oil shale

Oil shale is an organic-rich fine-grained sedimentary rock containing kerogen (a solid mixture of organic chemical compounds) from which liquid hydrocarbons can be produced. In addition to kerogen, general composition of oil shales constitutes inorganic substance and bitumens. Based on their deposition environment, oil shales are classified as marine, lacustrine and terrestrial oil shales. Oil shales differ from oil-bearing shales, shale deposits that contain petroleum (tight oil) that is sometimes produced from drilled wells. Examples of oil-bearing shales are the Bakken Formation, Pierre Shale, Niobrara Formation, and Eagle Ford Formation. Accordingly, shale oil produced from oil shale should not be confused with tight oil, which is also frequently called shale oil.

A 2016 estimate of global deposits set the total world resources of oil shale equivalent of 6.05 trillion barrels (962 billion cubic metres) of oil in place. Oil shale has gained attention as a potential abundant source of oil. However, the various attempts to develop oil shale deposits have had limited success. Only Estonia and China have well-established oil shale industries, and Brazil, Germany, and Russia utilize oil shale to some extent.