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Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black
liquid A liquid is a nearly Compressibility, incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of State of matter#Four fundamental states, the four fund ...
mixture of mainly
hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic, and their odors are usuall ...
s, and is found in
geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock expo ...
s. The name ''petroleum'' covers both naturally occurring unprocessed crude oil and
petroleum product Petroleum products are materials derived from crude oil (petroleum) as it is processed in oil refineries. Unlike petrochemicals, which are a collection of well-defined usually pure organic compounds, petroleum products are complex mixtures. The m ...
s that consist of refined crude oil. A
fossil fuel A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and combustion, burned as a fuel. The main fossil fuels are coal, petroleum, oil, and natura ...
, petroleum is formed when large quantities of dead organisms, mostly
zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...
and
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthesis, photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from u ...
, are buried underneath
sedimentary rock Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at Earth#Surface, Earth's surface, followed by cementation (geology), cementation. Sedimentati ...
and subjected to both prolonged heat and pressure. Petroleum is primarily recovered by
oil drilling An oil well is a drillhole boring in Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large list of largest lakes and seas in the Solar System, volumes of water can be found th ...
. Drilling is carried out after studies of structural geology, sedimentary basin analysis, and reservoir characterisation. Recent developments in technologies have also led to exploitation of other unconventional reserves such as
oil sands Oil sands, tar sands, crude bitumen, or bituminous sands, are a type of unconventional oil, unconventional petroleum deposit. Oil sands are either loose sands or partially consolidated sandstone containing a naturally occurring mixture of s ...
and
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 ...
. Once extracted, oil is refined and separated, most easily by
distillation Distillation, or classical distillation, is the process of separation process, separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distilla ...
, into innumerable products for direct use or use in manufacturing. Products include fuels such as
gasoline Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most Spark-ignition engine, spark-ignited internal combustion engines (also known as petrol engines). It consists ...
(petrol), diesel,
kerosene Kerosene, paraffin, or lamp oil 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 el, κηρός (''keros' ...
and
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 c ...
among many others;
asphalt Asphalt, also known as bitumen (, ), is a sticky, black, highly viscosity, viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a Pitch (resin), pitch. Before the ...
and
lubricants A lubricant (sometimes shortened to lube) is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, t ...
; chemical
reagent In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...
s used to make
plastic Plastics are a wide range of synthetic polymers, synthetic or semi-synthetic materials that use polymers as a main ingredient. Their Plasticity (physics), plasticity makes it possible for plastics to be Injection moulding, moulded, Extrusion, e ...
s;
solvents A solvent (s) (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 ...
,
textiles Textile is an Hyponymy and hypernymy, umbrella term that includes various Fiber, fiber-based materials, including fibers, yarns, Staple (textiles)#Filament fiber, filaments, Thread (yarn), threads, different #Fabric, fabric types, etc. At f ...
,
refrigerants A refrigerant is a working fluid used in the refrigeration cycle of air conditioning Air conditioning, often abbreviated as A/C or AC, is the process of removing heat In thermodynamics, heat is defined as the form of energy crossing ...
,
paint Paint is any pigmented liquid, liquefiable, or solid mastic composition that, after application to a substrate in a thin layer, converts to a solid film. It is most commonly used to protect, color, or provide texture. Paint can be made in ma ...
,
synthetic rubber A synthetic rubber is an artificial elastomer. They are polymers synthesized from petroleum byproducts. About 32-million metric tons of rubbers are produced annually in the United States, and of that amount two thirds are synthetic. Synthetic rubbe ...
,
fertilizers A fertilizer (American English) or fertiliser (British English; American and British English spelling differences#-ise, -ize (-isation, -ization), see spelling differences) is any material of natural or synthetic origin that is applied to soil ...
,
pesticide Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, ...
s,
pharmaceuticals A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, treat, or preventive medicine, prevent disease. Drug therapy (pharmacotherapy) is an imp ...
, and thousands of others. Petroleum is used in manufacturing a vast variety of materials essential for modern life, and it is estimated that the world consumes about each day. Petroleum production can be extremely profitable and was critical to global economic development in the 20th century, with some countries, so called " oil states", gaining significant economic and international power because of their control of oil production. Petroleum exploitation and use has had significant negative environmental and social consequences. Extraction,
refining {{Unreferenced, date=December 2009 Refining (also perhaps called by the mathematical term affining) is the process of List of purification methods in chemistry, purification of a (1) chemical compound, substance or a (2) Theory of Forms, form. The ...
and
burning Combustion, or burning, is a high-temperature exothermic redox chemical reaction A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances ...
of petroleum fuels all release large quantities of
greenhouse gas A greenhouse gas (GHG or GhG) is a gas that Absorption (electromagnetic radiation), absorbs and Emission (electromagnetic radiation), emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse ...
es, so petroleum is one of the major contributors to climate change. Other negative environmental effects include
oil spill An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially the marine ecosystem, due to human activity, and is a form of pollution. The term is usually given to marine oil spills, where oil is released into th ...
s, and air and water pollution. Some of these effects have direct and indirect health consequences for humans. Oil has also been a source of conflict leading to both state-led-wars and other conflicts. Production of petroleum is speculated to reach
peak oil Peak oil is the hypothetical point in time when the maximum rate of global Extraction of petroleum, oil production is reached, after which it is argued that production will begin an irreversible decline. It is related to the distinct concept ...
before 2035 as global economies lower dependencies on petroleum as part of
climate change mitigation Climate change mitigation is action to limit climate change by reducing Greenhouse gas emissions, emissions of greenhouse gases or Carbon sink, removing those gases from the atmosphere. The recent rise in global average temperature is mostly caus ...
and a transition towards
renewable energy Renewable energy is energy that is collected from renewable resources that are naturally replenished on a Orders of magnitude (time), human timescale. It includes sources such as Solar power, sunlight, wind power, wind, the movement of Hydropo ...
and
electrification Electrification is the process of powering by electricity and, in many contexts, the introduction of such power by changing over from an earlier power source. The broad meaning of the term, such as in the history of technology, economic history ...
.


Etymology

The word ''petroleum'' comes from Medieval Latin (literally 'rock oil'), which comes from Latin
petra Petra ( ar, ٱلْبَتْرَاء, Al-Batrāʾ; grc, Πέτρα, "Rock", Nabataean Aramaic, Nabataean: ), originally known to its inhabitants as Raqmu or Raqēmō, is an historic and archaeological city in southern Jordan. It is adjacent to t ...
'rock' (from Greek ) and oleum 'oil' (from Greek ). The term was used in the treatise ''
De Natura Fossilium ''De Natura Fossilium'' is a scientific text written by Georg Bauer also known as Georgius Agricola, first published in 1546. The book represents the first scientific attempt to categorize minerals, rocks and sediments since the publication of Pl ...
'', published in 1546 by the German mineralogist Georg Bauer, also known as Georgius Agricola. In the 19th century, the term ''petroleum'' was often used to refer to
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, ...
s produced by distillation from mined organic solids such as cannel coal (and later
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 ...
) and refined oils produced from them; in the United Kingdom, storage (and later transport) of these oils were regulated by a series of Petroleum Acts, from the ''Petroleum Act 1863'' onwards.


History


Early

Petroleum, in one form or another, has been used since ancient times. More than 4300 years ago,
bitumen Asphalt, also known as bitumen (, ), is a sticky, black, highly viscosity, viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a Pitch (resin), pitch. Before the ...
was mentioned when the Sumerians used it to make boats. Tablet of the legend of the birth of
Sargon of Akkad Sargon of Akkad (; akk, ''Šarrugi''), also known as Sargon the Great, was the first ruler of the Akkadian Empire, known for his conquests of the Sumerian Sumerian city-states, city-states in the 24th to 23rd centuries BC.The date of the re ...
, mentioned a basket which was closed by straw and bitumen. More than 4000 years ago, according to
Herodotus Herodotus ( ; grc, , }; BC) was an ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided in ...
and
Diodorus Siculus Diodorus Siculus, or Diodorus of Sicily ( grc-gre, wikt:Διόδωρος, Διόδωρος ;  1st century BC), was an ancient Greece, ancient Greek historian. He is known for writing the monumental universal history ''Bibliotheca historica' ...
,
asphalt Asphalt, also known as bitumen (, ), is a sticky, black, highly viscosity, viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a Pitch (resin), pitch. Before the ...
was used in the construction of the walls and towers of
Babylon ''Bābili(m)'' * sux, 𒆍𒀭𒊏𒆠 * arc, 𐡁𐡁𐡋 ''Bāḇel'' * syc, ܒܒܠ ''Bāḇel'' * grc-gre, Βαβυλών ''Babylṓn'' * he, בָּבֶל ''Bāvel'' * peo, 𐎲𐎠𐎲𐎡𐎽𐎢 ''Bābiru'' * elx, 𒀸𒁀𒉿𒇷 ''Babi ...
; there were oil pits near Ardericca (near Babylon), and a pitch spring on Zacynthus. Great quantities of it were found on the banks of the river Issus, one of the tributaries of the
Euphrates The Euphrates () is the longest and one of the most historically important rivers of Western Asia. Tigris–Euphrates river system, Together with the Tigris, it is one of the two defining rivers of Mesopotamia ( ''the land between the rivers'') ...
. Ancient Persian tablets indicate the medicinal and lighting uses of petroleum in the upper levels of their society. The use of petroleum in ancient China dates back to more than 2000 years ago. The ''
I Ching The ''I Ching'' or ''Yi Jing'' (, ), usually translated ''Book of Changes'' or ''Classic of Changes'', is an ancient Chinese divination text that is among the oldest of the Chinese classics. Originally a divination manual in the Western Z ...
'', one of the earliest Chinese writings, cites that oil in its raw state, without refining, was first discovered, extracted, and used in China in the first century BCE. In addition, the Chinese were the first to record the use of petroleum as fuel as early as the fourth century BCE. By 347 CE, oil was produced from bamboo-drilled wells in China.
Crude oil Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crude ...
was often distilled by Persian chemists, with clear descriptions given in Arabic handbooks such as those of Muhammad ibn Zakarīya Rāzi (Rhazes). The streets of
Baghdad Baghdad (; ar, بَغْدَاد , ) is the capital of Iraq and the list of largest cities in the Arab world, second-largest city in the Arab world after Cairo. It is located on the Tigris near the ruins of the ancient city of Babylon and the ...
were paved with
tar Tar is a dark brown or black viscosity, viscous liquid of hydrocarbons and free carbon, obtained from a wide variety of organic matter, organic materials through destructive distillation. Tar can be produced from coal, wood, petroleum, or peat. ...
, derived from petroleum that became accessible from natural fields in the region. In the 9th century,
oil field A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in porous or fractured rock formations. Such reservoirs form when kerogen (ancient plant matter) is created in surrounding rock by the prese ...
s were exploited in the area around modern
Baku Baku (, ; az, Bakı ) is the capital and largest city of Azerbaijan, as well as the largest city on the Caspian Sea The Caspian Sea is the world's largest inland body of water, often described as the List of lakes by area, world's largest ...
,
Azerbaijan Azerbaijan (, ; az, Azərbaycan ), officially the Republic of Azerbaijan, , also sometimes officially called the Azerbaijan Republic is a transcontinental country, transcontinental country located at the boundary of Eastern Europe and Wester ...
. These fields were described by the Arab geographer Abu al-Hasan 'Alī al-Mas'ūdī in the 10th century, and by
Marco Polo Marco Polo (, , ; 8 January 1324) was a Republic of Venice, Venetian merchant, explorer and writer who travelled through Asia along the Silk Road between 1271 and 1295. His travels are recorded in ''The Travels of Marco Polo'' (also known as ...
in the 13th century, who described the output of those wells as hundreds of shiploads. Arab and Persian chemists also distilled crude oil in order to produce
flammable A combustible material is something that can burn (i.e., ''combust'') in air. A combustible material is flammable if it ignites easily at ambient temperatures. In other words, a combustible material ignites with some effort and a flammable mat ...
products for military purposes. Through Islamic Spain, distillation became available in
Western Europe Western Europe is the western region of Europe. The region's countries and territories vary depending on context. The concept of "the West" appeared in Europe in juxtaposition to "the East" and originally applied to the ancient Mediterranean ...
by the 12th century. It has also been present in Romania since the 13th century, being recorded as păcură. Sophisticated oil pits, deep, were dug by the
Seneca People The Seneca () ( see, Onödowáʼga:, "Great Hill People") are a group of Indigenous Iroquoian-speaking people who historically lived south of Lake Ontario, one of the five Great Lakes in North America North America is a continent ...
and other
Iroquois The Iroquois ( or ), officially the Haudenosaunee ( meaning "people of the longhouse"), are an Iroquoian Peoples, Iroquoian-speaking Confederation#Indigenous confederations in North America, confederacy of First Nations in Canada, First Natio ...
in
Western Pennsylvania Western Pennsylvania is a region in the U.S. state of Pennsylvania, covering the western third of the state. Pittsburgh is the region's principal city, with a Greater Pittsburgh Region, metropolitan area population of about 2.4 million people, ...
as early as 1415–1450. The French General Louis-Joseph de Montcalm encountered Seneca using petroleum for ceremonial fires and as a healing lotion during a visit to Fort Duquesne in 1750. Early British explorers to
Myanmar Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John C. Wells, Joh ...
documented a flourishing oil extraction industry based in Yenangyaung that, in 1795, had hundreds of hand-dug wells under production. Pechelbronn (Pitch fountain) is said to be the first European site where petroleum has been explored and used. The still active Erdpechquelle, a spring where petroleum appears mixed with water has been used since 1498, notably for medical purposes. Oil sands have been mined since the 18th century. In Wietze in lower Saxony, natural asphalt/bitumen has been explored since the 18th century. Both in Pechelbronn as in Wietze, the coal industry dominated the petroleum technologies.


