BISMARCK, N.D. - Dozens of fruitful wells beneath the rich Bakken shale in North Dakota continue to fuel a hunch among oilmen and geologists that another vast crude-bearing formation may be buried in the state's vast oil patch.

Lynn Helms, director of the state Department of Mineral Resources, said recent production results from 103 newly tapped wells in the Three Forks-Sanish formation show many that are "as good or better" than some in the Bakken, which lies two miles under the surface in western North Dakota and holds billions of barrels of oil.

"I think it's a big deal and we're pretty fired up about it," Helms said.

Companies have reported some Three Forks wells recovering more than 800 barrels daily, considered decent by Bakken standards.

Denver-based Whiting Petroleum Corp. has drilled two wells in the Three Forks formation, with one that recorded more than 1,000 barrels of oil a day, said John Kelso, a company spokesman.

"We are excited about Three Forks but it's early on in the play," Kelso said. "I do know a lot of companies are redirecting focus from the Bakken to Three Forks."

Whiting has one Bakken well that recorded more than 4,000 barrels a day last year, thought to be a record for the formation and about double the highest Three Forks well drilled to date.

Kelso said Whiting's primary focus at present is on the Bakken. The company has more than 300,000 acres under lease in North Dakota.

"With the turbulence in crude oil prices, we've kind of backed off Three Forks for the Bakken," Kelso said. "We will very likely get after Three Forks in 2010, depending on oil prices.

The Bakken formation encompasses some 25,000 square miles within the Williston Basin in North Dakota and Montana. The U.S. Geological Survey has called it the largest continuous oil accumulation it has ever assessed.

The Three Forks-Sanish formation is made up of sand and porous rock directly below the Bakken shale. But geologists don't know whether the Three Forks-Sanish is a separate oil-producing formation or if it catches oil that flows from the Bakken shale above.

Fort Worth, Texas-based XTO Energy Inc. has reported to the state that one of its Three Forks wells pulled more than 2,100 barrels a day. An ETO Energy spokeswoman said the company does not comment on its operations publicly.

State and industry officials are conducting a study to determine whether the Three Forks is a unique reservoir. The plan is to compare results from closely spaced wells, one aiming for the Three Forks, and the other at the Bakken. Researchers will look at pressure changes in the formations to determine if they are connected.