Unconventional oil is petroleum produced or extracted using techniques other than the conventional (oil well) method. Oil industries and governments across the globe are investing in unconventional oil sources due to the increasing scarcity of conventional oil reserves. Although the depletion of such reserves is evident, unconventional oil production is a less efficient process and has greater environmental impacts than that of conventional oil production.
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According to the International Energy Agency's Oil Market Report unconventional oil includes the following sources:
Extra heavy oils are extremely viscous, with a consistency ranging from that of heavy molasses to a solid at room temperature. Heavy crude oils have a density (specific gravity) approaching or even exceeding that of water. As a result, they cannot be produced, transported, and refined by conventional methods. Heavy crude oils usually contain high concentrations of sulfur and several metals, particularly nickel and vanadium. These properties make them difficult to pump out of the ground or through a pipeline and interfere with refining. These properties also present serious environmental challenges to the growth of heavy oil production and use. Venezuela's Orinoco heavy oil belt is the best known example of this kind of unconventional reserve. Estimated reserves: 1.2 trillion barrels (1.9×1011 m3).[2]
Heavy oils and oil sands occur world-wide, but the two most important deposits are the Athabasca Oil Sands in Alberta, Canada and the Orinoco extra heavy oil deposit in Venezuela. The hydrocarbon content of these deposits is called bitumen, on which the fuel Orimulsion is based. The Venezuelan extra heavy oil deposits differs from oil sands in that they flow more readily at ambient temperature and could be produced by cold-flow techniques, but the recovery rates would be less than the Canadian techniques (about 8% versus up to 90% for surface mining and 60% for steam assisted gravity drainage).
It is estimated by oil companies that the Athabasca and Orinoco sites (both of similar size) have as much as two-thirds of total global oil deposits. However, they have only recently been considered proven reserves of oil as cost to extract the oil declined to less than $15 per barrel at the Suncor and Syncrude mines while world oil prices rose to over $140 during the oil price increases since 2003.
Extracting a significant percentage of world oil production from these fossil fuels will be difficult since the extraction process takes a great deal of capital, manpower and land. Another minor constraint is energy for heat and electricity generation, currently coming from natural gas, which in recent years has seen a surge in production and a corresponding drop in price. A bitumen upgrader is under construction at Fort McMurray, Alberta to supply syngas to replace natural gas, and there were proposals to build nuclear reactors using fuel from nearby Uranium City, Saskatchewan to supply steam and electricity. However with the new supply of shale gas the need for alternatives to natural gas has greatly diminished.
At rate of production projected for 2015, about 3 million barrels per day (480,000 m3/d), the Athabasca oil sands reserves would last less than 160 years.[3] The oil extraction process requires either strip mining or in-situ processing, steam and caustic soda (NaOH). The process is more energy intensive than conventional oil and thus more expensive.
A 2009 study by CERA estimated that production from Canada's oil sands emits "about 5–15% more carbon dioxide, over the "well-to-wheels" lifetime analysis of the fuel, than average crude oil."[4] Author and investigative journalist David Strahan that same year stated that IEA figures show that carbon dioxide emissions from the tar sands are 20% higher than average emissions from oil [5] With coal's CO2 emissions about one-third higher than convention oil's, this would make the oil sands' emissions equal to about 90% of the CO2 released from coal.
Oil shale is an organic-rich fine-grained sedimentary rock containing significant amounts of kerogen (a solid mixture of organic chemical compounds) from which technology can extract liquid hydrocarbons (shale oil) and combustible oil shale gas. The kerogen in oil shale can be converted to shale oil through the chemical processes of pyrolysis, hydrogenation, or thermal dissolution.[6][7] The temperature when perceptible decomposition of oil shale occurs depends on the time-scale of the pyrolysis; in the above ground retorting process the perceptible decomposition occurs at 300 °C (570 °F), but proceeds more rapidly and completely at higher temperatures. The rate of decomposition is the highest at a temperature of 480 °C (900 °F) to 520 °C (970 °F). The ratio of shale gas to shale oil depends on the retorting temperature and as a rule increases with the rise of temperature.[6] For the modern in-situ process, which might take several months of heating, decomposition may be conducted as low as 250 °C (480 °F). Depending on the exact properties of oil shale and the exact processing technology, the retorting process may be water and energy extensives. Oil shale has also been burnt directly as a low-grade fuel.[8][9]
