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Petroleum (L. petroleum, from Latin: petra rock + oleum oil^[1]) or crude oil is a naturally occurring, toxic, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights, and other organic compounds, that are found in geologic formations beneath the Earth’s surface. Petroleum is recovered mostly through oil drilling. It is refined and separated, most easily by boiling point, into a large number of consumer products, from gasoline and kerosene to asphalt and chemical reagents used to make plastics and pharmaceuticals.^[2]

The term petroleum was first used in the treatise De Natura Fossilium, published in 1546 by the German mineralogist Georg Bauer, also known as Georgius Agricola.^[3]

Contents 1 Composition 2 Chemistry 3 Empirical equations for the thermal properties of petroleum products 3.1 Heat of combustion 3.2 Thermal conductivity 3.3 Specific heat 3.4 Latent heat of vaporization 4 Formation 4.1 Abiogenic origin 5 Crude oil 5.1 Crude oil reservoirs 5.2 Unconventional oil reservoirs 6 Classification 7 Petroleum industry 8 History 9 Price 10 Uses 10.1 Fuels 10.2 Other derivatives 11 Petroleum by country 11.1 Consumption statistics 11.2 Consumption 11.3 Production 11.4 Export 11.5 Import 11.6 Non-producing consumers 12 Environmental effects 12.1 Extraction 12.2 Oil spills 12.3 Tarballs 12.4 Whales 13 Alternatives to petroleum 13.1 Alternatives to petroleum-based vehicle fuels 13.2 Alternatives to using oil in industry 13.3 Alternatives to burning petroleum for electricity 14 Future of petroleum production 14.1 Hubbert peak theory 15 See also 16 Notes 17 References 18 External links

Composition

In its strictest sense, petroleum includes only crude oil, but in common usage it includes both crude oil and natural gas. Both crude oil and natural gas are predominantly a mixture of hydrocarbons. Under surface pressure and temperature conditions, the lighter hydrocarbons methane, ethane, propane and butane occur as gases, while the heavier ones from pentane and up are in the form of liquids or solids. However, in the underground oil reservoir the proportion which is gas or liquid varies depending on the subsurface conditions, and on the phase diagram of the petroleum mixture.^[4]

An oil well 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 predominately natural gas. However, because the underground temperature and pressure are higher than at the surface, the gas may contain heavier hydrocarbons such as pentane, hexane, and heptane in the gaseous state. Under surface conditions these will condense out of the gas and form natural gas condensate, often shortened to condensate. Condensate resembles gasoline in appearance and is similar in composition to some volatile light crude oils.

The proportion of light hydrocarbons in the petroleum mixture is highly variable between different oil fields and ranges from as much as 97% by weight in the lighter oils to as little as 50% in the heavier oils and bitumens.

The hydrocarbons in crude oil are mostly alkanes, cycloalkanes and various aromatic hydrocarbons while the other organic compounds contain nitrogen, oxygen and sulfur, and trace amounts of metals such as iron, nickel, copper and vanadium. The exact molecular composition varies widely from formation to formation but the proportion of chemical elements vary over fairly narrow limits as follows:^[5]

Composition by weight

Element	Percent range
Carbon	83 to 87%
Hydrogen	10 to 14%
Nitrogen	0.1 to 2%
Oxygen	0.1 to 1.5%
Sulfur	0.5 to 6%
Metals	< 0.1%

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.^[4]

Composition by weight

Hydrocarbon	Average	Range
Paraffins	30%	15 to 60%
Naphthenes	49%	30 to 60%
Aromatics	15%	3 to 30%
Asphaltics	6%	remainder

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 which, being heavier than most forms of crude oil, generally sinks beneath it. Crude oil may also be found in 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. In Canada, bitumen is considered a sticky, tar-like form of crude oil which is so thick and heavy that it must be heated or diluted before it will flow.^[7] 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. 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 contain an estimated 3.6 trillion barrels (570×10^⁹ m³) of bitumen and extra-heavy oil, about twice the volume of the world’s reserves of conventional oil.^[8]

Petroleum is used mostly, by volume, for producing fuel oil and gasoline (petrol), both important “primary energy“ sources.^[9] 84% 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.^[10] 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 to convert the longer, more complex molecules in the oil to the shorter, simpler ones in the fuels.

Due to its high energy density, 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 products, including pharmaceuticals, solvents, fertilizers, pesticides, and plastics; the 16% 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. There is also petroleum in oil sands (tar sands). Known reserves of petroleum are typically estimated at around 190 km³ (1.2 trillion (short scale) barrels) without oil sands,^[11] or 595 km³ (3.74 trillion barrels) with oil sands.^[12] Consumption is currently around 84 million barrels (13.4×10^⁶ m³) per day, or 4.9 km³ per year.

Chemistry

Petroleum is a mixture of a very large number of different hydrocarbons; the most commonly found molecules are alkanes (linear or branched), cycloalkanes, aromatic hydrocarbons, or more complicated chemicals like asphaltenes. Each petroleum variety has a unique mix of molecules, which define its physical and chemical properties, like color and viscosity.

The alkanes, also known as paraffins, are saturated hydrocarbons with straight or branched chains which contain only carbon and hydrogen and have the general formula C_nH_2n+2. 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 (C₈H₁₈) are refined into gasoline (petrol), the ones from nonane (C₉H₂₀) to hexadecane (C₁₆H₃₄) into diesel fuel and kerosene (primary component of many types of jet fuel), and the ones from hexadecane upwards into fuel oil and lubricating oil. At the heavier end of the range, paraffin wax is an alkane with approximately 25 carbon atoms, while asphalt 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 liquified petroleum gas 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 butane’s high vapor 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 cycloalkanes, also known as naphthenes, are saturated hydrocarbons which have one or more carbon rings to which hydrogen atoms are attached according to the formula C_nH_2n. Cycloalkanes have similar properties to alkanes but have higher boiling points.

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 C_nH_n. 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 at an oil refinery to produce gasoline, jet fuel, kerosene, and other hydrocarbons. For example, 2,2,4-trimethylpentane (isooctane), widely used in gasoline, has a chemical formula of C₈H₁₈ and it reacts with oxygen exothermically:^[13]

2 C₈H₁₈(l) + 25 O₂(g) → 16 CO₂(g) + 18 H₂O(g) + 10.86 MJ/mol (of octane)

The amount of various molecules in an oil sample can be determined in laboratory. The molecules are typically extracted in a solvent, then separated in a gas chromatograph, and finally determined with a suitable detector, such as a flame ionization detector or a mass spectrometer.^[14]

Incomplete combustion of petroleum or gasoline results in production of toxic byproducts. Too little oxygen results in carbon monoxide. Due to the high temperatures and high pressures involved, exhaust gases from gasoline combustion in car engines usually include nitrogen oxides which are responsible for creation of photochemical smog.

Empirical equations for the thermal properties of petroleum products

Heat of combustion

At a constant volume the heat of combustion of a petroleum product can be approximated as follows:

Q_v = 12,400 − 2,100d²

where Q_v is measured in cal/gram and d is the specific gravity at 60 °F.

