Oil sands (also called tar sands) are a combination of clay, sand, water and bitumen (a heavy, black, viscous oil). They can be mined and processed to extract the oil-rich bitumen, which is then refined into oil. The bitumen in oil sands cannot be pumped from the ground in its natural state; instead oil sand deposits are mined, usually using strip mining or open pit techniques, or the oil is extracted by underground heating with additional upgrading. Oil sands are mined and processed to generate oil similar to oil pumped from conventional oil wells, but extracting oil from tar sands is more complex than conventional oil recovery.
Much of the world's oil (more than 2 trillion barrels) is in the form of oil sands, although it is not all recoverable. While they are found in many places worldwide, the largest deposits are found in Canada and Venezuela, and much of the rest is found in various countries in the Middle East. In the U.S., resources are primarily concentrated in eastern Utah, where the in-place oil sands oil resources are estimated at 12 billion to 19 billion barrels. (Source: EIS / Photo: Flickr)