Associated Press

Forty drilling rigs are working in North Dakota's Williston Basin, and the outlook remains positive despite a recent drop in oil prices, North Dakota's mineral resources director says.

It can cost as much as $6 million to drill a well in the shale formation known as the middle Bakken, where the oil is about two miles under the surface, director Lynn Helms said.

"The drop in oil prices from $78 (a barrel) on the world price to $59, $58 was pretty sobering," said Helms, who met with the state Industrial Commission on Thursday. "It tended to slow people up a little bit, to take a pause and look at the prospects and just decide how economic they were going to be.

"Had it happened several months ago when people were struggling as much as they were with the middle Bakken, it would have been pretty serious," Helms said. "But there are some very significant wells being drilled out there now."

OPEC announced it would cut output by a greater-than-expected 1.2 million barrels a day to reverse a three-month price slide, but oil prices fell Friday in a sign of traders' skepticism that OPEC would follow through. OPEC is currently producing about 29.5 million barrels of oil per day.

Light sweet crude for November delivery on the New York Mercantile Exchange fell 70 cents to $57.80 a barrel, after rising on Thursday.