PI Regulation in CBHP-MPD Simulation using a Transient Flow Model

Abstract

An introduction to control engineering theory is given. The thesis further explores the implementation of a PI regulator in a transient flow model based on the AUSMV scheme. Optimal regulator parameters are important in CBHP-MPD when a control system is used to regulate an automatic choke. an overview of various MPD techniques is also given. Simulations of connection and kick has been performed when a PI regulator is implemented in the transient flow model. The purpose of the cases was to see if the implemented PI regulator was able to maintain the bottom hole constant when disturbances such as pressure pulses, during a connection due to friction loss in the well. A second scenario looked at a slower process where kick is taken at the bottom. and due to expansion if it was possible to circulate different kick volumes through the MPD system. The results show that for the pressure pulses disturbance the regulator manages to keep the bottom hole constant. Other findings are related to the change in viscosity and sampling time where there was need of tuning the PI parameters. The regulator also manages to keep the BHP close to the setpoint when different kick volumes was taken when water-based mud and free gas was simulated. Although in an MPD operation only small influxes can be circulated through the MPD system due to limitations on the RCD and mud gas separator.