I've read that the Monterrey shale was a disappointment. But estimates of potential reserves diverge widely. Incidentally, the Bakken extends into South Dakota where it is called the Red River play.

Fracking may be an old idea but not until the second decade of the 21st century did it come into wide use, combined with horizontal drilling. Both techniques have evolved resulting in higher productivity and lower costs, but companies that only drill, and that need to keep drilling to maintain profits, are struggling when prices go below $50/bbl. There are tremendous unexploited reserves in the US and worldwide, but until Saudi oil production slows, those resources will remain untouched. It i reasonable to believe that oil in quantity and affordable price will be with us through this century. Only cheaper and better renewable energy will partly replace petroleum.