Modern

Chemist James Young noticed a natural petroleum seepage in the Riddings
colliery Coal mining is the process of resource extraction, extracting coal from the ground. Coal is valued for its Energy value of coal, energy content and since the 1880s has been widely used to generate electricity. Steel and cement industries use c ...
at
Alfreton Alfreton ( ) is a town and civil parishes in England, civil parish in the Amber Valley district of Derbyshire, England. The town was formerly a Norman Manor and later an Urban District. The population of the Alfreton parish was 7,971 at the 2011 ...
,
Derbyshire Derbyshire ( ) is a ceremonial county in the East Midlands, England. It includes much of the Peak District, Peak District National Park, the southern end of the Pennines, Pennine range of hills and part of the The National Forest (England), Nat ...
from which he distilled a light thin oil suitable for use as lamp oil, at the same time obtaining a more viscous oil suitable for lubricating machinery. In 1848, Young set up a small business refining the crude oil. Young eventually succeeded, by distilling cannel coal at a low heat, in creating a fluid resembling petroleum, which when treated in the same way as the seep oil gave similar products. Young found that by slow distillation he could obtain a number of useful liquids from it, one of which he named "paraffine oil" because at low temperatures it congealed into a substance resembling paraffin wax. The production of these oils and solid
paraffin wax Paraffin wax (or petroleum wax) is a soft colorless solid derived from petroleum, coal, or oil shale that consists of a mixture of hydrocarbon molecules containing between 20 and 40 carbon atoms. It is solid at room temperature and melting poin ...
from coal formed the subject of his patent dated 17 October 1850. In 1850 Young & Meldrum and Edward William Binney entered into partnership under the title of E.W. Binney & Co. at Bathgate in West Lothian and E. Meldrum & Co. at Glasgow; their works at Bathgate were completed in 1851 and became the first truly commercial oil-works in the world with the first modern oil refinery. The world's first oil refinery was built in 1856 by Ignacy Łukasiewicz. His achievements also included the discovery of how to distill kerosene from seep oil, the invention of the modern kerosene lamp (1853), the introduction of the first modern street lamp in Europe (1853), and the construction of the world's first modern oil well (1854). The demand for petroleum as a fuel for lighting in North America and around the world quickly grew. Edwin Drake's 1859 well near Titusville, Pennsylvania, is popularly considered the first modern well. Already 1858 Georg Christian Konrad Hunäus had found a significant amount of petroleum while drilling for
lignite Lignite, often referred to as brown coal, is a soft, brown, combustion, combustible, sedimentary rock formed from naturally compressed peat. It has a carbon content around 25–35%, and is considered the coal rank, lowest rank of coal due to its ...
1858 in Wietze, Germany. Wietze later provided about 80% of the German consumption in the Wilhelminian Era. The production stopped in 1963, but Wietze has hosted a Petroleum Museum since 1970. Drake's well is probably singled out because it was drilled, not dug; because it used a steam engine; because there was a company associated with it; and because it touched off a major boom. However, there was considerable activity before Drake in various parts of the world in the mid-19th century. A group directed by Major Alexeyev of the Bakinskii Corps of Mining Engineers hand-drilled a well in the Baku region of Bibi-Heybat in 1846. There were engine-drilled wells in West Virginia in the same year as Drake's well. An early commercial well was hand dug in
Poland Poland, officially the Republic of Poland, is a country in Central Europe. It is divided into 16 administrative provinces called Voivodeships of Poland, voivodeships, covering an area of . Poland has a population of over 38 million and is ...
in 1853, and another in nearby
Romania Romania ( ; ro, România ) is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern, and Southeast Europe, Southeastern Europe. It borders Bulgaria to the south, Ukraine to the north, Hungary to the west, S ...
in 1857. At around the same time the world's first, small, oil refinery was opened at Jasło in Poland, with a larger one opened at Ploiești in Romania shortly after. Romania is the first country in the world to have had its annual crude oil output officially recorded in international statistics: 275 tonnes for 1857. The first commercial oil well in Canada became operational in 1858 at Oil Springs, Ontario (then Canada West).Oil Museum of Canada, Black Gold: Canada's Oil Heritage, Oil Springs: Boom & Bust
Businessman James Miller Williams dug several wells between 1855 and 1858 before discovering a rich reserve of oil four metres below ground. Williams extracted 1.5 million litres of crude oil by 1860, refining much of it into kerosene lamp oil. Williams's well became commercially viable a year before Drake's Pennsylvania operation and could be argued to be the first commercial oil well in North America. The discovery at Oil Springs touched off an oil boom which brought hundreds of speculators and workers to the area. Advances in drilling continued into 1862 when local driller Shaw reached a depth of 62 metres using the spring-pole drilling method. On January 16, 1862, after an explosion of
natural gas Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbon di ...
, Canada's first oil gusher came into production, shooting into the air at a recorded rate of per day. By the end of the 19th century the Russian Empire, particularly the
Branobel The Petroleum Production Company Nobel Brothers, Limited, or Branobel (short for братьев Нобель "brat'yev Nobel" — "Nobel Brothers" in Russian language , Russian), was an oil company set up by Ludvig Nobel and Baron Peter von Bilde ...
company in
Azerbaijan Azerbaijan (, ; az, Azərbaycan ), officially the Republic of Azerbaijan, , also sometimes officially called the Azerbaijan Republic is a transcontinental country, transcontinental country located at the boundary of Eastern Europe and Wester ...
, had taken the lead in production.Akiner(2004), p. 5 Access to oil was and still is a major factor in several military conflicts of the twentieth century, including
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
, during which oil facilities were a major strategic asset and were extensively bombed. The German invasion of the Soviet Union included the goal to capture the Baku oilfields, as it would provide much needed oil-supplies for the German military which was suffering from blockades. Oil exploration in North America during the early 20th century later led to the US's becoming the leading producer by mid-century. As petroleum production in the US peaked during the 1960s, however, the United States was surpassed by Saudi Arabia and the Soviet Union. In 1973, Saudi Arabia and other Arab nations imposed an oil embargo against the United States, United Kingdom, Japan and other Western nations which supported
Israel Israel (; he, יִשְׂרָאֵל, ; ar, إِسْرَائِيل, ), officially the State of Israel ( he, מְדִינַת יִשְׂרָאֵל, label=none, translit=Medīnat Yīsrāʾēl; ), is a country in Western Asia. It is situated ...
in the
Yom Kippur War The Yom Kippur War, also known as the Ramadan War, the October War, the 1973 Arab–Israeli War, or the Fourth Arab–Israeli War, was an armed conflict fought from 6 to 25 October 1973 between Israel and a coalition of Arab world, Arab states ...
of October 1973. The embargo caused an oil crisis. This was followed by the 1979 oil crisis, which was caused by a drop in
oil production Petroleum is a fossil fuel that can be drawn from beneath the earth's surface. Reservoirs of petroleum was formed through the mixture of plants, algae, and sediments in shallow seas under high pressure. Petroleum is mostly recovered from oil dri ...
in the wake of the
Iranian Revolution The Iranian Revolution ( fa, انقلاب ایران, Enqelâb-e Irân, ), also known as the Islamic Revolution ( fa, انقلاب اسلامی, Enqelâb-e Eslâmī), was a series of events that culminated in the overthrow of the Pahlavi dynas ...
and caused oil prices to more than double. The two oil price shocks had many short- and long-term effects on global politics and the global economy. In particular, they led to sustained reductions in demand as a result of substitution to other fuels (especially coal and nuclear) and improvements in energy efficiency, facilitated by government policies. High oil prices also induced investment in oil production by non-OPEC countries, including Prudhoe Bay in Alaska, the North Sea offshore fields of the United Kingdom and Norway, the Cantarell offshore field of Mexico, and oil sands in Canada. Today, about 90 percent of vehicular fuel needs are met by oil. Petroleum also makes up 40 percent of total energy consumption in the United States, but is responsible for only 1 percent of electricity generation. Petroleum's worth as a portable, dense energy source powering the vast majority of vehicles and as the base of many industrial chemicals makes it one of the world's most important
commodities In economics, a commodity is an economic goods, good, usually a resource, that has full or substantial fungibility: that is, the Market (economics), market treats instances of the good as equivalent or nearly so with no regard to who Production ...
. The top three oil producing countries are the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
,
Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...
, and
Saudi Arabia Saudi Arabia, officially the Kingdom of Saudi Arabia (KSA), is a country in Western Asia. It covers the bulk of the Arabian Peninsula, and has a land area of about , making it the List of Asian countries by area, fifth-largest country in Asia ...
. In 2018, due in part to developments in
hydraulic fracturing Fracking (also known as hydraulic fracturing, hydrofracturing, or hydrofracking) is a well stimulation technique involving the fracturing of bedrock Formation (geology), formations by a pressurized liquid. The process involves the high-pressure ...
and horizontal drilling, the United States became the world's largest producer. About 80 percent of the world's readily accessible reserves are located in the Middle East, with 62.5 percent coming from the Arab 5:
Saudi Arabia Saudi Arabia, officially the Kingdom of Saudi Arabia (KSA), is a country in Western Asia. It covers the bulk of the Arabian Peninsula, and has a land area of about , making it the List of Asian countries by area, fifth-largest country in Asia ...
,
United Arab Emirates The United Arab Emirates (UAE; ar, اَلْإِمَارَات الْعَرَبِيَة الْمُتَحِدَة ), or simply the Emirates ( ar, الِْإمَارَات ), is a country in Western Asia (Middle East, The Middle East). It is ...
,
Iraq Iraq,; ku, عێراق, translit=Êraq officially the Republic of Iraq, '; ku, کۆماری عێراق, translit=Komarî Êraq is a country in Western Asia. It is bordered by Turkey to Iraq–Turkey border, the north, Iran to Iran–Iraq ...
,
Qatar Qatar (, ; ar, قطر, Qaṭar ; local vernacular pronunciation: ), officially the State of Qatar,) is a country in Western Asia. It occupies the Qatar Peninsula on the northeastern coast of the Arabian Peninsula in the Middle East; it sha ...
and
Kuwait Kuwait (; ar, الكويت ', or ), officially the State of Kuwait ( ar, دولة الكويت '), is a country in Western Asia. It is situated in the northern edge of Eastern Arabia at the tip of the Persian Gulf, bordering Iraq to Iraq–Ku ...
. A large portion of the world's total oil exists as unconventional sources, such as
bitumen Asphalt, also known as bitumen (, ), is a sticky, black, highly viscosity, viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a Pitch (resin), pitch. Before the ...
in Athabasca oil sands and
extra heavy oil Heavy crude oil (or extra heavy crude oil) is highly-viscous oil that cannot easily flow from production wells under normal reservoir conditions. It is referred to as "heavy" because its density or specific gravity is higher than that of light cru ...
in the Orinoco Belt. While significant volumes of oil are extracted from oil sands, particularly in Canada, logistical and technical hurdles remain, as oil extraction requires large amounts of heat and water, making its net energy content quite low relative to conventional crude oil. Thus, Canada's oil sands are not expected to provide more than a few million barrels per day in the foreseeable future.


