How green is my oil? A detailed look at greenhouse gas accounting for CO 2 -enhanced oil recovery (CO 2 -EOR) sites

Abstract This study presents the results of a detailed life cycle analysis of greenhouse gas (GHG) emissions associated with carbon dioxide-enhanced oil recovery (CO2-EOR) where the CO2 is sourced from a coal-fired power plant. This work builds upon previous investigations and integrates new information to provide more plausible ranges for CO2 storage in the reservoir during CO2-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 CO2-EOR site determined the emissions from upstream, gate-to-gate, and downstream processes to be 117, 98, and 470 kg CO2e/bbl (CO2 equivalents per barrel of incremental oil produced), respectively, for total emissions of 685 kg CO2e/bbl. However, these emissions are offset by CO2 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 CO2e/bbl. Therefore, CO2-EOR produces oil with a lower emission factor than conventional oil (∼500 kg CO2e/bbl). Optimization scenarios are presented that define a performance envelope based on the CO2 capture rate and net CO2 utilization and suggest that lower emission factors below 300 kg CO2e/bbl are achievable. Based on these results, CO2-EOR where the CO2 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.