Thermal conductivity

The thermal conductivity of petroleum based liquids can be modeled as follows:

,

where K is measured in BTU · hr⁻¹ft⁻² , t is measured in °F and d is the specific gravity at 60 °F.

Specific heat

The specific heat of a petroleum oils can be modeled as follows:

,

where c is measured in BTU/lbm-°F, t is the temperature in Fahrenheit and d is the specific gravity at 60 °F.

In units of kcal/(kg·°C), the formula is:

,

where the temperature t is in Celsius and d is the specific gravity at 15 °C.

Latent heat of vaporization

The latent heat of vaporization can be modeled under atmospheric conditions as follows:

,

where L is measured in BTU/lbm, t is measured in °F and d is the specific gravity at 60 °F.

In units of kcal/kg, the formula is:

,

where the temperature t is in Celsius and d is the specific gravity at 15 °C.^[15]

Formation

According to generally accepted theory, petroleum is derived from ancient biomass.^[16] It is a fossil fuel derived from ancient fossilized organic materials. The theory was initially based on the isolation of molecules from petroleum that closely resemble known biomolecules.

More specifically, crude oil and natural gas are products of heating of ancient organic materials (i.e. kerogen) over geological time. Formation of petroleum occurs from hydrocarbon pyrolysis, in a variety of mostly endothermic reactions at high temperature and/or pressure.^[17] Today’s oil formed from the preserved remains of prehistoric zooplankton and algae, which had settled to a sea or lake bottom in large quantities under anoxic conditions (the remains of prehistoric terrestrial plants, on the other hand, tended to form coal). Over geological time the organic matter mixed with mud, and was buried under heavy layers of sediment resulting in high levels of heat and pressure (diagenesis). This process caused the organic matter to change, 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 via a process known as catagenesis.

Geologists often refer to the temperature range in which oil forms as an “oil window”^[18]—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. Sometimes, oil which is formed at extreme depths may migrate and become trapped at much shallower depths than where it was formed. The Athabasca Oil Sands is one example of this.

Abiogenic origin

A small number of geologists adhere to the abiogenic petroleum origin hypothesis and maintain that hydrocarbons of purely inorganic origin exist within Earth’s interior. Chemists Marcellin Berthelot and Dmitri Mendeleev, as well as astronomer Thomas Gold championed the theory in the Western world by supporting the work done by Nikolai Kudryavtsev and Vladimir Porfiriev in the 1950s. It is currently supported primarily by Jack F. Kenney, Vladilen Krayushkin, and Vladimir Kutcherov.^[19][20]

The abiogenic origin hypothesis has not yet been ruled out, but it has little support among modern petroleum geologists.^[21] Its advocates consider that it is “still an open question”^[22] Extensive research into the chemical structure of kerogen has identified algae as the primary source of oil. The abiogenic origin hypothesis fails to explain the presence of these markers in kerogen and oil, as well as failing to explain how inorganic origin could be achieved at temperatures and pressures sufficient to convert kerogen to graphite. It has not been successfully used in uncovering oil deposits by geologists, as the hypothesis lacks any mechanism for determining where the process may occur.^[23] More recently scientists at the Carnegie Institution for Science have found that ethane and heavier hydrocarbons can be synthesized under conditions of the upper mantle.^[24]

Crude oil

Crude oil reservoirs

Three conditions must be present for oil reservoirs to form: a source rock rich in hydrocarbon material buried deep enough for subterranean heat to cook it into oil; a porous and permeable reservoir rock for it to accumulate in; and a cap rock (seal) or other mechanism that prevents it 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 lighter than rock or water, 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 forms, from which the liquid can be extracted by drilling and pumping.

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 plants and oil refineries.

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 many reservoirs, however, eventually dissipates. Then the oil must be pumped out using “artificial lift” created by mechanical pumps powered by gas or electricity. 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% of the oil produced on a daily basis, secondary methods account for about half, and tertiary recovery the remaining 10%. 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 out the oil-saturated liquid.

Unconventional oil reservoirs

Oil-eating bacteria biodegrades oil that has escaped to the surface. Oil sands 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. 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 really shales and do not really contain oil, but are usually relatively hard rocks called marls containing a waxy substance called kerogen. The kerogen trapped 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 quantityes of pitch, tarr, and oyle out of a sort of stone.” Although oil shales are found in many countries, the United States has the world’s largest deposits.^[25]

Classification

The petroleum industry generally classifies crude oil by the geographic location it is produced in (e.g. West Texas Intermediate, Brent, or Oman), its API gravity (an oil industry measure of density), and by its sulfur content. Crude oil may be considered light if it has low density or heavy if it has high density; and it may be referred to as sweet if it contains relatively little sulfur or sour 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 understood 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 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, comprising 15 oils from fields in the Brent and Ninian systems in the East Shetland Basin of the North Sea. The oil is landed at Sullom Voe terminal in Shetland. 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, used as a reference for light Far East oil)
• Minas (from Indonesia, 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) countries
• Midway Sunset Heavy, by which heavy oil in California is priced ^[26]

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 delivered at Hardisty, Alberta, and for a Brent Blend delivered at Shetland, it may be a Russian Export Blend delivered at the port of Primorsk.^[27]

Petroleum industry

The petroleum industry is involved in the global processes of exploration, extraction, refining, transporting (often with oil tankers and pipelines), and marketing petroleum products. The largest volume products of the industry are fuel oil and gasoline (petrol). Petroleum is also the raw material for many chemical products, including pharmaceuticals, solvents, fertilizers, pesticides, and plastics. The industry is usually divided into three major components: upstream, midstream and downstream. Midstream operations are usually included in the downstream category.

Petroleum is vital to many industries, and is of importance to the maintenance of industrialized civilization itself, and thus is critical concern to many nations. Oil accounts for a large percentage of the world’s energy consumption, ranging from a low of 32% for Europe and Asia, up to a high of 53% for the Middle East. Other geographic regions’ consumption patterns are as follows: South and Central America (44%), Africa (41%), and North America (40%). The world at large consumes 30 billion barrels (4.8 km³) of oil per year, and the top oil consumers largely consist of developed nations. In fact, 24% of the oil consumed in 2004 went to the United States alone ^[28], though by 2007 this had dropped to 21% of world oil consumed.^[29]

In the US, in the states of Arizona, California, Hawaii, Nevada, Oregon and Washington, the Western States Petroleum Association (WSPA) represents companies responsible for producing, distributing, refining, transporting and marketing petroleum. This non-profit trade association was founded in 1907, and is the oldest petroleum trade association in the United States.^[30]

History

Petroleum, in one form or another, has been used since ancient times, and is now important across society, including in economy, politics and technology. The rise in importance was mostly due to the invention of the internal combustion engine, the rise in commercial aviation and the increasing use of plastic.

