Framework for produced water discharge management with flow-weighted mean concentration based economic model predictive control

Abstract

Offshore discharges of produced water (PW) is heavily regulated by government authorities through flow-weighted mean concentration (FWMC). To cope with regulations, treatment facilities are commissioned to reduce the oil content in water. However, disturbances may affect their performance, leading to regulation infringement. Produced water re-injection (PWRI) facilities can affect the FWMC by reducing oil discharge, and increasing re-injection. This strategy can aid the offshore facility in achieving the regulation requirements. Nevertheless, if improperly done, energy consumption can significantly increase, and regulations might still be violated. Therefore, we developed a framework for an Economical Model Predictive Control (EMPC) based on FWMC. It comprises an EMPC to which FWMCs are added as constraints; and a logic algorithm to maintain the necessary conditions for feasibility of the environmental constraint. Closed-loop results show that this strategy complies with environmental regulation, and adapts discharges of PW and pumping energy consumption based on facilities’ historical data.