Shale oil is an unconventional oil produced from oil shale rock fragments by pyrolysis, hydrogenation, or thermal dissolution. These processes convert the organic matter within the rock (kerogen) into synthetic oil and gas. The resulting oil can be used immediately as a fuel or upgraded to meet refinery feedstock specifications by adding hydrogen and removing impurities such as sulfur and nitrogen. The refined products can be used for the same purposes as those derived from crude oil.
The term "shale oil" is also used for crude oil produced from shales of other very low permeability formations. However, to reduce the risk of confusion of shale oil produced from oil shale with crude oil in oil-bearing shales, the term "tight oil" is preferred for the latter. The International Energy Agency recommends to use the term "light tight oil" and World Energy Resources 2013 report by the World Energy Council uses the term "tight oil" for crude oil in oil-bearing shales.
Oil shale was one of the first sources of mineral oil used by humans. Its earliest recorded use was in Switzerland and Austria in the early 14th century. In 1596, the personal physician of Frederick I, Duke of Württemberg wrote of its healing properties. Shale oil was used to light the streets of Modena, Italy at the turn of the 17th century. The British Crown granted a patent in 1694 to three persons who had "found a way to extract and make great quantities of pitch, tarr and oyle out of a sort of stone." Later sold as Betton's British Oil, the distilled product was said to have been "tried by divers persons in Aches and Pains with much benefit." Modern shale oil extraction industries were established in France during the 1830s and in Scotland during the 1840s. The oil was used as fuel, as a lubricant and lamp oil; the Industrial Revolution had created additional demand for lighting. It served as a substitute for the increasingly scarce and expensive whale oil.
During the late 19th century, shale-oil extraction plants were built in Australia, Brazil and the United States. China, Estonia, New Zealand, South Africa, Spain, Sweden and Switzerland produced shale oil in the early 20th century. The discovery of crude oil in the Middle East during mid-century brought most of these industries to a halt, although Estonia and Northeast China maintained their extraction industries into the early 21st century. In response to rising petroleum costs at the turn of the 21st century, extraction operations have commenced, been explored, or been renewed in the United States, China, Australia and Jordan.
Shale oil contains polycyclic aromatic hydrocarbons and is a known carcinogen reported as being responsible for Mule spinners' cancer and the World Health Organization classifies shale oil as Group 1 carcinogens to humans.
Shale oil is extracted by pyrolysis, hydrogenation, or thermal dissolution of oil shale. The pyrolysis of the rock is performed in a retort, situated either above ground or within the rock formation itself. As of 2008, most oil shale industries perform the shale oil extraction process after the rock is mined, crushed and transported to a retorting facility, although several experimental technologies perform the process in place (in-situ). The temperature at which the kerogen decomposes into usable hydrocarbons varies with the time-scale of the process; in the above-ground retorting process decomposition begins at 300 °C (570 °F), but proceeds more rapidly and completely at higher temperatures. Decomposition takes place most quickly at a temperature between 480 and 520 °C (900 and 970 °F).
Hydrogenation and thermal dissolution (reactive fluid processes) extract the oil using hydrogen donors, solvents, or a combination of these. Thermal dissolution involves the application of solvents at elevated temperatures and pressures, increasing oil output by cracking the dissolved organic matter. Different methods produce shale oil with different properties.
A critical measure of the viability of extraction of shale oil lies in the ratio of the energy produced by the oil shale to the energy used in its mining and processing, a ratio known as "Energy Returned on Energy Invested" (EROEI). An EROEI of 2 (or 2:1 ratio) would mean that to produce 2 barrels of actual oil the equivalent in energy of 1 barrel of oil has to be burnt/consumed. A 1984 study estimated the EROEI of the various known oil-shale deposits as varying between 0.7–13.3. More recent studies estimates the EROEI of oil shales to be 1–2:1 or 2–16:1 – depending on whether self-energy is counted as a cost or internal energy is excluded and only purchased energy is counted as input. Royal Dutch Shell reported an EROEI of three to four in 2006 on its in situ development in the "Mahogany Research Project."
The amount of oil that can be recovered during retorting varies with the oil shale and the technology used. About one sixth of the oil shales in the Green River Formation have a relatively high yield of 25 to 100 US gallons (95 to 379 l; 21 to 83 imp gal) of shale oil per ton of oil shale; about one third yield from 10 to 25 US gallons (38 to 95 l; 8.3 to 20.8 imp gal) per ton. (Ten US gal/ton is approximately 3.4 tons of oil per 100 tons of shale.) About half of the oil shales in the Green River Formation yield less than 10 US gal/ton.
