Oil shale is a general term applied to a group of fine black to dark brown shales rich enough in bituminous material (called kerogen) to yield petroleum upon distillation. The kerogen in oil shale can be converted to oil through the chemical process of pyrolysis. During pyrolysis the oil shale is heated to 500° C in the absence of air and the kerogen is converted to oil and separated out, a process called "retorting". The US Geological Survey estimates the world supply of oil shale at 2.6 trillion barrels (413 km³) of which 2.1 trillion barrels (334 km³) is in the United States. Estonia, Russia, Brazil, and China currently mine oil shale, however production is declining due to economic and environmental factors.

Geology

Oil shale was formed in the distant past by the simultaneous deposit of silt and organic debris on lakebeds and sea bottoms. As the raw materials accumulated, heat and pressure transformed them into a stable mixture of inorganic minerals and solidified organic sludge. However the heat and pressure were not as great as in the similar process that forms petroleum. Oil shale is called 'the rock that burns'.

History

Oil shale has been used since ancient times and like coal can be used directly as a fuel. The modern use of oil shale to produce oil dates to Scotland in the 1850s. In 1847 Dr James Young prepared lighting oil, lubricating oil and wax from coal. Then he moved his operations to Edinburgh where oil shale deposits were found. In 1850 he patented the process of "cracking" oil into its constituent parts. Oil from oil shale was produced in that region from 1857 until 1962 when production was cancelled due to the much lower cost of petroleum.

Estonia began exploiting its oil shale deposits in the 1920s and is currently the largest user of oil shale. Today however most of it is burnt directly to produce electricity.

Oil from shale is an alternative fuel to gasoline in cars. Exxon and other oil companies plan to switch to oil shale when conventional oil wells are fully exhausted or when oil shale becomes cheaper than conventional oil.

Economics

Below forty dollars a barrel, oil shale is not competitive with conventional oil fields. If oil prices were to definitely stay at over forty dollars a barrel (with no chance of them declining), then companies would pursue oil shale. By some methods, the oil shale has to be mined, transported, retorted, and then disposed of so at least 40% of the energy value is consumed in production. Water is also needed to add hydrogen to the oil shale oil before it can be shipped to a conventional oil refinery. The largest deposit of oil shale in the United States is in western Colorado (the Green River Shale deposits) a dry region without surplus water. The oil shale can be ground into a slurry and transported via pipeline to a more suitable pre-refining location.

During the oil crisis of the seventies, people thought that oil supplies were peaking, expected oil prices to be around seventy dollars a barrel for some time to come, and invested huge amounts of money in refining oil shale — money that they lost. Because of the astronomical sums that were lost last time around there is considerable reluctance to invest in oil shale this time around. Investors are waiting to see if oil prices really will remain this high. Prices are rising because the newly capitalist Chinese are buying cars. Will high prices result in the discovery of more oil, as happened in the seventies, or will alternatives to drilling for oil have to be developed? Investors, burnt badly in the eighties for their enthusiasms of the seventies, are in no hurry to develop oil shale. Those who lost money in the eighties are inclined to believe that more oil will be found bye and bye.

China is the country suffering most severely from high oil prices. The Chinese government has sponsored a project to extract oil from shale, but because this project is government sponsored, the private investors may well be planning to extract profits from taxpayers, rather than shale.

Environmental considerations

Some forms of oil shale exploitation has all the normal environmental effects from open-pit mining, the pre-refining stage to get crude oil may emit ash, pipelines must be built to an oil refinery, and the waste rock must be disposed of, rock which incidentally is a known carcinogen. Oil shale rock expands by around 30% after processing due to a popcorn effect from the heating. Some scientists have found that shale oil produces four times as much greenhouse gases as conventional oil. But then again, that is only some methods.

See also

• Non-conventional oil
• Future energy development