More than 4000 years ago, according to Herodotus and Diodorus Siculus, asphalt was used in the construction of the walls and towers of Babylon; there were oil pits near Ardericca (near Babylon), and a pitch spring on Zacynthus.^[31] Great quantities of it were found on the banks of the river Issus, one of the tributaries of the Euphrates. Ancient Persian tablets indicate the medicinal and lighting uses of petroleum in the upper levels of their society.

In the 1850s, the process to distill kerosene from petroleum was invented by Ignacy Łukasiewicz, providing a cheaper alternative to whale oil. The demand for the petroleum as a fuel for lighting in North America and around the world quickly grew.^[32] The world’s first commercial oil well was drilled in Poland in 1853. Oil exploration developed in many parts of the world with the Russian Empire, particularly the Branobel company in Azerbaijan, taking the lead in production by the end of the 19th century.^[33] Oil exploration in North America during the early 20th century later led to the U.S. becoming the leading producer by the mid 1900s. As petroleum production in the U.S. peaked during the 1960s, however, Saudi Arabia and Russia surpassed the U.S.

Today, about 90% of vehicular fuel needs are met by oil. Petroleum also makes up 40% of total energy consumption in the United States, but is responsible for only 2% 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.

The top three oil producing countries are Saudi Arabia, Russia, and the United States.^[34] About 80% of the world’s readily accessible reserves are located in the Middle East, with 62.5% coming from the Arab 5: Saudi Arabia, UAE, Iraq, Qatar and Kuwait. A large portion of the world’s total oil exists as unconventional sources, such as bitumen in Canada and Venezuela and oil shale. While significant volumes of oil are extracted from oil sands, particularly in Canada, logistical and technical hurdles remain, and Canada’s oil sands are not expected to provide more than a few million barrels per day in the foreseeable future.

Price

After the collapse of the OPEC-administered pricing system in 1985, and a short lived experiment with netback pricing, oil-exporting countries adopted a market-linked pricing mechanism.^[35] First adopted by PEMEX in 1986, market-linked pricing was widely accepted, and by 1988 became and still is the main method for pricing crude oil in international trade.^[35] The current reference, or pricing markers, are Brent, WTI, and Dubai/Oman.^[35]

Uses

The chemical structure of petroleum is heterogeneous, composed of hydrocarbon chains of different lengths. Because of this, petroleum may be taken to oil refineries and the hydrocarbon chemicals separated by distillation and treated by other chemical processes, to be used for a variety of purposes. See Petroleum products.

Fuels

The most common distillations of petroleum are fuels. Fuels include (by increasing molecular masses):

• Liquefied petroleum gas (LPG)
• Ethane and other short-chain alkanes
• Gasoline (Petrol)
• Diesel fuel (petrodiesel)
• Kerosene
• Jet fuel
• Fuel oils

Other derivatives

Certain types of resultant hydrocarbons may be mixed with other non-hydrocarbons, to create other end products:

• Alkenes (olefins) which can be manufactured into plastics or other compounds
• Lubricants (produces light machine oils, motor oils, and greases, adding viscosity stabilizers as required).
• Wax, used in the packaging of frozen foods, among others.
• Sulfur or Sulfuric acid. These are a useful industrial materials. Sulfuric acid is usually prepared as the acid precursor oleum, a byproduct of sulfur removal from fuels.
• Bulk tar.
• Asphalt
• Petroleum coke, used in speciality carbon products or as solid fuel.
• Paraffin wax
• Aromatic petrochemicals to be used as precursors in other chemical production.

Petroleum by country

Consumption statistics

Global fossil carbon emissions, an indicator of consumption, for 1800–2007. Total is black, Oil is in blue.

World energy consumption, 1980–2030. Source: International Energy Outlook 2006.

daily oil consumption from 1980 to 2006

oil consumption by percentage of total per region from 1980 to 2006: red=USA, blue=Europe, yellow=Asia+Oceania

Consumption

This table orders the amount of petroleum consumed in 2008 in thousand barrels (bbl) per day and in thousand cubic metres (m³) per day:^[36][37][38]

Consuming Nation 2008	(1000 bbl/day)	(1000 m3/day)	population in millions	bbl/year per capita
United States 1	19,497.95	3,099.9	314	22.6
China	7,831.00	1,245.0	1345	2.1
Japan 2	4,784.85	760.7	127	13.7
India 2	2,962.00	470.9	1198	0.9
Russia 1	2,916.00	463.6	140	7.6
Germany 2	2,569.28	408.5	82	11.4
Brazil	2,485.00	395.1	193	4.7
Saudi Arabia (OPEC)	2,376.00	377.8	25	33.7
Canada	2,261.36	359.5	33	24.6
South Korea 2	2,174.91	345.8	48	16.4
Mexico 1	2,128.46	338.4	109	7.1
France 2	1,986.26	315.8	62	11.6
Iran (OPEC)	1,741.00	276.8	74	8.6
United Kingdom 1	1,709.66	271.8	61	10.1
Italy 2	1,639.01	260.6	60	10

Source: US Energy Information Administration

Population Data:^[39]

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.

#	Producing Nation	103bbl/d (2006)	103bbl/d (2007)	103bbl/d (2008)
1	Saudi Arabia (OPEC)	10,665	10,234	10,782
2	Russia 1	9,677	9,876	9,789
3	United States 1	8,331	8,481	8,514
4	Iran (OPEC)	4,148	4,043	4,174
5	China	3,845	3,901	3,973
6	Canada 2	3,288	3,358	3,350
7	Mexico 1	3,707	3,501	3,185
8	United Arab Emirates (OPEC)	2,945	2,948	3,046
9	Kuwait (OPEC)	2,675	2,613	2,742
10	Venezuela (OPEC) 1	2,803	2,667	2,643
11	Norway 1	2,786	2,565	2,466
12	Brazil	2,166	2,279	2,401
13	Iraq (OPEC) 3	2,008	2,094	2,385
14	Algeria (OPEC)	2,122	2,173	2,179
15	Nigeria (OPEC)	2,443	2,352	2,169
16	Angola (OPEC)	1,435	1,769	2,014
17	Libya (OPEC)	1,809	1,845	1,875
18	United Kingdom	1,689	1,690	1,584
19	Kazakhstan	1,388	1,445	1,429
20	Qatar (OPEC)	1,141	1,136	1,207
21	Indonesia	1,102	1,044	1,051
22	India	854	881	884
23	Azerbaijan	648	850	875
24	Argentina	802	791	792
25	Oman	743	714	761
26	Malaysia	729	703	727
27	Egypt	667	664	631
28	Colombia	544	543	601
29	Australia	552	595	586
30	Ecuador (OPEC)	536	512	505
31	Sudan	380	466	480
32	Syria	449	446	426
33	Equatorial Guinea	386	400	359
34	Thailand	334	349	361
35	Vietnam	362	352	314
36	Yemen	377	361	300
37	Denmark	344	314	289
38	Gabon	237	244	248
39	South Africa	204	199	195
40	Turkmenistan	No data	180	189

Source: U.S. Energy Information Administration

¹ Peak production of conventional oil already passed in this state

² Although Canadian conventional oil production is declining, total oil production is increasing as oil sands production grows. If oil sands are included, it has the world’s second largest oil reserves after Saudi Arabia.

