aromatics, naphthenes and resins, and these are mostly found in Western Africa (Chad), Central Africa (Angola) and East Africa (Madagascar). See also References External links Gushor Inc. - Heavy Oil Geoscience & Reservoir Engineering OTS Heavy Oil Science Centre Schlumberger map of global heavy oil resources Molecular Basis of Heavy Organics in Petroleum and Heavy Oil Crude Oil Technical Views Unconventional oil et:Raske nafta zh:重油