A new study says the oil-producing region of North Dakota and Montana leaks 275,000 tons of methane annually, an amount that's less than previously reported.
Researchers say it's the first field study of methane emissions from the Bakken shale formation. Methane is a greenhouse gas that contributes to global warming. It's the primary component of natural gas.
The study released Wednesday was based on air samples a National Oceanic and Atmospheric Administration airplane took from over the Bakken region in May 2014. The study says the methane emissions were less than what had been reported by some satellites and slightly lower than U.S. Environmental Protection Agency estimates.
Researchers say the amount of methane leaking from the Bakken is similar to the emission rate from the oil-rich Denver-Julesburg Basin in Colorado.