We measured fluxes of methane, non-methane hydrocarbons, and carbon dioxide from natural gas well pad soils and from nearby undisturbed soils in eastern Utah. Methane fluxes varied from less than zero to more than 38,000 mg m-2 h-1. Fluxes from well pad soils were almost always greater than from undisturbed soils. Fluxes were greater from locations with higher concentrations of total combustible gas in soil and were inversely correlated with distance from well heads. Several lines of evidence show that the majority of emission fluxes (about 70%) were due to subsurface sources of raw gas that migrated to the atmosphere, with the remainder likely caused by re-emission of spilled liquid hydrocarbons. Total hydrocarbon fluxes in summer were only 27% as high as during winter, likely because soil bacteria consumed the majority of hydrocarbons during summer months, converting them to carbon dioxide. While this study shows that well pad soils are a meaningful hydrocarbon emission source at some wells, well pad soil emissions are not significant relative to the oil and gas industry overall. We estimate that well pad soils account for much less than 1% of total emissions of methane and non-methane hydrocarbons from the oil and gas industry in Utah's Uinta Basin.
US Dept. of Interior, Bureau of Land Management
US Dept. of Energy
Research Partnership to Secure Energy for America
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Available at: http://works.bepress.com/seth-lyman/15/