Composition

Petroleum includes not only crude oil, but all liquid, gaseous and solid
hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic, and their odors are usuall ...
s. Under surface pressure and temperature conditions, lighter hydrocarbons
methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Eart ...
,
ethane Ethane ( , ) is an Organic compound, organic chemical compound with chemical formula . At Standard conditions for temperature and pressure, standard temperature and pressure, ethane is a colorless, odorless gas. Like many hydrocarbons, ethane ...
,
propane Propane () is a three-carbon alkane with the molecular formula . It is a gas at standard temperature and pressure, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used as ...
and
butane Butane () or ''n''-butane is an alkane with the formula C4H10. Butane is a gas at room temperature and atmospheric pressure. Butane is a highly flammable, colorless, easily liquefied gas that quickly vaporizes at room temperature. The name b ...
exist as gases, while pentane and heavier hydrocarbons are in the form of liquids or solids. However, in an underground oil reservoir the proportions of gas, liquid, and solid depend on subsurface conditions and on the
phase diagram A phase diagram in physical chemistry, engineering, mineralogy, and materials science is a type of chart used to show conditions (pressure, temperature, volume, etc.) at which thermodynamically distinct phase (matter), phases (such as solid, liq ...
of the petroleum mixture. An
oil well An oil well is a drillhole boring (earth), boring in Earth that is designed to bring petroleum oil hydrocarbons to the surface. Usually some natural gas is released as associated petroleum gas along with the oil. A well that is designed to produ ...
produces predominantly crude oil, with some natural gas dissolved in it. Because the pressure is lower at the surface than underground, some of the gas will come out of solution and be recovered (or burned) as ''associated gas'' or ''solution gas''. A gas well produces predominantly
natural gas Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbon di ...
. However, because the underground temperature is higher than at the surface, the gas may contain heavier hydrocarbons such as pentane, hexane, and
heptane Heptane or ''n''-heptane is the straight-chain alkane with the chemical formula H3C(CH2)5CH3 or C7H16. When used as a test fuel component in Engine knocking, anti-knock test engines, a 100% heptane fuel is the zero point of the octane rating sca ...
in the gaseous state. At surface conditions these will condense out of the gas to form " natural-gas condensate", often shortened to ''condensate.'' Condensate resembles gasoline in appearance and is similar in composition to some volatile
light crude oil Light crude oil is liquid petroleum that has a low density and flows freely at standard conditions, room temperature. It has a low viscosity, low specific gravity and high API gravity due to the presence of a high proportion of light hydrocarbon fra ...
s. The proportion of light hydrocarbons in the petroleum mixture varies greatly among different
oil fields A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in Porosity, porous or fractured rock formations. Such reservoirs form when kerogen (ancient plant matter) is created in surrounding rock by the ...
, ranging from as much as 97 percent by weight in the lighter oils to as little as 50 percent in the heavier oils and
bitumen Asphalt, also known as bitumen (, ), is a sticky, black, highly viscosity, viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a Pitch (resin), pitch. Before the ...
s. The hydrocarbons in crude oil are mostly
alkane In organic chemistry Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms tha ...
s,
cycloalkane In organic chemistry, the cycloalkanes (also called naphthenes, but distinct from naphthalene) are the ring (chemistry), monocyclic Saturated and unsaturated compounds, saturated hydrocarbons. In other words, a cycloalkane consists only of hydroge ...
s and various aromatic hydrocarbons, while the other organic compounds contain
nitrogen Nitrogen is the chemical element with the Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the pnictogens. It is a common element in the ...
,
oxygen Oxygen is the chemical element with the 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 Chemical reaction, reactive nonmetal, and an oxidizing a ...
and
sulfur Sulfur (or sulphur in British English British English (BrE, en-GB, or BE) is, according to Oxford Dictionaries, " English as used in Great Britain, as distinct from that used elsewhere". More narrowly, it can refer specifically to the ...
, and trace amounts of metals such as iron, nickel, copper and vanadium. Many oil reservoirs contain live bacteria. The exact molecular composition of crude oil varies widely from formation to formation but the proportion of
chemical element A chemical element is a species of atoms that have a given number of protons in their atomic nucleus, nuclei, including the pure Chemical substance, substance consisting only of that species. Unlike chemical compounds, chemical elements canno ...
s varies over fairly narrow limits as follows: Four different types of hydrocarbon molecules appear in crude oil. The relative percentage of each varies from oil to oil, determining the properties of each oil. Crude oil varies greatly in appearance depending on its composition. It is usually black or dark brown (although it may be yellowish, reddish, or even greenish). In the reservoir it is usually found in association with natural gas, which being lighter forms a "gas cap" over the petroleum, and
saline water Saline water (more commonly known as salt water) is water that contains a high concentration of solvation, dissolved salts (mainly sodium chloride). On the United States Geological Survey (USGS) salinity scale, saline water is saltier than brack ...
which, being heavier than most forms of crude oil, generally sinks beneath it. Crude oil may also be found in a semi-solid form mixed with sand and water, as in the Athabasca oil sands in Canada, where it is usually referred to as crude
bitumen Asphalt, also known as bitumen (, ), is a sticky, black, highly viscosity, viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a Pitch (resin), pitch. Before the ...
. In Canada, bitumen is considered a sticky, black, tar-like form of crude oil which is so thick and heavy that it must be heated or diluted before it will flow. Venezuela also has large amounts of oil in the Orinoco oil sands, although the hydrocarbons trapped in them are more fluid than in Canada and are usually called
extra heavy oil Heavy crude oil (or extra heavy crude oil) is highly-viscous oil that cannot easily flow from production wells under normal reservoir conditions. It is referred to as "heavy" because its density or specific gravity is higher than that of light cru ...
. These oil sands resources are called unconventional oil to distinguish them from oil which can be extracted using traditional oil well methods. Between them, Canada and
Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many Federal Dependencies of V ...
contain an estimated of bitumen and extra-heavy oil, about twice the volume of the world's reserves of conventional oil. Petroleum is used mostly, by volume, for refining into
fuel oil Fuel oil is any of various fractional distillation, fractions obtained from the distillation of petroleum (crude oil). Such oils include distillates (the lighter fractions) and residue (chemistry), residues (the heavier fractions). Fuel oils inclu ...
and gasoline, both important ''
primary energy Primary energy (PE) is an energy In physics, energy (from Ancient Greek: wikt:ἐνέργεια#Ancient_Greek, ἐνέργεια, ''enérgeia'', “activity”) is the physical quantity, quantitative physical property, property that is ...
'' sources. Eight-four percent by volume of the hydrocarbons present in petroleum is converted into energy-rich fuels (petroleum-based fuels), including gasoline, diesel, jet, heating, and other fuel oils, and
liquefied petroleum gas Liquefied petroleum gas (LPG or LP gas) is a fuel gas which contains a flammable mixture of hydrocarbon gases, specifically propane, propylene, butylene, isobutane and n-butane. LPG is used as a fuel gas in HVAC, heating appliances, cookin ...
. The lighter grades of crude oil produce the best yields of these products, but as the world's reserves of light and medium oil are depleted, oil refineries are increasingly having to process heavy oil and bitumen, and use more complex and expensive methods to produce the products required. Because heavier crude oils have too much carbon and not enough hydrogen, these processes generally involve removing carbon from or adding hydrogen to the molecules, and using
fluid catalytic cracking Fluid Catalytic Cracking (FCC) is the conversion process used in Oil refinery, petroleum refineries to convert the high-boiling point, high-molecular weight hydrocarbon fractions of petroleum (crude oils) into gasoline, olefinic gases, and other p ...
to convert the longer, more complex molecules in the oil to the shorter, simpler ones in the fuels. Due to its high
energy density In physics, energy density is the amount of energy stored in a given system or region of space per unit volume. It is sometimes confused with energy per unit mass which is properly called specific energy or . Often only the ''useful'' or ex ...
, easy transportability and relative abundance, oil has become the world's most important source of energy since the mid-1950s. Petroleum is also the raw material for many
chemical A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent Chemical element, elements by physical separation m ...
products, including
pharmaceutical A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, treat, or preventive medicine, prevent disease. Drug therapy (pharmacotherapy) is an imp ...
s,
solvent A solvent (s) (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 ...
s,
fertilizer A fertilizer (American English) or fertiliser (British English; American and British English spelling differences#-ise, -ize (-isation, -ization), see spelling differences) is any material of natural or synthetic origin that is applied to soil ...
s,
pesticide Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, ...
s, and plastics; the 16 percent not used for energy production is converted into these other materials. Petroleum is found in porous rock formations in the upper strata of some areas of the
Earth's crust Earth's crust is Earth's thin outer shell of Rock (geology), rock, referring to less than 1% of Earth's radius and volume. It is the top component of the lithosphere, a division of Earth's layers that includes the Crust (geology), crust and the ...
. There is also petroleum in oil sands (tar sands). Known
oil reserves An oil is any polarity (chemistry), nonpolar chemical substance that is composed primarily of Hydrocarbon, hydrocarbons and is hydrophobe, hydrophobic (does not mix with water) & lipophilicity, lipophilic (mixes with other oils). Oils are usu ...
are typically estimated at 190 km3 (1.2 trillion (short scale) barrels) without oil sands, or 595 km3 (3.74 trillion barrels) with oil sands. Consumption is currently around per day, or 4.9 km3 per year, yielding a remaining oil supply of only about 120 years, if current demand remains static. More recent studies, however, put the number at around 50 years.


