Fugitive methane from abandoned oil and gas infrastructure

Abstract:

Anthropogenic methane (CH₄) released into the atmosphere has a global warming potential 84-86× that of carbon dioxide (CO₂) over a 20-year period and 25× that of CO₂ over a 100-year period. Proper regulation and mitigation of CH₄ emissions depends upon a complete understanding of the sources and severity of emissions from anthropogenic activities. Abandoned wells in a previously unstudied region of the continental United States reveal the importance of geographical location in well emissions factors and reveal other well characteristics, including depth and plugging status, that correlate with observed leaks. Unplugged wells in the Cherokee Platform near Chelsea, Oklahoma had an emissions factor of 0.060 ±0.289 kg/day (n = 159) while plugged wells had a slightly higher emissions factor of 0.096 ±0.429 kg/day (n = 20). Yet, similar to other oil and natural gas infrastructure studies in which super-emitters are observed, only a small proportion of wells are is responsible for total observed emissions, resulting in skewed data. Additionally, a complete geochemical analysis of gas was carried out to estimate ethane emissions from abandoned wells for the first time. The results in Oklahoma reveal knowledge gaps in the current EPA Greenhouse Gas Inventory and the need for adjustment of current inventory values to better reflect experimental results. Creating additional regional and status categories for abandoned wells will reduce uncertainty in the Greenhouse Gas Inventory estimations for fugitive emissions from abandoned wells.