Severe slugging in a riser system: experiments and modeling

Abstract

Previous analysis showed that “severe” slugging would exist in a pipeline—riser system when the liquid in the riser is unstable and gas penetrates into the riser. This would then result in an unstable blowout and a cyclic process. When the liquid column is stable, a steady state is assumed to exist. However, observations made on a small-scale test facility have demonstrated that when the liquid column is stable there is still a tendency for a cyclic process to occur. This cyclic process can be damped and become a steady flow or it can continue indefinitely. From these observations a new theory is developed for predicting the behavior in the stable region and is verified with experimental results. It is also shown that in the region predicted by the Boe criterion to be a steady flow, the flow can be unstable and lead to a severe slugging type of behavior.