Fugitive Methane Emissions in the Marcellus Shale Region:Characterizing the Natural Gas Emissions Distribution Using a Mobile Measurement Platform

Abstract

United States natural gas production has skyrocketed in recent years largely due to the wide scale introduction of hydraulic fracturing. Several studies have measured these new natural gas wells and found higher fugitive emissions than official estimates suggest. The emitted gas is primarily methane, a potent greenhouse gas that induces faster short-term warming than similar CO2 emissions. As natural gas continues to play an important role in the US energy market, scientists are looking to quantify the radiative impact of natural gas leaks on the overall fuel viability. This senior thesis investigates the fugitive emissions distribution from natural gas well pads in the Marcellus Shale region of Pennsylvania. The data used was collected over two field campaigns for a NOAA funded study led by Princeton researchers. A ground based mobile laboratory was used for measurements. Field measurements from 286 sites were analyzed, and emission rates were calculated using the Inverse Gaussian Plume method. Error analysis demonstrated that modeling assumptions introduced bounded uncertainty to results. An examination of repetitive sampling also revealed that local meteorology causes variation with average calculated emissions RSD of 1. Site emissions demonstrated a skewed distribution similar to those observed in other shale basins. The emissions followed a lognormal distribution and had a geometric mean of 0.67 g/s. Within the skewed distribution, 7.3% of sites emitted more than 10 g/s, and 9.5% of wells emitted more than 2% of the cumulative site production. Higher emissions were correlated with certain companies and regions, and the emissions as a percentage of production correlated negatively with overall production. Measured emissions were significantly higher than EPA estimates.