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Petroleum (from Latin petra – rock and oleum – oil ) or crude oil (also known as black gold) is a black, dark brown or greenish liquid found in formations in the earth. The American Petroleum Institute, in its Manual of Petroleum Measurement Standards (MPMS), defines it as "a substance, generally liquid, occurring naturally in the earth and composed mainly of mixtures of chemical compounds of carbon and hydrogen with or without other nonmetallic elements such as sulfur, oxygen, and nitrogen." Petroleum is found in porous rock formations in the upper strata of some areas of the Earth's crust. It consists of a complex mixture of hydrocarbons, mostly alkanes, but may vary greatly in appearance and composition. Petroleum is used mostly, by volume, for producing fuel oil and petrol (gasoline), both important "primary energy" sources (IEA Key World Energy Statistics). Petroleum is also the raw material for many chemical products, including solvents, fertilizers, pesticides, and plastics. 84% (37 of 42 gallons in a typical barrel) of all petroleum extracted is processed as fuels, including gasoline, diesel, jet, heating, and other fuel oils, and liquefied petroleum gas the other 16% is converted into other materials such as plastic. Known reserves of petroleum are estimated at around 1000 gigabarrels, (that is, one thousand billion), and consumption is currently around 84 million barrels per day, or 31 gigabarrels per year. At current consumption levels, world oil supply will be gone in about 33 years. As the supply of petroleum becomes more scarce, consumers will look to alternative fuel sources such as ethanol, fuel cells, or clean-burning hydrogen. Petroleum forms naturally within the earth too slowly to be sustainable for human use. Chemistry
Biogenic theory Most geologists view crude oil, like coal and natural gas, as the product of compression and heating of ancient organic materials over geological time. According to this theory, oil is formed from the preserved remains of prehistoric zooplankton and algae which have been settled to the sea bottom in large quantities under anoxic conditions. (Terrestrial plants tend to form coal) Over geological time this organic matter, mixed with mud, is buried under heavy layers of sediment. The resulting high levels of heat and pressure cause the remains to metamorphose, first into a waxy material known as kerogen which is found in various oil shales around the world, and then with more heat into liquid and gaseous hydrocarbons in a process known as catagenesis. Because most hydrocarbons are lighter than rock or water, these sometimes migrate upward through adjacent rock layers until they become trapped beneath impermeable rocks, within porous rocks called reservoirs. Concentration of hydrocarbons in a trap forms an oil field, from which the liquid can be extracted by drilling and pumping. Geologists often refer to an "oil window" which is the temperature range that oil forms in—below the minimum temperature oil remains trapped in the form of kerogen, and above the maximum temperature the oil is converted to natural gas through the process of thermal cracking. Though this happens at different depths in different locations around the world, a 'typical' depth for the oil window might be 4–6 km. Note that even if oil is formed at extreme depths, it may be trapped at much shallower depths, even if it is not formed there. (In the case of the Athabasca Oil Sands, it is found right at the surface.) Three conditions must be present for oil reservoirs to form: first, a source rock rich in organic material buried deep enough for subterranean heat to cook it into oil; second, a porous and permeable reservoir rock for it to accumulate in; and last a cap rock (seal) that prevents it from escaping to the surface. If an oil well were to run dry and be capped, it would likely fill back to its original supply eventually. There is considerable question about how long this would take. Some formations appear to have a regeneration time of decades. Majority opinion is that oil is being formed at less than 1% of the current consumption rate. The vast majority of oil that has been produced by the earth has long ago escaped to the surface and been biodegraded by oil-eating bacteria. What oil companies are looking for is the small fraction that has been trapped by this rare combination of circumstances. Oil sands are reservoirs of partially biodegraded oil still in the process of escaping, but 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. On the other hand, oil shales are source rocks that have never been buried deep enough to convert their trapped kerogen into oil. The reactions that produce oil and natural gas are often modeled as first order breakdown reactions, where kerogen is 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 first set was originally patented in 1694 under British Crown Patent No. 330 covering "a way to extract and make great quantityes of pitch, tarr, and oyle out of a sort of stone." The latter set is regularly used in petrochemical plants and oil refineries. Abiogenic theory The idea of abiogenic petroleum origin was championed in the Western world by astronomer Thomas Gold based on thoughts from Russia, mainly on studies of Nikolai Kudryavtsev. The