³ Though still a member, Iraq has not been included in production figures since 1998

Export

See also: Fossil fuel exporters

In order of net exports in 2006 in thousand bbl/d and thousand m³/d:

#	Exporting Nation (2006)	(103bbl/d)	(103m3/d)
1	Saudi Arabia (OPEC)	8,651	1,376
2	Russia 1	6,565	1,044
3	Norway 1	2,542	404
4	Iran (OPEC)	2,519	401
5	United Arab Emirates (OPEC)	2,515	400
6	Venezuela (OPEC) 1	2,203	350
7	Kuwait (OPEC)	2,150	342
8	Nigeria (OPEC)	2,146	341
9	Algeria (OPEC) 1	1,847	297
10	Mexico 1	1,676	266
11	Libya (OPEC) 1	1,525	242
12	Iraq (OPEC)	1,438	229
13	Angola (OPEC)	1,363	217
14	Kazakhstan	1,114	177
15	Canada 2	1,071	170

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 2.5 MMbbl/d in August 2007. [2].

Total world production/consumption (as of 2005) is approximately 84 million barrels per day (13,400,000 m³/d).

See also: Organization of Petroleum Exporting Countries.

Import

In order of net imports in 2006 in thousand bbl/d and thousand m³/d:

#	Importing Nation (2006)	(103bbl/day)	(103m3/day)
1	United States 1	12,220	1,943
2	Japan	5,097	810
3	China 2	3,438	547
4	Germany	2,483	395
5	South Korea	2,150	342
6	France	1,893	301
7	India	1,687	268
8	Italy	1,558	248
9	Spain	1,555	247
10	Republic of China (Taiwan)	942	150
11	Netherlands	936	149
12	Singapore	787	125
13	Thailand	606	96
14	Turkey	576	92
15	Belgium	546	87

Source: US Energy Information Administration^{[not in citation given]}

¹ peak production of oil already passed in this state

² Major oil producer whose production is still increasing

Non-producing consumers

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

#	Consuming Nation	(bbl/day)	(m³/day)
1	Japan	5,578,000	886,831
2	Germany	2,677,000	425,609
3	South Korea	2,061,000	327,673
4	France	2,060,000	327,514
5	Italy	1,874,000	297,942
6	Spain	1,537,000	244,363
7	Netherlands	946,700	150,513
8	Turkey	575,011	91,663

Source: CIA World Factbook^{[not in citation given]}

Environmental effects

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 (like seismic exploration, drilling, extraction, refining and combustion). Phenomena such as seeps^[41] and tar pits are examples of areas that petroleum naturally affects. Regardless of source, petroleum’s effects when released into the environment are similar.

Extraction

Oil extraction is simply the removal of oil from the reservoir (oil pool). 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 seeps. Offshore exploration and extraction of oil disturbs the surrounding marine environment.^[42]

Oil spills

Crude oil and refined fuel spills from tanker ship accidents have damaged natural ecosystems in Alaska, the Galapagos 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., Atlantic Empress, Amoco Cadiz). 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 Torrey Canyon wreck produced poor results;^[43] modern techniques would include pumping the oil from the wreck, like in the Prestige oil spill or the Erika oil spill.^[44]

Though crude oil is predominantly composed of various hydrocarbons, certain nitrogen heterocylic compounds, such as pyridine, picoline, 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 and have been shown to degrade these contaminants. ^[45]

Tarballs

A tarball is a blob of oil (not to be confused with tar, which is typically derived from pine trees rather than petroleum) which has been weathered after floating in the ocean. Tarballs are an aquatic pollutant in most environments, although they can occur naturally, for example, in the Santa Barbara Channel of California.^[46][47] 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,^[48][49] and tarballs themselves may be dispersed over long distances by deep sea currents.^[47] They are slowly decomposed by bacteria, including Chromobacterium violaceum, Cladosporium resinae, Bacillus submarinus, Micrococcus varians, Pseudomonas aeruginosa, Candida marina and Saccharomyces estuari.^[46]

Whales

James S. Robbins has argued that the advent of petroleum-refined kerosene saved some species of great whales from extinction by providing an inexpensive substitute for whale oil, thus eliminating the economic imperative for open-boat whaling.^[50]

Alternatives to petroleum

In the United States in 2007 about 70% of petroleum was used for transportation (e.g. gasoline, diesel, jet fuel), 24% by industry (e.g. production of plastics), 5% for residential and commercial uses, and 2% for electricity production.^[51] Outside of the US, a higher proportion of petroleum tends to be used for electricity.^[52]

Alternatives to petroleum-based vehicle fuels

Alternative propulsion refers to both:

• Alternative fuels used in standard or modified internal combustion engines (i.e. biofuels or combustion hydrogen).
• propulsion systems not based on internal combustion, such as those based on electricity (for example, all-electric or hybrid vehicles), compressed air, or fuel cells (i.e. hydrogen fuel cells).

Currently, cars can be classified into the following groups:

• Internal combustion engine cars, which may use
  • gasoline, fuel and/or biofuels (e.g. alcohol, biodiesel and biobutanol)
  • compressed natural gas used by natural gas vehicles
  • hydrogen in hydrogen vehicles.

• Advanced technology cars such as hybrid vehicles which use petroleum and/or biofuels, albeit far more efficiently.^[53]
• Plug-in hybrids, that can store and use externally produced electricity in addition to petroleum.
• electric cars

Alternatives to using oil in industry

Please help improve this article by expanding it. Further information might be found on the talk page. (July 2008)

Biological feedstocks do exist for industrial uses such as plastic production.^[54]

Alternatives to burning petroleum for electricity

In oil producing countries with little refinery capacity, oil is sometimes burned to produce electricity. Renewable energy technologies such as solar power, wind power, micro hydro, biomass and biofuels might someday be used to replace some of these generators, but today the primary alternatives remain large scale hydroelectricity, nuclear and coal-fired generation.

Future of petroleum production

Consumption in the twentieth century has been abundantly pushed by automobile growth; the 1985-2003 oil glut even fuelled the sales of low economy vehicles (SUVs) in OECD countries. In 2008, the economic crisis seems to have some impact on the sales of such vehicles; still, the 2008 oil consumption shows a small increase. The BRIC countries might also kick in, as China briefly was the first automobile market in December 2009.^[55] The immediate outlook still hints upwards. In the long term, uncertainties linger; the OPEC believes that the OECD countries will push low consumption policies at some point in the future; when that happens, it will definitely curb the oil sales, and both OPEC and EIA kept lowering their 2020 consumption estimates during the past 5 years.^[56] Oil products are more and more in competition with alternative sources, mainly coal and natural gas, both cheaper sources.

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 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 ^[57] ) will continue to play a major role in increasing the world’s recoverable oil.

