The shale oil fields in the two states remain largely unknown to energy investors.
As Money Morning reported Nov. 27, fracking technology has opened vast shale oil and gas fields that previously had been uneconomical to exploit.
With rapid growth in recent years, so-called unconventional oil has accounted for about 2 million barrels per day of production in 2012.
In Oklahoma, where oil was discovered in 1897, conventional oil production peaked in 1927, and the state's fields were thought to be exhausted.
Oklahoma's main field, the Anadarko Basin in the western half of the state, has yielded most of Oklahoma's oil and natural gas in recent years.
Now drillers are targeting the basin's Woodford shale layer.
One of the Most Unknown -and Promising - Shale Oil FieldsOne of the companies drilling in the Woodford shale layer is Continental Resources (NYSE: CLR), who told Reuters the site is "one of the thickest, best-quality resource shale reservoirs in the country."
Continental is known for its success drilling in North Dakota's Bakken, one of the best-known shale oil fields.
At 3,300 square miles in area, the Woodford shale layer is smaller than the 13,000-square-mile Bakken shale oil field or the 5,000-square-mile Eagle Ford field in Texas. But the Woodford shale reservoir is thicker, at 150 to 400 feet thick, compared with Eagle Ford at 100 to 250 feet and Bakken at 10 to 250 feet.
The U.S. Geological Survey estimates Woodford contains 400 million barrels of recoverable oil. The site is also believed to contain 250 million barrels of condensates and lots of natural gas.
Continental Resources is one of the bigger players in the Woodford reservoir. The company has increased its acreage holdings in Woodford at an even faster rate than it has in the Bakken. From 2009 to October 2012, Continental's net acreage in Woodford rose 1135 to 316,000 acres while its net acreage in the Bakken increased by 51% to 915,000 acres.