On the sustainability of CO2 storage through CO2 – Enhanced oil recovery

• Published in: Applied energy 2020-03, Vol.261, p.114467, Article 114467
• Main Authors: Farajzadeh, R., Eftekhari, A.A., Dafnomilis, G., Lake, L.W., Bruining, J.
• Format: Article
• Language: English
• Subjects: Climate change; CO2 storage; CO2 utilization factor; CO2-EOR; Exergy analysis
• ISSN: 0306-2619; 1872-9118
• DOI: 10.1016/j.apenergy.2019.114467

•The net storage efficiency of carbon capture projects is maximally 6–56%.•The CO2 capture and storage process re-emits 0.43–0.94 kg of CO2 per kg of CO2 stored.•Exergy recovery factor of CO2 enhanced oil recovery depends on CO2 utilization factor.•30–50% of fossil fuel energy is required to capture released CO2 from its combustion. This work uses pilot examples of CO2 enhanced oil recovery to analyze whether and under which circumstances it is exergetically favorable to sequester CO2 through enhanced oil recovery. We find that the net storage efficiency (ratio between the stored and captured CO2) of the carbon capture and storage (CCS)-only projects is maximally 6–56% depending on the fuel used in the power plants. With the current state of technology, the CCS process will re-emit a minimum of 0.43–0.94 kg of CO2 per kg of CO2 stored. From thermodynamics point of view, CO2 enhanced oil recovery (EOR) with CCS option is not sustainable, i.e., during the life cycle of the process more energy is consumed than the energy produced from oil. For the CCS to be efficient in reducing CO2 levels (1) the exergetic cost of CO2 separation from flue gas should be reduced, and/or (2) the capture process should not lead to additional carbon emission. Furthermore, we find that the exergy recovery factor of CO2-EOR depends on the CO2 utilization factor, which is currently in the low range of 2–4 bbl/tCO2 based on the field data. Exergetically, CO2 EOR with storage option produces 30–40% less exergy compared to conventional CO2 enhanced oil recovery projects with CO2 supplied from natural sources; however, this leads to storage of >400 kg of extra CO2 per barrel of oil produced.