Hubbert peak theory

The Hubbert peak theory (also known as peak oil) posits 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.^[58]

Controversy surrounds predictions of the timing of the global peak, as these predictions are dependent on the past production and discovery data used in the calculation as well as how unconventional reserves are considered.^{[citation needed]} Also, these predictions do not take into account outside elements such as the current economic crisis (2008).^{[citation needed]} Also, many Peak Oil promoters proposed many different dates, some of them passed already.^{[citation needed]} Despite these uncertainties, Hubbert applied his theory to predict the peak of U.S. oil production at a date between 1966 and 1970. This prediction was based on data available at the time of his publication in 1956. In the same paper, Hubbert predicts the world Peak Oil for the year 2000.^[59]

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.^[60] 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 reduction 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.

See also

Wikinews has news related to: Energy

• Abiogenic petroleum origin
• Barrel of oil equivalent
• Gas oil ratio
• List of oil fields
• List of petroleum companies
• Oil burden
• Oil reserves
• Petroleum geology
• Thermal depolymerization
• Peak oil
• Waste oil
• List of countries by proven oil reserves

Notes

References

• Akiner, Shirin; Aldis, Anne, ed (2004). The Caspian: Politics, Energy and Security. New York: Routledge. ISBN 978-0-7007-0501-6. 
• Bauer Georg, Bandy Mark Chance (tr.), Bandy Jean A.(tr.) (1546). De Natura Fossilium.  translated 1955
• Hyne, Norman J. (2001). Nontechnical Guide to Petroleum Geology, Exploration, Drilling, and Production. PennWell Corporation. ISBN 087814823X. 
• Mabro, Robert; Organization of Petroleum Exporting Countries (2006). Oil in the 21st century: issues, challenges and opportunities. Oxford Press. ISBN 0199207380, 9780199207381. 
• Maugeri, Leonardo (2005). The Age of Oil: What They Don’t Want You to Know About the World’s Most Controversial Resource. Guilford, CT: Globe Pequot. p. 15. ISBN 978-1-59921-118-3. http://books.google.com/?id=mzHt5hYeXlIC. 
• Speight, James G. (1999). The Chemistry and Technology of Petroleum. Marcel Dekker. ISBN 0824702174. 

External links

Wikimedia Commons has media related to: Petroleum

Wikinews has related news: Commodities

• Petroleum at the Open Directory Project
• Petroleum Online e-Learning resource from IHRDC
• U.S. Energy Information Administration
  • U.S. Department of Energy EIA – World supply and consumption
  • Who are the major players supplying the world oil market?
• American Petroleum Institute – the trade association of the US oil industry.
• Oil survey – OECD International Energy Agency
• Oil volume-weight and price converter
• Oil and Gas Industry Learning Center – information on oil and gas processes

v • d • e Petroleum industry Exploration Petroleum engineering (Reservoir simulation • Seismic to simulation) · Petroleum geology · Geophysics · Seismic (Seismic inversion) · Petrophysics · Core sampling Drilling Drilling engineering · Underbalanced drilling · Directional drilling (Measurement • Geosteering) · Drilling fluid · Drill stem test Development Completion (Squeeze job) · Well logging · Pipeline transport · Tracers Production Artificial lift (Pumpjack • Submersible pump (ESP) • Gas lift) · Enhanced oil recovery (EOR) (Steam injection • Gas reinjection) · Water injection · Well intervention · Upstream · Midstream · Downstream · Refining Technical challenges Differential sticking · Drilling fluid invasion · Blowouts · Lost circulation Oil and gas agreements Production sharing agreements · Concessions · Service agreements · Risk agreements Data by country Total energy (consumption per capita • intensity) · Natural gas (consumption • production • reserves • imports • exports) · Petroleum (consumption • production • reserves • imports • exports) Supermajors ExxonMobil · Royal Dutch Shell · BP · Chevron Corporation · ConocoPhillips · Total S.A. Major oil provinces North Sea · East Texas · Persian Gulf · Athabasca oil sands · Gulf of Mexico · Venezuela · Niger Delta · Russia Related articles OPEC (Organization of the Petroleum Exporting Countries) · History of petroleum · Peak oil · Oil price increases since 2003 · Price of petroleum · Society of Petroleum Engineers · Swing producer See also National oil companies

Natural gas is a gas consisting primarily of methane. It is found associated with other fossil fuels, in coal beds, as methane clathrates, and is created by methanogenic organisms in marshes, bogs, and landfills. It is an important fuel source, a major feedstock for fertilizers, and a potent greenhouse gas.

Before natural gas can be used as a fuel, it must undergo extensive processing to remove almost all materials other than methane. The by-products of that processing include ethane, propane, butanes, pentanes, and higher molecular weight hydrocarbons, elemental sulfur, carbon dioxide, water vapor, and sometimes helium and nitrogen.

Natural gas is often informally referred to as simply gas, especially when compared to other energy sources such as oil or coal.

Contents 1 Sources 1.1 Fossil natural gas 1.2 Town gas 1.3 Biogas 1.4 Crystallized natural gas – Hydrates 2 Natural gas processing 3 Uses 3.1 Power generation 3.2 Domestic use 3.3 Transportation 3.4 Fertilizers 3.5 Aviation 3.6 Hydrogen 3.7 Other 4 Storage and transport 5 Environmental effects 5.1 CO2 emissions 5.2 Other pollutants 6 Safety 7 Energy content, statistics and pricing 7.1 United Kingdom 7.2 European Union 7.3 United States 7.4 Elsewhere 8 See also 9 References 10 External links

Sources

Fossil natural gas

In the 1800s, natural gas was usually produced as a byproduct of producing oil, since the small, light gas carbon chains come out of solution as it undergoes pressure reduction from the reservoir to the surface, similar to uncapping a bottle of soda pop where the carbon dioxide effervesces. Unwanted natural gas can be a disposal problem at the well site. If there is not a market for natural gas near the wellhead it was virtually valueless since it must be piped to the end user. In the 1800s and early 1900s, such unwanted gas was usually burned off at the wellsite. Often, unwanted gas (or ‘stranded’ gas without a market) is pumped back into the reservoir with an ‘injection’ well for disposal or repressurizing the producing formation. In locations (such as the United States) with a high natural gas demand, pipelines are constructed to take the gas from the wellsite to the end consumer.

Another solution is to export the natural gas as a liquid.^[1] Gas-to-liquid, (GTL) is a developing technology that converts stranded natural gas into synthetic gasoline, diesel or jet fuel through the Fischer-Tropsch process developed in World War II Germany. Such fuels can be transported through conventional pipelines and tankers to users. Proponents claim GTL fuels burn cleaner than comparable petroleum fuels. Most major international oil companies are in advanced development stages of GTL production, with a world-scale (140,000 barrels a day) GTL plant in Qatar scheduled to come online before 2010.

