BISMARCK, N.D.—Companies tapping the rich Bakken shale and the formation below it in western North Dakota have reported excessive natural gas emissions from oil storage tanks and are working to burn or capture it, state and industry officials say.
The finding was surprising, and officials said it was unique to the Bakken formation, though they were not sure why.
“We haven’t measured any affect on North Dakota’s air quality from it,” said Lynn Helms, director of the state Department of Mineral Resources. “I think it’s a fairly easy problem to solve.”
Jim Semerad, manager of permitting and compliance for the state Health Department, said oil companies notified state and federal regulators in May that untreated natural gas was being discharged from oil storage tanks at some well sites.
The gas is a byproduct of the oil production process and is unique to high-quality crude from the Bakken shale and the Three Forks-Sanish formation directly below it, Helms said.
North Dakota’s oil patch has nearly 4,550 producing oil wells, including 1,700 Bakken wells and about 200 wells aimed at the Three Forks-Sanish formation below the Bakken, Helms said.
Machines called “heater-treaters” are used at well sites to remove gas and water from crude to improve its quality. It was at the storage tanks for processed oil that companies detected the leaking gas.
“It is not significant enough to cause health issues but it is significant enough to have requirements for control,” Semerad said.
State and federal regulators have tested dozens of Bakken wells, measuring the release of hydrocarbons. Rules also are being crafted to monitor air quality at the well sites, Semerad said.
Brent Miller, an operations manager for Whiting Petroleum Corp., said his company and five other major companies working in the state’s oil patch have formed a task force to share information about the emissions.
“We’ve taken hold of the problem and are dealing with it far faster than the agencies could force us to do,” he said.
The Denver-based oil and gas company has about 300 traditional wells in the Williston Basin, which includes North Dakota and Montana, and some 60 Bakken wells.
“Not until we began developing Bakken crude did we see this,” Miller said. “It is a very unique crude.”
Officials say the rich crude from the Bakken likely contains more hydrocarbons than traditional oil-bearing rock in the state’s oil patch. Unlike the Bakken or the Three Forks, traditional wells sometimes contain the potentially deadly chemical hydrogen sulfide, which is flared before being released to the atmosphere.
Miller’s company already has retrofitted its oil storage tanks to capture or flare the raw natural gas for the Bakken oil storage tanks.
“We will capture it 99 percent of the time,” he said.
Semerad, of the state Health Department, hopes most companies will capture and sell the natural gas instead of flaring it.
“The fastest fix likely would be to burn it,” Semerad said. “It’s cheaper to flare, but we’d like them to optimize collection as much as they can.”
Helms estimated it would cost between $15,000 to $50,000 to upgrade a storage tank to burn or capture the natural gas.
