Oil sands is a colloquialism for what are technically described as bituminous sands, and commonly known as oil sands or (in Venezuela) extra heavy oil. The sands are naturally occurring mixtures of sand or clay, water and an extremely dense and viscous form of petroleum called bitumen. They are found in large amounts in many countries throughout the world, but are found in extremely large quantities in Canada and Venezuela.  Together, Canada and Venezuela oil sands reserves are about equal to the world’s total reserves of conventional crude oil.