Ensemble based co-optimization of carbon dioxide sequestration and enhanced oil recovery

Sequestration of carbon dioxide (CO2) in depleted or partially depleted oil reservoirs is a plausible option to reduce CO2 emissions into the atmosphere. Carbon dioxide has been used as the injection fluid in enhanced oil recovery (EOR) operations. The goal of such projects is to improve the profitability by maximizing the oil production (to increase the revenue) and minimizing the CO2 injection (to decrease the costs). However, in sequestration projects, subsurface storage of the injected CO2 needs to be maximized. The objective of this study is to develop a framework to co-optimize the oil extraction and CO2 sequestration. In our work, factors such as the cost of capturing the produced CO2, CO2 transportation and recycling are taken into account. In the proposed framework, the net present value (NPV) of the project is selected as the optimization objective function. The ensemble-based optimization (EnOpt) algorithm has been chosen as the optimization algorithm and the well injection patterns and rates as the controlling variables. A synthetic case is used to demonstrate the applicability of the developed technique. Our results show that the oil recovery and the NPV can be increased significantly. The proposed methodology is fairly robust as it does not require adjoint programming and can be readily used with any reservoir simulator. The workflow presented in this work can be used to design and co-optimize the coupled CO2 sequestration and EOR. (C) 2012 Elsevier Ltd. All rights reserved.