Study finds ‘significant’ methane leaking from abandoned wells

WASHINGTON — As the Obama administration nears a decision on whether — and how — to clamp down on methane leaking from active oil and gas operations, new research suggests abandoned wells may be a significant source of the potent greenhouse gas.

The study, published Monday in the Proceedings of the National Academy of Sciences, focuses on 19 representative abandoned oil and gas wells in Pennsylvania, it can be extrapolated to the approximately 3 million across the country.

And while federal regulators are now concentrating on methane emitted during oil and gas production, the new study conducted by researchers with Princeton University suggests that accumulating leaks from abandoned wells over decades may be a bigger problem.

“Methane emission from abandoned oil and gas wells appear to be a significant source of methane emissions to the atmosphere,” wrote lead researcher Mary Kang, now a postdoctoral research fellow at Stanford University. “The cumulative emissions from abandoned wells may be significantly larger than the cumulative leakage associated with oil and gas production, which has a shorter lifetime of operation.”

The research team made direct measurements of methane flow rates from 19 wells across McKean and Potter counties in Pennsylvania, with the sites chosen mainly based on ease of access and no distinction drawn between the type of wells; both oil- and gas-producers were included. The samples were taken in July, August and October 2013, as well as January 2014, with control measurements taken.

Methane flow rates were found to be about 0.27 kilograms per day per well on average — and appeared unaffected by their forest, river or other covering.

The research suggests that there is little link between the amount of leaking methane and whether a well had been plugged, a technique designed to limit the vertical movement of oil and gas from formations deep below the surface.

“In the grassland area, both the largest and the second lowest methane fluxes originated from plugged wells,” the researchers noted.