Petroleum (L. petroleum, from Greek: petra (rock) + Latin: oleum (oil)^[1]) or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth’s surface. A fossil fuel, it is formed when large quantities of dead organisms, usually zooplankton and algae, are buried underneath sedimentary rock and undergo intense heat and pressure.

Petroleum is recovered mostly through oil drilling. This comes after the studies of structural geology (at the reservoir scale), sedimentary basin analysis, reservoir characterization (mainly in terms of porosity and permeable structures).^[2][3] It is refined and separated, most easily by boiling point, into a large number of consumer products, from petrol (or gasoline) and kerosene to asphalt and chemical reagents used to make plastics and pharmaceuticals.^[4] Petroleum is used in manufacturing a wide variety of materials,^[5] and it is estimated that the world consumes about 88 million barrels each day.

The use of fossil fuels such as petroleum can have a negative impact on Earth’s biosphere, releasing pollutants and greenhouse gases into the air and damaging ecosystems through events such as oil spills. Concern over the depletion of the earth’s finite reserves of oil, and the effect this would have on a society dependent on it, is a field known as peak oil.

Contents 1 Etymology 2 Composition 3 Chemistry 4 Empirical equations for thermal properties 4.1 Heat of combustion 4.2 Thermal conductivity 4.3 Specific heat 4.4 Latent heat of vaporization 5 Formation 6 Reservoirs 6.1 Crude oil reservoirs 6.2 Unconventional oil reservoirs 7 Classification 8 Petroleum industry 9 History 10 Price 11 Uses 11.1 Fuels 11.2 Other derivatives 11.3 Agriculture 12 Petroleum by country 12.1 Consumption statistics 12.2 Consumption 12.3 Production 12.4 Export 12.5 Import 12.6 Import by country 2010 12.7 Non-producing consumers 13 Environmental effects 13.1 Global warming 13.2 Extraction 13.3 Oil spills 13.4 Tarballs 13.5 Whales 14 Alternatives to petroleum 14.1 Alternatives to petroleum-based vehicle fuels 14.2 Alternatives to using oil in industry 14.3 Alternatives to burning petroleum for electricity 15 Future of petroleum production 15.1 Peak oil 16 See also 17 Notes 18 References 19 External links

Etymology

The word petroleum comes from Greek “petra” for rock and “elaion” for oil. The term was found (in the spelling “petraoleum”) in 10th-century Old English sources.^[6] It was used in the treatise De Natura Fossilium, published in 1546 by the German mineralogist Georg Bauer, also known as Georgius Agricola.^[7] In the 19th century, the term petroleum was frequently used to refer to mineral oils produced by distillation from mined organic solids such as cannel coal (and later oil shale), and refined oils produced from them; in the United Kingdom, storage (and later transport) of these oils were regulated by a series of Petroleum Acts, from the Petroleum Act 1862 c. 66 onward.

Composition

In its strictest sense, petroleum includes only crude oil, but in common usage it includes all liquid, gaseous, and solid (e.g., paraffin) hydrocarbons. Under surface pressure and temperature conditions, lighter hydrocarbons methane, ethane, propane and butane occur as gases, while pentane and heavier ones are in the form of liquids or solids. However, in an underground oil reservoir the proportions of gas, liquid, and solid depend on subsurface conditions and on the phase diagram of the petroleum mixture.^[8]

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 predominantly 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. At surface conditions these will condense out of the gas to form natural gas condensate, often shortened to condensate. Condensate resembles petrol in appearance and is similar in composition to some volatile light crude oils.

The proportion of light hydrocarbons in the petroleum mixture varies greatly among different oil fields, ranging 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:^[9]

Composition by weight

Element	Percent range
Carbon	83 to 87%
Hydrogen	10 to 14%
Nitrogen	0.1 to 2%
Oxygen	0.05 to 1.5%
Sulfur	0.05 to 6.0%
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.^[8]

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, black, tar-like form of crude oil which is so thick and heavy that it must be heated or diluted before it will flow.^[11] 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.^[12]

Petroleum is used mostly, by volume, for producing fuel oil and petrol, both important “primary energy“ sources.^[13] 84% by volume of the hydrocarbons present in petroleum is converted into energy-rich fuels (petroleum-based fuels), including petrol, diesel, jet, heating, and other fuel oils, and liquefied petroleum gas.^[14] 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 oil reserves are typically estimated at around 190 km³ (1.2 trillion (short scale) barrels) without oil sands,^[15] or 595 km³ (3.74 trillion barrels) with oil sands.^[16] Consumption is currently around 84 million barrels (13.4×10^⁶ m³) per day, or 4.9 km³ per year. Which in turn yields a remaining oil supply of only about 120 years, if current demand remain static.

