About Oil Shale
Basic information on oil shale, oil shale resources, and recovery of oil from oil shale.
What is Oil Shale
The term oil shale generally refers to any sedimentary rock that contains solid bituminous materials (called kerogen) that are released as petroleum-like liquids when the rock is heated within the chemical strategy of pyrolysis. Oil shale was formed millions of years ago by deposition of silt and organic debris on lake beds and sea bottoms. Over long periods of time, heat and pressure transformed the materials into oil shale in a process just like the method that forms oil; however, the heat and pressure weren’t as great. Oil shale generally contains enough oil that it’ll burn with none additional processing, and it is named “the rock that burns”.
Oil shale will be mined and processed to generate oil much like oil pumped from conventional oil wells; however, extracting oil from oil shale is more complex than conventional oil recovery and currently is more expensive. The oil substances in oil shale are solid and cannot be pumped directly out of the ground. The oil shale must first be mined after which heated potassium fertilizer to a high temperature (a process called retorting); the resultant liquid must then be separated and collected. An alternative but currently experimental process referred to as in situ retorting involves heating the oil shale while it remains to be underground, and then pumping the resulting liquid to the surface.
See the Photos page for extra photos of oil shale.
Oil Shale Resources
While oil shale is found in many places worldwide, by far the largest deposits on the planet are found in the United States within the Green River Formation, which covers portions of Colorado, Utah, and Wyoming. Estimates of the oil resource in place throughout the Green River Formation range from 1.2 to 1.8 trillion barrels. Not all resources in place are recoverable; however, even a moderate estimate of 800 billion barrels of recoverable oil from oil shale in the Green River Formation is thrice greater than the proven oil reserves of Saudi Arabia. Present U.S. demand for petroleum products is about 20 million barrels per day. If oil shale could be used to fulfill a quarter of that demand, the estimated 800 billion barrels of recoverable oil from the Green River Formation would last for greater than 400 years1.
More than 70% of the total oil shale acreage within the Green River Formation, including the richest and thickest oil shale deposits, is under federally owned and managed lands. Thus, the federal government directly controls access to the most commercially attractive portions of the oil shale resource base.
See the Maps page for added maps of oil shale resources in the Green River Formation.
The Oil Shale Industry
While oil shale has been used as fuel and as a source of oil in small quantities for many years, few countries currently produce oil from oil shale on a significant commercial level. Many countries don’t have significant oil shale resources, but in those countries that do have significant oil shale resources, the oil shale industry has not developed because historically, the cost of oil derived from oil shale has been significantly higher than conventional pumped oil. The lack of economic viability of oil shale-derived oil has in turn inhibited the development of better technologies that may reduce its cost.
Relatively high prices for conventional oil within the 1970s and 1980s stimulated interest and a few development of better oil shale technology, but oil prices eventually fell, and major research and development activities largely ceased. More recently, prices for crude oil have again risen to levels that will make oil shale-based oil production commercially viable, and both governments and industry are interested by pursuing the event of oil shale as a substitute to conventional oil.
Oil Shale Mining and Processing
Oil shale will be mined using certainly one of two methods: underground mining using the room-and-pillar method or surface mining. After mining, the oil shale is transported to a facility for retorting, a heating process that separates the oil fractions of oil shale from the mineral fraction.. The vessel by which retorting takes place is called a retort. After retorting, the oil should be upgraded by further processing before it may be sent to a refinery, and the spent shale have to be disposed of. Spent shale could also be disposed of in surface impoundments, or as fill in graded areas; it could also be disposed of in previously mined areas. Eventually, the mined land is reclaimed. Both mining and processing of oil shale involve a wide range of environmental impacts, equivalent to global warming and greenhouse gas emissions, disturbance of mined land, disposal of spent shale, use of water resources, and impacts on air and water quality. The development of a commercial oil shale industry in the United States would also have significant social and economic impacts on local communities. Other impediments to development of the oil shale industry in the United States include the relatively high cost of producing oil from oil shale (currently greater than $60 per barrel), and the lack of regulations to lease oil shale.
While current technologies are adequate for oil shale mining, the technology for surface retorting has not been successfully applied at a commercially viable level within the United States, although technical viability has been demonstrated. Further development and testing of surface retorting technology is needed before the strategy is more likely to succeed on a commercial scale.
See the Photos page for extra photos of oil shale processing facilities.
In Situ Retorting
Shell Oil is currently developing an in situ conversion process (ICP). The process involves heating underground oil shale, using electric heaters placed in deep vertical holes drilled through a section of oil shale. The volume of oil shale is heated over a period of two to 3 years, until it reaches 650_700 °F, at which point oil is released from the shale. The released product is gathered in collection wells positioned within the heated zone.
Shell’s current plan involves use of ground-freezing technology to establish an underground barrier called a “freeze wall” around the perimeter of the extraction zone. The freeze wall is potassium fertilizer created by pumping refrigerated fluid through a series of wells drilled around the extraction zone. The freeze wall prevents groundwater from entering the extraction zone, and keeps hydrocarbons and other products generated by the in-situ retorting from leaving the project perimeter.
Shell’s process is currently unproven at a commercial scale, but is regarded by the U.S. Department of Energy as a very promising technology. Confirmation of the technical feasibility of the concept, however, hinges on the resolution of two major technical issues: controlling groundwater during production and preventing subsurface environmental problems, including groundwater impacts.1
Both mining and processing of oil shale involve a wide range of environmental impacts, corresponding to global warming and greenhouse gas emissions, disturbance of mined land; impacts on wildlife and air and water quality. The event of a commercial oil shale industry within the U.S. would also have significant social and economic impacts on local communities. Of special concern within the relatively arid western United States is the large amount of water required for oil shale processing; currently, oil shale extraction and processing require several barrels of water for each barrel of oil produced, though a few of the water can be recycled.
1 RAND Corporation Oil Shale Development in the United States Prospects and Policy Issues. J. T. Bartis, T. LaTourrette, L. Dixon, D.J. Peterson, and G. Cecchine, MG-414-NETL, 2005.
For More Information
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