Chemistry

Petroleum is mainly a mixture of
hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic, and their odors are usuall ...
s, i.e. containing only carbon and hydrogen. The most common components are
alkane In organic chemistry Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms tha ...
s (paraffins),
cycloalkane In organic chemistry, the cycloalkanes (also called naphthenes, but distinct from naphthalene) are the ring (chemistry), monocyclic Saturated and unsaturated compounds, saturated hydrocarbons. In other words, a cycloalkane consists only of hydroge ...
s ( naphthenes), and aromatic hydrocarbons. They generally have from 5 to 40 carbon atoms per molecule, although trace amounts of shorter or longer molecules may be present in the mixture. The alkanes from pentane (C5H12) to
octane Octane is a hydrocarbon and an alkane with the chemical formula , and the condensed structural formula . Octane has many structural isomers that differ by the amount and location of branching in the carbon chain. One of these isomers, 2,2,4-Tri ...
(C8H18) are refined into gasoline, the ones from
nonane Nonane is a linear alkane hydrocarbon with the chemical formula C9H20. It is a colorless, flammable liquid, occurring primarily in the component of the Petrochemical, petroleum distillate fraction commonly called kerosene, which is used as a heati ...
(C9H20) to hexadecane (C16H34) into
diesel fuel Diesel fuel , also called diesel oil, is any liquid fuel specifically designed for use in a diesel engine The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which Combustion, ignition of the diesel fuel, f ...
,
kerosene Kerosene, paraffin, or lamp oil 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 el, κηρός (''keros' ...
and
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 c ...
. Alkanes with more than 16 carbon atoms can be refined into
fuel oil Fuel oil is any of various fractional distillation, fractions obtained from the distillation of petroleum (crude oil). Such oils include distillates (the lighter fractions) and residue (chemistry), residues (the heavier fractions). Fuel oils inclu ...
and lubricating oil. At the heavier end of the range,
paraffin wax Paraffin wax (or petroleum wax) is a soft colorless solid derived from petroleum, coal, or oil shale that consists of a mixture of hydrocarbon molecules containing between 20 and 40 carbon atoms. It is solid at room temperature and melting poin ...
is an alkane with approximately 25 carbon atoms, while
asphalt Asphalt, also known as bitumen (, ), is a sticky, black, highly viscosity, viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a Pitch (resin), pitch. Before the ...
has 35 and up, although these are usually cracked by modern refineries into more valuable products. The shortest molecules, those with four or fewer carbon atoms, are in a gaseous state at room temperature. They are the petroleum gases. Depending on demand and the cost of recovery, these gases are either flared off, sold as
liquefied petroleum gas Liquefied petroleum gas (LPG or LP gas) is a fuel gas which contains a flammable mixture of hydrocarbon gases, specifically propane, propylene, butylene, isobutane and n-butane. LPG is used as a fuel gas in HVAC, heating appliances, cookin ...
under pressure, or used to power the refinery's own burners. During the winter, butane (C4H10), is blended into the gasoline pool at high rates, because its high vapour pressure assists with cold starts. Liquified under pressure slightly above atmospheric, it is best known for powering cigarette lighters, but it is also a main fuel source for many developing countries. Propane can be liquified under modest pressure, and is consumed for just about every application relying on petroleum for energy, from cooking to heating to transportation. The ''aromatic hydrocarbons'' are unsaturated hydrocarbons which have one or more planar six-carbon rings called benzene rings, to which hydrogen atoms are attached with the formula CnH2n-6. They tend to burn with a sooty flame, and many have a sweet aroma. Some are carcinogenic. These different molecules are separated by
fractional distillation Fractional distillation is the separation process, separation of a mixture into its component parts, or fraction (chemistry), fractions. Chemical compounds are separated by heating them to a temperature at which one or more fractions of the mixtur ...
at an oil refinery to produce gasoline, jet fuel, kerosene, and other hydrocarbons. For example,
2,2,4-trimethylpentane 2,2,4-Trimethylpentane, also known as isooctane or iso-octane, is an organic compound with the formula (CH3)3CCH2CH(CH3)2. It is one of several isomers of octane (C8H18). This particular isomer is the standard 100 point on the octane rating scale ...
(isooctane), widely used in
gasoline Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most Spark-ignition engine, spark-ignited internal combustion engines (also known as petrol engines). It consists ...
, has a chemical formula of C8H18 and it reacts with oxygen
exothermic In thermodynamics, an exothermic process () is a thermodynamic process or Chemical reaction, reaction that releases energy from the system to its Environment (systems), surroundings, usually in the form of heat, but also in a form of light (e.g. ...
ally: :2 (''l'') + 25 (''g'') → 16 (''g'') + 18 (''g'') (ΔH = −5.51 MJ/mol of octane) The number of various molecules in an oil sample can be determined by laboratory analysis. The molecules are typically extracted in a
solvent A solvent (s) (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 ...
, then separated in a
gas chromatograph Gas chromatography (GC) is a common type of chromatography used in analytical chemistry for Separation process, separating and analyzing compounds that can be vaporized without Chemical decomposition, decomposition. Typical uses of GC include tes ...
, and finally determined with a suitable detector, such as a flame ionization detector or a mass spectrometer. Due to the large number of co-eluted hydrocarbons within oil, many cannot be resolved by traditional gas chromatography and typically appear as a hump in the chromatogram. This Unresolved Complex Mixture (UCM) of hydrocarbons is particularly apparent when analysing weathered oils and extracts from tissues of organisms exposed to oil. Some of the components of oil will mix with water: the water associated fraction of the oil. Incomplete combustion of petroleum or gasoline results in production of toxic byproducts. Too little oxygen during combustion results in the formation of
carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
. Due to the high temperatures and high pressures involved, exhaust gases from gasoline combustion in car engines usually include
nitrogen oxide Nitrogen oxide may refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds: Charge-neutral *Nitric oxide (NO), nitrogen(II) oxide, or nitrogen monoxide *Nitrogen dioxide (), nitrogen(IV) oxide *Nitrogen trioxide (), or ni ...
s which are responsible for creation of
photochemical smog Smog, or smoke fog, is a type of intense air pollution. The word "smog" was coined in the early 20th century, and is a portmanteau of the words ''smoke'' and ''fog'' to refer to smoky fog due to its opacity, and odor. The word was then inten ...
.


Formation


Fossil petroleum

Petroleum is a
fossil fuel A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and combustion, burned as a fuel. The main fossil fuels are coal, petroleum, oil, and natura ...
derived from ancient fossilized
organic material Organic matter, organic material, or natural organic matter refers to the large source of Carbon compounds, carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic comp ...
s, such as
zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...
and
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthesis, photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from u ...
. Vast amounts of these remains settled to sea or lake bottoms where they were covered in stagnant water (water with no dissolved
oxygen Oxygen is the chemical element with the 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 Chemical reaction, reactive nonmetal, and an oxidizing a ...
) or
sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently sediment transport, transported by the action of wind, water, or ice or by the force of gravity acting on the particles. ...
s such as mud and
silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension (chemistry), suspension with water. Silt usually ...
faster than they could decompose aerobically. Approximately 1 m below this sediment, water oxygen concentration was low, below 0.1 mg/L, and anoxic conditions existed. Temperatures also remained constant. As further layers settled to the sea or lake bed, intense heat and pressure built up in the lower regions. This process caused the organic matter to change, first into a waxy material known as kerogen, found in various
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 ...
s around the world, and then with more heat into liquid and gaseous
hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic, and their odors are usuall ...
s via a process known as catagenesis. Formation of petroleum occurs from hydrocarbon
pyrolysis The pyrolysis (or devolatilization) process is the thermal decomposition of materials at elevated temperatures, often in an inert atmosphere. It involves a change of chemical composition. The word is coined from the Greek language, Greek-derived ...
in a variety of mainly
endothermic In thermochemistry, an endothermic process () is any thermodynamic process with an increase in the enthalpy (or internal energy ) of the system.Oxtoby, D. W; Gillis, H.P., Butler, L. J. (2015).''Principle of Modern Chemistry'', Brooks Cole. p. ...
reactions at high temperature or pressure, or both. These phases are described in detail below.


