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Petroleum

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[[Nodding donkey
pumping an oil well near Sarnia, Ontario, 2001]]

Petroleum (from Latin petrus–rock and oleum–oil) or mineral oil is a thick, dark brown or greenish flammable liquid, which, at certain points, exists in the upper strata of 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 Petroleum properties. It can be shortened to the prefix petro-, as in "petrodiesel".

Table of contents
1 Formation
2 Composition
3 Petroleum history
4 List of petroleum companies
5 See also
6 External link

Formation

There are two primary theories of the origin of oil.

The biogenic theory, which is supported by most petroleum geologists, is based upon the burial of dead biological matter, which breaks down to a waxy material known as kerogen. Under the influence of heat and pressure, kerogen breaks down first into liquids and to gases.

The abiogenic petroleum origin theory is based upon large amounts of carbon existing in the planet, some of which are hydrocarbons. Hydrocarbons are lighter than rocks so it seeps upward. Deep microbial life converts it to various hydrocarbon deposits.

For details, see the article: fossil fuel.

Composition

Petroleum comes from carbon deposits exposed to great pressure and heat. Both the liquid oil (petroleum) and gas phases (natural gas) tend to migrate through porous rocks until they encounter impermeable beds where packets/pools will tend to collect. After a drilling and pumping process to extract it from the strata, petroleum is refined by distillation. The products based on refined crude oil include kerosene, benzene, gasoline, paraffin wax, asphalt, etc.

Strictly speaking, petroleum consists entirely of aliphatic hydrocarbons, those composed of nothing but hydrogen and carbon.

The four lightest hydrocarbons -- 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:

Petroleum history

Petroleum's worth as a portable, dense energy source (powering the vast majority of vehicles (automobiles, trucks, trains, ships, aircraft) and as the base of many industrial chemicals makes it one of the world's most important commodities. Access to it was a major factor in several military conflicts, including World War Two and the Gulf War. Much of the world's readily accessible reserves are located in the Middle East, a politically unstable region.

Oil field in California, 1938

The petroleum industry was initialized by Edwin Drake in the 1850s, near Titusville, Pennsylvania. The industry grew slowly in the 1800s and did not become a real national concern until the early part of the 20th century; the introduction of the internal combustion engine provided a demand that has largely sustained the industry to this day. Early "local" finds like those in Pennsylvania and Ontario were quickly exhausted, leading to "oil booms" in Texas, Oklahoma, and California. Other countries had sizable oil reserves as a part of their colonial holdings, and started to develop them at an industrial level.

While even in 1955 coal was still the world's foremost fuel, oil began to take over. Today about 90% of fuel needs are met by oil. Following the 1973 energy crisis and the 1979 energy crisis there was significant media coverage of oil supply levels. This brought to light the concern that oil is a limited resource that we will eventually run out of, at least as an economically viable energy source. At the time, the most common and popular predictions were always quite dire, and when they did not come true, many dismissed all such discussion. The future of petroleum as a fuel remains somewhat controversial. Some would argue that because the total amount of petroleum is finite, the dire predictions of the 1970s have merely been postponed. Others argue that technology will continue to allow for the production of cheap hydrocarbons and that the earth has vast sources of unconventional petroleum reserves in the form of tar sands, bitumen fields, oil shale, and methyl hydrate that will allow for petroleum use to continue for an extremely long period in the future.

The presence of the oil industry has significant social and environmental impacts, from accidents and from routine activities such as seismic exploration, drilling, and generation of polluting wastes. Oil extraction is costly and often environmentally damaging. Offshore exploration and extraction of oil disturbs the surrounding marine environment. Extraction may involve dredging, which stirs up the sea bed, killing the sea plants that marine creatures need to survive. Crude oil and refined fuel spills from tanker ship accidents have damaged fragile ecosystems in Alaska, the Galapagos Islands, Spain, and many other places. Renewable energy source alternatives do exist, although the degree to which they can replace petroleum and the possible environmental damage they may cause is controversial.

List of petroleum companies

See also

External link