Fossil natural gas can be “associated” (found in oil fields) or “non-associated” (isolated in natural gas fields), and is also found in coal beds (as coalbed methane). It sometimes contains significant quantities of ethane, propane, butane, and pentane—heavier hydrocarbons removed prior to use as a consumer fuel—as well as carbon dioxide, nitrogen, helium and hydrogen sulfide.^[2]

Natural gas is commercially produced from oil fields and natural gas fields. Gas produced from oil wells is called casinghead gas or associated gas. The natural gas industry is producing gas from increasingly more challenging resource types: sour gas, tight gas, shale gas and coalbed methane.

The world’s largest proven gas reserves are located in Russia, with 4.757 × 10¹³ m³ (1.6 × 10¹⁵ cubic feet). Russia is also the world’s largest natural gas producer, through the Gazprom company. Major proven resources (with year of estimate) (in billion cubic metres) are world 175,400 (2006), Russia 47,570 (2006), Iran 26,370 (2006), Qatar 25,790 (2007), Saudi Arabia 6,568 (2006) and United Arab Emirates 5,823 (2006). It is estimated that there are also about 900 tetrillion cubic metres of “unconventional” gas such as shale gas, of which 180 tetrillion may be recoverable.^[3]

The world’s largest gas field is Qatar‘s offshore North Field, estimated to have 25 trillion cubic metres^[4] (9.0 × 10¹⁴cubic feet) of gas in place—enough to last more than 200 years at optimum production levels. The second largest natural gas field is the South Pars Gas Field in Iranian waters in the Persian Gulf. Connected to Qatar’s North Field, it has estimated reserves of 8 to 14 trillion cubic metres^[5] (2.8 × 10¹⁴ to 5.0 × 10¹⁴ cubic feet) of gas.

Because natural gas is not a pure product, as the reservoir pressure drops when non-associated gas is extracted from a field under supercritical (pressure/temperature) conditions, the higher molecular weight components may partially condense upon isothermic depressurizing—an effect called retrograde condensation. The liquids thus formed may get trapped by depositing in the pores of the gas reservoir. One method to deal with this problem is to reinject dried gas free of condensate to maintain the underground pressure and to allow reevaporation and extraction of condensates.

Town gas

Town gas is a mixture of methane and other gases, mainly the highly toxic carbon monoxide, that can be used in a similar way to natural gas and can be produced by treating coal chemically. This is a historic technology, still used as ‘best solution’ in some local circumstances, although coal gasification is not usually economic at current gas prices. However, depending upon infrastructure considerations, it remains a future possibility.

Most town “gashouses” located in the eastern United States in the late nineteenth and early twentieth centuries were simple by-product coke ovens which heated bituminous coal in air-tight chambers. The gas driven off from the coal was collected and distributed through town-wide networks of pipes to residences and other buildings where it was used for cooking and lighting purposes. (Gas heating did not come into widespread use until the last half of the twentieth century.) The coal tar that collected in the bottoms of the gashouse ovens was often used for roofing and other water-proofing purposes, and also, when mixed with sand and gravel, was used for creating bitumen for the surfacing of local streets.

Biogas

When methane-rich gases are produced by the anaerobic decay of non-fossil organic matter (biomass), these are referred to as biogas (or natural biogas). Sources of biogas include swamps, marshes, and landfills (see landfill gas), as well as sewage sludge and manure^[6] by way of anaerobic digesters, in addition to enteric fermentation particularly in cattle.

Methanogenic archaea are responsible for all biological sources of methane, some in symbiotic relationships with other life forms, including termites, ruminants, and cultivated crops. Methane released directly into the atmosphere would be considered a pollutant. However, methane in the atmosphere is oxidized, producing carbon dioxide and water. Methane in the atmosphere has a half life of seven years, meaning that if a tonne of methane were emitted today, 500 kilograms would have broken down to carbon dioxide and water after seven years.

Other sources of methane, the principal component of natural gas, include landfill gas, biogas and methane hydrate. Biogas, and especially landfill gas, are already used in some areas, but their use could be greatly expanded. Landfill gas is a type of biogas, but biogas usually refers to gas produced from organic material that has not been mixed with other waste.

Landfill gas is created from the decomposition of waste in landfills. If the gas is not removed, the pressure may get so high that it works its way to the surface, causing damage to the landfill structure, unpleasant odor, vegetation die-off and an explosion hazard. The gas can be vented to the atmosphere, flared or burned to produce electricity or heat. Experimental systems were being proposed for use in parts Hertfordshire, UK and Lyon in France.

Once water vapor is removed, about half of landfill gas is methane. Almost all of the rest is carbon dioxide, but there are also small amounts of nitrogen, oxygen and hydrogen. There are usually trace amounts of hydrogen sulfide and siloxanes, but their concentration varies widely. Landfill gas cannot be distributed through utility natural gas pipelines unless it is cleaned up to less than 3% CO2, and a few parts per million H2S, because CO2 and H2S corrode the pipelines. ^[7] It is usually more economical to combust the gas on site or within a short distance of the landfill using a dedicated pipeline. Water vapor is often removed, even if the gas is combusted on site. If low temperatures condense water out of the gas, siloxanes can be lowered as well because they tend to condense out with the water vapor. Other non-methane components may also be removed in order to meet emission standards, to prevent fouling of the equipment or for environmental considerations. Co-firing landfill gas with natural gas improves combustion, which lowers emissions.

Gas generated in sewage treatment plants is commonly used to generate electricity. For example, the Hyperion sewage plant in Los Angeles burns 8 million cubic feet of gas per day to generate power ^[8] New York City utilizes gas to run equipment in the sewage plants, to generate electricity, and in boilers. ^[9] Using sewage gas to make electricity is not limited to large cities. The city of Bakersfield, California uses cogeneration at its sewer plants. ^[10] California has 242 sewage wastewater treatment plants, 74 of which have installed anaerobic digesters. The total biopower generation from the 74 plants is about 66 MW. ^[11]

Biogas is usually produced using agricultural waste materials, such as otherwise unusable parts of plants and manure. Biogas can also be produced by separating organic materials from waste that otherwise goes to landfills. Such method is more efficient than just capturing the landfill gas it produces. Using materials that would otherwise generate no income, or even cost money to get rid of, improves the profitability and energy balance of biogas production.

Anaerobic lagoons produce biogas from manure, while biogas reactors can be used for manure or plant parts. Like landfill gas, biogas is mostly methane and carbon dioxide, with small amounts of nitrogen, oxygen and hydrogen. However, with the exception of pesticides, there are usually lower levels of contaminants.

Crystallized natural gas – Hydrates

Huge quantities of natural gas (primarily methane) exist in the form of hydrates under sediment on offshore continental shelves and on land in arctic regions that experience permafrost such as those in Siberia (hydrates require a combination of high pressure and low temperature to form). However, as of 2010^[update] no technology has been developed to produce natural gas economically from hydrates.

It costs anywhere between once and twice as much to produce usable natural gas from crystallized natural gas, using current technology.^[13]

Natural gas processing

The image below is a schematic block flow diagram of a typical natural gas processing plant. It shows the various unit processes used to convert raw natural gas into sales gas pipelined to the end user markets.

