title: Identification and characterization of high methane-emitting abandoned oil and gas wells.
abstract: Recent measurements of methane emissions from abandoned oil/gas wells show that these wells can be a substantial source of methane to the atmosphere, particularly from a small proportion of high-emitting wells. However, identifying high emitters remains a challenge. We couple 163 well measurements of methane flow rates; ethane, propane, and n-butane concentrations; isotopes of methane; and noble gas concentrations from 88 wells in Pennsylvania with synthesized data from historical documents, field investigations, and state databases. Using our databases, we (i) improve estimates of the number of abandoned wells in Pennsylvania; (ii) characterize key attributes that accompany high emitters, including depth, type, plugging status, and coal area designation; and (iii) estimate attribute-specific and overall methane emissions from abandoned wells. High emitters are best predicted as unplugged gas wells and plugged/vented gas wells in coal areas and appear to be unrelated to the presence of underground natural gas storage areas or unconventional oil/gas production. Repeat measurements over 2 years show that flow rates of high emitters are sustained through time. Our attribute-based methane emission data and our comprehensive estimate of 470,000-750,000 abandoned wells in Pennsylvania result in estimated state-wide emissions of 0.04-0.07 Mt (1012g) CH4per year. This estimate represents 5-8% of annual anthropogenic methane emissions in Pennsylvania. Our methodology combining new field measurements with data mining of previously unavailable well attributes and numbers of wells can be used to improve methane emission estimates and prioritize cost-effective mitigation strategies for Pennsylvania and beyond.
authors.affiliation: Earth System Science, Stanford University, Stanford, CA 94305; cm1kang@gmail.com.
authors.forename: Mary
authors.initials: M
authors.lastname: Kang
authors.affiliation: Geosciences, Princeton University, Princeton, NJ 08544.
authors.forename: Shanna
authors.initials: S
authors.lastname: Christian
authors.affiliation: Civil and Environmental Engineering, Princeton University, Princeton, NJ 08544.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Celia
authors.affiliation: Civil and Environmental Engineering, Princeton University, Princeton, NJ 08544.|Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton, NJ 08544.
authors.forename: Denise L
authors.initials: DL
authors.lastname: Mauzerall
authors.affiliation: Earth and Environmental Sciences, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
authors.forename: Markus
authors.initials: M
authors.lastname: Bill
authors.affiliation: Civil and Environmental Engineering, Princeton University, Princeton, NJ 08544.
authors.forename: Alana R
authors.initials: AR
authors.lastname: Miller
authors.affiliation: Geosciences, Princeton University, Princeton, NJ 08544.
authors.forename: Yuheng
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Earth and Environmental Sciences, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
authors.forename: Mark E
authors.initials: ME
authors.lastname: Conrad
authors.affiliation: Division of Solid Earth Dynamics and Water, Climate, and the Environment, Ohio State University, Columbus, OH 43210.
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Darrah
authors.affiliation: Earth System Science, Stanford University, Stanford, CA 94305.|Woods Institute for the Environment and Precourt Institute for Energy, Stanford University, Stanford, CA 94305.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Jackson
keywords: abandoned wells; climate change; high emitters; methane emissions; oil and gas development