The U.S. Geologic Survey’s (USGS) assessment of the Williston Basin’s Bakken Shale and Three Forks formation in North Dakota, Montana and South Dakota, which combined was estimated at 7.4 billion bbl of technically recoverable oil, is “very conservative,” according to North Dakota’s chief oil and gas regulator.

Lynn Helms, director of North Dakota’s Department of Mineral Resources, told reporters Wednesday that he doesn’t expect the assessment to accelerate or depress ongoing exploration and production (see Shale Daily, May 1).

“One thing to keep in mind is that not all current producing levels were included in the assessment,” Helms said. “There are about 1 billion bbl of oil that already are being produced or are going to be produced in existing wells that aren’t part of the 7.4 billion bbl estimate. It is actually an 8.4 billion bbl total.”

North Dakota’s mean estimate of future recoverable reserves is equal to the USGS’s maximum estimates. “Their maximum is 11.4 billion bbl, and that’s our mean estimate for production from eastern Montana and western North Dakota.”

North Dakota probably will update its state assessment in 2014; the previous one was completed in 2010, he noted. “Our intention is to wait until this exploration phase of the Three Forks’ third and fourth bench is further along, and that is going to happen over the next nine to 12 months. Once we have that data, we think it will be a good idea at that time for us to update our 2010 assessments…”

Helms said the federal agency’s estimates on average per-well production were less than what North Dakota officials predict. USGS estimates ranged from 200,000-350,000 bbl/well, while North Dakota’s estimate is an average of about 600,000 bbl/well.

The USGS seemed to have “a desire to be on the conservative side,” but he said it was good to have the assessment come out at this time. “It was nice to have it come out and to be double what it was before, but it is still conservative.”