Slug flow regime in a flowline with U-shape riser

A suitable initial point for understanding multiphase flows is a phenomenological description of the mechanism of geometric distributions or flow patterns that are observed. The challenge however is the prediction of the flow patterns for a combination of flow operating conditions and the characteristics of the phases as well as points of transition from one pattern to the other. Different flow patterns occur in different pipeline configurations for which U-shape risers are part. In the quest to stabilise unstable slug flow in the U-shape riser, an experimental study of gas-liquid flow mixture is conducted to understand the behaviour of the flow in the riser.

This paper seeks to understand the flow dynamics in a 2-inch internal diameter U-shape pipeline riser system with much emphasis on unstable slug flow. The initiation of this flow instabilities in the U-shape pipeline riser system and the impact of the downcomer on the flow behaviour is investigated experimentally. Understanding the flow behaviour in the U-shape riser could help in developing effective control techniques to stabilise the multiphase flows in the flowlines. Experimentally, flow patterns observed from the U-shape pipeline riser configuration is used to develop a flow regime map which was then compared to that observed in literature and similarly to a purely vertical riser with similar pipe diameter. Thus, a slug envelope was developed for the U-shape riser to help identify which regions slugging could occur in the system.