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 (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 CO(2)e/bbl (CO2 equivalents per barrel of incremental oil produced), respectively, for total emissions of 685 kg CO(2)e/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 CO(2)e/bbl. Therefore, CO2-EOR produces oil with a lower emission factor than conventional oil (similar to 500 kg CO(2)e/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 CO(2)e/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. (C) 2016 Published by Elsevier Ltd.