Anaerobic decay

In the absence of plentiful oxygen, ''aerobic'' bacteria were prevented from decaying the organic matter after it was buried under a layer of sediment or water. However, ''anaerobic'' bacteria were able to reduce
sulfate The sulfate or sulphate ion is a polyatomic ion, polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salt (chemistry), ...
s and
nitrate Nitrate is a polyatomic ion with the chemical formula . salt (chemistry), Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are solubility, soluble in wat ...
s among the matter to H2S and N2 respectively by using the matter as a source for other reactants. Due to such anaerobic bacteria, at first this matter began to break apart mostly via
hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...
:
polysaccharide Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic bond, glycosidic linkages. This carbohydrate c ...
s and
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metabo ...
s were hydrolyzed to simple sugars and
amino acid Amino acids are organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon chemical bond, bonds. Due to carbon's ability to Catenation, catenate (form chains with ot ...
s respectively. These were further anaerobically
oxidized Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate (chemistry), substrate change. Oxidation is the loss of Electron, electrons or an increase in the oxidation state, while reduction ...
at an accelerated rate by the
enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...
s of the bacteria: e.g., amino acids went through oxidative deamination to imino acids, which in turn reacted further to
ammonia Ammonia is an inorganic chemical compound, compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a dis ...
and α-keto acids.
Monosaccharide Monosaccharides (from Greek language, Greek ''wikt:μόνος, monos'': single, ''wikt:σάκχαρ, sacchar'': sugar), also called simple sugars, are the simplest forms of sugar and the most basic units (monomers) from which all carbohydrates a ...
s in turn ultimately decayed to CO2 and
methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Eart ...
. The anaerobic decay products of amino acids, monosaccharides,
phenols In organic chemistry, phenols, sometimes called phenolics, are a class of chemical compounds consisting of one or more hydroxyl Functional group, groups (—Oxygen, OHydrogen, H) Chemical bond, bonded directly to an aromatic hydrocarbon group. The ...
and
aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group ...
s combined to fulvic acids.
Fat In nutrition Nutrition is the biochemistry, biochemical and physiology, physiological process by which an organism uses food to support its life. It provides organisms with Nutrient, nutrients, which can be Metabolism, metabolized to ...
s and waxes were not extensively hydrolyzed under these mild conditions.


Kerogen formation

Some phenolic compounds produced from previous reactions worked as bactericides and the actinomycetales order of bacteria also produced antibiotic compounds (e.g., streptomycin). Thus the action of anaerobic bacteria ceased at about 10 m below the water or sediment. The mixture at this depth contained fulvic acids, unreacted and partially reacted fats and waxes, slightly modified
lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and Bark (botany), bark, because they l ...
, resins and other hydrocarbons. As more layers of organic matter settled to the sea or lake bed, intense heat and pressure built up in the lower regions. As a consequence, compounds of this mixture began to combine in poorly understood ways to kerogen. Combination happened in a similar fashion as
phenol Phenol (also called carbolic acid) is an aromaticity, aromatic organic compound with the molecular chemical formula, formula . It is a white crystalline solid that is volatility (chemistry), volatile. The molecule consists of a phenyl group () ...
and
formaldehyde Formaldehyde ( , ) (Preferred IUPAC name, systematic name methanal) is a naturally occurring organic compound with the chemical formula, formula and structure . The pure compound is a pungent, colourless gas that Polymerization, polymerises s ...
molecules react to urea-formaldehyde resins, but kerogen formation occurred in a more complex manner due to a bigger variety of reactants. The total process of kerogen formation from the beginning of anaerobic decay is called diagenesis, a word that means a transformation of materials by dissolution and recombination of their constituents.


Transformation of kerogen into fossil fuels

Kerogen formation continued to the depth of about 1 km from the Earth's surface where temperatures may reach around 50 °C. Kerogen formation represents a halfway point between organic matter and fossil fuels: kerogen can be exposed to oxygen, oxidize and thus be lost, or it could be buried deeper inside the
Earth's crust Earth's crust is Earth's thin outer shell of Rock (geology), rock, referring to less than 1% of Earth's radius and volume. It is the top component of the lithosphere, a division of Earth's layers that includes the Crust (geology), crust and the ...
and be subjected to conditions which allow it to slowly transform into fossil fuels like petroleum. The latter happened through catagenesis in which the reactions were mostly radical rearrangements of kerogen. These reactions took thousands to millions of years and no external reactants were involved. Due to radical nature of these reactions, kerogen reacted towards two classes of products: those with low H/C ratio (
anthracene Anthracene is a solid polycyclic aromatic hydrocarbon (PAH) of formula C14H10, consisting of three fused benzene rings. It is a component of coal tar. Anthracene is used in the Economic production, production of the red dye alizarin and other dyes ...
or products similar to it) and those with high H/C ratio (
methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Eart ...
or products similar to it); i.e., carbon-rich or hydrogen-rich products. Because catagenesis was closed off from external reactants, the resulting composition of the fuel mixture was dependent on the composition of the kerogen via reaction
stoichiometry Stoichiometry refers to the relationship between the quantities of reactants and products before, during, and following chemical reactions. Stoichiometry is founded on the law of conservation of mass where the total mass of the reactants equ ...
. Three types of kerogen exist: type I (algal), II (liptinic) and III (humic), which were formed mainly from
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthesis, photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from u ...
,
plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a cru ...
and
woody plant A woody plant is a plant that produces wood as its structural tissue and thus has a hard stem. In cold climates, woody plants further survive winter or dry season above ground, as opposite to Herbaceous plant, herbaceous plants that die back to t ...
s (this term includes
tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondar ...
s,
shrub A shrub (often also called a bush) is a small-to-medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees ...
s and lianas) respectively. Catagenesis was pyrolytic despite the fact that it happened at relatively low temperatures (when compared to commercial pyrolysis plants) of 60 to several hundred °C. Pyrolysis was possible because of the long reaction times involved. Heat for catagenesis came from the decomposition of
radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive Decay chain, disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nucl ...
materials of the crust, especially 40K, 232Th, 235U and 238U. The heat varied with geothermal gradient and was typically 10-30 °C per km of depth from the Earth's surface. Unusual
magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...
intrusions, however, could have created greater localized heating.


Oil window (temperature range)

Geologists often refer to the temperature range in which oil forms as an ''"oil window"''. Below the minimum temperature oil remains trapped in the form of kerogen. Above the maximum temperature the oil is converted to natural gas through the process of
thermal cracking In petrochemistry, petroleum geology and organic chemistry, cracking is the process whereby complex organic compound, organic molecules such as kerogens or long-chain hydrocarbons are broken down into simpler molecules such as light hydrocarbons, b ...
. Sometimes, oil formed at extreme depths may migrate and become trapped at a much shallower level. The Athabasca Oil Sands are one example of this.


Abiogenic petroleum

An alternative mechanism to the one described above was proposed by Russian scientists in the mid-1850s, the hypothesis of abiogenic petroleum origin (petroleum formed by inorganic means), but this is contradicted by geological and
geochemical Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the e ...
evidence. Abiogenic sources of oil have been found, but never in commercially profitable amounts. "The controversy isn't over whether abiogenic oil reserves exist," said Larry Nation of the American Association of Petroleum Geologists. "The controversy is over how much they contribute to Earth's overall reserves and how much time and effort geologists should devote to seeking them out."


Reservoirs

Three conditions must be present for oil reservoirs to form: * a source rock rich in
hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic, and their odors are usuall ...
material buried deeply enough for subterranean heat to cook it into oil, * a porous and permeable reservoir rock where it can accumulate, * a caprock (seal) or other mechanism to prevent the oil from escaping to the surface. Within these reservoirs, fluids will typically organize themselves like a three-layer cake with a layer of water below the oil layer and a layer of gas above it, although the different layers vary in size between reservoirs. Because most hydrocarbons are less dense than rock or
water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...
, they often migrate upward through adjacent rock layers until either reaching the surface or becoming trapped within porous rocks (known as reservoirs) by impermeable rocks above. However, the process is influenced by underground water flows, causing oil to migrate hundreds of kilometres horizontally or even short distances downward before becoming trapped in a reservoir. When hydrocarbons are concentrated in a trap, an
oil field A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in porous or fractured rock formations. Such reservoirs form when kerogen (ancient plant matter) is created in surrounding rock by the prese ...
forms, from which the liquid can be extracted by
drill A drill is a tool used for making round holes or driving fasteners. It is fitted with a bit, either a drill bit, drill or Screwdriver#Powered screwdriving, driverChuck (engineering)#Drill, chuck. Hand-operated types are dramatically decreasing ...
ing and
pump A pump is a device that moves fluids (liquids or gases), or sometimes Slurry, slurries, by mechanical action, typically converted from electrical energy into hydraulic energy. Pumps can be classified into three major groups according to the metho ...
ing. The reactions that produce oil and natural gas are often modeled as first order breakdown reactions, where hydrocarbons are broken down to oil and natural gas by a set of parallel reactions, and oil eventually breaks down to natural gas by another set of reactions. The latter set is regularly used in
petrochemical Petrochemicals (sometimes abbreviated as petchems) are the product (chemistry), chemical products obtained from petroleum by refining. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural ...
plants and oil refineries. Petroleum has mostly been recovered by
oil drilling An oil well is a drillhole boring in Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large list of largest lakes and seas in the Solar System, volumes of water can be found th ...
(natural petroleum springs are rare). Drilling is carried out after studies of structural geology (at the reservoir scale), sedimentary basin analysis, and reservoir characterisation (mainly in terms of the
porosity Porosity or void fraction is a measure of the Void (composites), void (i.e. "empty") spaces in a material, and is a volume fraction, fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Str ...
and permeability of geologic reservoir structures). Recent improvements to technologies have also led to exploitation of other unconventional reserves such as
oil sands Oil sands, tar sands, crude bitumen, or bituminous sands, are a type of unconventional oil, unconventional petroleum deposit. Oil sands are either loose sands or partially consolidated sandstone containing a naturally occurring mixture of s ...
and
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 ...
. Wells are drilled into oil reservoirs to extract the crude oil. "Natural lift" production methods that rely on the natural reservoir pressure to force the oil to the surface are usually sufficient for a while after reservoirs are first tapped. In some reservoirs, such as in the Middle East, the natural pressure is sufficient over a long time. The natural pressure in most reservoirs, however, eventually dissipates. Then the oil must be extracted using " artificial lift" means. Over time, these "primary" methods become less effective and "secondary" production methods may be used. A common secondary method is "waterflood" or injection of water into the reservoir to increase pressure and force the oil to the drilled shaft or "wellbore." Eventually "tertiary" or "enhanced" oil recovery methods may be used to increase the oil's flow characteristics by injecting steam, carbon dioxide and other gases or chemicals into the reservoir. In the United States, primary production methods account for less than 40 percent of the oil produced on a daily basis, secondary methods account for about half, and tertiary recovery the remaining 10 percent. Extracting oil (or "bitumen") from oil/tar sand and oil shale deposits requires mining the sand or shale and heating it in a vessel or retort, or using "in-situ" methods of injecting heated liquids into the deposit and then pumping the liquid back out saturated with oil.


