Importance of Superemitter Natural Gas Well Pads in the Marcellus Shale

Abstract

A large-scale study of methane emissions from well pads was conducted in the Marcellus shale (Pennsylvania), the largest producing natural gas shale play in the United States, to better identify the prevalence and characteristics of superemitters. Roughly 2100 measurements were taken from 673 unique unconventional well pads corresponding to ∼18% of the total population of active sites and ∼32% of the total statewide unconventional natural gas production. A log-normal distribution with a geometric mean of 2.0 kg h −1 and arithmetic mean of 5.5 kg h −1 was observed, which agrees with other independent observations in this region. The geometric standard deviation (4.4 kg h −1 ) compared well to other studies in the region, but the top 10% of emitters observed in this study contributed 77% of the total emissions, indicating an extremely skewed distribution. The integrated proportional loss of this representative sample was equal to 0.53% with a 95% confidence interval of 0.45−0.64% of the total production of the sites, which is greater than the U.S. Environmental Protection Agency inventory estimate (0.29%), but in the lower range of other mobile observations (0.09−3.3%). These results emphasize the need for a sufficiently large sample size when characterizing emissions distributions that contain superemitters.

Single-blind inter-comparison of methane detection technologies – results from the Stanford/EDF Mobile Monitoring Challenge

“…For example, BHGE performed well in the class of leaks >8 scfh and could be re-tested with more samples in that regime. This is especially important considering that a recent study of emissions in the Marcellus shale found that the average emission rate at the pad-level was 5.5 kg/h, corresponding to ~3 50 scfh (Caulton, et al, 2019). However, these are pad-level estimates, and component-level emissions can be significantly smaller -testing at the METEC facility between 0-15 scfh therefore provides a reasonable test of performance for technologies that detect emissions component-level detection.…”

Analysis of Oil and Gas Ethane and Methane Emissions in the Southcentral and Eastern United States Using Four Seasons of Continuous Aircraft Ethane Measurements

“…This decrease is driven primarily by projected decreases in emissions from the energy sector, despite a 50% increase in gas production and a greater than 200% increase in oil production during the 10 year period (US Energy Information Administration, 2020b). Over the last several years, various atmospheric studies monitoring emissions from O&G from individual wellpads (Caulton et al, 2019;Rella et al, 2015;Robertson et al, 2017), basins (Barkley et al, 2017;Karion et al, 2013Karion et al, , 2015Peischl et al, 2015Peischl et al, , 2016Peischl et al, , 2018Pétron et al, 2012Pétron et al, , 2014, and entire regions have consistently found emission rates larger than the EPA inventory, raising concerns of a broad underestimation of leaks from the O&G sector (Alvarez et al, 2018). However, large-scale CH 4 inversion studies involving the US have not been as conclusive, with differing findings as to the accuracy of inventory emissions from O&G, animal agriculture, and wetlands (Maasakkers et al, 2019;Miller et al, 2013;Sheng et al, 2018;Yu et al, 2020).…”

Analysis of Oil and Gas Ethane and Methane Emissions in the Southcentral and Eastern United States Using Four Seasons of Continuous Aircraft Ethane Measurements

“…EPA inventory estimates (Barkley, Lauvaux et al, 2019;Caulton et al, 2019 Alvarez et al (2018). However, in all of these comparisons, we note that the year each study took place varies, such that differences in the solution may include changes due to temporal variability in the O&G activity of a basin.…”