BISMARCK Another formation in the Williston Basin, the Tyler Formation, is creating interest among North Dakota minerals experts because it is similar to the Bakken Formation.
On Monday, the N.D. Geological Survey/N.D. Department of Mineral Resources released a detailed poster on the "Resource Potential of the Tyler Formation" by Stephan H. Nordeng and Timothy O. Nesheim, geologists with the Geological Survey in Bismarck.
Ninety-five percent of the drilling being done in North Dakota is in the Bakken and Three Forks," said Lynn Helms, director of the N.D. Mineral Resources Department in Bismarck. "One of the hot topics that we're beginning to promote is something called the Tyler Formation."
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The color filled circles on this map, courtesy of the North Dakota Geological Survey/N.D. Department of Mineral Resources and its new Tyler Formation poster, show where Tyler production has already been established with vertical wells within North Dakota. The color of the circles reflect the total amount of oil produced from each well. The color filled contours represent the degree of oil generation potential based on modern heat flow measurements and the thickness of the overlying rock. The shades of yellow and green are areas in which the Tyler Formation is most likely to be capable of generating oil. The shades of blue and purple are areas in which the Tyler could be capable of generating oil.
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"The Tyler Formation is of interest because it is similar to the Bakken Formation in that it covers a large part of the Williston Basin, contains significant amounts of organic matter and is a proven oil-producing interval," said Nordeng.
"Unlike the Bakken, the Tyler Formation contains sandstone reservoirs that produced commercial quantities of oil from conventional vertical wells. However these reservoirs are small in comparison to the total extent of the Tyler. Therefore it seems likely that in places that don't have sandstone reservoirs additional production from the Tyler Formation might be possible using the technologies developed in the Bakken," Nordeng said.
"Understandably, companies are focused on the Bakken and Three Forks. In addition to our work on those rock units, we are generating information that might point companies to other potential targets, such as the Tyler and Spearfish Formations, in areas outside of traditional Bakken production," said Ed Murphy, state geologist with the N.D. Geological Survey.
Nordeng said oil production from the Tyler Formation was first established early in 1954 from the Dan Cheadle Unit No. 1 drilled by Amerada-Hess and Northern Pacific in the Fryburg Field. The Fryburg Field is in the Medora.
"This well initially produced 117 barrels of oil per day with little water and no gas from vertical well drilled to a depth of 8,271 to 8,278 feet," Nordeng said.
Areas of production
Nordeng said most of the current and historic Tyler production is limited to the parts of the state that have sandstone reservoirs that lie within the Tyler shale.
"These sandstone reservoirs are the preserved remnants of barrier islands that trend roughly parallel to an ancient coast line that runs east-west through these counties (sort of like the sand islands that lie along the coast of Texas near Galveston)," Nordeng said.
"However, some small production has been found in a couple of wells one in McKenzie County and one in northwestern Dunn County well away from the established production. This isolated production demonstrates that oil generation within the Tyler is not limited to the known fields," Nordeng said. "The question, of course, is that with the modern drilling and stimulation technologies used in the Bakken Formation. is it possible to obtain new production from the Tyler in places that don't have the conventional sandstone reservoir?"
The Tyler lies about 2,000 feet above the Bakken, Nordeng said.
He said the Tyler does not extend into Canada as does the Bakken but it apparently does extend, unlike the Bakken, into South Dakota. "Otherwise, the Tyler covers about the same area as does the Bakken/Three Forks," he said.
Compared to Bakken
"From the conventional standpoint (vertical wells) the wells drilled into the Tyler sandstones are better producers than most of the vertical wells drilled into the Bakken/Three Forks," Nordeng said. "This is because the Tyler contains reservoir rocks (sandstones) that allow economic oil production from vertical wells whereas the Bakken/Three Forks wells (outside the Antelope Field) do not. However, the new horizontal Bakken/Three Forks wells are much better producers, at least initially, than the old vertical Tyler wells.
"To date only one, short, horizontal well has been attempted in the Tyler. This well apparently had technical difficulties and was not successful. This, of course, leaves the open question as to whether or not modern horizontal drilling methods could be used to substantially increase the area in which oil could be produced from the Tyler," Nordeng said. As far as he knows, no oil company currently is targeting the Tyler Formation.
He said it is not expected that the Tyler will become what the Bakken has.
"The shale in the Bakken Formation contains literally world-class quantities of organic matter that is prone to oil generation. The shale in the Tyler, though organic rich, is not in the same class as the Bakken. Also, the Tyler has not been buried as deeply and therefore has not been heated/matured as much as the Bakken," Nordeng said.
Nordeng said there are other formations the N.D. Geological Survey/N.D. Department of Mineral Resources is investigating which might become of interest to companies. But he said that work is only in the most preliminary stages.