idea proposes that hydrocarbons of purely geological origin exist in the planet. Hydrocarbons are less dense than aqueous pore fluids, and are proposed to migrate upward through deep fracture networks. Thermophilic, rock-dwelling microbial life-forms are proposed to be in part responsible for the biomarkers found in petroleum. However, this theory is a minority opinion, especially amongst geologists and no oil companies are currently known to explore for oil based on this theory. Extraction Locating an oil field is the first obstacle to be overcome. Today, geologists use seismic surveys to search for geological structures that may form oil reservoirs. The "classic" method includes making underground explosion nearby and observing the seismic response that provides information about the geological structures under the ground *. However the "passive" methods that extract information from naturally-occurring seismic waves are also known . Other instruments such as gravimeters and magnetometers are also sometimes used in the search for petroleum. Generally, the first stage in the extraction of crude oil is to drill a well into the underground reservoir. When an oil bearing structure has been tapped, the wellsite geologist (known on the rig as the "mudlogger") will note its presence. Historically, in the USA, some oil fields existed where the oil rose naturally to the surface, but most of these fields have long since been depleted, except for certain remote locations in Alaska. Often many wells (called multilateral wells) are drilled into the same reservoir, to ensure that the extraction rate will be economically viable. Also, some wells (secondary wells) may be used to pump water, steam, acids or various gas mixtures into the reservoir to raise or maintain the reservoir pressure, and so maintain an economic extraction rate. If the underground pressure in the oil reservoir is sufficient, then the oil will be forced to the surface under this pressure. Gaseous fuels, natural gas or water are usually present, which also supply needed underground pressure. In this situation it is sufficient to place a complex arrangement of valves (the Christmas tree) on the well head to connect the well to a pipeline network for storage and processing. This is called primary oil recovery. Usually, only about 20% of the oil in a reservoir can be extracted this way. The amount of oil that is recoverable is determined by a number of factors including the permeability of the rocks, the strength of natural drives (the gas present, pressure from adjacent water or gravity), and the viscosity of the oil. When the reservoir rocks are "tight" such as shale, oil generally cannot flow through but when they are permeable such as in sandstone, oil flows freely. The flow of oil is often helped by natural pressures surrounding the reservoir rocks including natural gas that may be dissolved in the oil, natural gas present above the oil, water below the oil and the strength of gravity. Oils tend to span a large range of viscosity from liquids as light as gasoline to heavy as tar. The lightest forms tend to result in higher production rates. Over the lifetime of the well the pressure will fall, and at some point there will be insufficient underground pressure to force the oil to the surface. If economical, as often is, the remaining oil in the well is extracted using secondary oil recovery methods (see: energy balance and net energy gain). Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs. Sometimes pumps, such as beam pumps and electrical submersible pumps (ESPs), are used to bring the oil to the surface. Other secondary recovery techniques increase the reservoir's pressure by water injection, natural gas reinjection and gas lift, which injects air, carbon dioxide or some other gas into the reservoir. Together, primary and secondary recovery allow 25% to 35% of the reservoir's oil to be recovered. Tertiary oil recovery reduces the oil's viscosity to increase oil production. Tertiary recovery is started when secondary oil recovery techniques are no longer enough to sustain production, but only when the oil can still be extracted profitably. This depends on the cost of the extraction method and the current price of crude oil. When prices are high, previously unprofitable wells are brought back into production and when they are low, production is curtailed. Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract. Steam injection is the most common form of TEOR, and is often done with a cogeneration plant. In this type of cogeneration plant, a gas turbine is used to generate electricity and the waste heat is used to produce steam, which is then injected into the reservoir. This form of recovery is used extensively to increase oil production in the San Joaquin Valley, which has very heavy oil, yet accounts for 10% of the United States' oil production. In-situ burning is another form of TEOR, but instead of steam, some of the oil is burned to heat the surrounding oil. Occasionally, detergents are also used to decrease oil viscosity. Tertiary recovery allows another 5% to 15% of the reservoir's oil to be recovered. Drilling Please See: History
