New slug control strategies, tuning rules and experimental results

The challenge of handling intermittent flow with liquid slugs followed by gas pockets in multiphase flow lines becomes more important when the number of satellite fields increases. Oil, gas and water are transported from the wells in some km long flow lines along the seabed and up through a riser to the oil rig. Slugging may cause several problems for topside processing. This paper concerns suppression of slug flow by active use of the topside choke. Process measurements such as pressure and density are used in a PID controller. Slugging has been reduced significantly with such a system in operation offshore since April 2001. This paper contains results within simplified modelling of flow dynamics. New experimental results verify the dynamic model. A control scheme in operation offshore has been tested and a new control scheme independent of subsea measurements has been developed and tested in experiments.