Estimates of global deposits range from 2.8 to 3.3 trillion barrels (450×109 to 520×109 m3) of recoverable oil.[8][10][11][12] There are around 600 known oil shale deposits around the world, including major deposits in the United States of America.[13] Although oil shale deposits occur in many countries, only 33 countries possess known deposits of possible economic value.[14][15] The largest deposits in the world occur in the United States in the Green River Formation, which covers portions of Colorado, Utah, and Wyoming; about 70% of this resource lies on land owned or managed by the United States federal government.[16] Deposits in the United States constitute 62% of world resources; together, the United States, Russia and Brazil account for 86% of the world's resources in terms of shale-oil content.[14] These figures remain tentative, with exploration or analysis of several deposits still outstanding.[8][9] Well-explored deposits, potentially possessing economic value, include the Green River deposits in the western United States, the Tertiary deposits in Queensland, Australia, deposits in Sweden and Estonia, the El-Lajjun deposit in Jordan, and deposits in France, Germany, Brazil, Morocco, China, southern Mongolia and Russia. These deposits have given rise to expectations of yielding at least 40 litres (0.25 bbl) of shale oil per tonne of shale, using the Fischer Assay method.[9][17]
According to a survey conducted by the RAND Corporation, the cost of producing a barrel of oil at a surface retorting complex in the United States (comprising a mine, retorting plant, upgrading plant, supporting utilities, and spent shale reclamation), would range between US$70–95 ($440–600/m3, adjusted to 2005 values).[18] As of 2008[update], industry uses oil shale for shale oil production in Brazil, China and Estonia. Several additional countries started assessing their reserves or had built experimental production plants.[8] In the USA, if oil shale could be used to meet a quarter of the current 20 million barrels per day (3,200,000 m3/d) demand, 800 billion barrels (1.3×1011 m3) of recoverable resources would last for more than 400 years.[18]
Thermal depolymerization (TDP) has the potential to recover energy from existing sources of waste such as petroleum coke as well as pre-existing waste deposits. This process, which imitates those that occur in nature, uses heat and pressure to break down organic and inorganic compounds through a method known as hydrous pyrolysis. Because energy output varies greatly based on feedstock, it is difficult to estimate potential energy production. According to Changing World Technologies, Inc., this process even has the ability to break down several types of materials, many of which are poisonous to both humans and the environment.[19]
Using synthetic fuel processes, the conversion of coal and natural gas has the potential to yield great quantities of unconventional oil and/or refined products, albeit at much lower net energy output than the historic average for conventional oil extraction.
In its day - prior to the drilling of oilwells to tap reservoirs of crude oil- the pyrolysis of mined solid organic-rich deposits was the conventional method of producing mineral oils. Historically, petroleum was already being produced on an industrial scale in the United Kingdom and the United States by dry distillation of cannel coal or oil shale in the first half of the 19th Century . Yields of oil from simple pyrolysis, however, are limited by the composition of the material being pyrolysed, and modern 'oil-from-coal' processes aim for a much higher yield of organic liquids, brought about by chemical reaction with the solid feedstuff.
The four primary conversion technologies used for the production of unconventional oil and refined products from coal and gas are the indirect conversion processes of the Fischer-Tropsch process and the Mobil Process (also known and Methanol to Gasoline), and the direct conversion processes of the Bergius process and the Karrick process.
Sasol has run a 150,000 barrels per day (24,000 m3/d) coal-to-liquids plant based on Fischer Tropsch conversion in South Africa since the 1970s.
Because of the high cost of transporting natural gas, many known but remote fields were not being developed. On-site conversion to liquid fuels are making this energy available under present market conditions. Fischer Tropsch fuels plants converting natural gas to fuel, a process broadly known as gas-to-liquids are operating in Malaysia, South Africa, and Qatar. Large direct conversion coal to liquids plants are currently under construction, or undergoing start-up in China.
Total global synthetic fuel production capacity exceeds 240,000 barrels per day (38,000 m3/d), and is expected to grow rapidly in coming years, with multiple new plants currently under construction.
As with all forms of mining, there are large amounts of hazardous tailings and waste generated from the varied processes of oil extraction and production.[20]
Environmental concerns with heavy oils are similar to those with lighter oils. However, they provide additional concerns, such as the need to heat heavy oils to pump them out of the ground. Extraction also requires large volumes of water.[21]
The environmental impacts of oil shale differ depending on the type of extraction; however, there are some common trends. The mining process releases carbon dioxide, in addition to other oxides and pollutants, as the shale is heated. Furthermore, there is some concern about some of the chemicals mixing with ground water (either as runoff or through seeping). There are processes either in use or under development to help mitigate some of these environmental concerns.[22]
The conversion of coal or natural gas into oil generates large amounts of carbon dioxide in addition to all the impacts of gaining these resources to begin with. however placing plants in key areas can reduce the effective emotions due to pumping the carbon dioxide into oil beds or coal beds to enhance the recovery of oil and methane.[23]
Sources of unconventional oil will be increasingly relied upon as motor fuel for transportation purposes when conventional oil becomes "economically non-viable" due to depletion. Conventional oil sources are currently preferred due to the fact that they provide a much higher ratio of extracted energy over energy used in regards to the extraction and refining processes it undergoes. New technologies, such as Steam injection (oil industry) for oil sands deposits, are being developed to increase unconventional oil production efficiency.