Significant Methane Emissions from Abandoned Oil and Gas wells in Northwest Pennsylvania
Abstract
Abandoned (no longer operated), Orphaned (abandoned and responsible party unavailable), and/or Lost (location unknown, cannot be confirmed, or not on record) (AOL) wells provide a potential pathway for subsurface migration, and emissions to the atmosphere, of methane and other volatile hydrocarbons. However, little is known about methane fluxes from AOL wells. Of the 12,000 abandoned and orphaned oil and gas wells on the Pennsylvania Department of Environmental Protection's (PA DEP) list, 36% are in McKean County. McKean County is home to the Bradford Oil Field, the world's first large oil field, which in 1881 produced 83% of America's output. A large fraction of the oil and gas wells in McKean County are AOL and some estimates of the number of AOL wells exceed the number of wells listed by the PA DEP by factors of 20 or more. To characterize AOL wells' potential as a significant methane source, we made first-of-a-kind measurements of methane fluxes from 8 abandoned wells in McKean County using static flux chambers. These wells are on a 40-acre lot, which includes various land cover types. Four of the eight measured wells are in forested areas, while three are in grassland, and one is in wetland areas. Two of the eight wells, one in a forested area and one in the grassland area, are plugged. Fluxes of methane, ethane, propane, and n-butane were measured using flame ionization gas chromatography. To gain insight into the source of methane (biogenic vs. thermogenic), carbon and hydrogen isotopes of methane were analyzed and the ratio of methane to heavier hydrocarbons were computed. In addition, a LI-7700 open path methane analyzer was used to provide on-line methane concentration measurement in the vicinity of AOL wells and in flux chambers. We found methane fluxes from the measured AOL wells to be significantly higher than fluxes observed in similar natural environments. Methane emissions from the two plugged wells were smaller than those from unplugged wells but non-negligible. The atmospheric methane concentration in the vicinity of some wells was elevated up to fifteen times higher than the background concentration, indicating that methane concentrations near the land surface can be used to detect emissions from AOL wells. Given the large number of AOL wells in Pennsylvania and across the country, methane emissions from AOL wells may be a significant anthropogenic source of methane and other hydrocarbons to the atmosphere. An improved understanding of the role of AOL wells as methane emission sources can aid in bridging the current gap in global and regional methane budgets, while plugging wells could provide a future opportunity for emissions reduction. Furthermore, with the growth of unconventional oil and gas production in Pennsylvania and across the globe, characterization of AOL wells as a methane source is useful for determining impacts of past, current, and future oil and gas production.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.A53H..04K
- Keywords:
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- 3394 ATMOSPHERIC PROCESSES Instruments and techniques;
- 1831 HYDROLOGY Groundwater quality;
- 1610 GLOBAL CHANGE Atmosphere;
- 1803 HYDROLOGY Anthropogenic effects