The link above is to a Rigzone article discussing the April 2013 USGS Bakken/Three Forks estimate, which was referenced by Robert Rapier at
The USGS slide presentation can be found at
and click on the slide presentation pdf link near the bottom of that page.
Near the end of that slide presentation it breaks out the 7.4 BBO for all of the US Bakken/Three Forks into Montana and North Dakota sections of the play. North Dakota has a mean estimate of 5.8 BBO of undiscovered technologically recoverable resources (TRR) in the Bakken/ Three Forks.
I had been ignoring the "undiscovered" and was incorrectly interpreting the estimate as the full TRR, until I read the following in the Rigzone article: