Shale Oil
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Shale oil is an
unconventional oil Unconventional (oil and gas) reservoirs, or unconventional resources (resource plays) are Petroleum geology, accumulations where oil and gas Phase (matter), phases are tightly bound to the rock fabric by strong capillary action, capillary forces, ...
produced from
oil shale Oil shale is an organic-rich Granularity, fine-grained sedimentary rock containing kerogen (a solid mixture of Organic compound, organic chemical compounds) from which liquid hydrocarbons can be produced. In addition to kerogen, general compos ...
rock fragments by
pyrolysis Pyrolysis is a process involving the Bond cleavage, separation of covalent bonds in organic matter by thermal decomposition within an Chemically inert, inert environment without oxygen. Etymology The word ''pyrolysis'' is coined from the Gree ...
,
hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to redox, reduce or Saturated ...
, or thermal dissolution. These processes convert the organic matter within the rock (
kerogen Kerogen is solid, insoluble organic matter in sedimentary rocks. It consists of a variety of organic materials, including dead plants, algae, and other microorganisms, that have been compressed and heated by geological processes. All the kero ...
) into synthetic oil and gas. The resulting oil can be used immediately as a fuel or upgraded to meet
refinery A refinery is a production facility composed of a group of chemical engineering unit processes and unit operations refining certain materials or converting raw material into products of value. Types of refineries Different types of refineries ...
feedstock A raw material, also known as a feedstock, unprocessed material, or primary commodity, is a basic material that is used to produce goods, finished goods, energy, or intermediate materials/Intermediate goods that are feedstock for future finishe ...
specifications by adding
hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...
and removing impurities such as
sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...
and
nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...
. The refined products can be used for the same purposes as those derived from
crude oil Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring u ...
. The term "shale oil" is also used for crude oil produced from shales of other unconventional, very low permeability formations. However, to reduce the risk of confusion of shale oil produced from oil shale with crude oil in oil-bearing shales, the term "
tight oil Tight oil (also known as shale oil, shale-hosted oil or light tight oil, abbreviated LTO) is light crude oil contained in Unconventional (oil & gas) reservoir, unconventional petroleum-bearing formations of low Permeability (earth sciences), perme ...
" is preferred for the latter. The
International Energy Agency The International Energy Agency (IEA) is a Paris-based autonomous intergovernmental organization, established in 1974, that provides policy recommendations, analysis and data on the global energy sector. The 31 member countries and 13 associatio ...
recommends to use the term "
light tight oil Tight oil (also known as shale oil, shale-hosted oil or light tight oil, abbreviated LTO) is light crude oil contained in unconventional petroleum-bearing formations of low permeability, often shale or tight sandstone. Economic production from ...
" and World Energy Resources 2013 report by the
World Energy Council The World Energy Council is a global forum for thought-leadership and tangible engagement with headquarters in London. Its mission is 'To promote the sustainable supply and use of energy for the greatest benefit of all people'. The idea for the fo ...
uses the term "
tight oil Tight oil (also known as shale oil, shale-hosted oil or light tight oil, abbreviated LTO) is light crude oil contained in Unconventional (oil & gas) reservoir, unconventional petroleum-bearing formations of low Permeability (earth sciences), perme ...
" for crude oil in oil-bearing shales.


History

Oil shale was one of the first sources of
mineral oil Mineral oil is any of various colorless, odorless, light mixtures of higher alkanes from a mineral source, particularly a distillate of petroleum, as distinct from usually edible vegetable oils. The name 'mineral oil' by itself is imprecise, ...
used by humans. In the 10th century, the Arabic physician Masawaih al-Mardini (Mesue the Younger) first described a method of extracting oil from "some kind of bituminous shale". It was also reported to have been used in
Switzerland Switzerland, officially the Swiss Confederation, is a landlocked country located in west-central Europe. It is bordered by Italy to the south, France to the west, Germany to the north, and Austria and Liechtenstein to the east. Switzerland ...
and
Austria Austria, formally the Republic of Austria, is a landlocked country in Central Europe, lying in the Eastern Alps. It is a federation of nine Federal states of Austria, states, of which the capital Vienna is the List of largest cities in Aust ...
in the early 14th century. In 1596, the personal physician of Frederick I, Duke of Württemberg wrote of its healing properties. Shale oil was used to light the streets of
Modena Modena (, ; ; ; ; ) is a city and ''comune'' (municipality) on the south side of the Po Valley, in the Province of Modena, in the Emilia-Romagna region of northern Italy. It has 184,739 inhabitants as of 2025. A town, and seat of an archbis ...
,
Italy Italy, officially the Italian Republic, is a country in Southern Europe, Southern and Western Europe, Western Europe. It consists of Italian Peninsula, a peninsula that extends into the Mediterranean Sea, with the Alps on its northern land b ...
at the turn of the 18th century. The British Crown granted a patent in 1694 to three persons who had "found a way to extract and make great quantities of pitch, tarr and oyle out of a sort of stone." Later sold as Betton's British Oil, the distilled product was said to have been "tried by diverse persons in Aches and Pains with much benefit." Modern
shale oil extraction Shale oil extraction is an industrial process for unconventional oil production. This process converts kerogen in oil shale into shale oil by pyrolysis, hydrogenation, or thermal dissolution. The resultant shale oil is used as fuel oil or ...
industries were established in
France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...
during the 1830s and in
Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...
during the 1840s. The oil was used as fuel, as a lubricant and lamp oil; the
Industrial Revolution The Industrial Revolution, sometimes divided into the First Industrial Revolution and Second Industrial Revolution, was a transitional period of the global economy toward more widespread, efficient and stable manufacturing processes, succee ...
had created additional demand for lighting. It served as a substitute for the increasingly scarce and expensive
whale oil Whale oil is oil obtained from the blubber of whales. Oil from the bowhead whale was sometimes known as train-oil, which comes from the Dutch word ''traan'' ("tear drop"). Sperm oil, a special kind of oil used in the cavities of sperm whales, ...
. During the late 19th century, shale-oil extraction plants were built in
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
,
Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...
and the
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
.
China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
,
Estonia Estonia, officially the Republic of Estonia, is a country in Northern Europe. It is bordered to the north by the Gulf of Finland across from Finland, to the west by the Baltic Sea across from Sweden, to the south by Latvia, and to the east by Ru ...
,
New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...
,
South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...
,
Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...
,
Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...
and
Switzerland Switzerland, officially the Swiss Confederation, is a landlocked country located in west-central Europe. It is bordered by Italy to the south, France to the west, Germany to the north, and Austria and Liechtenstein to the east. Switzerland ...
produced shale oil in the early 20th century. The discovery of crude oil in the Middle East during mid-century brought most of these industries to a halt, although Estonia and
Northeast China Northeast China () is a geographical region of China, consisting officially of three provinces Liaoning, Jilin and Heilongjiang. The heartland of the region is the Northeast China Plain, the largest plain in China with an area of over . The regi ...
maintained their extraction industries into the early 21st century. In response to rising petroleum prices at the turn of the 21st century, extraction operations have commenced, been explored, or been renewed in the United States, China, Australia and
Jordan Jordan, officially the Hashemite Kingdom of Jordan, is a country in the Southern Levant region of West Asia. Jordan is bordered by Syria to the north, Iraq to the east, Saudi Arabia to the south, and Israel and the occupied Palestinian ter ...
.


