A crude-bearing cache known as the Birdbear, beneath North Dakota's already booming oil patch, can be tapped using new technology that would expand horizontal drilling to parts of the state that have never seen it, geologists believe.
The Birdbear is a thin oil formation _ only a few feet _ locked within muddy limestone and dolomite more than 2 miles underground, immediately beneath the rich Bakken shale and Three Forks-Sanish formations in North Dakota, said Julie LeFever, a geologist with the state Geological Survey in Grand Forks.
"If the Bakken and Three Forks don't work out, here's another target," LeFever said.
Denver-based Whiting Petroleum Corp. already has about 50 horizontal wells aimed at the Birdbear in Billings and Golden Valley counties in southwestern North Dakota, said John Kelso, a company spokesman. The wells there produce up to 400 barrels daily, compared with the company's Bakken or Three Forks wells that can top 2,000 barrels daily, he said.
Kelso called the Birdbear an important but tertiary target for his company, which has more than 600,000 acres leased for oil exploration in North Dakota.
"Our primary focus over the next three to five years is the Bakken and Three Forks," he said.
Still, LeFever said, "it's hard to ignore" the production coming from the two counties where horizontal drilling is fetching oil from the Birdbear.
The formation in southwestern North Dakota is nearly identical to a Birdbear formation Bottineau County, about 250 miles away in north central North Dakota and just beyond the Bakken and on the far fringe of the state's existing oil patch.
"North central is where the rocks are similar," said LeFever, who has studied the state's oil patch for more than two decades.
The state is pitching the area to companies as an area of additional production potential. But most oilmen are having too much success with the rich Bakken and the Three Forks-Sanish formations above the Birdbear to busy themselves with it for now.
"Most of the operators in North Dakota can only raise a certain amount of capital, and that capital is pretty much being spent on the Bakken and Three Forks," said Lynn Helms, director of the state Department of Mineral Resources. "There will come a time when some companies that drill up their acres in the Bakken will be looking at something else."
Jack Stark, head of exploration for Continental Resources Inc., said the potential for the Birdbear is known by his Enid, Okla.-based company, one of the biggest and oldest players in the state's oil patch.
"Our primary focus is going to be on the Bakken and Three Forks," he said. The Birdbear "would be an objective further down the road for us. We have it in our sights," he said.
LeFever said the Birdbear was created during the Devonian period, some 350 million years ago, when the land mass that is now North Dakota was located just south of the equator.
State geologist Ed Murphy said the formation was named for Solomon Bird Bear, a Fort Berthold reservation landowner. The formation was discovered beneath his land in the 1950s.
The formation extends throughout the Williston Basin, into Saskatchewan and Montana, where it is called the Nisku, and has been drilled using conventional methods since the 1960s. Vertical wells have been tapping oil from the Birdbear in North Dakota for about 30 years, geologist say.
Horizontal drilling and well completion technology developed for the Bakken and Three Forks in the western part of the state could be applied to fetch oil from the Birdbear in north central North Dakota, geologists say.
Instead of piercing an oil zone at a single point with a vertical well, pipe is placed horizontally through the zone to suck out crude. The so-called laterals can extend nearly 2 miles.
Some vertical wells already exist in far-western Bottineau County but they are aimed at shallower formations far above the Birdbear, Murphy said.
Troy Marsden, a city council member in the town of Bottineau, said more rigs and wells in the region would boost tax revenue and jobs.
"I think we would welcome the activity," Marsden said.
"Quite of few guys from here work on the rigs but they've got a long distance to travel," Marsden said. "If those rigs came closer, it would be a benefit to them."