That's the most recent estimate of North Dakota's oil reserves in the Bakken shale according to this Houston Chronicle article. "Eleven billion barrels is double the previous estimate of reserves, and could eventually push North Dakota into second place among the states for oil production, leapfrogging over California and Alaska and trailing only Texas. We won't know for sure for a couple of years, but this is considered likely by experts, according to an Associated Press story published in the Chronicle ("North Dakota oil patch larger than expected: If estimate is correct, state might soon pass all but Texas in production," Page B1, Jan. 3)."