Subsea solution for anti-slug control of multiphase risers

A top-side choke valve is usually used as the manipulated variable for anti-slug control of multi-phase risers at offshore oil-fields. With new advances in the subsea technology, it is now possible to move top-side facilities to the sea floor. The two main contributions in this paper are to consider an alternative location for the control valve and to consider how to deal with nonlinearity. This research involved controllability analysis based on a simplified model fitted to experiments, simulations using the OLGA simulator, as well as an experimental study. It was concluded that a control valve close to the riser-base is very suitable for anti-slug control, and its operation range is the same as the top-side valve. However, a subsea choke valve placed at the well-head can not be used for preventing the riser-slugging.