is a general term applied to a fine-grained sedimentary rock
containing significant traces of kerogen
(a solid mixture of organic chemical compounds
) that have not been buried for sufficient time to produce conventional fossil fuels
. 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 unconventional oil
- and combustible 'shale gas'.
The kerogen in oil shale can be converted to oil through the chemical process of pyrolysis. Oil shale can also be burnt directly as a low-grade fuel for power generation and heating, and be used as a raw material in the chemical and construction materials industries. Currently oil shales are used commercially for oil production 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.