Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2016-861
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
15 Dec 2016
Review status
This discussion paper is under review for the journal Atmospheric Chemistry and Physics (ACP).
Quantifying alkane emissions in the Eagle Ford Shale using boundary layer enhancement
Geoffrey Roest and Gunnar Schade Department of Atmospheric Sciences, Texas A&M University, 3150 TAMU, College Station, Texas 77843-3150
Abstract. The Eagle Ford Shale in southern Texas is home to a booming unconventional oil and gas industry, the climate and air quality impacts of which remain poorly quantified due to uncertain emissions estimates. We used the atmospheric enhancement of alkanes from Texas Commission on Environmental Quality volatile organic compound monitors across the shale, in combination with back trajectory and dispersion modeling, to quantify C2–C4 alkane emissions for a region in southern Texas, including the core of the Eagle Ford, for a set of 68 days from July 2013 to December 2015. Emissions were partitioned into raw natural gas and liquid storage tank sources using gas and headspace composition data, respectively, and observed enhancement ratios. We also estimate methane emissions based on typical ethane-to-methane ratios in gaseous emissions. The median emission rate from raw natural gas sources in the shale, calculated as a percentage of the total produced natural gas in the upwind region, was 0.8 % with an interquartile range (IQR) of 0.5 %–1.4 %, close to the U.S. Environmental Protection Agency's (EPA) current estimates. However, storage tanks contributed 24 % of methane emissions, 54 % of ethane, 82% percent of propane, 90 % of n-Butane, and 83 % of isobutane emissions. The inclusion of liquid storage tank emissions results in an emission rate of 2.2 % (IQR of 0.9 4.9 %) relative to produced natural gas, exceeding the EPA estimate by a factor of two. We conclude that leaks from liquid storage tanks are likely a major source for the observed non-methane hydrocarbon enhancements in the northern hemisphere.

Citation: Roest, G. and Schade, G.: Quantifying alkane emissions in the Eagle Ford Shale using boundary layer enhancement, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-861, in review, 2016.
Geoffrey Roest and Gunnar Schade
Geoffrey Roest and Gunnar Schade
Geoffrey Roest and Gunnar Schade

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Short summary
We used atmospheric concentrations of hydrocarbons to estimate emissions from regional oil and gas activities in the Eagle Ford Shale in southern Texas to better understand their air quality impacts. While higher hydrocarbons emissions are underestimated, emissions of methane from raw natural gas sources appear close to the US-EPA’s current estimate. However, we identified liquid storage tanks as an additional source of methane and as the dominant source of regional hydrocarbon emissions.
We used atmospheric concentrations of hydrocarbons to estimate emissions from regional oil and...
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