Sustainable and clean oilfield development: Optimal operation of wastewater treatment and recycling system

With the increasing concerns over sustainable development and environmental protection, wastewater treatment and recycling, a crucial issue to address to ensure an oilfield's economic and clean production, is of great significance to achieve water pollution prevention and rational and scientific use of water resources. In this paper, aiming at the optimal operation of oilfield wastewater treatment and recycling system, a multi-objective mixed-integer linear programming model is proposed to ensure minimum costs and maximum amounts of recycled water. Various technical and operational constraints of wastewater treatment stations, waterflooding stations, and water allocation rooms are taken into consideration. For the safe and efficient operation of the system, the flowrate and energy balance equations of water delivery and waterflooding networks are also included. The augmented ε-constraint method is introduced to deal with the two conflicting objectives and generate the Pareto front. Lastly, taking a real-world wastewater treatment and recycling system in the Xinjiang Oilfield, China, as an example, the model's validity and applicability as well as analysis of the conflicting objectives trade-offs are demonstrated. Compared with manually developed plans, the model solution could not only lower the total costs but also improve the staff working efficiency and the correlation of sub-systems. With different levels of importance given to sustainable development and operational economy, a set of optimal operation schemes can also be provided for reference and decision-support.