Natural Soils‐Based Oxidation Mitigates Methane Leakage From Integrity Compromised Legacy Wells

Abstract An increasing number of legacy petroleum wells are reported to suffer integrity failure, releasing methane (CH 4 ) into the subsurface and atmosphere. Subsurface released methane is reactively transported toward ground surface with a portion converted to carbon dioxide by soil microbes. Currently, the extent to which fugitive CH 4 oxidation occurs, including microbial taxa responsible and controlling parameters are poorly understood. Here, we examined fugitive CH 4 leakage at a legacy well in the Montney region of British Columbia, Canada and find up to 90% is oxidized at rates as high as 230 g of CH 4 /m 2 of soils/day during summer. Meanwhile, a profound difference in microbiome between soils at the wellhead and background was observed, while modeling suggests that prevailing seasonal temperature will moderate CH 4 oxidation extent. Overall, we find that filtration of fugitive CH 4 through natural soils can significantly reduce emissions of CH 4 and mitigate climate impacts from such sources.