Unconventional oil reservoirs

Oil-eating bacteria biodegrade oil that has escaped to the surface.
Oil sands Oil sands, tar sands, crude bitumen, or bituminous sands, are a type of unconventional oil, unconventional petroleum deposit. Oil sands are either loose sands or partially consolidated sandstone containing a naturally occurring mixture of s ...
are reservoirs of partially biodegraded oil still in the process of escaping and being biodegraded, but they contain so much migrating oil that, although most of it has escaped, vast amounts are still present—more than can be found in conventional oil reservoirs. The lighter fractions of the crude oil are destroyed first, resulting in reservoirs containing an extremely heavy form of crude oil, called crude bitumen in Canada, or extra-heavy crude oil in
Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many Federal Dependencies of V ...
. These two countries have the world's largest deposits of oil sands. On the other hand, oil shales are source rocks that have not been exposed to heat or pressure long enough to convert their trapped hydrocarbons into crude oil. Technically speaking, oil shales are not always shales and do not contain oil, but are fined-grain sedimentary rocks containing an insoluble organic solid called kerogen. The kerogen in the rock can be converted into crude oil using heat and pressure to simulate natural processes. The method has been known for centuries and was patented in 1694 under British Crown Patent No. 330 covering, "A way to extract and make great quantities of pitch, tar, and oil out of a sort of stone." Although oil shales are found in many countries, the United States has the world's largest deposits.


Classification

The
petroleum industry The petroleum industry, also known as the oil industry or the oil patch, includes the global processes of hydrocarbon exploration, exploration, extraction of petroleum, extraction, oil refinery, refining, Petroleum transport, transportation (of ...
generally classifies crude oil by the geographic location it is produced in (e.g., West Texas Intermediate, Brent, or
Oman Oman ( ; ar, عُمَان ' ), officially the Sultanate of Oman ( ar, سلْطنةُ عُمان ), is an Arabian country located in southwestern Asia. It is situated on the southeastern coast of the Arabian Peninsula, and spans the mouth of t ...
), its API gravity (an oil industry measure of density), and its sulfur content. Crude oil may be considered ''
light Light or visible light is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequency, fr ...
'' if it has low density, '' heavy'' if it has high density, or ''medium'' if it has a density between that of ''light'' and ''heavy''. Additionally, it may be referred to as '' sweet'' if it contains relatively little sulfur or ''
sour The gustatory system or sense of taste is the sensory system that is partially responsible for the perception of taste (flavor). Taste is the perception produced or stimulated when a substance in the mouth biochemistry, reacts chemically with ta ...
'' if it contains substantial amounts of sulfur. The geographic location is important because it affects transportation costs to the refinery. ''Light'' crude oil is more desirable than ''heavy'' oil since it produces a higher yield of gasoline, while ''sweet'' oil commands a higher price than ''sour'' oil because it has fewer environmental problems and requires less refining to meet sulfur standards imposed on fuels in consuming countries. Each crude oil has unique molecular characteristics which are revealed by the use of Crude oil assay analysis in petroleum laboratories. Barrels from an area in which the crude oil's molecular characteristics have been determined and the oil has been classified are used as pricing
references Reference is a relationship between objects in which one object designates, or acts as a means by which to connect to or link to, another object. The first object in this relation is said to ''refer to'' the second object. It is called a ''name'' ...
throughout the world. Some of the common reference crudes are: * West Texas Intermediate (WTI), a very high-quality, sweet, light oil delivered at Cushing, Oklahoma for North American oil * Brent Blend, consisting of 15 oils from fields in the Brent and Ninian systems in the East Shetland Basin of the
North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea, epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the ...
. The oil is landed at Sullom Voe terminal in
Shetland Shetland, also called the Shetland Islands and formerly Zetland, is a subarctic archipelago in Scotland lying between Orkney, the Faroe Islands and Norway. It is the northernmost region of the United Kingdom. The islands lie about to the no ...
. Oil production from Europe, Africa and Middle Eastern oil flowing West tends to be priced off this oil, which forms a benchmark * Dubai-Oman, used as benchmark for Middle East sour crude oil flowing to the Asia-Pacific region * Tapis (from
Malaysia Malaysia ( ; ) is a country in Southeast Asia. The federation, federal constitutional monarchy consists of States and federal territories of Malaysia, thirteen states and three federal territories, separated by the South China Sea into two r ...
, used as a reference for light Far East oil) * Minas (from
Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. It consists of over List of islands of Indonesia, 17,000 islands, including Sumatr ...
, used as a reference for heavy Far East oil) * The OPEC Reference Basket, a weighted average of oil blends from various
OPEC The Organization of the Petroleum Exporting Countries (OPEC, ) is a cartel of countries. Founded on 14 September 1960 in Baghdad by the first five members (Iran, Iraq, Kuwait, Saudi Arabia, and Venezuela), it has, since 1965, been headquart ...
(The Organization of the Petroleum Exporting Countries) countries * Midway Sunset Heavy, by which heavy oil in California is priced * Western Canadian Select the benchmark crude oil for emerging heavy, high TAN (acidic) crudes. There are declining amounts of these benchmark oils being produced each year, so other oils are more commonly what is actually delivered. While the reference price may be for West Texas Intermediate delivered at Cushing, the actual oil being traded may be a discounted Canadian heavy oil—Western Canadian Select—delivered at Hardisty,
Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada, provinces and territories of Canada. It is part of Western Canada and is one of the three Canadian Prairies, prairie provinces. Alberta is bordered by British Columbia to t ...
, and for a Brent Blend delivered at Shetland, it may be a discounted Russian Export Blend delivered at the port of Primorsk. Once extracted, oil is refined and separated, most easily by
distillation Distillation, or classical distillation, is the process of separation process, separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distilla ...
, into numerous products for direct use or use in manufacturing, such as
petrol Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most Spark-ignition engine, spark-ignited internal combustion engines (also known as petrol engines). It consists ...
(gasoline), diesel and
kerosene Kerosene, paraffin, or lamp oil 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 el, κηρός (''keros' ...
to
asphalt Asphalt, also known as bitumen (, ), is a sticky, black, highly viscosity, viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a Pitch (resin), pitch. Before the ...
and chemical
reagent In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...
s (
ethylene Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon-carbon double ...
,
propylene Propylene, also known as propene, is an Unsaturated compound, unsaturated organic compound with the chemical formula CH3CH=CH2. It has one double bond, and is the second simplest member of the alkene class of hydrocarbons. It is a colorless gas ...
, butene,
acrylic acid Acrylic acid (IUPAC: propenoic acid) is an organic compound with the formula CH2=CHCOOH. It is the simplest unsaturated compound, unsaturated carboxylic acid, consisting of a vinyl group connected directly to a carboxylic acid terminus. This colo ...
, para-xylene) used to make
plastic Plastics are a wide range of synthetic polymers, synthetic or semi-synthetic materials that use polymers as a main ingredient. Their Plasticity (physics), plasticity makes it possible for plastics to be Injection moulding, moulded, Extrusion, e ...
s,
pesticide Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, ...
s and
pharmaceuticals A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, treat, or preventive medicine, prevent disease. Drug therapy (pharmacotherapy) is an imp ...
.


Industry


Transport

In the 1950s, shipping costs made up 33 percent of the price of oil transported from the
Persian Gulf The Persian Gulf ( fa, خلیج فارس, translit=xalij-e fârs, lit=Gulf of Persis, Fars, ), sometimes called the ( ar, اَلْخَلِيْجُ ٱلْعَرَبِيُّ, Al-Khalīj al-ˁArabī), is a Mediterranean sea (oceanography), me ...
to the United States, but due to the development of supertankers in the 1970s, the cost of shipping dropped to only 5 percent of the price of Persian oil in the US. Due to the increase of the value of the crude oil during the last 30 years, the share of the shipping cost on the final cost of the delivered commodity was less than 3% in 2010.


Price


Trade

Crude oil is traded as a future on the Nymex exchange. Futures contracts are agreements in which buyers and sellers agree to purchase and deliver specific amounts of physical crude oil on a given date in the future. Each contract covers 1000 barrels and can be purchased up to nine years into the future. Below are the contract specifications for crude oil:


Uses

The chemical structure of petroleum is
heterogeneous Homogeneity and heterogeneity are concepts often used in the sciences and statistics relating to the Uniformity (chemistry), uniformity of a Chemical substance, substance or organism. A material or image that is homogeneous is uniform in compos ...
, composed of hydrocarbon chains of different lengths. Because of this, petroleum may be taken to oil refineries and the hydrocarbon chemicals separated by
distillation Distillation, or classical distillation, is the process of separation process, separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distilla ...
and treated by other
chemical process In a Process (science), scientific sense, a chemical process is a method or means of somehow changing one or more chemicals or chemical compounds. Such a chemical process can occur by itself or be caused by an outside force, and involves a chemic ...
es, to be used for a variety of purposes. The total cost per plant is about 9 billion dollars.


Fuels

The most common distillation fractions of petroleum are
fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work (physics), work. The concept was originally applied solely to those materials capable of releasing chem ...
s. Fuels include (by increasing boiling temperature range): Petroleum classification according to chemical composition.


