Comparative lifecycle inventory (LCI) of greenhouse gas (GHG) emissions of enhanced oil recovery (EOR) methods using different CO2 sources

This study uses a process lifecycle inventory (LCI) to compare the lifecycle greenhouse gas (GHG) emissions of enhanced oil recovery (EOR) operations using different sources for CO2 and to non-CO2 EOR methods. All EOR techniques were compared to the base case of natural-source CO2-EOR, which had net emissions of 0.52 +/- 0.03 metric tons of CO2-e per barrel of oil recovered (t/bbl) (85.1 +/- 4.9g CO2-e/MJ oil (g/MJ)), the same as the net emissions of 0.52 +/- 0.02 t/bbl (84.3 +/- 3.0 g/MJ) when using CO2 derived from a coal-fueled synthetic natural gas (SNG) plant. Net emissions were lowered to 0.36 +/- 0.03 t/bbl (58.5 +/- 5.2 g/MJ) for EOR using CO2 derived from a coal-fed Integrated Gasification Combined Cycle (IGCC) plant. Net emissions were further reduced to 0.18 +/- 0.11 t/bbl (28.6 +/- 18.7 g/MJ) using switchgrass grown on marginal land in an IGCC plant. Similar to coal, net emissions were 0.34 +/- 0.03 t/bbl (55.3 +/- 5.5 g/MJ) for EOR using CO2 derived from a Natural Gas Combined Cycle (NGCC) plant, and 039 +/- 0.03 t/bbl (63.3 +/- 4.4 g/MJ) when using livestock manure biogas for NGCC. Net emissions of methane- and nitrogen-EOR were 10-15% greater than for natural-source CO2-EOR. For the allocations used in this study, all sources of CO2 derived from IGCC or NGCC plants resulted in between about 25% and 60% lower net CO2-e emissions per barrel of oil recovered compared to natural-source CO2-EOR, and were also approximately 25-60% lower than average domestic U.S. oil lifecycle emissions of 0.50 +/- 0.02 t/bbl (82.4 +/- 2.5 g/MJ). These results suggest that coal and biomass IGCC CO2-EOR, as well as natural gas and biogas NGCC CO2-EOR, may be alternatives for reducing GHG emissions associated with fossil fuel use during the slow transition from fossil fuels to other energy sources. (C) 2013 Elsevier Ltd. All rights reserved.