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Leasing begins on Tyler Formation

The North Dakota Department of Mineral Resources released details Monday about an oil formation in southwest North Dakota believed to be similar to the Bakken and leasing has already begun.

Stephan Nordeng, DMR geologist, said the Tyler Formation, which encompasses nearly all of western and southwestern North Dakota, extending into South Dakota, is a very large and complicated formation.

"Up to the north it probably doesn't cover quite as much area as the Bakken, but it extends further south than the Bakken, but otherwise they lay pretty much on top of each other," Nordeng said.

The Tyler Formation is most likely one-third to one-half the size of the Bakken in terms of coverage area and reserves, said DMR Director Lynn Helms.

"It's still absolutely huge," Helms said. "I would think within the next year we should start to see some initial test wells ... I think it'll take them one to two years to sort of figure out how to make it work."

There are several factors indicating the play could be similar to the Bakken, including samples rich in organic matter, two producing wells in the Tyler, a higher than expected pressure within rock beds, along with matured organic matter to the point where it could create oil, Nordeng said.

"What we're just beginning to recognize is that the entire Tyler package is another unconventional play like the Bakken," Helms said during an October town hall meeting in Dickinson. "It contains several really hot shale beds and when you get a high gamma ray signature in those shale beds, it means there's lots of organic material in there."

In order to reach the Bakken, oil companies must drill through the Tyler Formation.

"Instead of having just three basic layers like the Bakken does, it has little sand bodies that come and go -- the shales aren't stacked as neatly as in the Bakken so from that standpoint, it's more complicated in attempting to understand what's going on with it," Nordeng said.

The formation has the potential to produce natural gas, but it is unknown how many barrels of recoverable oil are in the Tyler, Nordeng said.

More than 100 oil wells have been drilled in the Tyler Formation, producing about 200 million barrels of oil to date, Nordeng said.

Shallower than the Bakken, the Tyler is comprised of a similar source rock.

"The source and the reservoir could be the same, that's one of the exciting parts of all of this is that the rocks that we used to look at and wish we could do something with we can now," Nordeng said.

Helms said no horizontal wells have been drilled in the Tyler, only vertical, an infrequently used drilling method.

Interest in the formation is picking up and Slope County has a lot of potential in the Tyler, Helms said.

"There's a lot of excitement about the fact it goes into South Dakota and there's also been already some leasing going on south of Dickinson and east of Dickinson," Helms said.

But, methods of recovering oil in the Tyler Formation, one Helms cites as having "all the marks of an unconventional resource play," could be a "whole new ballgame."

"The lithology is different than the middle Bakken and Three Forks," Helms said. "The specifics about how to drill for it and frac it will have to be experimented with."