Switched Control for Pressure Regulation and Kick Attenuation in a Managed Pressure Drilling System

This paper presents a switched control scheme for regulation of the annular pressure in a well during drilling. The main feature is automatic kick attenuation while drilling reservoir sections. A simple mathematical model is presented that captures the dominant phenomena of the drilling system and forms the basis for observer and control design. A switched pressure control algorithm for feedback control of the choke valve opening and the back-pressure pump is proposed, and asymptotic stability properties are established. Kick attenuation is guaranteed for a set of reservoir models, including the most common ones. As part of the control scheme, novel observers for estimation of the flow rate through the bit and kick detection are developed. Simulation results obtained with a high fidelity drilling simulator are presented to demonstrate the effectiveness of the proposed switched control scheme.