They tried a nuclear detonation to get the crude oil out but it left a huge underground cavern and they got little oil.
I believe it was for Natural Gas.
Project Gasbuggy tests Nuclear Fracking
http://aoghs.org/technology/project-gasbuggy/
It did release more gas, but the gas was radioactive. Although a 50-kiloton nuclear explosion to fracture deep oil shale deposits – Project Bronco – was proposed, it never took place.