Extraction process

Shale oil is extracted by pyrolysis, hydrogenation, or thermal dissolution of oil shale. The pyrolysis of the rock is performed in a
retort In a chemistry laboratory, a retort is a device used for distillation or dry distillation of substances. It consists of a sphere, spherical vessel with a long downward-pointing neck. The liquid to be distilled is placed in the vessel and heat ...
, situated either above ground or within the rock formation itself. As of 2008, most oil shale industries perform the shale oil extraction process after the rock is mined, crushed and transported to a retorting facility, although several experimental technologies perform the process in place. The temperature at which the kerogen decomposes into usable hydrocarbons varies with the time-scale of the process; in the above-ground retorting process decomposition begins at , but proceeds more rapidly and completely at higher temperatures. Decomposition takes place most quickly at a temperature between . Hydrogenation and thermal dissolution (reactive fluid processes) extract the oil using hydrogen donors,
solvent A solvent (from the Latin language, Latin ''wikt:solvo#Latin, solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a Solution (chemistry), solution. A solvent is usually a liquid but can also be a solid, a gas ...
s, or a combination of these. Thermal dissolution involves the application of solvents at elevated temperatures and pressures, increasing oil output by cracking the dissolved organic matter. Different methods produce shale oil with different properties. A critical measure of the viability of extraction of shale oil lies in the ratio of the energy produced by the oil shale to the energy used in its mining and processing, a ratio known as "Energy Returned on Energy Invested" ( EROEI). An EROEI of 2 (or 2:1 ratio) would mean that to produce 2 barrels of actual oil the equivalent in energy of 1 barrel of oil has to be burnt/consumed. A 1984 study estimated the EROEI of the various known oil-shale deposits as varying between 0.7 and 13.3. More recent studies estimates the EROEI of oil shales to be 1–2:1 or 2–16:1 – depending on whether self-energy is counted as a cost or internal energy is excluded and only purchased energy is counted as input.
Royal Dutch Shell Shell plc is a British multinational oil and gas company, headquartered in London, England. Shell is a public limited company with a primary listing on the London Stock Exchange (LSE) and secondary listings on Euronext Amsterdam and the New ...
reported an EROEI of three to four in 2006 on its ''in situ'' development in the " Mahogany Research Project." The amount of oil that can be recovered during retorting varies with the oil shale and the technology used. About one sixth of the oil shales in the
Green River Formation The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes in three basins along the present-day Green River (Colorado River), Green River in Colorado, Wyoming, and Utah. The sedimen ...
have a relatively high yield of of shale oil per ton of oil shale; about one third yield from per ton. (Ten US gal/ton is approximately 3.4 tons of oil per 100 tons of shale.) About half of the oil shales in the Green River Formation yield less than 10 US gal/ton. The major global shale oil producers have published their yields for their commercial operations.
Fushun Mining Group Fushun Mining Group (, FMG) is a large state-owned coal and oil shale company located in Fushun, Liaoning Province, China. The corporation consists of about 30 companies with about 28,000 employees. The main business includes coal min ...
reports producing 300,000 tons per year of shale oil from 6.6 million tons of shale, a yield of 4.5% by weight. VKG Oil claims to produce 250,000 tons of oil per year from 2 million tons of shale, a yield of 13%.
Petrobras Petróleo Brasileiro S.A., better known by and Trade name, trading as the portmanteau Petrobras (), is a Brazilian state-owned enterprise, majority state-owned multinational corporation in the petroleum industry headquartered in Rio de Janeiro. ...
produces in their Petrosix plant 550 tons of oil per day from 6,200 tons of shale, a yield of 9%.


