An implementable zone NMPC applied to an ESP-lifted oil well system: Handling the lack of measurements with nonlinear state estimator coupling

Abstract

This paper addresses the first application of a nonlinear model predictive control (NMPC) scheme, coupled with an extended Kalman filter (EKF), for oil production processes with electric submersible pump (ESP) installations. The resulting nonlinear program of the proposed NMPC is most computationally tractable by the use of zone control scheme to deal with the downthrust and upthrust operational envelope-type ESP time-varying constraints, making it implementable in practice. The coupling of EKF seeks to solve the challenger problem of lack of measurements in ESP-lifted oil wells, besides is strategically used to compute downthrust and upthrust ESP head bounds from the estimated average flow rate in the production column. The implementable zone NMPC+EKF scheme is also flexible to incorporate optimizing targets in its formulation aiming at economic performance improvements. The effectiveness of the proposal is carried out in noisy plant-model mismatch scenarios for fairly different operating condition tracking, including cases of rejection of significant disturbances on manifold pressure. Analysis on the inclusion (or not) of optimizing target on the choke valve opening also demonstrates the economic gains in terms of ESP power savings, in addition, the computational effort evaluation corroborates with the feasibility of the controller in real-time implementation purposes.