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Oil shale is a sedimentary rock containing kerogen, comprised of solid bituminous materials, which takes on a petroleum-like form when released. Pyrolysis is the chemical process that heats the rock and releases the kerogen. This shale represents a source of a large supply of oil, waiting to be accessed.

Millions of years ago, oil shale was created by organic debris and silt deposited at the bottom of the sea and in lakebeds. In a method similar the way oil is created, the debris and silt were subject to pressure and heat that turned them into oil shale. Oil shale is often referred to as the rock that burns because it contains a large enough quantity of oil to burn without any processing.

Companies mine and process oil shale to produce oil but the process is more complex and also more expensive than pumping the substance from a well. Since the oil substance in the shale is solid, it cannot be directly extracted from the ground. The shale has to be mined and heated, or retorted, so the resulting liquid can be separated and then collected. A process currently in the experimental phase is in situ retorting. In this process, the shale is heated while underground and the resulting liquid is pumped to the surface.

The largest deposits of oil shale in the world are located in the Green River Formation within the United States. This area spans the states of Wyoming, Utah, and Colorado and is estimated to hold between 1.2 and 1.8 trillion barrels of oil. Though not all of it is recoverable, even a more conservative 800 billion barrel estimate is three times more than the amount of proven oil reserves located in Saudi Arabia.

U.S. petroleum demand is currently approximately 20 billion barrels daily. Using oil shale to meet just one quarter of that demand would result in more than a 400-year supply from the Green River Formation, based on the conservative recoverable estimate. The federal government owns over 70 percent of the oil shale acreage located in this area.