Controllability analysis of severe slugging in well-pipeline-riser systems

Active control of the production choke valve is the recommended solution to prevent severe slugging flow conditions at offshore oilfields. The focus of this work is to find the structure of a simple, yet robust anti-slug control system. In order to find suitable control variables for stabilization, a controllability analysis of the system with different available measurements or different combinations of them was performed. Moreover, for including robustness and performance requirements at the same time, the controllability analysis was extended to a mixed sensitivity ℋ∞ optimization problem. Two case studies were considered; first, the controllability analysis was performed on a pipeline-rise system using a 4-state model for comparing the results to the previous works. Next, using a 6-state model, the results were extended to a more general well-pipeline-riser system. The controllability results were in accordance with the practical experience in anti-slug control.