Severe Slugging Control Through Open Loop Unstable PID Tuning to Increase Oil Production

A method of eliminating severe slugging by implementing active control at open-loop unstable operating point is presented. This method overcomes the high back-pressure imposed on the riser-pipeline system by manual choking or some existing active control solutions using the riser top valve. Firstly, a simplified riser-separator model is developed by extending an existing simplified riser model. A relay auto-tuning approach is then developed for a slug controller to work at an open-loop unstable operating point, where the choking valve can open wider than manual choking so that overall production can be increased. The aforementioned tuning approach is successfully applied to the riser-separator model through simulation and demonstrated with the laboratory risers at Cranfield University. Simulation through a commercial multiphase simulator on an industrial riser system shows that the proposed approach eliminates severe slugging with increased oil production.