Tar sands (also known as oil sands and bituminous sands) are sand deposits which are impregnated with dense viscous petroleum. Ultimate world reserves of bitumen in tar sands are about equal to ultimate reserves of crude oil in the United States. However, the only tar-sand deposit of present commercial importance is in the Athabasca area of Alberta, Canada. The pioneer venture to produce synthetic crude oil from tar sands began in 1967, operated by Great Canadian Oil Sands Limited (GCOS).

Tar sand is mined and transported to a processing plant where the bitumen is extracted, after which the sand is discharged into a tailings pond. At 10 weight percent bitumen saturation, two tons of processed tar sand produces 1 bbl of bitumen. Because tar sand is a relatively low-value ore, mining and transportation costs must be minimized. A key economic factor to be considered is the removal of overburden. The overburden ratio at GCOS (that is, the thickness of overburden which must be removed to expose a unit thickness of tar sands) is approximately 0.4.

The fact that large tar sands reserves are readily available in a friendly, stable country, and further that the material shipped is almost pollution free, should lend impetus to development.

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