Comparative study of different Methods for Slug control

Abstract

This thesis looks into how to create a dynamic model of riser slugging. The model created is a six-state model based on mass conservation of the gas and liquid phases in the well, pipeline and riser. Matlab is used to create the model. The model is created in such a way that the process uses an integrator with variable step length while the sampling of data uses a fixed sampling rate. This gives the model properties resembling a real scenario. The model is used to test out different control systems based around the top side valve. A subsea valve was also tested, but gave poor results. The model worked very well when testing out the control solutions. It is easy to get the data required, and very intuitive to use. The active control of the top side valve gave an average increased production of 8.43%. Control based on the well head pressure had problems with flow spikes in the transitions every time the set point changed. The control based on the mass flow out fixed this problems, but was not able to stabilize already slugging flow.