Advanced Automatic Control for Dual-Gradient Drilling

Abstract

Abstract Managed pressure drilling offers unprecedented capabilities for precise pressure control in drilling operations. This capability, created by the availability of new hardware tools, creates the need for tight coordination of such tools, to ensure reliable and safe operation. The use of model predictive control is proposed as a multivariable control framework that can coordinate multiple variables to offer both better performance and higher reliability and safety compared to current practice. A case study on a dual-gradient drilling system is presented to demonstrate how model predictive control can simultaneously control bottomhole pressure and hook position during drill string movement, by simultaneously manipulating the main pump flow rate, seabed pump flow rate, and drill string velocity. Computer simulations show that the proposed approach results in much lower bottomhole pressure deviations during drill string movement that manual control of hook position alone. The implications of this study as well as future directions for integration of additional variables and use of appropriate model predictive control variants are discussed.