How green is my oil? A detailed look at greenhouse gas accounting for CO2-enhanced oil recovery (CO2-EOR) sites

This study presents the results of a detailed life cycle analysis of greenhouse gas (GHG) emissions associated with carbon dioxide-enhanced oil recovery (CO 2 -EOR) where the CO 2 is sourced from a coal-fired power plant. This work builds upon previous investigations and integrates new information to provide more plausible ranges for CO 2 storage in the reservoir during CO 2 -EOR. The system model includes three segments: upstream, gate-to-gate, and downstream processes. Our base case model using Ryan–Holmes gas separation technology for the CO 2 -EOR site determined the emissions from upstream, gate-to-gate, and downstream processes to be 117, 98, and 470 kg CO 2 e/bbl (CO 2 equivalents per barrel of incremental oil produced), respectively, for total emissions of 685 kg CO 2 e/bbl. However, these emissions are offset by CO 2 storage in the reservoir and the resulting displacement credit of U.S. grid electricity, which results in a net life cycle emission factor of 438 kg CO 2 e/bbl. Therefore, CO 2 -EOR produces oil with a lower emission factor than conventional oil (∼500 kg CO 2 e/bbl). Optimization scenarios are presented that define a performance envelope based on the CO 2 capture rate and net CO 2 utilization and suggest that lower emission factors below 300 kg CO 2 e/bbl are achievable. Based on these results, CO 2 -EOR where the CO 2 is sourced from a coal-fired power plant provides one potential means for addressing the energy demand–climate change conundrum, by simultaneously producing electricity and oil to meet growing energy demand and reducing GHG emissions to abate global warming.