Shale oil extraction is process of generating useful hydrocarbon-based fuels from organic compounds removed from oil shale, which is a form of underground sedimentary rock that contains bitumen. Bitumen is a mixture of solid hydrocarbon compounds that can be converted to liquids that resemble petroleum when the rock in which they are contained is heated. The process of removing useful hydrocarbons from oil shale has been of interest to many governments including the US since the 1980s and earlier. The expense and the environmental and technological issues with the process have precluded wide-scale development of the resource, however, until oil prices on the commodities market reached record highs in the early 21st century.
The United States is particularly interested in extracting fuel from oil shale since, as of 2005, it is believed to have the largest deposits of oil shale in the world, with estimated reserves at 1,650,000,000 barrels of oil. Half of these reserves are considered to be technologically recoverable as of 2005, which is a volume three times higher than the crude oil petroleum reserves that were known to exist in Saudi Arabia at the time. These US reserves could also supply all of the nation's oil needs at current 2005 consumption levels for at least 100 years if they could be economically and rapidly extracted at a level of 20,000,000 barrels a day.
The concept of shale oil extraction is not a new one, though it has not been feasible in large quantities to satisfy the huge demand for fuel on the commercial market until recently. The Arabian doctor Masawaih al-Mardini proposed a method for shale oil extraction in the 10th century, and the first patent for the process was granted in 1694 to three people in the United Kingdom who were deriving compounds like pitch and tar from oil shale reserves. The first modern technological method for shale oil extraction using a retort heating process is believed to have been developed in France in 1838, and, a decade later, the process was being used in many nations from Australia to Canada.
Nations such as South Africa also began large industrial shale oil extraction in the 20th century, but most of these projects were halted worldwide in the early 1920s when crude oil was discovered in the US state of Texas. When crude oil extraction was proven to be much easier on which to capitalize, it began to drop market prices for the commodity, which made shale oil extraction uneconomical. This situation once again changed as of 2009, however, with rapidly rising prices on the oil market as of 2007 to 2008. The nations of Morocco, Jordan, and the US are currently world leaders in developing the commercial implementation of shale oil extraction as of 2011.
While there are dozens of different methodologies for shale oil extraction, they are generally grouped into three main categories. These are methods that focus on the location of the processing which can be done above or below ground, methods focused on the heating of the shale to liquefy and extract bitumen, and methods that use the retort approach which involves a wide range of chemical reactions to extract useful compounds. Since the bitumen in oil shale is in a natural solid state, all of the approaches to extracting it are looked at from a mining perspective with techniques that vary based on whether solid rock is being removed or the deposits require oil sands extraction.
The simplest method of exploiting shale oil reserves has been to mine the rock or sand and process it above ground. New technology as of 2011 is making it economical to heat the bitumen underground until it liquifies, and then extract it in the same way that crude oil is piped to the surface. Where the technology and pioneering of shale oil extraction takes precedence is in nations that lack their own petroleum reserves, but either have a large demand for oil, or see it as a valuable natural resource to exploit. As of 2010, this has meant that nations like Estonia, Brazil, and China have all invested heavily in developing their own shale oil extraction industries.