Oil Shale and Tar Sands
From Thermal-FluidsPedia
Two potentially rich sources of fossil fuel are oil shale (or shale oil) and tar sands (or oil sands). Oil shale is actually a misnomer. It is not shale, but a rock, and it doesn’t contain oil, but rather a solid organic compound kerogen, which is tightly packed in clay, mud, and silt. Tar sands are grains of sand containing thick, viscous, soluble organic liquid called bitumen (Figure 7-18). Th e United States has two-thirds of the entire world’s oil shale (along shores of Green River in Wyoming, Colorado, and Utah), and Canada has the largest percentage of tar sands in the world (in Alberta). In fact, if tar sand reserves are included, Canada would have the second largest amount of petroleum reserves in the world after Saudi Arabia (1). Russia and Brazil are also rich in oil shale, whereas Venezuela has the second largest deposits of tar sands (aft er Canada). Worldwide resources of tar sands are estimated at around two trillion barrels (2). An additional 2.8-3.3 trillion barrels of oil can be recovered from oil shale (3). Mining operations are very energy intensive; oil shale resides deeply underground and must be heated to high temperatures (around 400-500oC) before it releases any oil. In fact, the oil extract is not petroleum, but liquid kerogen. Steam is needed to hydrogenate kerogen into hydrocarbons that may then be refined into gasoline and other petroleum products. Tar sands must also undergo a similar process. Heating them to high temperatures causes the viscosity of the bitumen to drop, making it flow more easily out of the sand. Various petroleum products, such as kerosene can be manufactured by distilling the kerogen and bitumen oils.
In addition to their low yield (50-100 liters per ton of rock), oil shale and tar sands are not clean. These resources are rich in sulfur and nitrogen which can contribute significantly to the acid rain problem. Another environmental concern is the disposal of residues, called tailing, which occupy many times the volume of crude they produce. These problems have hindered widespread use of oil shale and tar sands. Canada is pursuing mining tar sand deposits aggressively; Estonia, Brazil, and China use oil shale to produce electricity and in production of cements. As the price of petroleum rise, these resources will find a more prominent role to meet our energy needs.
References
(1) George, R L, “Mining for Oil,” Scientifi c American, March 1998.
(2) Duncan, D. C., and Swanson, V. E., “Organic-rich shale of the United States and world land areas,” US Geological Survey Circular 523, 1965.
(3) “Annual Energy Outlook 2006,” Energy Information Energy, February 2006.
(4) Toossi Reza, "Energy and the Environment:Sources, technologies, and impacts", Verve Publishers, 2005
Further Reading
Berkowitz, N., Fossil Hydrocarbons: Chemistry and Technology, Elsevier Academic Press, 1997.
Deff eyes, K. S., Hubbert’s Peak: Th e Impending World Oil Shortage, Princeton University Press, Princeton, N. J., 2001.
Campbell, C. J., Th e Coming Oil Crisis, Multi-Science Publishing Company, 2004.
Tariq Ali, Th e Clash of Fundamentalisms: Crusades, Jihads and Modernity, Verso, 2002.
Pelletiere, S., Iraq and the International Oil System: Why America Went to War in the Gulf, Praeger Publishing, 2001.
Oil and Gas Journal, Technology, news, statistics, special reports, and analysis (http://ogj.pennnet.com).
Journal of Petroleum Technology, The official journal of Society of Petroleum Engineers, Dallas.
The Petroleum Engineer, Petroleum Engineer Pub. Co.
Journal of Petroleum Science and Engineering, Elsevier, covers the fields of petroleum (and natural gas) exploration, production and flow.
External Links
National Energy Technology Laboratory: Th e Strategic Center for Coal (http://www.netl.doe.gov/coal).
National Petroleum Technology Office (http://www.npto.doe.gov).
US Geological Survey (http://www.usgs.gov).
Organization of Petroleum Exporting Countries (OPEC) (http://www.opec.org).
Society of Petroleum Engineers (http://sae.org).