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 pPetroleum roperties. It can be shortened to the prefix petro-, as in "petrodiesel".

Table of contents

1 Formation

1.1 Alternative Theories

2 Composition

3 Petroleum History

4 List of Petroleum Companies

5 See also

Formation

Biological material in rocks starts off largely as a waxy material known as kerogen. Under the influence of heat and pressure, kerogen breaks down first into liquids and to gases. 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 include kerosene, benzene, gasoline, paraffin wax, asphalt, etc.

Alternative Theories

Some scientists have proposed that the current understanding of petroleum and its orgins are incomplete. Some Russian scientists propose that petroleum is abiotic in nature. This theory also argues that oil supplies slowly replenish themselves, and that oil reserves are thus much larger than current estimates. Such theories are not widely accepted in the West.

There is also a new theory, presented in Scientific American, where the mineral origin of oil is discussed. It is based on active nuclear activity in the core of Earth that regenerates hydrocarbons.

Other theories include the regeneration of oil reserves by bacteria, as bacteria are often found in oil reserves despite the environment being anaerobic (preventing the possibility of the petroleum being used as a food source).

Some recent cases have supported alternative theories, such as the White Tiger field in Vietnam, in which oil and natural gas are produced from granite basement rock. Production from fields in which the oil lies in granite are problematic for conventional theories of oil production, because granite is plutonic. Some possible conventional explanations include the oil seeping into such fields from distant rock.

Composition

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 C_5-7 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:

petrol ether: 40 - 70 (used as solvent)
light petrol: 60 - 100 (automobile fuel)
heavy petrol: 100 - 150 (automobile fuel)
light kerosene: 120 - 150 (household solvent and fuel)
kerosene: 150 - 300 (jet engine fuel)
gas oil: 250 - 350 (Diesel fuel/ heating)
lubrication oil: > 300 (engine oil)
remaining fractions: tar, asphalt, residual fuel

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.

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.