Predictions of Droplet Distribution in Low Liquid Loading, Stratified Flow in a Large Diameter Pipeline

In the pipeline transport of natural gas and condensates, large diameter (typically 38 inch, 0.9176 m) pipes are employed. In such systems, the two-phase flow is often in the stratifying annular regime in which there is a liquid layer on the wall with a dispersion of droplets in the gas core. A crucial issue in such systems is the distribution of the liquid phase around the tube periphery. It is vital (from the point of view of flow assurance risk) to understand the relationship between the continuous liquid film around the periphery and the thicker liquid pool at the bottom of the pipe. For large diameter pipes, the dominant mechanism for maintaining a liquid film at the top of the pipe is that of entrainment of liquid droplets from the thicker liquid layer at the bottom of the pipe and the deposition of these droplets in the upper part of the pipe. The project described here was commissioned and led by ConocoPhillips, with both analytical and computational modelling work being carried out. The two approaches gave broadly consistent results, allowing conclusions to be drawn about the likely liquid distribution and its implications for scale up of hydraulics to manage flow assurance risk in large diameter pipe.