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Oil shale is a fine-grained sedimentary rock, containing significant amounts of kerogen (a solid mixture of organic chemical compounds), from which liquid hydrocarbons are manufactured. The name oil shale can be somewhat misleading as it need not be a shale, nor is the hydrocarbon in it a oil.[1] World deposits of oil shale—estimated to equal 2.9–3.3 trillion barrels of recoverable oil—are located around the world with major deposits in the United States.[2][3][4][5]
The kerogen in oil shale can be converted to synthetic crude oil through the chemical process of pyrolysis. When heated to a sufficiently high temperature a vapor is driven off which can be distilled (retorted) to yield a petroleum-like shale oil—a form of non-conventional oil—and combustible shale gas (shale gas can also refer to gas occurring naturally in shales). Oil shale can also be burnt directly as a low-grade fuel for power generation and heating purposes, and be used as a raw material in the chemical and construction materials industries.[6][7]
Attempts to develop world's oil shale deposits, over a period of over 150 years, have had temporary success, as the feasibility of shale oil production depends of the crude oil price.[8] Currently oil shales are exploited commercially for oil production only in Estonia, Brazil and China, for power generation in Estonia, China, Israel and Germany, for cement production in Estonia, Germany and China, and for chemical industry in Estonia and Russia.[9][10][11] World production of oil shale reached a peak of 46 million tonnes in 1980 before falling to about 16 million tonnes in 2000, due to low cost of conventional petroleum.[12][13] The oil shale industry can have a negative impact on the surrounding environments, if the risks associated with it are not managed correctly. Environmental concerns raised over the extraction of shale oil have thus caused the oil shale industry in some countries to come to a grinding halt.[13][14]