Means of producing oil As oil prices continue to escalate, other alternatives to producing oil have been gaining importance. The best known such methods involve extracting oil from sources such as oil shale or tar sands. These resources are known to exist in large quantities; however, extracting the oil at low cost without negatively impacting the environment remains a challenge. It is also possible to transform natural gas or coal into oil (or, more precisely, the various hydrocarbons found in oil). The best-known such method is the Fischer-Tropsch process. It was a concept pioneered in Nazi Germany when imports of petroleum were restricted due to war and Germany found a method to extract oil from coal. It was known as Ersatz ("substitute" in German), and accounted for nearly half the total oil used in WWII by Germany. However, the process was used only as a last resort as naturally occurring oil was much cheaper. As crude oil prices increase, the cost of coal to oil conversion becomes comparatively cheaper. The method involves converting high ash coal into synthetic oil in a multistage process. Ideally, a ton of coal produces nearly 200 liters (1.25 bbl, 52 US gallons) of crude, with by-products ranging from tar to rare chemicals. Currently, two companies have commercialised their Fischer-Tropsch technology. Shell in Bintulu, Malaysia, uses natural gas as a feedstock, and produces primarily low-sulfur diesel fuels. Sasol in South Africa uses coal as a feedstock, and produces a variety of synthetic petroleum products. The process is today used in South Africa to produce most of the country's diesel fuel from coal by the company Sasol. The process was used in South Africa to meet its energy needs during its isolation under Apartheid. This process has received renewed attention in the quest to produce low sulfur diesel fuel in order to minimize the environmental impact from the use of diesel engines. An alternative method is the Karrick process, which converts coal into crude oil, pioneered in the 1930s in the United States. More recently explored is thermal depolymerization (TDP). In theory, TDP can convert any organic waste into petroleum. Production, consumption and alternatives The term alternative propulsion or "alternative methods of propulsion" includes both Nowadays, cars can be classified between the next main groups: See also: renewable energy, greenhouse gas, climate change. Image:Hubbert world 2004.png|2004 U.S. government predictions for oil production other than in OPEC and the former Soviet Union Image:World energy consumption, 1970-2025, EIA.png|World energy consumption, 1970-2025. Source: International Energy Outlook 2004. Image:EIA_IEO2006.jpg|World energy consumption, 1980-2030. Source: International Energy Outlook 2006. Black Gold Black gold, in most of the world, refers to Petroleum. The name is derived from the black color of crude oil combined with its status as a highly valuable resource, serving in the industrial age, in many ways, the same role that gold did in the pre-industrial era. In the Appalachian Mountains of the United States, a major coal-producing region, the term refers to coal. In Taiwan, it means iron, petroleum, and coal. The term was used in the theme song of the TV show The Beverly Hillbillies, along with the term "Texas Tea", another synonym for crude oil. Environmental effects The presence of oil has significant social and environmental impacts, from accidents and routine activities such as seismic exploration, drilling, and generation of polluting wastes. Oil extraction is costly and sometimes environmentally damaging, although Dr. John Hunt of the Woods Hole Oceanographic Institution pointed out in a 1981 paper that over 70% of the reserves in the world are associated with visible macroseepages, and many oil fields are found due to natural leaks. Offshore exploration and extraction of oil disturbs the surrounding marine environment. Extraction may involve dredging, which stirs up the seabed, 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. Burning oil releases carbon dioxide into the atmosphere, which contributes to global warming. Per energy unit, oil produces less CO2 than coal, but more than natural gas. However, oil's unique role as a transportation fuel makes reducing its CO2 emissions a particularly thorny problem; amelioration strategies such as carbon sequestering are generally geared for large power plants, not individual vehicles. Renewable energy alternatives do exist, although the degree to which they can replace petroleum and the possible environmental damage they may cause are uncertain and controversial. Sun, wind, geothermal, and other renewable electricity sources cannot directly replace high energy density liquid petroleum for transportation use; instead automobiles and other equipment must be altered to allow using electricity (in batteries) or hydrogen (via fuel cells or internal combustion) which can be produced from renewable sources. Other options include using biomass-origin liquid fuels (ethanol, biodiesel). Any combination of solutions to replace petroleum as a liquid transportation fuel will be a very large undertaking. (See also Hydrogen economy.) Future of oil The Hubbert peak theory, also known as peak oil, is a theory concerning the long-term rate of production of conventional oil and other fossil fuels. It assumes that oil reserves are not replenishable (i.e. that abiogenic replenishment, if it exists