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Petroleum (from Latin petrus – rock and oleum – oil), mineral oil, or crude oil, sometimes colloquially called black gold, is a thick, dark brown or greenish flammable liquid, which exists in the upper strata of some areas of the Earth's crust. It consists of a complex mixture of various hydrocarbons, largely of the methane series, but may vary much in appearance, composition, and purity. It can be referenced with the prefix petro-, as in " petrodiesel".
Most geologists view crude oil, like coal and natural gas, as the product of compression of ancient vegetation over geological timescales. According to this theory, it was formed from the decayed remains of prehistoric marine animals and terrestrial plants. Over many centuries this organic matter, mixed with mud, was buried under thick sedimentary layers of material. The resulting high levels of heat and pressure caused the remains to metamorphose, first into a waxy material known as kerogenKerogens are chemical compounds formed by the low-grade metamorphism (i. diagenesis) of organic molecules derived from decaying plant and animal matter. Kerogens are the precursors to hydrocarbons ( fossil fuels). Labile kerogen breaks down to form heavy, and then into liquid and gaseous hydrocarbons. These then moved through adjacent rock layers until they became trapped underground in porous rocks called reservoirs, forming an oil fieldDrilling in a small oil fieldNear Sarnia, Ontario, 2001 An oil field is an area with an abundance of wells extracting petroleum (oil) from below ground. Because the underground formations containing oil typically extend over a large area, possibly several, from which the liquid can be extracted by drilling and pumping.
A few scientists, notably Thomas GoldThomas Gold ( May 22 1920 June 22 2004) was an Austrian astrophysicist and a member of the US National Academy of Sciences. Astrophysics Gold carried out research on cosmology and on magnetic fields, and coined the term " magnetosphere" for the Earth's ma, have suggested other, abiogenicThe theory of abiogenic petroleum origin states that petroleum is produced by non-biological processes deep in the Earth. This stands in contrast to the more widely held view that it is created from the fossilization of ancient organic matter. According t, theories for the origins of crude oil. This theory suggests that large amounts of carbon exist naturally in the planet, some in the form of hydrocarbons. Hydrocarbons are lighter than rocks so they seep upward. Deep microbial life convert them into the various hydrocarbon deposits.
There is also a new theory, presented in Scientific AmericanScientific American is one of the oldest and most serious popular-science magazines. Founded by Rufus Porter, Scientific American has been published monthly since August 28, 1845. Among science periodicals, Scientific American (informally abbreviated to S in 2003, which proposes that hydrocarbons are generated by active nuclearIn physics, fission is a nuclear process, meaning it occurs in the nucleus of an atom. Fission is when the nucleus splits into two or more smaller nuclei plus some by-products. These by-products include free neutrons and photons (usually gamma rays). activity in the Earth's core.
The component chemicals of petroleum are separated by distillationDistillation is a means of separating liquids through differences in their boiling points. Known since antiquity, the concentration of alcohol by the application of heat to a fermented liquid mixture is perhaps the oldest form of distillation. However, th. Products based on refined crude oil include kerosene, benzene, gasoline, paraffin wax, asphalt, etc.
Strictly speaking, petroleum consists entirely of hydrocarbons, compounds of hydrogen and carbon.
The four lightest alkanes — CH4 ( methane), C2H6 ( ethane), C3H8 ( propane) and C4H10 ( butane) — are all gases, boiling at -107°C, -67°C, -43°C, and -18°C, respectively (-161°, -88°, -46°, and -1° degrees F).
The chains in the C5-7 range are all light, easily vaporized, clear naphthas. They are used as solvents, dry cleaning fluids, and other quick-drying products. The chains from C6H14 through C12H26 are blended together and used for gasoline. Kerosene is made up of chains in the C10 to C15 range, followed by diesel fuel/heating oil (C10 to C20) and heavier fuel oils as the ones used in ship engines. These petroleum compounds are all liquid at room temperature.
Lubricating oils and semi-solid greases (including Vaseline®) range from C16 up to C20.
Chains above C20 form solids, starting with paraffin wax, then tar and asphaltic bitumen.
Boiling ranges of petroleum atmospheric pressure distillation fractions in degrees Celsius:
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