Properties

The properties of raw shale oil vary depending on the composition of the parent oil shale and the extraction technology used. Like conventional oil, shale oil is a complex
mixture In chemistry, a mixture is a material made up of two or more different chemical substances which can be separated by physical method. It is an impure substance made up of 2 or more elements or compounds mechanically mixed together in any proporti ...
of hydrocarbons, and is characterized according to the bulk properties of the oil. It usually contains large quantities of
olefin In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as α-olefins. The International Union of Pu ...
ic and
aromatic In organic chemistry, aromaticity is a chemical property describing the way in which a conjugated system, conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected from conjugati ...
hydrocarbons. It can also contain significant quantities of
heteroatom In chemistry, a heteroatom () is, strictly, any atom that is not carbon or hydrogen. Organic chemistry In practice, the term is mainly used more specifically to indicate that non-carbon atoms have replaced carbon in the backbone of the molecular ...
s. A typical shale oil composition includes 0.5–1% of
oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
, 1.5–2% of
nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...
and 0.15–1% of
sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...
; some deposits contain more heteroatoms than others. Mineral particles and metals are often present as well. Generally, the oil is less fluid than crude oil, becoming pourable at temperatures between , while conventional crude oil is pourable at temperatures between ; this property affects shale oil's ability to be transported in existing oil pipelines. Shale oil contains polycyclic aromatic hydrocarbons, which are
carcinogenic A carcinogen () is any agent that promotes the development of cancer. Carcinogens can include synthetic chemicals, naturally occurring substances, physical agents such as ionizing and non-ionizing radiation, and Biological agent, biologic agent ...
. The US EPA has concluded that raw shale oil has a mild carcinogenic potential, comparable to some intermediate petroleum refinery products, while upgraded shale oil has lower carcinogenic potential, as most of the polycyclic aromatics are believed to have been broken down by
hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to redox, reduce or Saturated ...
. The
World Health Organization The World Health Organization (WHO) is a list of specialized agencies of the United Nations, specialized agency of the United Nations which coordinates responses to international public health issues and emergencies. It is headquartered in Gen ...
classifies shale oil as a Group 1 carcinogen to humans.


Upgrading

Although raw shale oil can be immediately burnt as a fuel oil, many of its applications require that it be upgraded. The differing properties of the raw oils call for correspondingly various pre-treatments before it can be sent to a conventional
oil refinery An oil refinery or petroleum refinery is an industrial processes, industrial process Factory, plant where petroleum (crude oil) is transformed and refining, refined into products such as gasoline (petrol), diesel fuel, Bitumen, asphalt base, ...
.
Particulate Particulate matter (PM) or particulates are microscopic particles of solid or liquid matter suspended in the air. An ''aerosol'' is a mixture of particulates and air, as opposed to the particulate matter alone, though it is sometimes define ...
s in the raw oil clog downstream processes;
sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...
and
nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...
create
air pollution Air pollution is the presence of substances in the Atmosphere of Earth, air that are harmful to humans, other living beings or the environment. Pollutants can be Gas, gases like Ground-level ozone, ozone or nitrogen oxides or small particles li ...
. Sulfur and nitrogen, along with the
arsenic Arsenic is a chemical element; it has Symbol (chemistry), symbol As and atomic number 33. It is a metalloid and one of the pnictogens, and therefore shares many properties with its group 15 neighbors phosphorus and antimony. Arsenic is not ...
and
iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
that may be present, also destroy the
catalyst Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...
s used in refining.
Olefin In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as α-olefins. The International Union of Pu ...
s form insoluble sediments and cause instability. The
oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
within the oil, present at higher levels than in
crude oil Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring u ...
, lends itself to the formation of destructive
free radical A daughter category of ''Ageing'', this category deals only with the biological aspects of ageing. Ageing Biogerontology Biological processes Causes of death Cellular processes Gerontology Life extension Metabolic disorders Metabolism ...
s.
Hydrodesulfurization Hydrodesulfurization (HDS), also called hydrotreatment or hydrotreating, is a catalytic chemical process widely used to desulfurization, remove sulfur (S) from natural gas and from oil refinery, refined petroleum products, such as gasoline, g ...
and hydrodenitrogenation can address these problems and result in a product comparable to benchmark crude oil.
Phenols In organic chemistry, phenols, sometimes called phenolics, are a class of chemical compounds consisting of one or more hydroxyl groups (− O H) bonded directly to an aromatic hydrocarbon group. The simplest is phenol, . Phenolic compounds ar ...
can be first removed by water extraction. Upgrading shale oil into transport fuels requires adjusting hydrogen–carbon ratios by adding hydrogen ( hydrocracking) or removing carbon (
coking Coking is the process of heating coal in the absence of oxygen to a temperature above to drive off the volatile components of the raw coal, leaving behind a hard, strong, porous material with a high carbon content called coke. Coke is predomina ...
). Shale oil produced by some technologies, such as the Kiviter process, can be used without further upgrading as an oil constituent and as a source of phenolic compounds. Distillate oils from the Kiviter process can also be used as
diluent A diluent (also referred to as a filler, dilutant or thinner) is a diluting agent. Certain fluids are too viscous to be pumped easily or too dense to flow from one particular point to the other. This can be troublesome, because it might not be ...
s for petroleum-originated heavy oils and as an adhesive-enhancing additive in bituminous materials such as asphalt.


