Nonlinear model predictive control of gas kick in a managed pressure drilling system

Managed pressure drilling (MPD) operation utilizes a fully automated control system to manage kicks during drilling which typically utilizes a proportional-integral (PI) controller and a single-phase flow model. This study proposes an MPD control system that uses a nonlinear model predictive controller (NMPC) and a two-phase flow model for computing annular pressure and choke valve dynamics during kick control operation. The performance of the proposed model is demonstrated by simulating kick control operation and compared their results with a single-phase linear model. The results confirm that the single-phase model underestimates key well control parameters (including kick size, bottomhole pressure and choke pressure), which may be due to ignoring gas-phase flow behaviour on mud density and the choke valve performance. Additionally, the performance of the proposed model is tested by validating the gas kick simulation results from a lab-scale MPD setup and a gas kick event from a field's case study based on North Sea drilling operation. The comparison of the control performance between the proposed NMPC model against the PI controller utilized in the field study confirms that the NMPC response more swiftly to disturbance, such as kick than the PI controller.