http://www.ourpubliclands.org/colorado/oilshale:

:The United States is home to approximately 50% of the world’s oil shale deposits, most of which are located in the Green River Formation of Colorado, Utah, and Wyoming. The Piceance Basin in northwestern Colorado alone is estimated to hold nearly 500 billion barrels of recoverable shale oil, which is more than double the proven reserves of Saudi Arabia. Approximately 72% of the oil shale resources of the Green River Formation are under federal ownership and control; in the Piceance Basin, federal lands managed by the Bureau of Land Management (BLM) overlie about 80% of the in-place shale resources.