Heavy Oil: the important energy resource for 21st century

In this paper, an introduction was made on the heavy oil, extra heavy oil, and natural bitumen resources in the world, as well as in Iran. These mixtures were categorized according to their physical properties and chemical composition. According to existing information, the giant extra heavy oil, and natural bitumen reserves are located in the western hemisphere. However, the Middle East countries, including Iran have considerable heavy oil reserves. In Iran, the major heavy oil resources are located in the south and south-west of the country, and the reserves are reported in this paper. Also, the challenges during development, production, transport, and processing of heavy oil and bitumen are addressed. The common and innovative methods of heavy oil production are introduced.