The oil lies underground in a shale rock formation stretching across western North Dakota, northeast Montana, and into Canada's Saskatchewan Province known as the Bakken.

(CNNMoney)
HOUSTON -- In the grasslands of western North Dakota, one of the country's richest oil men is using a controversial gas drilling technology to develop what could be the biggest domestic oil discovery in the last 40 years.
The oil lies underground in a shale rock formation stretching across western North Dakota, northeast Montana, and into Canada's Saskatchewan Province known as the Bakken.
Thanks to hydraulic fracturing or "fracking" and high oil prices, oil production in the Bakken has exploded.
It went from a mere 3,000 barrels a day in 2005 to 225,000 in 2010, according to the government's Energy Information Administration.
EIA thinks it will produce 350,000 barrels a day by 2035, but most analysts think that estimate is far too low.
According to Harold Hamm, president of the energy company Continental Resources, it could produce a million barrels a day by 2020.
That's only a fraction of the 9.8 million barrels a day the country produces and an even smaller fraction of the 19.2 million it consumes, but it's significant.
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