Since Hess Oil discovered oil near Tioga in 1951, companies have economically produced oil and natural gas from more than 20 geologic formations in North Dakota’s share of the Williston Basin. For nearly a decade, exploration and production has centered on the Bakken formation, which now accounts for about 95 percent of the state’s annual production and gets the lion’s share of oil patch press.
However, companies continue to “kick the tires,” so to speak, by searching for resources in other formations. During the past few years, for example, exploration and production has steadily grown in the Red River, Spearfish and Madison formations. More recently, the Tyler formation has drawn some attention as a possible “Baby Bakken.” Whether the Tyler formation deserves the moniker and will live up to some early expectations, however, is probably a few years down the road.
A long production history
“Exploration and production in the Tyler formation is not new,” says Timothy Nesheim, staff geologist with the North Dakota Geological Survey. “Amerada Petroleum drilled the first well in late 1953 in eastern Billings County. Subsequent wells were completed in the Fryburg trend along Highway 10 (now Interstate 94) between Dickinson and Fryburg.” Nesheim says drillers used conventional (vertical) drilling techniques in a number of scattered fields along the trend and that the Tyler formation has been a good producer of oil and a moderate producer of natural gas.
“The heyday of drilling was in the late 1960s to early 1970s – drillers were averaging about one successful well per month,” Nesheim says. “During the past 60 years only 285 productive wells have been drilled into the Tyler formation. More than 85 million barrels of oil have been produced.” The Tyler formation also produces oil in central Montana’s Snowy Mountain Trough region where it overlies the black Heath shale, which has proven to be a challenging candidate for Bakken-like drilling technology.
The most recent “surge” of drilling into the Tyler was the development of the Tracy Mountain field in 1992 in southern Billings County. Nesheim says that, although vertical drilling into the Tyler has peaked, PetroHunt has recently drilled a successful vertical well in northeastern McKenzie County and Williston Exploration has been successful with a single well in southern Billings and Stark Counties.”
He says two companies, Upton Resources and Axem Resources, have employed horizontal drilling in the past within the Fryburg and Tracy Mountain fields with mixed results. (The Axem well was fracked, while the Upton Resource wells were not.) “The wells included one-half-mile laterals into the Tyler sandstone, which has good natural permeability but was pretty hard on drill bits. Two of Upton’s wells are still producing,” he says.
Nesheim says the oil thus far produced from the Tyler formation is of high quality and is classified by the American Petroleum Institute as a light crude although, on average, slightly heavier than Bakken crude. He says Tyler oil is very waxy having a paraffin content of 30-40 percent.
Lots of work ahead
“As for the present, the Tyler formation is about where the Bakken play was in the early 2000s before the discovery of the Parshall field – call it the ‘prospect mode,'” Nesheim says. “The formation is still untested with regard to how well it will respond to Bakken-style horizontal drilling and hydraulic fracking, which is what it will most likely take to make it a highly successful unconventional play.”
Nesheim says there’s no question that the Tyler has serious potential. “There are two petroleum systems – a northern located primarily in McKenzie and Dunn Counties, and a southern in Stark, Billings and Slope Counties; the total organic content (oil content) is good to excellent in both systems. The reservoirs in the northern system are mostly shale, while sandstone and limestone predominate to the south.” To date, virtually all Tyler production has come from sandstone reservoirs. The limestone and shale beds should be considered “prospective unconventional reservoirs.”
What lies ahead, according to Nesheim, is a substantial amount of data collection to better understand the petroleum geology of the Tyler formation, especially to find continuous horizontal drilling targets and to figure out their vertical extent and distribution of oil. In addition, he says more data must be collected to determine the formation’s porosity, natural permeability, and oil saturation vs. water content. “Right now, a number of companies have cut cores into the Tyler formation including: Williston Exploration, Marathon, Continental Resources, XTO and others,” he says.
Alison Ritter, public information officer with the North Department of Mineral Resources, emphasizes that the preliminary work yet to be done will take time. “Everyone, especially communities in its footprint, should know that it is still very early with the Tyler formation,” she says. “Being so close to the Bakken is both a blessing and a curse – blessing to have Bakken technology so close at hand, a curse to have such a successful play like the Bakken competing for exploration and production companies’ attention.”
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