Characterizing Methane Emissions and Sources from Abandoned Oil and Gas Wells in the United States

Abstract:

Recent work indicates that methane (CH₄) inventories for the United States are underestimated. We made direct measurements of CH₄ emissions from 144 abandoned oil and gas wells, a source currently missing from inventories. Most abandoned wells do not emit CH₄, but about 2% of wells surveyed contributed 95% of the observed emissions, particularly unplugged wells. Isotopic analyses indicate that wells emit CH₄ from natural gas and/or coal bed CH₄. Using emission factors developed from these measurements we provide basin wide estimates of CH₄ emissions from abandoned wells in the Uintah and Denver-Julesburg basins. Extrapolated nationally, leakage from abandoned wells may contribute significantly to the current CH₄ inventory for oil and gas activities. Additional data on emissions and activity factors are needed to accurately determine the contribution of abandoned wells to CH₄ budgets, particularly a better characterization of the distribution of high emitters.