The block flow diagram also shows how processing of the raw natural gas yields byproduct sulfur, byproduct ethane, and natural gas liquids (NGL) propane, butanes and natural gasoline (denoted as pentanes +).^{[14][15][16][17][18]}

Uses

Power generation

Natural gas is a major source of electricity generation through the use of gas turbines and steam turbines. Most grid peaking power plants and some off-grid engine-generators use natural gas. Particularly high efficiencies can be achieved through combining gas turbines with a steam turbine in combined cycle mode. Natural gas burns more cleanly than other fossil fuels, such as oil and coal, and produces less carbon dioxide per unit energy released. For an equivalent amount of heat, burning natural gas produces about 30% less carbon dioxide than burning petroleum and about 45% less than burning coal.^[19] Combined cycle power generation using natural gas is thus the cleanest source of power available using fossil fuels, and this technology is widely used wherever gas can be obtained at a reasonable cost. Fuel cell technology may eventually provide cleaner options for converting natural gas into electricity, but as yet it is not price-competitive.

Domestic use

The examples and perspective in this article deal primarily with the United States and do not represent a worldwide view of the subject. Please improve this article and discuss the issue on the talk page.

Natural gas is supplied to homes where it is used for such purposes as cooking in natural gas-powered ranges and ovens, natural gas-heated clothes dryers, heating/cooling and central heating. Home or other building heating may include boilers, furnaces, and water heaters. CNG is used in rural homes without connections to piped-in public utility services, or with portable grills. Natural gas is also supplied by independent natural gas suppliers through Natural Gas Choice programs throughout the United States. However, due to CNG being less economical than LPG, LPG (propane) is the dominant source of rural gas.

Transportation

Compressed natural gas (methane) is a cleaner alternative to other automobile fuels such as gasoline (petrol) and diesel. As of 2008 there were 9.6 million natural gas vehicles worldwide, led by Pakistan (2.0 million), Argentina (1.7 million), Brazil (1.6 million), Iran (1.0 million), and India (650,000).^[20][21] The energy efficiency is generally equal to that of gasoline engines, but lower compared with modern diesel engines. Gasoline/petrol vehicles converted to run on natural gas suffer because of the low compression ratio of their engines, resulting in a cropping of delivered power while running on natural gas (10%-15%). CNG-specific engines, however, use a higher compression ratio due to this fuel’s higher octane number of 120–130.^[22]

Fertilizers

Natural gas is a major feedstock for the production of ammonia, via the Haber process, for use in fertilizer production.

Aviation

Russian aircraft manufacturer Tupolev is currently running a development program to produce LNG- and hydrogen-powered aircraft.^[23] The program has been running since the mid-1970s, and seeks to develop LNG and hydrogen variants of the Tu-204 and Tu-334 passenger aircraft, and also the Tu-330 cargo aircraft. It claims that at current market prices, an LNG-powered aircraft would cost 5,000 roubles (~ $218/ £112) less to operate per ton, roughly equivalent to 60%, with considerable reductions to carbon monoxide, hydrocarbon and nitrogen oxide emissions.

The advantages of liquid methane as a jet engine fuel are that it has more specific energy than the standard kerosene mixes do and that its low temperature can help cool the air which the engine compresses for greater volumetric efficiency, in effect replacing an intercooler. Alternatively, it can be used to lower the temperature of the exhaust.

Hydrogen

Natural gas can be used to produce hydrogen, with one common method being the hydrogen reformer. Hydrogen has various applications: it is a primary feedstock for the chemical industry, a hydrogenating agent, an important commodity for oil refineries, and a fuel source in hydrogen vehicles.

Other

Natural gas is also used in the manufacture of fabrics, glass, steel, plastics, paint, and other products.

Storage and transport

Because of its low density, it is not easy to transport or store natural gas. Natural gas pipelines are impractical across oceans. Many existing pipelines in North America are close to reaching their capacity, prompting some politicians representing northern states to speak of potential shortages. In Europe, the gas pipeline network is already dense in the West^[24]. New pipelines are planned or under construction in Eastern Europe and between gas fields in Russia, Near East and Northern Africa and Western Europe. See also List of natural gas pipelines.

LNG carriers transport liquefied natural gas (LNG) across oceans, while tank trucks can carry liquefied or compressed natural gas (CNG) over shorter distances. Sea transport using CNG carrier ships that are now under development may be competitive with LNG transport in specific conditions.

Gas is turned into liquid at a liquefaction plant, and is returned to gas form at regasification plant at the terminal. Shipborne regasification equipment is also used. LNG is the preferred form for long distance, high volume transportation of natural gas, whereas pipeline is preferred for transport for distances up to 4,000 km over land and approximately half that distance offshore.

CNG is transported at high pressure, typically above 200 bars. Compressors and decompression equipment are less capital intensive and may be economical in smaller unit sizes than liquefaction/regasification plants. Natural gas trucks and carriers may transport natural gas directly to end-users, or to distribution points such as pipelines.

In the past, the natural gas which was recovered in the course of recovering petroleum could not be profitably sold, and was simply burned at the oil field in a process known as flaring. Flaring is now illegal in many countries.^[25] Additionally, companies now recognize that gas may be sold to consumers in the form of LNG or CNG, or through other transportation methods. The gas is now re-injected into the formation for later recovery. The re-injection also assists oil pumping by keeping underground pressures higher.

A “master gas system” was invented in Saudi Arabia in the late 1970s, ending any necessity for flaring. Satellite observation, however, shows that flaring^[26] and venting^[27] are still practiced in some gas-producing countries.

Natural gas is used to generate electricity and heat for desalination. Similarly, some landfills that also discharge methane gases have been set up to capture the methane and generate electricity.

Natural gas is often stored underground inside depleted gas reservoirs from previous gas wells, salt domes, or in tanks as liquefied natural gas. The gas is injected in a time of low demand and extracted when demand picks up. Storage nearby end users helps to meet volatile demands, but such storage may not always be practicable.

With 15 countries accounting for 84% of the worldwide production, access to natural gas has become an important issue in international politics, and countries vie for control of pipelines.^[28] In the 2000s, Gazprom, the state-owned energy company in Russia, engaged in disputes with Ukraine and Belarus over the price of natural gas, which have created worries that gas deliveries to parts of Europe could be cut off for political reasons.^[29]

Environmental effects

CO₂ emissions

Natural gas is often described as the cleanest fossil fuel, producing less carbon dioxide per joule delivered than either coal or oil.^[19], and far fewer pollutants than other fossil fuels. However, in absolute terms, it does contribute substantially to global carbon emissions, and this contribution is projected to grow. According to the IPCC Fourth Assessment Report (Working Group III Report, chapter 4), in 2004, natural gas produced about 5.3 billion tons a year of CO₂ emissions, while coal and oil produced 10.6 and 10.2 billion tons respectively (figure 4.4). According to an updated version of the SRES B2 emissions scenario, however, by the year 2030, natural gas would be the source of 11 billion tons a year, with coal and oil now 8.4 and 17.2 billion respectively^[30] (Total global emissions for 2004 were estimated at over 27,200 million tons).

