BISMARCK, N.D. — North Dakota oil drillers have surpassed a milestone of half a million barrels of oil a day, the state's top oil regulator said Tuesday.

State Mineral Resources Director Lynn Helms said North Dakota now accounts for about 10 percent of total U.S. crude oil production, up from just 1 percent in 2007.

Ron Ness, president of the North Dakota Petroleum Council, which represents about 250 companies working in the oil patch in the western part of the state, called North Dakota's meteoric oil production growth incredible and said it's helping make the U.S. become less dependent on foreign oil.

The state Industrial Commission said crude production in November totaled 510,000 barrels a day, or about 150,000 more barrels than in November 2010. November statistics are the latest available because oil production numbers typically lag at least two months.

North Dakota produced a record 113 million barrels of oil in 2010; the state ended November with about 136 million barrels.

North Dakota went from the ninth-biggest producer in 2006 to fourth in 2009. Helms said North Dakota is on track to become the nation's No.2 oil producer early next year, surpassing California and Alaska, and trailing only Texas.

Helms said the move to leapfrog to the nation's second-biggest oil producer could come quicker but North Dakota has been hamstrung by the lack of crews to perform hydraulic fracturing, a process that uses pressurized fluid and sand to break open oil-bearing rock 2 miles underground.

Oil companies are competing for so-called frac crews working in fields in Texas and Pennsylvania, Helms said. North Dakota wells are typically coming on line in 135 days, but could be finished and producing in 90 days if more frac crews were available, he said.

On Tuesday, 200 rigs were drilling in western North Dakota, nearly all aiming for the rich Bakken and Three Forks formations.

The state had a record 6,300 producing oil wells in November, up about 1,200 more than in November 2010.