at all, is negligible), and predicts that future world oil production must inevitably reach a peak and then decline as these reserves are exhausted. Controversy surrounds the theory, as predictions for when the global peak will actually take place are highly dependent on the past production and discovery data used in the calculation. Proponents of peak oil theory also refer as an example of their theory, that when any given oil well produces oil in similar volumes to the amount of water used to obtain the oil, it tends to produce less oil afterwards, leading to the relatively quick exhaustion and/or commercial unviability of the well in question. The issue can be considered from the point of view of individual regions or of the world as a whole. His prediction turned out to be correct, and after the US peaked in 1971 - and thus lost its excess production capacity - OPEC was finally able to manipulate oil prices, which led to the oil crisis in 1973. Since then, most other countries have also peaked: Scotland's North Sea, for example in the late 1990s. China has confirmed that two of its largest producing regions are in decline, and Mexico's national oil company, Pemex, has announced that Cantarell Field, one of the world's largest offshore fields, is expected to peak in 2006, and then decline 14% per annum. For various reasons (perhaps most importantly the lack of transparency in accounting of global oil reserves), it is difficult to predict the oil peak in any given region. Based on available production data, proponents have previously (and incorrectly) predicted the peak for the world to be in years 1989, 1995, or 1995-2000. However these predictions date from before the recession of the early 1980s, and the consequent reduction in global consumption, the effect of which was to delay the date of any peak by several years. A new prediction by Goldman Sachs picks 2007 for oil and some time later for natural gas. 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. One signal is that 2005 saw a dramatic fall in announced new oil projects coming to production from 2008 onwards. Since it takes on average four to six years for a new project to start producing oil, in order to avoid the peak, these new projects would have to not only make up for the depletion of current fields, but increase total production annually to meet increasing demand. 2005 also saw substantial increases in oil prices due to temporary circumstances, which then failed to be controlled by increasing production. The inability to increase production in the short term, indicating a general lack of spare capacity, and the corresponding uncontrolled price fluctuations, can be interpreted as a sign that peak oil has occurred or is presently in the process of occurring. Classification The oil industry classifies "crude" by the location of its origin (e.g., "West Texas Intermediate, WTI" or "Brent") and often by its relative weight (API gravity) or viscosity ("light", "intermediate" or "heavy"); refiners may also refer to it as "sweet," which means it contains relatively little sulfur, or as "sour," which means it contains substantial amounts of sulfur and requires more refining in order to meet current product specifications. Each crude oil has unique molecular characteristics which are understood by the use of crude oil assay analysis in petroleum laboratories. The world reference barrels are: OPEC attempts to keep the price of the Opec Basket between upper and lower limits, by increasing and decreasing production. This makes the measure important for market analysts. The OPEC Basket, including a mix of light and heavy crudes, is heavier than both Brent and WTI. See also: http://tonto.eia.doe.gov/ask/crude_types1.html In June 15, 2005 the OPEC basket was changed to reflect the characteristics of the oil produced by OPEC members. The new OPEC Reference Basket (ORB) is made up of the following: Saharan Blend (Algeria), Minas (Indonesia), Iran Heavy (Islamic Republic of Iran), Basra Light (Iraq), Kuwait Export (Kuwait), Es Sider (Libya), Bonny Light (Nigeria), Qatar Marine (Qatar), Arab Light (Saudi Arabia), Murban (UAE) and BCF 17 (Venezuela). See also: http://www.opec.org/home/basket.aspx Pricing
Top petroleum-producing countries Source: Energy Statistics from the U.S. Government. For oil reserves by country, see Oil reserves by country. In order of amount produced in 2004 in MMbbl/d (millions of barrels per day): 2 Though still a member, Iraq has not been included in production figures since 1998 3 Canada has the world's second largest oil reserves when tar sands are included, and is the leading source of U.S. imports, averaging 1.7 MMbbl/d in April 2006 *. In order of amount exported in 2003: Note that the USA consumes almost all of its own production, while the UK has recently become a net-importer rather than net-exporter. Total world production/consumption (as of 2005) is approximately 84 million barrels per day. See also: Organization of Petroleum Exporting Countries. Petroleum in Military Strategy Books about the petroleum industry Books about petroleum supply Films about petroleum Writers covering the petroleum industry See also that does not use or sell petroleum (i.e. petro-free fuel station). Articles Data | |||||||||||||
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