Uses

Before
World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
, most shale oil was upgraded for use as transport fuels. Afterwards, it was used as a raw material for chemical intermediates, pure chemicals and industrial resins, and as a railroad wood
preservative A preservative is a substance or a chemical that is added to products such as food products, beverages, pharmaceutical drugs, paints, biological samples, cosmetics, wood, and many other products to prevent decomposition by microbial growth or ...
. As of 2008, it is primarily used as a heating oil and marine fuel, and to a lesser extent in the production of various chemicals. Shale oil's concentration of high-boiling point compounds is suited for the production of middle distillates such as
kerosene Kerosene, or paraffin, is a combustibility, combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in Aviation fuel, aviation as well as households. Its name derives from the Greek (''kērós'') meaning " ...
,
jet fuel Jet fuel or aviation turbine fuel (ATF, also abbreviated avtur) is a type of aviation fuel designed for use in aircraft powered by Gas turbine, gas-turbine engines. It is colorless to straw-colored in appearance. The most commonly used fuels for ...
and
diesel fuel Diesel fuel, also called diesel oil, heavy oil (historically) or simply diesel, is any liquid fuel specifically designed for use in a diesel engine, a type of internal combustion engine in which fuel ignition takes place without a spark as a re ...
. Additional cracking can create the lighter hydrocarbons used in gasoline. "Pale sulfonated shale oil" (PSSO), a sulfonated and ammonia-neutralized variant named "Ichthammol" (chemical name: Ammonium bituminosulfonate) is still in application today.


Reserves and production

Global technically recoverable oil shale reserves have recently been estimated at of shale oil, with the largest reserves in the
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
, which is thought to have . Worldwide production of shale oil was estimated at in 2008. The leading producers were China (), Estonia (), and Brazil (). The production of shale oil has been hindered because of technical difficulties and costs. In March 2011, the United States
Bureau of Land Management The Bureau of Land Management (BLM) is an agency within the United States Department of the Interior responsible for administering federal lands, U.S. federal lands. Headquartered in Washington, D.C., the BLM oversees more than of land, or one ...
called into question proposals for commercial operations in Colorado, Utah and Wyoming, stating that "(t)here are no economically viable ways yet known to extract and process oil shale for commercial purposes". The US Energy Information Administration sometimes uses the phrase "shale (tight) oil" to refer to tight oil, "crude oil ... produced directly from tight oil resources". In 2021, the US produced 7.23 million barrels of such
tight oil Tight oil (also known as shale oil, shale-hosted oil or light tight oil, abbreviated LTO) is light crude oil contained in Unconventional (oil & gas) reservoir, unconventional petroleum-bearing formations of low Permeability (earth sciences), perme ...
each day, equal to about 64% of total U.S. crude oil production. The IEA also occasionally calls tight oil "shale oil", but classifies any products from oil shale with
solid fuels Solid fuel refers to various forms of solid material that can be burnt to release energy, providing heat and light through the process of combustion. Solid fuels can be contrasted with liquid fuels and gaseous fuels. Common examples of solid fu ...
.


See also

*
Unconventional (oil & gas) reservoir Unconventional (oil and gas) reservoirs, or unconventional resources (resource plays) are accumulations where oil and gas phases are tightly bound to the rock fabric by strong capillary forces, requiring specialized measures for evaluation and ...
* Oil shale economics * Oil shale gas * Underground coal gasification * Spent shale * Vaca Muerta * Creveney shale mining operation


References

{{DEFAULTSORT:Shale Oil Oil shale Synthetic fuels Arab inventions Egyptian inventions