Shale oil

Oil shale, an organic-rich fine-grained sedimentary rock, contains significant amounts of kerogen (a solid mixture of organic chemical compounds) from which liquid hydrocarbons called shale oil can be produced. Shale oil is a substitute for conventional crude oil; however, extracting shale oil from oil shale is more costly than the production of conventional crude oil both financially and in terms of its environmental impact.[1][2] Deposits of oil shale occur around the world, including major deposits in the United States of America. Estimates of global deposits range from 2.8 trillion to 3.3 trillion barrels (450×109 to 520×109 m3) of recoverable oil.[2][3][4][5]

Heating oil shale to a sufficiently high temperature causes the chemical process of pyrolysis to yield a vapor. Upon cooling the vapor, the liquid shale oil—an unconventional oil—is separated from combustible oil-shale gas (the term shale gas can also refer to gas occurring naturally in shales). Oil shale can also be burnt directly in furnaces as a low-grade fuel for power generation and district heating or used as a raw material in chemical and construction-materials processing.[2][6]

Oil shale gains attention as a potential abundant domestic source of oil whenever the price of crude oil rises.[7][8] At the same time, oil-shale mining and processing raise a number of environmental concerns, such as land use, waste disposal, water use, waste-water management, greenhouse-gas emissions and air pollution.[9][10] Estonia and China have well-established oil shale industries, and Brazil, Germany, Israel and Russia also utilize oil shale.[2]

Oil shales are very different from oil-bearing shales, shale deposits which contain oil that is sometimes produced from drilled wells. Examples of oil-bearing shales are the Bakken Formation, Pierre Shale, Niobrara Formation, and Eagle Ford