....Pretty much all of NDak could be an oilfield.
Oil and coal deposits are pretty much all over Eastern Montana, Wyoming, Colorado and Western North/South Dakota. (Then on up into Canada)
What could be the play in this case is to use the Mineral rights and especially the Water Rights to control the land around their purchase.
Wouldn't be the first time.
This whole place is basically semi-arid. Water is life and the majority of real bad fights (legal and otherwise) over the past 150 years...at least...have been over nothing at all but water.
If this IS what Gates is doing, he's quite literally playing with fire. Too many people have already been pushed too far.
Continental shield prohibits exploiting both ND and MN