Other derivatives

Certain types of resultant hydrocarbons may be mixed with other non-hydrocarbons, to create other end products: *
Alkenes In organic chemistry Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms th ...
(olefins), which can be manufactured into plastics or other compounds *
Lubricant A lubricant (sometimes shortened to lube) is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, t ...
s (produces light machine oils,
motor oil Motor oil, engine oil, or engine lubricant is any one of various substances used for the lubrication of internal combustion engines. They typically consist of base oils enhanced with various additives, particularly antiwear additives, detergen ...
s, and greases, adding
viscosity The viscosity of a fluid is a measure of its drag (physics), resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quant ...
stabilizers as required) * Wax, used in the packaging of
frozen food Freezing food preserves it from the time it is prepared to the time it is eaten. Since early times, farmers, fishermen, and trappers have preserved grains and produce in unheated buildings during the winter season. Freezing food slows decompositi ...
s, among others *
Sulfur Sulfur (or sulphur in British English British English (BrE, en-GB, or BE) is, according to Oxford Dictionaries, " English as used in Great Britain, as distinct from that used elsewhere". More narrowly, it can refer specifically to the ...
or
sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen ...
. These are useful industrial materials. Sulfuric acid is usually prepared as the acid precursor oleum, a byproduct of sulfur removal from fuels. * Bulk
tar Tar is a dark brown or black viscosity, viscous liquid of hydrocarbons and free carbon, obtained from a wide variety of organic matter, organic materials through destructive distillation. Tar can be produced from coal, wood, petroleum, or peat. ...
*
Asphalt Asphalt, also known as bitumen (, ), is a sticky, black, highly viscosity, viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a Pitch (resin), pitch. Before the ...
* Petroleum coke, used in speciality carbon products or as solid fuel *
Paraffin wax Paraffin wax (or petroleum wax) is a soft colorless solid derived from petroleum, coal, or oil shale that consists of a mixture of hydrocarbon molecules containing between 20 and 40 carbon atoms. It is solid at room temperature and melting poin ...
*
Aromatic In chemistry, aromaticity is a chemical property of cyclic compound, cyclic (ring (chemistry), ring-shaped), ''typically'' plane (geometry), planar (flat) molecular structures with pi bonds in Resonance (chemistry), resonance (those containing ...
petrochemical Petrochemicals (sometimes abbreviated as petchems) are the product (chemistry), chemical products obtained from petroleum by refining. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural ...
s to be used as precursors in other
chemical A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent Chemical element, elements by physical separation m ...
production


Use by country


Consumption statistics

File:Global Carbon Emissions.svg, Global fossil carbon emissions, an indicator of consumption, from 1800. File:World energy consumption.svg, Rate of world energy usage per year from 1970.BP
Statistical Review of World Energy
, Workbook (xlsx), London, 2012
File:Oil consumption per day by region from 1980 to 2006.svg, Daily oil consumption from 1980 to 2006. File:Oil consumption per day by region from 1980 to 2006 solid3.svg, Oil consumption by percentage of total per region from 1980 to 2006: . File:World oil consumption 1980 to 2007 by region.svg, Oil consumption 1980 to 2007 by region.


Consumption

According to the US Energy Information Administration (EIA) estimate for 2017, the world consumes 98.8 million barrels of oil each day. This table orders the amount of petroleum consumed in 2011 in thousand barrels (1000 bbl) per day and in thousand cubic metres (1000 m3) per day: Source
US Energy Information Administration
Population Data: 1 peak production of oil already passed in this state 2 This country is not a major oil producer


Production

In petroleum industry parlance, ''production'' refers to the quantity of crude extracted from reserves, not the literal creation of the product.


Exportation

In order of net exports in 2011, 2009 and 2006 in thousand bbl/ d and thousand m3/d: Source
US Energy Information Administration
1 peak production already passed in this state 2 Canadian statistics are complicated by the fact it is both an importer and exporter of crude oil, and refines large amounts of oil for the U.S. market. It is the leading source of U.S. imports of oil and products, averaging in August 2007. Total world production/consumption (as of 2005) is approximately .


Importation

In order of net imports in 2011, 2009 and 2006 in thousand bbl/ d and thousand m3/d: Source
US Energy Information Administration


Non-producing consumers

Countries whose oil production is 10% or less of their consumption. Source


Environmental effects


Climate change

, about a quarter of annual global
greenhouse gas emissions Greenhouse gas emissions from human activities strengthen the greenhouse effect, contributing to climate change. Most is carbon dioxide from burning fossil fuels: coal, petroleum, oil, and natural gas. The top contributors to greenhouse gas emi ...
is the carbon dioxide from burning petroleum (plus methane leaks from the industry). Along with the burning of coal, petroleum combustion is the largest contributor to the increase in atmospheric CO2. Atmospheric CO2 has risen over the last 150 years to current levels of over 415  ppmv, from the 180–300 ppmv of the prior 800 thousand years. The rise in Arctic temperature has reduced the minimum
Arctic ice pack The Arctic ice pack is the sea ice cover of the Arctic Ocean and its vicinity. The Arctic ice pack undergoes a regular seasonal cycle in which ice melts in spring and summer, reaches a minimum around mid-September, then increases during fall a ...
to , a loss of almost half since satellite measurements started in 1979.
Ocean acidification Ocean acidification is the reduction in the pH value of the Earth’s ocean. Between 1751 and 2021, the average pH value of the ocean surface has decreased from approximately 8.25 to 8.14. The root cause of ocean acidification is carbon dioxide ...
is the increase in the acidity of the Earth's oceans caused by the uptake of
carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon Carbon () is a chemical element with the chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetraval ...
() from the
atmosphere An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...
. This increase in acidity inhibits all marine life—having a greater impact on smaller organisms as well as shelled organisms (see scallops).


Extraction

Oil extraction is simply the removal of oil from the reservoir (oil pool). Oil is often recovered as a water-in-oil emulsion, and specialty chemicals called demulsifiers are used to separate the oil from water. Oil extraction is costly and often environmentally damaging. Offshore exploration and extraction of oil disturb the surrounding marine environment.


Oil spills

Crude oil and refined fuel spills from
tanker ship A tanker (or tank ship or tankship) is a ship designed to transport or store liquids or gases in Bulk liquids, bulk. Major types of tankship include the oil tanker, the chemical tanker, and gas carrier. Tankers also carry commodities such as ve ...
accidents have damaged natural
ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
s and human livelihoods in
Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Central Alaskan Yup'ik language, Yup'ik: ''Alaskaq''; tli, Anáaski) is a U.S. state, state located in the Western United States on the northwest extremity o ...
, the
Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United ...
, the Galápagos Islands, France and many other places. The quantity of oil spilled during accidents has ranged from a few hundred tons to several hundred thousand tons (e.g.,
Deepwater Horizon oil spill The ''Deepwater Horizon'' oil spill (also referred to as the "BP oil spill") was an industrial disaster that began on 20 April 2010 off of the coast of the United States in the Gulf of Mexico on the BP-operated Macondo Prospect, considered ...
, SS Atlantic Empress,
Amoco Cadiz ''Amoco Cadiz'' was a VLCC (very large crude carrier) owned by Amoco, Amoco Transport Corp and transporting crude oil for Royal Dutch Shell, Shell Oil. Operating under the Liberian flag of convenience, she ran aground on 16 March 1978 on Portsal ...
). Smaller spills have already proven to have a great impact on ecosystems, such as the ''Exxon Valdez'' oil spill. Oil spills at sea are generally much more damaging than those on land, since they can spread for hundreds of nautical miles in a thin oil slick which can cover beaches with a thin coating of oil. This can kill sea birds, mammals, shellfish and other organisms it coats. Oil spills on land are more readily containable if a makeshift earth dam can be rapidly bulldozed around the spill site before most of the oil escapes, and land animals can avoid the oil more easily. Control of oil spills is difficult, requires ad hoc methods, and often a large amount of manpower. The dropping of bombs and incendiary devices from aircraft on the wreck produced poor results; modern techniques would include pumping the oil from the wreck, like in the ''Prestige'' oil spill or the ''Erika'' oil spill. Though crude oil is predominantly composed of various hydrocarbons, certain nitrogen heterocyclic compounds, such as
pyridine Pyridine is a basic (chemistry), basic heterocyclic compound, heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom. It is a highly flammable, weakl ...
,
picoline Picoline refers to any of three isomerism, isomers of methylpyridine (CH3C5H4N). They are all colorless liquids with a characteristic smell similar to that of pyridine. They are miscible with water and most organic solvents. The CAS registry numb ...
, and quinoline are reported as contaminants associated with crude oil, as well as facilities processing oil shale or coal, and have also been found at legacy wood treatment sites. These compounds have a very high water solubility, and thus tend to dissolve and move with water. Certain naturally occurring bacteria, such as '' Micrococcus'', '' Arthrobacter'', and '' Rhodococcus'' have been shown to degrade these contaminants. Because petroleum is a naturally occurring substance, its presence in the environment need not be the result of human causes such as accidents and routine activities (
seismic Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "Earthquake, earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes and the propagation of Linear elasticity#Elastic wave, elast ...
exploration,
drilling Drilling is a cutting process where a drill bit is spun to cut a hole of circular cross section (geometry), cross-section in solid materials. The drill bit is usually a rotary Cutting tool (machining), cutting tool, often multi-point. The bit i ...
, extraction, refining and combustion). Phenomena such as seeps and
tar pit Tar pits, sometimes referred to as asphalt pits, are large asphalt deposits. They form in the presence of oil, which is created when decayed organic matter is subjected to pressure underground. If this crude oil seeps upward via fractures, condu ...
s are examples of areas that petroleum affects without man's involvement.


Tarballs

A tarball is a blob of crude oil (not to be confused with
tar Tar is a dark brown or black viscosity, viscous liquid of hydrocarbons and free carbon, obtained from a wide variety of organic matter, organic materials through destructive distillation. Tar can be produced from coal, wood, petroleum, or peat. ...
, which is a man-made product derived from pine trees or refined from petroleum) which has been weathered after floating in the ocean. Tarballs are an aquatic
pollutant A pollutant or novel entity is a substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource. These can be both naturally forming (i.e. minerals or extracted compounds like Ex ...
in most environments, although they can occur naturally, for example in the Santa Barbara Channel of California or in the Gulf of Mexico off Texas. Their concentration and features have been used to assess the extent of oil spills. Their composition can be used to identify their sources of origin, and tarballs themselves may be dispersed over long distances by deep sea currents. They are slowly decomposed by bacteria, including '' Chromobacterium violaceum'', '' Cladosporium resinae'', '' Bacillus submarinus'', '' Micrococcus varians'', '' Pseudomonas aeruginosa'', '' Candida marina'' and '' Saccharomyces estuari''.


Whales

James S. Robbins has argued that the advent of petroleum-refined kerosene saved some species of great whales from
extinction Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the Endling, last individual of the species, although the Functional ext ...
by providing an inexpensive substitute for
whale oil Whale oil is oil obtained from the blubber of whales. Whale oil from the bowhead whale was sometimes known as train oil, which comes from the Dutch word ''traan'' ("tears, tear" or "drop"). Sperm oil, a special kind of oil obtained from the ...
, thus eliminating the economic imperative for open-boat
whaling Whaling is the process of hunting of whales for their usable products such as Whale meat, meat and blubber, which can be turned into Whale oil, a type of oil that became increasingly important in the Industrial Revolution. It was practiced as a ...
, but others say that fossil fuels increased whaling with most whales being killed in the 20th century.


Alternatives

In 2018 road transport used 49% of petroleum, aviation 8%, and uses other than energy 17%.
Electric vehicle An electric vehicle (EV) is a vehicle that uses one or more traction motor, electric motors for propulsion. It can be powered by a Current collector, collector system, with electricity from extravehicular sources, or it can be powered autonom ...
s are the main alternative for road transport and biojet for aviation. Single-use plastics have a high carbon footprint and may pollute the sea, but as of 2022 the best alternatives are unclear.


