The stability of fluid production from a flexible riser

The prediction of slug formation and slug size has a direct impact on the design of topsides separation facilities and flow assurance to the process. The characteristics and stability of liquid production from an S-shaped riser have been studied over a range of pressures, focusing on the implications for flow management. Severe slugging in an S-shaped riser gives a period of no liquid production, followed by a period of steady production and finally a large production spike, many times larger than the steady production. In contrast with classical severe slugging in a vertical or catenary riser, the transient spike is broken into two parts as a direct consequence of the bend in the line. Little attention has been paid to transition-type flows (between stable and unstable flow) previously. Data collected to date has shown transition flows have production peaks that are larger than those of classical severe slugging.