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The Environmental Protection Agency (EPA) estimates there are 3.2 million abandoned oil and gas wells across the U.S., and now a new study finds that harmful volatile organic compounds (VOCs), including the known carcinogen benzene, are leaking from some of them.
The study, conducted by researchers from PSE Healthy Energy, is the first study to measure the composition of emissions, including VOCs from abandoned wells, the emissions rate, and the proximity of wells to residences and other buildings in Western Pennsylvania. The study was recently published in the journal ACS Omega.
For the study, conducted with the help of the Pennsylvania Department of Environmental Resources staff, researchers located 48 abandoned wells in the Marcellus region and collected and analyzed the gas coming from them. Many of the wells were on public lands but a few were on private property.
Previous studies had focused on quantifying the emissions rate of methane from the wells because it is a potent greenhouse gas that contributes to climate change. The PSE study is the first that also looked at the concentrations of various VOCs also coming from those wells as well as the proximity of wells to structures. VOCs can cause health issues, including asthma, as well as contribute to the formation of smog, and benzene is a known human carcinogen.
The study concluded that VOCs, including benzene, are emitted from abandoned wells, and the amounts depend on the leakage rate and concentration of the gas. It found benzene concentrations as high as 250 parts per million, above a well-established safety threshold. In addition it found that many abandoned wells are located within a short distance to residences and other buildings in Western Pennsylvania. OF the 18,608 documented abandoned wells in the state, 93 percent are located within one kilometer of a building, and 23 percent are within 100 meters.
“Together, these observations indicate that further investigation is necessary to determine whether gas emissions pose an inhalation risk to people living, working, or congregating near abandoned wells,” the study states.
There are likely more emissions from abandoned wells, as Pennsylvania is estimated to have some 200,000 abandoned wells, many dating to the early years of oil and gas exploration before the state instituted record-keeping and permitting. At a conservative estimate of $33,000 each for plugging, the price tag to stop emissions is staggering.
Federal Bipartisan Infrastructure Law provides $21 billion for abandoned well plugging and brownfield cleanup, and Pennsylvania could receive as much as $395 million over the next decade. The DEP is now working to rapidly scale up its historically underfunded well plugging program to take advantage of the infusion of money.