International relations

Control of petroleum production has been a significant driver of international relations during much of the 20th and 21st centuries. Organizations like OPEC have played an outsized role in international politics. Some historians and commentators have called this the " Age of Oil" With the rise of
renewable energy Renewable energy is energy that is collected from renewable resources that are naturally replenished on a Orders of magnitude (time), human timescale. It includes sources such as Solar power, sunlight, wind power, wind, the movement of Hydropo ...
and addressing
climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate variability and change, Climate change in a broader sense also includes ...
some commentators expect a realignment of international power away from petrostates.


Corruption

"Oil rents" have been described as connected with corruption in political literature. A 2011 study suggested that increases in oil rents increased corruption in countries with heavy government involvement in the production of oil. The study found that increases in oil rents "significantly deteriorates political rights". The researchers noted oil exploitation gave politicians "an incentive to extend civil liberties but reduce political rights in the presence of oil windfalls to evade redistribution and conflict".


Conflict

Petroleum production can be linked with conflict: whether through direct aggression, trade wars such as the 2020 Russia–Saudi Arabia oil price war, or by indirectly funding aggressors, such as the
Islamic State of Iraq and the Levant An Islamic state is a State (polity), state that has a form of government based on sharia, Islamic law (sharia). As a term, it has been used to describe various historical Polity, polities and theories of governance in the Islamic world. As a t ...
.


OPEC


Future production

Consumption in the twentieth and twenty-first centuries has been abundantly pushed by automobile sector growth. The 1985–2003 oil glut even fueled the sales of low fuel economy vehicles in
OECD The Organisation for Economic Co-operation and Development (OECD; french: Organisation de coopération et de développement économiques, ''OCDE'') is an intergovernmental organization, intergovernmental organisation with 38 member countries ...
countries. The 2008 economic crisis seems to have had some impact on the sales of such vehicles; still, in 2008 oil consumption showed a small increase. In 2016 Goldman Sachs predicted lower demand for oil due to emerging economies concerns, especially China. The
BRICS BRICS is an acronym for five leading Emerging market, emerging economies: Brazil, Brazil, Russia, Russia, India, India, China, China, and South Africa, South Africa. The first four were initially grouped as "BRIC" (or "the BRICs") in 2001 by G ...
(Brasil, Russia, India, China, South Africa) countries might also kick in, as China briefly had the largest automobile market in December 2009. In the long term, uncertainties linger; the
OPEC The Organization of the Petroleum Exporting Countries (OPEC, ) is a cartel of countries. Founded on 14 September 1960 in Baghdad by the first five members (Iran, Iraq, Kuwait, Saudi Arabia, and Venezuela), it has, since 1965, been headquart ...
believes that the OECD countries will push low consumption policies at some point in the future; when that happens, it will definitely curb oil sales, and both OPEC and the
Energy Information Administration The U.S. Energy Information Administration (EIA) is a principal agency of the Federal Statistical System of the United States, U.S. Federal Statistical System responsible for collecting, analyzing, and disseminating energy information to promote ...
(EIA) kept lowering their 2020 consumption estimates during the past five years. A detailed review of
International Energy Agency The International Energy Agency (IEA) is a Paris-based autonomous Intergovernmental organization, intergovernmental organisation, established in 1974, that provides policy recommendations, analysis and data on the entire global energy sector, wit ...
oil projections have revealed that revisions of world oil production, price and investments have been motivated by a combination of demand and supply factors. All together, Non-OPEC conventional projections have been fairly stable the last 15 years, while downward revisions were mainly allocated to OPEC. Recent upward revisions are primarily a result of US tight oil. Production will also face an increasingly complex situation; while OPEC countries still have large reserves at low production prices, newly found reservoirs often lead to higher prices; offshore giants such as Tupi, Guara and
Tiber The Tiber ( ; it, Tevere ; la, Tiberis) is the third-longest List of rivers of Italy, river in Italy and the longest in Central Italy, rising in the Apennine Mountains in Emilia-Romagna and flowing through Tuscany, Umbria, and Lazio, where ...
demand high investments and ever-increasing technological abilities. Subsalt reservoirs such as Tupi were unknown in the twentieth century, mainly because the industry was unable to probe them. Enhanced Oil Recovery (EOR) techniques (example: DaQing, China) will continue to play a major role in increasing the world's recoverable oil. The expected availability of petroleum resources has always been around 35 years or even less since the start of the modern exploration. The oil constant, an insider pun in the German industry, refers to that effect. A growing number of divestment campaigns from major funds pushed by newer generations who question the sustainability of petroleum may hinder the financing of future oil prospection and production.


Peak oil

Peak oil is a term applied to the projection that future petroleum production (whether for individual oil wells, entire oil fields, whole countries, or worldwide production) will eventually peak and then decline at a similar rate to the rate of increase before the peak as these reserves are exhausted. The peak of oil discoveries was in 1965, and oil production per year has surpassed oil discoveries every year since 1980. However, this does not mean that potential oil production has surpassed oil demand. It is difficult to predict the oil peak in any given region, due to the lack of knowledge and/or transparency in accounting of global oil reserves. Based on available production data, proponents have previously predicted the peak for the world to be in years 1989, 1995, or 1995–2000. Some of these predictions date from before the recession of the early 1980s, and the consequent lowering in global consumption, the effect of which was to delay the date of any peak by several years. Just as the 1971 U.S. peak in oil production was only clearly recognized after the fact, a peak in world production will be difficult to discern until production clearly drops off. In 2020, according to BP's Energy Outlook 2020, peak oil had been reached, due to the changing energy landscape coupled with the economic toll of the COVID-19 pandemic. While there has been much focus historically on peak oil supply, focus is increasingly shifting to peak demand as more countries seek to transition to renewable energy. The GeGaLo index of geopolitical gains and losses assesses how the geopolitical position of 156 countries may change if the world fully transitions to renewable energy resources. Former oil exporters are expected to lose power, while the positions of former oil importers and countries rich in renewable energy resources is expected to strengthen.


Unconventional oil

Unconventional oil] is petroleum produced or extracted using techniques other than the conventional methods. The calculus for peak oil has changed with the introduction of unconventional production methods. In particular, the combination of horizontal drilling and
hydraulic fracturing Fracking (also known as hydraulic fracturing, hydrofracturing, or hydrofracking) is a well stimulation technique involving the fracturing of bedrock Formation (geology), formations by a pressurized liquid. The process involves the high-pressure ...
has resulted in a significant increase in production from previously uneconomic plays. Analysts expected that $150 billion would be spent on further developing North American tight oil fields in 2015. The large increase in tight oil production is one of the reasons behind the price drop in late 2014. Certain rock strata contain hydrocarbons but have low permeability and are not thick from a vertical perspective. Conventional vertical wells would be unable to economically retrieve these hydrocarbons. Horizontal drilling, extending horizontally through the strata, permits the well to access a much greater volume of the strata. Hydraulic fracturing creates greater permeability and increases hydrocarbon flow to the wellbore.


Hydrocarbons on other worlds

On Saturn's largest moon, Titan, lakes of liquid hydrocarbons comprising methane, ethane, propane and other constituents, occur naturally. Data collected by the space probe '' Cassini–Huygens'' yield an estimate that the visible lakes and seas of Titan contain about 300 times the volume of Earth's proven oil reserves. Drilled samples from the surface of
Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin atmosph ...
taken in 2015 by the ''Curiosity'' rover's
Mars Science Laboratory Mars Science Laboratory (MSL) is a robotic spacecraft, robotic space probe mission to Mars launched by NASA on November 26, 2011, which successfully landed ''Curiosity (rover), Curiosity'', a Mars rover, in Gale (crater), Gale Crater on August ...
have found organic molecules of
benzene Benzene is an Organic compound, organic chemical compound with the Chemical formula#Molecular formula, molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar Ring (chemistry), ring with one hydrogen atom ...
and
propane Propane () is a three-carbon alkane with the molecular formula . It is a gas at standard temperature and pressure, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used as ...
in 3-billion-year-old rock samples in Gale Crater.


In fiction


See also

* Barrel of oil equivalent *
Filling station A filling station, also known as a gas station () or petrol station (), is a facility that sells fuel and engine lubricants for motor vehicles. The most common fuels sold in the 2010s were gasoline (or petrol) and diesel fuel. Gasoline ...
* Gas oil ratio * List of oil exploration and production companies * List of oil fields * Manure-derived synthetic crude oil * Oil burden *
Petroleum geology Petroleum geology is the study of origin, occurrence, movement, accumulation, and exploration of Hydrocarbon fuel, hydrocarbon fuels. It refers to the specific set of geological disciplines that are applied to the search for hydrocarbons (oil expl ...
* Petroleum politics * Petrocurrency * Thermal depolymerization * Total petroleum hydrocarbon *
Waste oil Waste oil is defined as any petroleum-based or synthetic oil that, through contamination, has become unsuitable for its original purpose due to the presence of impurities or loss of original properties. Differentiating between "waste oil" and "use ...
* Unconventional (oil & gas) reservoir


Citations


Explanatory footnotes


General and cited references

* * translated 1955 * * * * * * * Mirbabayev M.F.(2017).Brief history of the first drilled oil well;and the people involved.-"Oil-Industry History"(US),vol.18,#1, p. 25-34.


Further reading

* Juhasz, Antonia, "The End of OIL?: The
pandemic A pandemic () is an epidemic of an infectious disease that has spread across a large region, for instance multiple continents or worldwide, affecting a substantial number of individuals. A widespread endemic (epidemiology), endemic disease wi ...
has battered an already struggling oil industry. Whether it survives is up to us", '' Sierra Magazine'', vol. 105, no. 5 (September / October 2020), pp. 36–40, 51. *


External links


Global Fossil Infrastructure Tracker

API – the trade association of the US oil industry.
(
American Petroleum Institute The American Petroleum Institute (API) is the largest U.S. trade association for the oil and natural gas industry. It claims to represent nearly 600 corporations involved in extraction of petroleum, production, oil refinery, refinement, pipeline ...
)
U.S. Energy Information Administration
*

* Oil and Gas Data Transparency
U.S. National Library of Medicine: Hazardous Substances Databank – Crude Oil

Best Dubai Desert Safari Deals
*
A Short History of Petroleum
,
Scientific American ''Scientific American'', informally abbreviated ''SciAm'' or sometimes ''SA'', is an American popular science magazine. Many famous scientists, including Albert Einstein and Nikola Tesla, have contributed articles to it. In print since 1845, it i ...
, 10 August 1878, p. 85 {{Authority control Causes of war Chemical mixtures Glassforming liquids and melts