Oil and gas finders are enamored with the Williston Basin these days, looking for the next big find in the upper Devonian-Lower Mississippian Bakken formation.
Even though there was considerable activity in the Bakken in the 1980s and 1990s, the focus was on the upper shale member, which yielded marginally economic, difficult-to-produce wells. This upper member became known as a re-entry bailout zone rather than a drilling target.
This take on the Bakken potential became passé beginning in 1995 when explorer Dick Findley determined there was good porosity and a likely oil zone in the fractured dolomitic middle section of the formation beneath the recognized source rock of the upper Bakken.
This was an idea that spurred Findley to action that ultimately lead to the development of the giant Elm Coulee field in the Bakken in eastern Montana.
The idea that became a reality was important for Findley on a personal level – it led to a high national profile and resulted in his receiving AAPG’s Explorer of the Year award in 2006 – and on a national level it sparked a flurry of activity.
Current activity in this region no doubt has been fueled in large part by a fairly recent announcement by the U.S. Geological Survey that its assessment of the Bakken in the Williston Basin in Montana and North Dakota revealed about 3.65 billion barrels of undiscovered technically recoverable oil.
On top of this, the agency added 1.85 Tcf of associated/dissolved natural gas and 148 mbo of natural gas liquids.
When Findley ventured east from Montana into North Dakota in search of another Elm Coulee-type trap and reservoir, he did not find the kind of reservoirs they were dealing with over a large regional extent. Instead, there seemed to be local accumulations of reservoirs in Elm Coulee-type facies.
“Where the true significance of Elm Coulee comes in is that we have a world class source rock sitting right next to a good reservoir,” Findley said.
“What the play really is, is looking for those occurrences.
“Once you take a look at that aspect of it,” he said, “I think you find several instances in North Dakota where you actually do have good reservoirs in different facies, but certainly associated with the world class source rock.
“What we believe now is there’s a huge amount of oil generated in these source rocks,” Findley noted, “and it stayed close to home. It’s difficult to find areas outside of the Lodgepole facies play where the oil actually migrated to other formations.
“This concept of the Bakken source system, I think, is a very significant piece of the puzzle,” Findley added. “That to me is the true significance of Elm Coulee – and it’s not just the Bakken.
“I refer to the Bakken and beyond because I think what we need to do is concentrate on this kind of unconventional reservoir worldwide,” he said.
“There’s obviously other world class source rocks, other reservoirs in that same situation,” he added, “so I think there are other plays to be had.”
Findley noted the bulk of the work in unconventional reservoirs in North America has concentrated on looking for natural gas. Elm Coulee takes on added import in that it has shown for the first time that oil can be produced in economic quantities owing to technology advances in these unconventional-type reservoirs.
However, patience is the name of the game given that one must navigate a steep learning curve to unlock the potential of these reservoirs.
“We first discovered Elm Coulee in 1996, and the first horizontal well was drilled in May 2000,” Findley said. “Then it took us maybe 18 wells before we actually got on the right track – and that learning curve to this day hasn’t ended.
“Before Parshall was discovered (in North Dakota), a lot of wells were drilled using Elm Coulee-type fracing, and they were very uneconomic,” Findley said. “Even now that learning curve is still being fine-tuned.”
He cautioned that every reservoir is different, which necessitates considerable adjustment of the stimulation technique.
“I’m very optimistic about North Dakota,” Findley said. “We’ve been hearing things like (it is) another Saudi Arabia and all those kinds of things, and I do believe very, very large amounts of oil have been generated.
“I think we’re only going to be able to make a small fraction of that economic,” he said. “But I think it will go a long way to reduce our dependence on foreign sources, so I think it will be a very important play for North America.
“It’s naive thinking we can replace coal, oil and gas with wind and solar,” Findley added. “But I think it will take a crisis before people wake up and start asking key questions about how do we solve our energy problems.”
Dick Findley, AAPG’s Explorer of the Year in 2006, presented his paper “Perspectives of Elm Coulee Field, Williston Basin – The True Significance for the Bakken and Beyond,” at the recent AAPG Annual Convention and Exhibition in Denver.
Findley’s talk was part of the Discovery Thinking technical session chaired by Charles Sternbach and Ed Dolly, which featured several geologists discussing the process and stories behind significant discoveries.
Findley said that the Bakken shows “there are other plays to be had.”