence and comparison of quantitative results of simulations with experimental tests, the effects of input water content and flow rates on flow patterns, phase distribution, holdup, and average velocity distribution along the pipeline were examined using a VoF approach. The results show a quantitative agreement between calculations and experimental data for the liquid holdup. Additionally, the flow pattern will change from bubble flow to cap flow and slug flow with the increase of input gas content when the flow rates of mixtures are unchanged, and it also will gradually transit from dispersed bubble flow to cap flow and slug flow with the increase of input flow rate when setting same input water contents. Furthermore, when the total flow rate less than 50 m3/d, the flow pattern of mixtures is stably bubble flow. In all simulation studies, the phase distribution of mixtures shows the same characteristics, i.e. the water holdup of the three section in the order of highest to lowest as follows: the top section of pipe, the bottom of pipe, and the whole section of pipe. While, the average velocity distribution of the mixture is affected by the input water content, and presents diversification in different ranges of water contents. When the input water contents in the range of 30% to 60%, the average velocity of the three section in the order of highest to lowest as follows: the top section of pipe, the whole of pipe, and the bottom section of pipe. While when the input water contents small than 30% or larger than 60%, the average velocity of the three section in the order of highest to lowest as follows: the bottom section of pipe, the whole of pipe, and the top section of pipe. The systematic analysis of flow characteristics for gas/liquid two-phase flow with low flow rate in a large-diameter pipe can lay a theoretical foundation for the study of logging data interpretative method of gas wells.