That's awfully big. Are you sure those numbers are correct, because that's bigger than the largest oil field in the world, which is in Saudi?
You are correct. It is awfully big.
Go here and check out the info on the Bakken Formation Reserve Estimates.here--,pdf file
While the estimates are "unofficial" until the USGS does their study, I have been working steadily as a geologist on these wells for 6 years now, with time off only for rig moves, running casing, and milling windows for secondary laterals. All the wells I have worked have been producers.