Mobile Laboratory Observations of Methane Emissions in the Barnett Shale Region

Abstract

Results of mobile ground-based atmospheric measurements conducted during the Barnett Shale Coordinated Campaign in spring and fall of 2013 are presented. Methane and ethane are continuously measured downwind of facilities such as natural gas processing plants, compressor stations, and production well pads. Gaussian dispersion simulations of these methane plumes, using an iterative forward plume dispersion algorithm, are used to estimate both the source location and the emission magnitude. The distribution of emitters is peaked in the 0-5 kg/h range, with a significant tail. The ethane/methane molar enhancement ratio for this same distribution is investigated, showing a peak at ∼1.5% and a broad distribution between ∼4% and ∼17%. The regional distributions of source emissions and ethane/methane enhancement ratios are examined: the largest methane emissions appear between Fort Worth and Dallas, while the highest ethane/methane enhancement ratios occur for plumes observed in the northwestern potion of the region. Individual facilities, focusing on large emitters, are further analyzed by constraining the source location.

Natural gas facility methane emissions: measurements by tracer flux ratio in two US natural gas producing basins

“…Since downwind concentration enhancements are directly related to the flow rates at the source, the unknown methane flow ( A major advantage of the tracer flux ratio method over other downwind techniques (Brantley et al, 2014;Thoma and Squier, 2014;Yacovitch et al, 2015) is that it requires no knowledge or simulation of atmospheric dispersion. Wind direction and speed are only used qualitatively, and no parameterization of atmospheric stability is required.…”

Analysis of local-scale background concentrations of methane and other gas-phase species in the Marcellus Shale

“…The larger CO median in NE PA is unexpected because NE PA is considered the more rural of the two study areas and the counties contained in the study area have a lower population density compared to the counties in SW PA, though all counties had a population density of less than 20% of the urbanized local Allegheny County (Bureau, 2012). While both study areas were in rural areas, the median background CO was within the 28-city range of Baker et al (2008) and above the WMO mid-latitude average of 125 ppbv (WMO, 2016). Additionally, because there is evidence that urban mole fractions in the US have decreased in the last decade (Warneke et al, 2012) it is possible that the CO backgrounds observed in this study are greater than some urban air masses.…”

“…The difference between the ground-based and aircraft platforms suggests that there may be some inherent systematic difference between the two measurement approaches, and assumptions of equivalently mixed boundary layers may not be appropriate. The aircraft measurements were within 20 ppbv of the WMO's 2012 estimated mean for methane of 1900 ppbv for the Northern Hemisphere between 30°N and 60°N latitude (WMO, 2016), which could indicate that the methane background in the Marcellus region at that time was not elevated compared to the mid-latitude average. Alternatively, if there is a systematic difference between the two measurement approaches, and ground-based measurements, which often have longer sampling durations, are considered to be more representative of a regional air mass, then the ground-based results from this study and in Swarthout et al (2015) demonstrate that methane in the Marcellus region is elevated compared to the Northern Hemisphere mid-latitude (30-60°N) mean.…”

“…When comparing sampling locations within 10 km proximity, the median local methane background was found to be 125 ppbv greater in 2015 compared to 2012. The World Meteorological Organization (WMO) Global Atmospheric Watch estimated global methane mole fractions increased by an average of 6 ppb per year over that same time period (WMO, 2016). An analysis of boundary layer heights and wind speed during the two study periods shows that the atmosphere was likely more dilute in 2015 compared to 2012 in NE PA with boundary layer heights equal to or greater than 2012 ( Figure S4) and with greater wind speeds ( Figure S6).…”

“…It is important to note however that the 28-city study values may no longer be representative of urban methane because the study was conducted over ten years ago and therefore does not represent the increasing global background on top of which urban emissions accumulate and changes in urban methane emissions over that time period. For example, between 2007 and 2012 the global mean mole fraction increased by 29 ppbv (WMO, 2016). Comparisons to Pétron et al (2012), demonstrate that background methane mole fractions were greater in the Marcellus region than the summertime median at Boulder Atmospheric Observatory (BAO) located in the Denver-Julesburg basin in Colorado.…”