Definition and world resources of natural bitumens

Natural bitumens, semisolid or solid mixtures of hydrocarbons and as much as 50 percent heterocyclic compounds, are composed largely of carbon and hydrogen but have substituents of nitrogen, oxygen, sulfur, and trace metals, especially iron, nickel, and vanadium. Bitumens are soluble in organic solvents such as toluene or chloroform. The natural bitumens are differentiated from less viscous crude oils on the basis of their absolute viscosity of more than 10,000 centipoises. Natural asphalt, commonly known as oil sand or tar sand, is the only natural bitumen variety of quantitative and economic significance and today serves as a source of road metal and as raw material for synthetic fuels. Canada's Alberta Province dominates world resources of natural asphalt; it has demonstrated and inferred resources totaling more than 2,500 billion barrels. Resources ranging from 10 billion to 70 billion barrels are in the U.S.S.R., the People's Republic of China, Venezuela, and the United States. Smaller amounts of natural asphalt resources are present in numerous other countries. At present, little use is being made of many of these deposits. However, with the depletion of conventional crude oil, natural asphalt will become more important as a source of hydrocarbons for fuels and petrochemicals.