Abstract

Enhanced oil recovery with carbon dioxide (CO₂-EOR) is considered to be a cost effective way for carbon capture and storage. However, due to the complexity of geological structure in underground reservoirs, long-term leakage is possible. A case study of CO₂-EOR has been conducted at Citronelle, Alabama in the United State of America. A total of 8,036-ton of CO₂ were injected from November 2009 to September 2010 and some leakages via production were identified by isotopic analysis in May 2010. In this study, remote sensing data of CO₂ and methane (CH₄) concentrations, and aerosol optical depth (AOD) at a large scale were used to monitor emissions to atmosphere at the study site. Based on the observed monthly CO₂ and CH₄ concentrations in the atmosphere at the study site and surrounding areas, some abnormal values related to possible emission were identified at different time scales by correlation, variance and entropy analysis. The annual average of ratios between CO₂ concentration and CH₄ concentration, which might be due to CO₂ emission, reached the highest value in 2009. In comparison with surrounding areas, the monthly values of AOD at the study site were relatively higher, especially during the time periods of 2008, 2009 and part of 2010. Our results might confirm the isotopic analysis at the ground and may provide more detailed information. Therefore, through this approach remote sensing data could be used to monitor and evaluate emissions from areas involved in CO₂-EOR at a large scale and provide helpful information for ecological assessment of CO₂-EOR.

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