Chemical Characterization of Natural Gas Leaking from Abandoned Oil and Gas Wells in Western Pennsylvania

Abstract

The U.S. Environmental Protection Agency estimates that there are over 3.2 million abandoned wells in the United States. Studies conducted on gas emissions from abandoned wells have been limited to methane, a powerful greenhouse gas, due to concerns regarding climate change. However, volatile organic compounds (VOCs), including benzene, a known human carcinogen, are known to be associated with upstream oil and gas development and hence could also be released when methane is emitted to the atmosphere. In this investigation, we analyze gas from 48 abandoned wells in western Pennsylvania for fixed gases, light hydrocarbons, and VOCs and estimate associated emission rates. We demonstrate that (1) gas from abandoned wells contains VOCs, including benzene; (2) VOCs are emitted from abandoned wells, the magnitude of which depends on the flow rate and concentration of VOCs in the gas stream; and (3) nearly one-quarter of abandoned wells are located within 100 m of buildings, including residences, in Pennsylvania. Together, these observations indicate that further investigation is necessary to determine whether emissions from abandoned wells pose an inhalation risk to people living, working, or congregating near abandoned wells.

The human health effects of unconventional oil and gas development (UOGD): A scoping review of epidemiologic studies

“…Exposure measurement is becoming increasingly sophisticated with more studies incorporating phase-specific metrics, flaring events, air and water pollution directional indicators, and adjustment for non-UOGD oil and gas development exposures in their models. Future exposure measurement should build on this multi-dimensional approach and also consider potential impacts of abandoned wells which have been identified as a growing concern (DiGiulio et al, 2023 ; Gross, 2023 ). Further examination of phase-specific contamination could better inform policies and regulations to protect communities from UOGD and other oil and gas development activities.…”

Environmental risks and opportunities of orphaned oil and gas wells in the United States

“…A recent study of measurements of air pollutants from abandoned oil and gas wells in Pennsylvania detected benzene at ∼70% of abandoned wells with maximum, mean, and median concentrations of 250, 36 and 2.8 ppmv, respectively [34] (figure 3(e)). Differences in concentrations of benzene and other volatile organic compounds in active and abandoned wells in Pennsylvania were not statistically significant [34]. Although air pollutant emissions from actively producing wells may not necessarily be representative of all orphaned wells, benzene concentrations in production and bradenhead gas have widely been detected at actively producing wells surveyed in seven southern and western states (figure S7).…”

“…Other non-methane air pollutants that can be co-emitted include hydrogen sulfide, toluene, ethylbenzene, and xylenes [33,34]. A recent study of measurements of air pollutants from abandoned oil and gas wells in Pennsylvania detected benzene at ∼70% of abandoned wells with maximum, mean, and median concentrations of 250, 36 and 2.8 ppmv, respectively [34] (figure 3(e)). Differences in concentrations of benzene and other volatile organic compounds in active and abandoned wells in Pennsylvania were not statistically significant [34].…”

“…Methane is not the only component of natural gas, and we can expect other non-methane air pollutants, including benzene, a known carcinogen, to be co-emitted [31,32]. Other non-methane air pollutants that can be co-emitted include hydrogen sulfide, toluene, ethylbenzene, and xylenes [33,34]. A recent study of measurements of air pollutants from abandoned oil and gas wells in Pennsylvania detected benzene at ∼70% of abandoned wells with maximum, mean, and median concentrations of 250, 36 and 2.8 ppmv, respectively [34] (figure 3(e)).…”

“…Moreover, available groundwater data is mainly for aquifers that are being used now, undermining our ability to monitor and protect groundwater aquifers that may be used in the future [44,[48][49][50]. In terms of air pollution, there is only one study based on wells in Pennsylvania [34]. For health studies, there are none specifically for abandoned (incl.…”