http://www.nytimes.com/2012/11/10/world/americas/rigs-departure-to-hamper-cubas-oil-prospects.html

“Lee Hunt, a former president of the International Association of Drilling Contractors, said there were still potential opportunities off the island. The first Repsol well, he said, was not productive, but a subsequent study of the drilling results concluded that there could be promising oil-producing rocks in nearby waters.

“The second well drilled by Petronas found only heavy oil that was so thick it could not be economically lifted out of the ground. And the third attempt by the Venezuelan state company found rock that was so hard and thick that it wore down drill bits before reaching oil.”