Monitoring technology ranking methodology for CO2-EOR sites using the Weyburn-Midale Field as a case study

In a carbon dioxide (CO2) enhanced oil recovery (EOR) operation, CO2 is injected into a hydrocarbon reservoir to enhance hydrocarbon production. Much of this CO2 is recycled for reinjection when the hydrocarbons are produced; however, a large amount is permanently stored in the reservoir. If a CO2-EOR operation intends to claim CO2 storage credit for this stored CO2, it needs to demonstrate that the CO2 is safely stored in the subsurface by strategically deploying monitoring technologies. For the operation to maintain profitability goals, these monitoring technologies also need to be cost-effective. If the safety of the CO2 storage is demonstrated, the project will be classified a carbon capture, utilization, and storage (CCUS) project. The main goal of CO2-EOR is oil production, not CO2 storage. Because CO2-EOR originated as an oil production technique, the EOR process is subject to a less stringent regulatory environment than CCUS projects. These differences in the CO2 storage accounting and the regulatory environment mean that CO2 EOR projects need to demonstrate the long-term containment of CO2 within the reservoir with additional monitoring in order to claim any CO2 emission credits. Converting a CO2-EOR project to a CCUS project requires a tailored site-specific approach. The methodology employed will differ from project to project due to differences in project risk, geology, operations history, and regulatory environment. This paper takes the CO2-EOR Weyburn-Midale Field (WMF) as a case study to rank monitoring strategies that may be required to shift the WMF from CO2-EOR to CCUS. This study consisted of an in-depth review of the identified risks, the potential leakage pathways, various regulatory requirements, and the already deployed monitoring techniques. The goal was to develop a risk-, economic-, and regulatory based monitoring technology ranking system that is suitable for the WMF. While specific to the WMF, the methodology presented here can be adapted by other CO2-EOR operators who endeavor to demonstrate that the non-recycled portion of the CO2 injected into the formation(s) by their project(s) is permanently stored. (C) 2016 Elsevier Ltd. All rights reserved.