The Bakken shale oil fields of North Dakota and Montana began production in 2005. They have produced approximately 11.5 days of world oil consumption since then.
Estimates indicate that the total oil available in the Bakken fields may be as high as eight months of world oil consumption.
The world consumes approximately 87 million barrels of oil per day. That means that it consumes a billion barrels of oil every 11.5 days.
The Bakken oil fields have produced one billion barrels of oil since 2005. The estimate is that the fields will produce a total of 20 billion barrels, or 230 days of world consumption: about 7.6 months.
The headline on Yahoo is that the fields have produced a billion barrels of oil. It is an impressive headline. But to understand the magnitude of the Bakken fields, we need to compare this with consumption.