The industrial process needed to extract the oil demands hot water, making it much more expensive and less energy-efficient than conventional oil. The mining operation is extremely damaging to the environment. As of 1997 no oil from oil shale is being produced anywhere in the world. A variety of processes have been tried. All have failed to be economically viable.
Incidence:
Oil shales are seen as the US government's energy stopgap. They exist in large quantities in ecologically sensitive parts of Colorado, Wyoming and Utah at varying depths. A number of oil companies and the US Bureau of Mines have made substantial efforts but with no commercial results.