The major global shale oil producers have published their yields for their commercial operations. Fushun Mining Group reports producing 300,000 tons per year of shale oil from 6.6 million tons of shale, a yield of 4.5% by weight. VKG Oil claims to produce 250,000 tons of oil per year from 2 million tons of shale, a yield of 13%. Petrobras produces in their Petrosix plant 550 tons of oil per day from 6,200 tons of shale, a yield of 9%.
The properties of raw shale oil vary depending on the composition of the parent oil shale and the extraction technology used. Like conventional oil, shale oil is a complex mixture of hydrocarbons, and it is characterized using bulk properties of the oil. Shale oil usually contains large quantities of olefinic and aromatic hydrocarbons. Shale oil can also contain significant quantities of heteroatoms. A typical shale oil composition includes 0.5–1% of oxygen, 1.5–2% of nitrogen and 0.15–1% of sulfur, and some deposits contain more heteroatoms. Mineral particles and metals are often present as well. Generally, the oil is less fluid than crude oil, becoming pourable at temperatures between 24 and 27 °C (75 and 81 °F), while conventional crude oil is pourable at temperatures between −60 to 30 °C (−76 to 86 °F); this property affects shale oil's ability to be transported in existing pipelines.
Although raw shale oil can be immediately burnt as a fuel oil, many of its applications require that it be upgraded. The differing properties of the raw oils call for correspondingly various pre-treatments before it can be sent to a conventional oil refinery.
Particulates in the raw oil clog downstream processes; sulfur and nitrogen create air pollution. Sulfur and nitrogen, along with the arsenic and iron that may be present, also destroy the catalysts used in refining. Olefins form insoluble sediments and cause instability. The oxygen within the oil, present at higher levels than in crude oil, lends itself to the formation of destructive free radicals. Hydrodesulfurization and hydrodenitrogenation can address these problems and result in a product comparable to benchmark crude oil. Phenols can be first be removed by water extraction. Upgrading shale oil into transport fuels requires adjusting hydrogen–carbon ratios by adding hydrogen (hydrocracking) or removing carbon (coking).
Shale oil produced by some technologies, such as the Kiviter process, can be used without further upgrading as an oil constituent and as a source of phenolic compounds. Distillate oils from the Kiviter process can also be used as diluents for petroleum-originated heavy oils and as an adhesive-enhancing additive in bituminous materials such as asphalt.
Before World War II, most shale oil was upgraded for use as transport fuels. Afterwards, it was used as a raw material for chemical intermediates, pure chemicals and industrial resins, and as a railroad wood preservative. As of 2008, it is primarily used as a heating oil and marine fuel, and to a lesser extent in the production of various chemicals.
Shale oil's concentration of high-boiling point compounds is suited for the production of middle distillates such as kerosene, jet fuel and diesel fuel. Additional cracking can create the lighter hydrocarbons used in gasoline.
Reserves and production
Global technically recoverable oil shale reserves have recently been estimated at about 2.8 to 3.3 trillion barrels (450×109 to 520×109 m3) of shale oil, with the largest reserves in the United States, which is thought to have 1.5–2.6 trillion barrels (240×109–410×109 m3). Worldwide production of shale oil was estimated at 17,700 barrels per day (2,810 m3/d) in 2008. The leading producers were China (7,600 barrels per day (1,210 m3/d)), Estonia (6,300 barrels per day (1,000 m3/d)), and Brazil (3,800 barrels per day (600 m3/d)).
The production of shale oil has been hindered because of technical difficulties and costs. In March 2011, the United States Bureau of Land Management called into question proposals in the U.S. for commercial operations, stating that "There are no economically viable ways yet known to extract and process oil shale for commercial purposes."
- Reinsalu, Enno; Aarna, Indrek (2015). "About technical terms of oil shale and shale oil" (PDF). Oil Shale. A Scientific-Technical Journal. Estonian Academy Publishers. 32 (4): 291–292. ISSN 0208-189X. Retrieved 2016-01-16.
- IEA (2013). World Energy Outlook 2013. OECD. p. 424. ISBN 978-92-64-20130-9.
- World Energy Resources 2013 Survey (PDF). World Energy Council. 2013. p. 2.46. ISBN 9780946121298.
- Dostrovsky, I. (1988). Energy and the Missing Resource: A View from the Laboratory. Cambridge University Press. p. 18. ISBN 978-0-521-31965-2. Retrieved 2009-06-02.
- "Oil Shale" (PDF). Colorado School of Mines. 2008: 2. Retrieved 2008-12-24.
- Moody, Richard (2007-04-20). "Oil & Gas Shales, Definitions & Distribution In Time & Space. In The History of On-Shore Hydrocarbon Use in the UK" (PDF). Geological Society of London: 1. Retrieved 2009-01-10.
