Yeah . . . except that there is a problem. The owners of that land know about the minerals underground - and although the Saudis may make the payoff of those minerals speculative, they cannot unring the bell of the knowledge of their potential value. I don’t think North Dakota “farmland” will be a glut on the mart. You can probably buy the land - but the mineral rights, not so much. The owners will be leaving those rights to their heirs in their wills.
I remember reading somewhere that the Chinese had bought a 33% stake in northeast Colorado gas lands, several hundred square miles worth. So while I was being snarky, it wasn’t entirely out of the realm of reason.
My point was that Bakken and other shale lands are reducing Saudi ability to control the price. I haven’t heard of the Saudis buying up foreign oil fields (although they own a large stake in Shell Oil I believe) but the Chinese are doing it. I think they just bought a large field in Alberta.
You’re right, though. In a lot of places the mineral rights just come with the surface rights, but once someone has found oil in the area, you can forget that. They’ll sell the surface but if you want the minerals you have to cough up real money.