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

Abstract

The Marcellus Shale is a rapidly developing unconventional natural gas resource found in part of the Appalachian region. Air quality and climate concerns have been raised regarding development of unconventional natural gas resources. Two ground-based mobile measurement campaigns were conducted to assess the impact of Marcellus Shale natural gas development on local scale atmospheric background concentrations of air pollution and climate relevant pollutants in Pennsylvania. The first campaign took place in Northeastern and Southwestern PA in the summer of 2012. Compounds monitored included methane (CH4), ethane, carbon monoxide (CO), nitrogen dioxide, and Proton Transfer Reaction Mass Spectrometer (PTR-MS) measured volatile organic compounds (VOC) including oxygenated and aromatic VOC. The second campaign took place in Northeastern PA in the summer of 2015. The mobile monitoring data were analyzed using interval percentile smoothing to remove bias from local unmixed emissions to isolate local-scale background concentrations. Comparisons were made to other ambient monitoring in the Marcellus region including a NOAA SENEX flight in 2013. Local background CH4 mole fractions were 140 ppbv greater in Southwestern PA compared to Northeastern PA in 2012 and background CH4 increased 100 ppbv from 2012 to 2015. CH4 local background mole fractions were not found to have a detectable relationship between well density or production rates in either region. In Northeastern PA, CO was observed to decrease 75 ppbv over the three year period. Toluene to benzene ratios in both study regions were found to be most similar to aged rural air masses indicating that the emission of aromatic VOC from Marcellus Shale activity may not be significantly impacting local background concentrations. In addition to understanding local background concentrations the ground-based mobile measurements were useful for investigating the composition of natural gas emissions in the region.

A review of close-range and screening technologies for mitigating fugitive methane emissions in upstream oil and gas

“…Given the necessary distance between piloted aircraft and potential methane sources, minimum detection limits tend to be much higher than with ground-based methods (table 1). As background methane concentrations are spatially dependent (Goetz et al 2017, Verhulst et al 2017, high aircraft velocities mean that considerable care must be taken to avoid unnecessary errors in the calculation of methane enhancements (Hirst et al 2013). Accounting for the high temporal variability of O&G and non-target emissions is also challenging (Allen et al 2017, Vaughn et al 2018).…”

Outcome‐based ventilation: A framework for assessing performance, health, and energy impacts to inform office building ventilation decisions

“…For heating natural gas, cost estimates were made for multiple SC-CO 2 values, for multiple methane leakage rates, and for two time horizons. Methane leakage can influence the climate impact of natural gas substantially, depending on the loss rate, for which a wide range of estimates exist,[73][74][75][76][77][78][79][80][81][82][83][84] and the time horizon for radiative forcing considered 85,86.…”

Synthesis and health-based evaluation of ambient air monitoring data for the Marcellus Shale region

“…The majority of air monitoring site datasets and studies provide data with 24-hour or longer averaging times, but there is a growing body of studies reporting data with averaging times of 1 hour or less that can be used to evaluate episodic short-term air quality impacts. More specifically, Goetz et al (2015Goetz et al ( , 2017 (Orak, Pekney, and Reeder 2017;Pekney et al 2013). A few other studies measured 1-hour or sub-hourly concentrations for a couple of air pollutants of interest (see Table S.1).…”

“…Air toxics data for PADEP air monitors were obtained from the PADEP website and were generally only available for sampling conducted through 2015. For one published study (Goetz et al 2017), the authors freely provided the full dataset of high-resolution measurements at the Dryad data repository (https://doi.org/10. 5061/dryad.g8h54).…”

“…Several of the studies that we evaluated are notable for the strong datasets that they provide, which enhance our understanding of air pollutant concentrations in the Marcellus Shale region. Goetz et al (2015) and Goetz et al (2017) collected a large quantity of 1-second data at sampling locations 480 to 1,100 meters downwind of a variety of OGD sites (production well pads, a well pad with a drill rig, a well pad undergoing a well completion, and compressor stations) in wet and dry Marcellus Shale gas regions in both southwest and northwest Pennsylvania as part of an emissions estimation study. The authors provided online access to the raw data for acetaldehyde, benzene, toluene, and NO 2 .…”