Oil resources in shale formations of North Dakota and Montana are 7.4 billion barrels, U.S. government researchers said, doubling an estimate for that area made five years ago.
The U.S. Geological Survey said today the shale-oil that could be tapped in those states is the largest so-called unconventional resource in the U.S., and the biggest potential oil supply in the nation after Alaska.
The estimate increased because government scientists for the first time studied the Three Forks formation, which is deeper than the Bakken shale region already being developed. Three Forks was considered out of reach five years ago.
“The Three Forks is up and coming,” Brenda Pierce, the USGS energy resources program coordinator, told reporters on a conference call. Before this report, it “was the big unknown.”
Oil production in North Dakota is booming, making the state the second-largest U.S. producer after Texas, according to the U.S. Energy Information Administration. Bakken production rose 39 percent from a year earlier to 715,000 barrels of oil a day in this year’s fourth quarter, according to data compiled by Bloomberg Industries.
The U.S. Geological Survey is assessing what it said are “undiscovered resources” in the area, known broadly as the Williston Basin. These estimates don’t include reservoirs that companies have already identified. The resources must be “technically recoverable” using current methods to count in the assessment.
“This new USGS study further confirms and reinforces the fact that the Williston Basin is a sustainable, long-term play warranting strong private-sector investment for decades,” Senator John Hoeven, a North Dakota Republican, said in a statement today.
In 2008, the agency estimated 3 billion to 4.3 billion barrels of oil in the Bakken formation, which is mostly in North Dakota. Even accounting for oil already pulled from the ground, the amount of oil left in that rock is now estimated to be about the same as in 2008. About 450 million barrels of oil have been produced in the Bakken region since 2008, the geological survey said in its report.
The report today includes the Three Forks shale, which is found beneath the Bakken, that extends through much of North Dakota, northeast Montana and parts of South Dakota. It holds 3.73 billion barrels of oil, the agency said.
Shale gas and shale oil is produced by horizontal drilling and hydraulic fracturing, in which millions of gallons of water, sand and chemicals are injected underground to break apart rock formations and free the trapped fuel.
In addition to the oil, the rock formations include 6.7 trillion feet of associated natural gas. By comparison, the Marcellus Shale, which is centered in Pennsylvania, contains about 84 trillion cubic feet of undiscovered, technically recoverable natural gas, according to a 2011 USGS report.