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 petrol, the ones from nonane (C₉H₂₀) to hexadecane (C₁₆H₃₄) into diesel fuel, kerosene and jet fuel. Alkanes with more than 16 carbon atoms can be refined 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 petrol 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 petrol, jet fuel, kerosene, and other hydrocarbons. For example, 2,2,4-Trimethylpentane (isooctane), widely used in petrol, has a chemical formula of C₈H₁₈ and it reacts with oxygen exothermically:^[17]

2 C₈H_18(l) + 25 O_2(g) → 16 CO_2(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.^[18] Due to the large number of co-eluted hydrocarbons within oil, many cannot be resolved by traditional gas chromatography and typically appear as a hump in the chromatogram. This unresolved complex mixture (UCM) of hydrocarbons is particularly apparent when analysing weathered oils and extracts from tissues of organisms exposed to oil.

Incomplete combustion of petroleum or petrol 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 petrol combustion in car engines usually include nitrogen oxides which are responsible for creation of photochemical smog.

Empirical equations for thermal properties

Heat of combustion

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

.

where is measured in cal/gram and d is the specific gravity at 60 °F (16 °C).

Thermal conductivity

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

0.547

where K is measured in BTU · hr⁻¹ft⁻² , t is measured in °F and d is the specific gravity at 60 °F (16 °C).

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 (16 °C).

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 (16 °C).

In units of kcal/kg, the formula is:

,

where the temperature t is in Celsius and d is the specific gravity at 15 °C.^[19]

Formation

Petroleum is a fossil fuel derived from ancient fossilized organic materials, such as zooplankton and algae.^[20] Vast quantities of these remains settled to sea or lake bottoms, mixing with sediments and being buried under anoxic conditions. As further layers settled to the sea or lake bed, intense heat and pressure built up in the lower regions. 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. Formation of petroleum occurs from hydrocarbon pyrolysis in a variety of mainly endothermic reactions at high temperature and/or pressure.^[21]

There were certain warm nutrient-rich environments such as the Gulf of Mexico and the ancient Tethys Sea where the large amounts of organic material falling to the ocean floor exceeded the rate at which it could decompose. This resulted in large masses of organic material being buried under subsequent deposits such as shale formed from mud. This massive organic deposit later became heated and transformed under pressure into oil.^[22]

Geologists often refer to the temperature range in which oil forms as an “oil window”^[23]—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 formed at extreme depths may migrate and become trapped at a much shallower level. The Athabasca Oil Sands are one example of this.

Reservoirs

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 less dense 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 biodegrade 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 always shales and do not contain oil, but are fined-grain sedimentary rocks containing an insoluble organic solid called kerogen. The kerogen 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 quantities of pitch, tar, and oil out of a sort of stone.” Although oil shales are found in many countries, the United States has the world’s largest deposits.^[24]

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 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 petrol, 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^[25]

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.^[26]

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 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,^[27] though by 2007 this had dropped to 21% of world oil consumed.^[28]

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.^[29]

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 and pesticides.

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.^[30] 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. By 347 AD, oil was produced from bamboo-drilled wells in China.^[31]

In the 1840s, the process to distill kerosene from petroleum was invented by James Young in Scotland and the first refinery was built 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 question of what constituted the first commercial oil well is a difficult one to answer. Edwin Drake‘s 1859 well near Titusville, Pennsylvania, is popularly considered the first modern well. Drake’s well is probably singled out because it was drilled, not dug; because it used a steam engine; because there was a company associated with it; and because it touched off a major boom. ^[33] However, there was considerable activity before Drake in various parts of the world in the mid-19th century. A group directed by Major Alexeyev of the Bakinskii Corps of Mining Engineers hand-drilled a well in the Baku region in 1848.^[34] There were engine-drilled wells in West Virginia in the same year as Drake’s well.^[35] An early commercial well was hand dug in Poland in 1853, and another in nearby Romania in 1857. At around the same time the world’s first, but small, oil refineries were opened at Jasło, in Poland, with a larger one being opened at Ploiești, in Romania, shortly after. Romania is the first country in the world to have its crude oil output officially recorded in international statistics, namely 275 tonnes.^[36][37] By the end of the 19th century the Russian Empire, particularly the Branobel company in Azerbaijan, had taken the lead in production.^[38]

Access to oil was and still is a major factor in several military conflicts of the twentieth century, including World War II, during which oil facilities were a major strategic asset and were extensively bombed.^[39] Operation Barbarossa included the goal to capture the Baku oilfields, as it would provide much needed oil-supplies for the German military which was suffering from blockades.^[40] 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, the United States was surpassed by Saudi Arabia and Russia.