- Louw, S.J.; Addison, J. (1985). Seaton, A., ed. "Studies of the Scottish oil shale industry. Vol.1 History of the industry, working conditions and mineralogy of Scottish and Green River formation shales. Final report on US Department of Energy" (PDF). Institute of Occupational Medicine: 35. DE-ACO2 – 82ER60036. Retrieved 2009-06-05.
- Cane, R.F. (1976). Teh Fu Yen; Chilingar, George V., eds. Oil Shale. Amsterdam: Elsevier. p. 56. ISBN 978-0-444-41408-3. Retrieved 2009-06-05.
- Forbes, R.J. (1970). A Short History of the Art of Distillation from the Beginnings Up to the Death of Cellier Blumenthal. Brill Publishers. p. 250. ISBN 978-90-04-00617-1. Retrieved 2009-06-02.
- Francu, Juraj; Harvie, Barbra; Laenen, Ben; Siirde, Andres; Veiderma, Mihkel (May 2007). "A study on the EU oil shale industry viewed in the light of the Estonian experience. A report by EASAC to the Committee on Industry, Research and Energy of the European Parliament" (PDF). European Academies Science Advisory Council: 1; 5; 12. Retrieved 2011-05-07.
- Doscher, Todd M. "Petroleum". MSN Encarta. Retrieved 2008-04-22.
- "Oil Shale". American Association of Petroleum Geologists. Retrieved 2008-03-31.
- Dyni, John R. (2010). "Oil Shale". In Clarke, Alan W.; Trinnaman, Judy A. Survey of energy resources (PDF) (22 ed.). World Energy Council. pp. 93–123. ISBN 978-0-946121-02-1.
- Dyni, John R. (2006). "Geology and resources of some world oil-shale deposits. Scientific Investigations Report 2005–5294" (PDF). United States Department of the Interior, United States Geological Survey: 1–42. Retrieved 2007-07-09.
- International Agency for Research on Cancer (17 June 2011). "Agents Classified by the IARC Monographs, Volumes 1–102" (PDF). Lyon, France: International Agency for Research on Cancer. p. 5. Retrieved 16 February 2016. External link in
- Koel, Mihkel (1999). "Estonian oil shale". Oil Shale. A Scientific-Technical Journal. Estonian Academy Publishers (Extra). ISSN 0208-189X. Retrieved 2008-12-24.
- Luik, Hans (2009-06-08). Alternative technologies for oil shale liquefaction and upgrading (PDF). International Oil Shale Symposium. Tallinn University of Technology. Tallinn, Estonia. Retrieved 2009-06-09.
- Gorlov, E.G. (October 2007). "Thermal Dissolution Of Solid Fossil Fuels" (PDF). Solid Fuel Chemistry. Allerton Press, Inc. 41 (5): 290–298. doi:10.3103/S0361521907050047. ISSN 1934-8029. Retrieved 2009-06-09.
- Koel, Mihkel; Ljovin, S.; Hollis, K.; Rubin, J. (2001). "Using neoteric solvents in oil shale studies" (PDF). Pure and Applied Chemistry. Blackwell Science. 73 (1): 153–159. doi:10.1351/pac200173010153. ISSN 0033-4545. Retrieved 2010-01-22.
- Baldwin, R. M.; Bennett, D. P.; Briley, R. A. (1984). "Reactivity of oil shale towards solvent hydrogenation" (PDF). American Chemical Society. Division of Petroleum Chemistry. American Chemical Society. 29 (1): 148–153. ISSN 0569-3799. Retrieved 2010-01-22.
- Cleveland, Cutler J.; Costanza, Robert; Hall, Charles A. S.; Kaufmann, Robert (1984-08-31). "Energy and the U.S. Economy: A Biophysical Perspective" (PDF). Science. American Association for the Advancement of Science. 225 (4665): 890–897. doi:10.1126/science.225.4665.890. ISSN 0036-8075. PMID 17779848. Retrieved 2007-08-28.
- Brandt, Adam R. (2009). "Converting Green River oil shale to liquid fuels with the Alberta Taciuk Processor: energy inputs and greenhouse gas emissions" (PDF). Energy & Fuels. American Chemical Society. 23 (12): 6253–6258. doi:10.1021/ef900678d. ISSN 0887-0624. (subscription required). Retrieved 2011-07-04.
- "Oil Shale Test Project. Oil Shale Research and Development Project" (PDF). Shell Frontier Oil and Gas. 2006-02-15. Retrieved 2007-06-30.
- Reiss, Spencer (2005-12-13). "Tapping the Rock Field". WIRED Magazine. Retrieved 2007-08-27.
