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Title: Improved Mechanistic Understanding of Natural Gas Methane Emissions from Spatially Resolved Aircraft Measurements

Divergence in recent oil and gas related methane emission estimates between aircraft studies (basin total for a midday window) and emissions inventories (annualized regional and national statistics) indicate the need for better understanding the experimental design, including temporal and spatial alignment and interpretation of results. In our aircraft-based methane emission estimates in a major U.S. shale gas basin resolved from west to east show (i) similar spatial distributions for 2 days, (ii) strong spatial correlations with reported NG production (R 2 = 0.75) and active gas well pad count (R 2 = 0.81), and (iii) 2× higher emissions in the western half (normalized by gas production) despite relatively homogeneous dry gas and well characteristics. Operator reported hourly activity data show that midday episodic emissions from manual liquid unloadings (a routine operation in this basin and elsewhere) could explain ~1/3 of the total emissions detected midday by the aircraft and ~2/3 of the west–east difference in emissions. The 22% emission difference between both days further emphasizes that episodic sources can substantially impact midday methane emissions and that aircraft may detect daily peak emissions rather than daily averages that are generally employed in emissions inventories. And while the aircraft approach is valid,more » quantitative, and independent, this study sheds new light on the interpretation of previous basin scale aircraft studies, and provides an improved mechanistic understanding of oil and gas related methane emissions.« less
Authors:
ORCiD logo [1] ;  [1] ; ORCiD logo [2] ;  [3] ;  [1] ;  [4] ;  [4] ;  [3] ;  [3] ; ORCiD logo [3] ;  [1] ;  [4] ;  [4] ;  [1] ;  [1] ;  [4]
  1. Univ. of Colorado, Boulder, CO (United States). Cooperative Inst. for Research in Environmental Sciences; National Oceanic and Atmospheric Administration (NOAA), Boulder, CO (United States). Earth System Research Lab.
  2. Scientific Aviation Inc., Boulder, CO (United States); Univ. of California, Davis, CA (United States). Dept. of Land, Air, and Water Resources
  3. Colorado State Univ., Fort Collins, CO (United States). Dept. of Mechanical Engineering
  4. National Oceanic and Atmospheric Administration (NOAA), Boulder, CO (United States). Earth System Research Lab.
Publication Date:
Grant/Contract Number:
AC26-07NT42677
Type:
Published Article
Journal Name:
Environmental Science and Technology
Additional Journal Information:
Journal Volume: 51; Journal Issue: 12; Journal ID: ISSN 0013-936X
Publisher:
American Chemical Society (ACS)
Research Org:
Colorado School of Mines, Golden, CO (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES
OSTI Identifier:
1361561
Alternate Identifier(s):
OSTI ID: 1372259