A41Q-05
Hydrogen stable isotopic constraints on methane emissions from oil and gas extraction in the Colorado Front Range, USA
Thursday, 17 December 2015: 09:00
3012 (Moscone West)
Amy Townsend-Small1, E. Claire Botner1, Kristine Jimenez1, Nicola J Blake2, Jason Schroeder2, Simone Meinardi2, Barbara Barletta2, Isobel Jane Simpson2, Donald Ray Blake2, Frank M Flocke3, Gabriele Pfister3, Daniel Bon4 and James H Crawford5, (1)University of Cincinnati, Cincinnati, OH, United States, (2)University of California Irvine, Irvine, CA, United States, (3)National Center for Atmospheric Research, Boulder, CO, United States, (4)Colorado Department of Public Health and Environment, Denver, CO, United States, (5)NASA Langley Research Center, Hampton, VA, United States
Abstract:
The climatic implications of a shift from oil and coal to natural gas depend on the magnitude of fugitive emissions of methane from the natural gas supply chain. Attempts to constrain methane emissions from natural gas production regions can be confounded by other sources of methane. Here we demonstrate the utility of stable isotopes, particularly hydrogen isotopes, for source apportionment of methane emissions. The Denver, Colorado area is home to a large oil and gas field with both conventional oil and gas wells and newer hydraulic fracturing wells. The region also has a large metropolitan area with several landfills and a sizable cattle population. As part of the DISCOVER-AQ and FRAPPE field campaigns in summer 2014, we collected three types of canister samples for analysis of stable isotopic composition of methane: 1), samples from methane sources; 2), samples from two stationary ground sites, one in the Denver foothills, and one in an oil and gas field; and 3), from the NCAR C-130 aircraft in samples upwind and downwind of the region. Our results indicate that hydrogen isotope ratios are excellent tracers of sources of methane in the region, as we have shown previously in California and Texas. Use of carbon isotope ratios is complicated by the similarity of natural gas isotope ratios to that of background methane. Our results indicate that, despite the large amount of natural gas production in the region, biological sources such as cattle feedlots and landfills account for at least 50% of total methane emissions in the Front Range. Future work includes comparison of isotopes and alkane ratios as tracers of methane sources, and calculation of total methane fluxes in the region using continuous measurements of methane concentrations during aircraft flights.