- "Fact Sheet: U.S. Oil Shale Resources" (PDF). United States Department of Energy. Retrieved 2009-01-10.
- Promitis, Guntis (2008-11-03). "Oil shale promise" (PDF). Oil & Gas Journal. PennWell Corporation: 16. Retrieved 2011-10-09.
- "VKG Oil AS". Viru Keemia Grupp. Retrieved 2011-10-09.
- Qian, Jialin; Wang Jianqiu (2006-11-07). World oil shale retorting technologies (PDF). International Oil Shale Conference. Amman, Jordan: Jordanian Natural Resources Authority. Retrieved 2007-06-29.
- McKetta, John J. (1994). Encyclopedia of Chemical Processing and Design. 50. CRC Press. p. 49. ISBN 978-0-8247-2601-0. Retrieved 2009-06-02.
- Lee, Sunggyu (1991). Oil Shale Technology. CRC Press. p. 7. ISBN 0-8493-4615-0. Retrieved 2008-12-24.
- Speight, James (2008). Synthetic Fuels Handbook. McGraw-Hill Professional. p. 188. ISBN 978-0-07-149023-8. Retrieved 2008-12-24.
- Wauquier, Jean-Pierre; Trambouze, Pierre; Favennec, Jean-Pierre (1995). Petroleum Refining: Crude Oil. Petroleum Products. Process Flowsheets. Editions TECHNIP. p. 317. ISBN 978-2-7108-0685-1. Retrieved 2008-12-24.
- "Market assessment for shale oil". Energy Citations Database. 1979. Retrieved 2008-12-24.
- Purga, Jaanus (2007-10-16). Shale Products – Production, Quality and Market Challenges (PDF). 27th Oil Shale Symposium. Golden, Colorado: Colorado School of Mines. Retrieved 2008-12-24.
- Bo Yu; Ping Xu; Shanshan Zhu; Xiaofeng Cai; Ying Wang; Li Li; Fuli Li; Xiaoyong Liu; Cuiqing Ma (March 2006). "Selective Biodegradation of S and N Heterocycles by a Recombinant Rhodococcus erythropolis Strain Containing Carbazole Dioxygenase" (PDF). Applied and Environmental Microbiology. American Society for Microbiology. 72 (3): 2235–2238. doi:10.1128/AEM.72.3.2235-2238.2006. PMC . PMID 16517679. Retrieved 2008-12-28.
- "Process for treating hot shale oil effluent from a retort – US Patent # 4181596". freepatentsonline.com. Retrieved 2008-12-28.
- Oja, Vahur (2006). "A brief overview of motor fuels from shale oil of kukersite" (PDF). Oil Shale. A Scientific-Technical Journal. Estonian Academy Publishers. 23 (2): 160–163. ISSN 0208-189X. Retrieved 2008-12-24.
- Mölder, Leevi (2004). "Estonian Oil Shale Retorting Industry at a Crossroads" (PDF). Oil Shale. A Scientific-Technical Journal. Estonian Academy Publishers. 21 (2): 97–98. ISSN 0208-189X. Retrieved 2008-12-25.
- Andrews, Anthony (2006-04-13). "Oil Shale: History, Incentives and Policy" (PDF). Congressional Research Service. RL33359. Retrieved 2008-12-24. Cite error: Invalid
<ref>tag; name "andrews" defined multiple times with different content (see the help page).
- Andrews, Anthony (2008-11-17). "Developments in Oil Shale" (PDF). Congressional Research Service. RL34748. Retrieved 2008-12-24.
- James Girard (2004). Principles of Environmental Chemistry. Jones & Bartlett. ISBN 978-0-7637-2471-9.
Fractional distillation yields mainly high molecular weight hydrocarbons, which can then be cracked to yield desirable hydrocarbons in the gasoline range.
- "Annual Energy Outlook 2006" (PDF). Energy Information Administration. February 2006. Retrieved 2007-06-22.
- "NPR's National Strategic Unconventional Resource Model" (PDF). United States Department of Energy. April 2006. Retrieved 2007-07-09.
- Kraushaar, Jack P., and Robert A. Ristinen. Energy and the Environment-2nd ed. New York, NY: Wiley & Sons Inc., 2006. 54–56.
- Bureau of Land Management (2011-04-14). "Notice of Intent To Prepare a Programmatic Environmental Impact Statement (EIS) and Possible Land Use Plan Amendments for Allocation of Oil Shale and Tar Sands Resources on Lands Administered by the Bureau of Land Management in Colorado, Utah and Wyoming" (PDF). Federal Register. 76 (72): 21003–21005. Retrieved 2011-10-09.