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 1% 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. Viability of the oil commodity is controlled by several key parameters, number of vehicles in the world competing for fuel, quantity of oil exported to the world market (Export Land Model), Net Energy Gain (economically useful energy provided minus energy consumed), political stability of oil exporting nations and ability to defend oil supply lines.

The top three oil producing countries are Saudi Arabia, Russia, and the United States.^[41] 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 oil shale in Venezuela. While significant volumes of oil are extracted from oil sands, particularly in Canada, logistical and technical hurdles remain, as oil extraction requires large amounts of heat and water, making its net energy content quite low relative to conventional crude oil. Thus, Canada’s oil sands are not expected to provide more than a few million barrels per day in the foreseeable future.

Conventional crude oil production, those having Net Energy Gain above 10 stopped growing in 2005 at about 74 million barrels per day (11,800,000 m³/d). The International Energy Agency‘s (IEA) 2010 World Energy Outlook estimated that conventional crude oil production has peaked and is depleting at 6.8% per year^{[citation needed]}. US Joint Forces Command‘s Joint Operating Environment 2010 issued this warning to all US military commands “By 2012, surplus oil production capacity could entirely disappear, and as early as 2015, the shortfall in output could reach nearly 10 million barrels per day.”

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.^[42] 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.^[42] The current reference, or pricing markers, are Brent, WTI, and Dubai/Oman.^[42]

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 distillation fractions of petroleum are fuels. Fuels include (by increasing boiling temperature range):^[43]

Common fractions of petroleum as fuels

Fraction	Boiling Range oC
Liquefied petroleum gas (LPG)	−40
Butane	−12 to −1
Petrol	−1 to 180
Jet fuel	150 to 205
Kerosene	205 to 260
Fuel oil	205 to 290
Diesel fuel	260 to 315

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.

Agriculture

Since the 1940s, agricultural productivity has increased dramatically, due largely to the increased use of energy-intensive mechanization, fertilizers and pesticides. Nearly all pesticides and many fertilizers are made from oil.^[44]

Petroleum by country

Consumption statistics

• 

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

• 

  EIA Primary Energy Outlook (retrieved on 2011-06)

• 

  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

• World Oil Consumption in 2010 by Region-Enerdata Energy Statistics.jpg

  Oil consumption in 2010 in the world and by region. Global Energy Statistical Yearbook 2011

Consumption

According to the CIA World Factbook estimate for 2010 the world consumes about 87 million barrels of oil each day.

This table orders the amount of petroleum consumed in 2008 in thousand barrels (1000 bbl) per day and in thousand cubic metres (1000 m³) per day:^[45][46][47]

Consuming Nation 2008	(1000 bbl/day)	(1000 m3/day)	population in millions	bbl/year per capita	m3/year per capita
United States 1	19,497.95	3,099.9	314	22.6	3.59
China	7,831.00	1,245.0	1345	2.1	0.33
Japan 2	4,784.85	760.7	127	13.7	2.18
India 2	2,962.00	470.9	1198	0.9	0.14
Russia 1	2,916.00	463.6	140	7.6	1.21
Germany 2	2,569.28	408.5	82	11.4	1.81
Brazil	2,485.00	395.1	193	4.7	0.75
Saudi Arabia (OPEC)	2,376.00	377.8	25	33.7	5.36
Canada	2,261.36	359.5	33	24.6	3.91
South Korea 2	2,174.91	345.8	48	16.4	2.61
Mexico 1	2,128.46	338.4	109	7.1	1.13
France 2	1,986.26	315.8	62	11.6	1.84
Iran (OPEC)	1,741.00	276.8	74	8.6	1.37
United Kingdom 1	1,709.66	271.8	61	10.1	1.61
Italy 2	1,639.01	260.6	60	10	1.6

Source: US Energy Information Administration

Population Data:^[48]

