Bakken study premature

BISMARCK — Sen. Byron Dorgan says the U.S. Geological Survey has denied his request to study a potentially rich oil reservoir below the Bakken shale formation in western North Dakota.

Dorgan asked the agency in December for a review of the Three Forks-Sanish formation to find out how much crude can be recovered from it.

Government scientists have said a study of the formation is premature. Dorgan said the agency informed him this week that it needs more information about oil production from the formation before it could perform an accurate assessment.

Dorgan said “that’s probably a reasonable thing.”

Geologists and oil companies are not sure if the Three Forks-Sanish is a separate oil-producing formation or if it acts as a trap, catching oil that leaks from the Bakken shale above. Some say it could be both.

New horizontal wells aimed at the Three Forks-Sanish in recent months have been successful. But those wells came online after the USGS released a study last April that estimated up to 4.3 billion barrels of oil can be recovered in the Bakken, where oil-producing rock is sandwiched between layers of shale about two miles under the ground.

The Geological Survey said the potential of the underlying Three Forks-Sanish formation was factored into the agency’s estimate for the Bakken, though it was based on production from traditional vertical wells that were spudded decades ago. The Three Forks-Sanish added about 500 million barrels to the estimate, the agency said.

The USGS said the last formal study on the formation in North Dakota was done 40 years ago.

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