Comparison of Methane Emission Estimates from Multiple Measurement Techniques at Natural Gas Production Pads

Garvin Heath, Clay Bell, Timothy Vaughn, Daniel Zimmerle, Scott Herndon, Tara Yacovitch, Gabrielle Petron, Rachel Edie, Robert Field, Shane Murphy, Anna Robertson, Jeffrey Soltis

Research output: Contribution to journalArticlepeer-review

53 Scopus Citations

Abstract

This study presents the results of a campaign that estimated methane emissions at 268 gas production facilities in the Fayetteville shale gas play using onsite measurements (261 facilities) and two downwind methods – the dual tracer flux ratio method (Tracer Facility Estimate – TFE, 17 facilities) and the EPA Other Test Method 33a (OTM33A Facility Estimate – OFE, 50 facilities). A study onsite estimate (SOE) for each facility was developed by combining direct measurements and simulation of unmeasured emission sources, using operator activity data and emission data from literature. The SOE spans 0–403 kg/h and simulated methane emissions from liquid unloadings account for 88% of total emissions estimated by the SOE, with 76% (95% CI [51%–92%]) contributed by liquid unloading at two facilities. TFE and SOE show overlapping 95% CI between individual estimates at 15 of 16 (94%) facilities where the measurements were paired, while OFE and SOE show overlapping 95% CI between individual estimates at 28 of 43 (65%) facilities. However, variance-weighted least-squares (VWLS) regressions performed on sets of paired estimates indicate statistically significant differences between methods. The SOE represents a lower bound of emissions at facilities where onsite direct measurements of continuously emitting sources are the primary contributor to the SOE, a sub-selection of facilities which minimizes expected inter-method differences for intermittent pneumatic controllers and the impact of episodically-emitting unloadings. At 9 such facilities, VWLS indicates that TFE estimates systematically higher emissions than SOE (TFE-to-SOE ratio = 1.6, 95% CI [1.2 to 2.1]). At 20 such facilities, VWLS indicates that OFE estimates systematically lower emissions than SOE (OFE-to-SOE ratio of 0.41 [0.26 to 0.90]). Given that SOE at these facilities is a lower limit on emissions, these results indicate that OFE is likely a less accurate method than SOE or TFE for this type of facility.

Original languageAmerican English
Article number79
Number of pages14
JournalElementa
Volume5
DOIs
StatePublished - 2017

Bibliographical note

Publisher Copyright:
© 2017 The Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International License

NREL Publication Number

  • NREL/JA-6A20-70835

Keywords

  • Climate change
  • Emissions
  • Methane
  • Natural gas

Fingerprint

Dive into the research topics of 'Comparison of Methane Emission Estimates from Multiple Measurement Techniques at Natural Gas Production Pads'. Together they form a unique fingerprint.

Cite this