Occurrence of severe slugging in oil production lines and mitigation methods: A numerical simulation approach using ALFAsim®

Abstract

Severe slugging represents a major challenge in offshore production systems, potentially compromising operational stability and the integrity of installations. Although established simulators such as OLGA® are widely used for its analysis, there is a gap in the literature regarding the application of the one‐dimensional simulator ALFAsim® for modelling and mitigating this phenomenon. In this context, this study aims to evaluate ALFAsim's® capability to identify severe slugging and analyze mitigation strategies in a system composed of a well, flowline, and riser. The methodology was based on one‐dimensional transient numerical simulations, including domain discretization with a linear mesh (10 m segments), solution of the mass and momentum conservation equations, and identification of flow patterns using the unit cell model. Boundary conditions of flow rate, pressure, temperature, and gas–oil ratio were imposed, with parametric variation of the oil flow rate between 800 and 1400 m 3 /d. For mitigation analysis, a choke valve located at the top of the riser was modelled using a C v (flow coefficient) versus opening curve, and gas injection at the base of the riser was performed at different rates. The results indicated that ALFAsim® reproduced the main hydrodynamic characteristics of the phenomenon, including cyclic flow oscillations and pressure variations, with an approximate cycle period of 7000 s. A choke valve opening of 92.5% and a gas injection of 660,000 m 3 /d are found to be the most effective conditions for flow stabilization. These findings demonstrate that ALFAsim® is a suitable tool for the analysis and mitigation of severe slugging.