In addition, natural gas itself is a greenhouse gas far more potent than carbon dioxide when released into the atmosphere, although natural gas is released in much smaller quantities. Natural gas is mainly composed of methane, which has a radiative forcing twenty times greater than carbon dioxide. Based on such composition, a ton of methane in the atmosphere traps in as much radiation as 20 tons of carbon dioxide. Carbon dioxide still receives the lion’s share of attention over greenhouse gases because it is released in much larger amounts. Still, it is inevitable when natural gas is used on a large scale that some of it will leak into the atmosphere. Current estimates by the EPA place global emissions of methane at 3 trillion cubic feet annually,^[31] or 3.2% of global production.^[32] Direct emissions of methane represented 14.3% of all global anthropogenic greenhouse gas emissions in 2004. ^[33]

Other pollutants

Natural gas produces far lower amounts of sulfur dioxide and nitrous oxides than any other fossil fuel.

Safety

In any form, a minute amount of odorant such as t-butyl mercaptan, with a rotting-cabbage-like smell, is added to the otherwise colorless and almost odorless gas, so that leaks can be detected before a fire or explosion occurs. Sometimes a related compound, thiophane is used, with a rotten-egg smell. Adding odorant to natural gas began in the United States after the 1937 New London School explosion. The buildup of gas in the school went unnoticed, killing three hundred students and faculty when it ignited. Odorants are considered non-toxic in the extremely low concentrations occurring in natural gas delivered to the end user.

In mines, where methane seeping from rock formations has no odor, sensors are used, and mining apparatuses have been specifically developed to avoid ignition sources such as the Davy lamp.

Explosions caused by natural gas leaks occur a few times each year. Individual homes, small businesses and boats are most frequently affected when an internal leak builds up gas inside the structure. Frequently, the blast will be enough to significantly damage a building but leave it standing. In these cases, the people inside tend to have minor to moderate injuries. Occasionally, the gas can collect in high enough quantities to cause a deadly explosion, disintegrating one or more buildings in the process. The gas usually dissipates readily outdoors, but can sometimes collect in dangerous quantities if weather conditions are right. However, considering the tens of millions of structures that use the fuel, the individual risk of using natural gas is very low.

Some gas fields yield sour gas containing hydrogen sulfide (H₂S). This untreated gas is toxic. Amine gas treating, an industrial scale process which removes acidic gaseous components, is often used to remove hydrogen sulfide from natural gas.^[34]

Extraction of natural gas (or oil) leads to decrease in pressure in the reservoir. Such decrease in pressure in turn may result in subsidence at ground level. Subsidence may affect ecosystems, waterways, sewer and water supply systems, foundations, and so on.

Natural gas heating systems are a minor source of carbon monoxide deaths in the United States. According to the US Consumer Product Safety Commission (2008), 56% of unintentional deaths from non-fire CO poisoning were associated with engine-driven tools like gas-powered generators and lawn mowers. Natural gas heating systems accounted for 4% of these deaths. Improvements in natural gas furnace designs have greatly reduced CO poisoning concerns. Detectors are also available that warn of carbon monoxide and/or explosive gas (methane, propane, etc.).

Energy content, statistics and pricing

Quantities of natural gas are measured in normal cubic meters (corresponding to 0°C at 101.325 kPa) or in standard cubic feet (corresponding to 60 °F (16 °C) and 14.73 psia). The gross heat of combustion of one cubic meter of commercial quality natural gas is around 39 megajoules (≈10.8 kWh), but this can vary by several percent. This comes to about 49 megajoules (≈13.5 kWh) for one kg of natural gas (assuming 0.8 kg/m^3, an approximate value).

The price of natural gas varies greatly depending on location and type of consumer. In 2007, a price of $7 per 1,000 cubic feet (28 m³) was typical in the United States. The typical caloric value of natural gas is roughly 1,000 British thermal units (BTU) per cubic foot, depending on gas composition. This corresponds to around $7 per million BTU, or around $7 per gigajoule. In April 2008, the wholesale price was $10 per 1,000 cubic feet (28 m³) ($10/MMBTU).^[35] The residential price varies from 50% to 300% more than the wholesale price. At the end of 2007, this was $12–$16 per 1,000 cu ft (28 m³).^[36] Natural gas in the United States is traded as a futures contract on the New York Mercantile Exchange. Each contract is for 10,000 MMBTU (~10,550 gigajoules), or 10 billion BTU. Thus, if the price of gas is $10 per million BTUs on the NYMEX, the contract is worth $100,000.

United Kingdom

Natural gas is also traded as a commodity in Europe, principally at the United Kingdom NBP and related European hubs, such as the TTF in the Netherlands.

European Union

As one of the world’s largest importers of natural gas, the EU is a major player on the international gas market. However, with Norway being one of the largest suppliers og natural gas in the world as part of the extended European Economic Area, most discussions can be conducted internally within the EU. However, the production in the North Sea will not last forever, so gas imports is expected to grow steadily. The main supplier is then expected to be the current number two: the Russian Federation.

Gas prices for end users vary greatly across the EU.^[37]. A single European energy market, one of the key objectives of the European Union, should level the prices of gas in all EU member states.

United States

In US units, one standard cubic foot of natural gas produces around 1,028 British thermal units (BTU). The actual heating value when the water formed does not condense is the net heat of combustion and can be as much as 10% less.^[38]

In the United States, retail sales are often in units of therms (th); 1 therm = 100,000 BTU. Gas meters measure the volume of gas used, and this is converted to therms by multiplying the volume by the energy content of the gas used during that period, which varies slightly over time. Wholesale transactions are generally done in decatherms (Dth), or in thousand decatherms (MDth), or in million decatherms (MMDth). A million decatherms is roughly a billion cubic feet of natural gas.

As of 2009, the Potential Gas Committee estimated that the United States has total future recoverable natural gas resources approximately 100 times greater than current annual consumption.^[39]

Elsewhere

In the rest of the world, LNG (liquified natural gas) and LPG (liquified petroleum gas) is traded in metric tons or mmBTU as spot deliveries. Long term contracts are signed in metric tons. The LNG and LPG is transported by specialized transport ships, as the gas is liquified at cryogenic temperatures. The specification of each LNG/LPG cargo will usually contain the energy content, but this information is in general not available to the public.

See also

Biogas Coalbed methane Compressed natural gas (CNG)       Drip gas Energy development Fuel injection Fuel station Gas leak

Gas oil ratio Giant oil and gas fields Landfill gas (LFG) Liquefied natural gas (LNG) Liquefied petroleum gas (LPG)       Natural gas by country Natural gas prices Natural gas processing

Natural gas storage Peak gas Renewable natural gas Shale gas World energy resources and consumption List of CO2 emitted per million Btu of energy from various fuels

References

External links

• CERA – collection of market and industry reports
• DOE/EIA EIA Natural Gas Weekly Update – current NG prices and market analysis
• Natural Gas Media- Natural Gas News and Analysis for Investment and Trading