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)	103bbl/d (2009)	Present Share
1	Saudi Arabia (OPEC)	10,665	10,234	10,782	9,760	11.8%
2	Russia 1	9,677	9,876	9,789	9,934	12.0%
3	United States 1	8,331	8,481	8,514	9,141	11.1%
4	Iran (OPEC)	4,148	4,043	4,174	4,177	5.1%
5	China	3,846	3,901	3,973	3,996	4.8%
6	Canada 2	3,288	3,358	3,350	3,294	4.0%
7	Mexico 1	3,707	3,501	3,185	3,001	3.6%
8	United Arab Emirates (OPEC)	2,945	2,948	3,046	2,795	3.4%
9	Kuwait (OPEC)	2,675	2,613	2,742	2,496	3.0%
10	Venezuela (OPEC) 1	2,803	2,667	2,643	2,471	3.0%
11	Norway 1	2,786	2,565	2,466	2,350	2.8%
12	Brazil	2,166	2,279	2,401	2,577	3.1%
13	Iraq (OPEC) 3	2,008	2,094	2,385	2,400	2.9%
14	Algeria (OPEC)	2,122	2,173	2,179	2,126	2.6%
15	Nigeria (OPEC)	2,443	2,352	2,169	2,211	2.7%
16	Angola (OPEC)	1,435	1,769	2,014	1,948	2.4%
17	Libya (OPEC)	1,809	1,845	1,875	1,789	2.2%
18	United Kingdom	1,689	1,690	1,584	1,422	1.7%
19	Kazakhstan	1,388	1,445	1,429	1,540	1.9%
20	Qatar (OPEC)	1,141	1,136	1,207	1,213	1.5%
21	Indonesia	1,102	1,044	1,051	1,023	1.2%
22	India	854	881	884	877	1.1%
23	Azerbaijan	648	850	875	1,012	1.2%
24	Argentina	802	791	792	794	1.0%
25	Oman	743	714	761	816	1.0%
26	Malaysia	729	703	727	693	0.8%
27	Egypt	667	664	631	678	0.8%
28	Colombia	544	543	601	686	0.8%
29	Australia	552	595	586	588	0.7%
30	Ecuador (OPEC)	536	512	505	485	0.6%
31	Sudan	380	466	480	486	0.6%
32	Syria	449	446	426	400	0.5%
33	Equatorial Guinea	386	400	359	346	0.4%
34	Thailand	334	349	361	339	0.4%
35	Vietnam	362	352	314	346	0.4%
36	Yemen	377	361	300	287	0.3%
37	Denmark	344	314	289	262	0.3%
38	Gabon	237	244	248	242	0.3%
39	South Africa	204	199	195	192	0.2%
40	Turkmenistan	No data	180	189	198	0.2%

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

In order of net exports in 2009 and 2006 in thousand bbl/d and thousand m³/d:

#	Exporting Nation	103bbl/d (2009)	103m3/d (2009)	103bbl/d (2006)	103m3/d (2006)
1	Saudi Arabia (OPEC)	7,322	1,164	8,651	1,376
2	Russia 1	7,194	1,144	6,565	1,044
3	Iran (OPEC)	2,486	395	2,519	401
4	United Arab Emirates (OPEC)	2,303	366	2,515	400
5	Norway 1	2,132	339	2,542	404
6	Kuwait (OPEC)	2,124	338	2,150	342
7	Nigeria (OPEC)	1,939	308	2,146	341
8	Angola (OPEC)	1,878	299	1,363	217
9	Algeria (OPEC) 1	1,767	281	1,847	297
10	Iraq (OPEC)	1,764	280	1,438	229
11	Venezuela (OPEC) 1	1,748	278	2,203	350
12	Libya (OPEC) 1	1,525	242	1,525	242
13	Kazakhstan	1,299	207	1,114	177
14	Canada 2	1,168	187	1,071	170
15	Qatar (OPEC)	1,066	169	–	–
–	Mexico 1	1,039	165	1,676	266

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 2,500,000 bbl/d (400,000 m³/d) in August 2007. [2].

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

Import

In order of net imports in 2009 and 2006 in thousand bbl/d and thousand m³/d:

#	Importing Nation	103bbl/day (2009)	103m3/day (2009)	103bbl/day (2006)	103m3/day (2006)
1	United States 1	9,631	1,531	12,220	1,943
2	China 2	4,328	688	3,438	547
3	Japan	4,235	673	5,097	810
4	Germany	2,323	369	2,483	395
5	India	2,233	355	1,687	268
6	South Korea	2,139	340	2,150	342
7	France	1,749	278	1,893	301
8	United Kingdom	1,588	252	–	–
9	Spain	1,439	229	1,555	247
10	Italy	1,381	220	1,558	248
11	Netherlands	973	155	936	149
12	Republic of China (Taiwan)	944	150	942	150
13	Singapore	916	146	787	125
14	Turkey	650	103	576	92
15	Belgium	597	95	546	87
–	Thailand	538	86	606	96

Source: US Energy Information Administration

¹ peak production of oil already passed in this state^{[citation needed]}

² Major oil producer whose production is still increasing^{[citation needed]}

Import by country 2010

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 (seismic exploration, drilling, extraction, refining and combustion). Phenomena such as seeps^[50] and tar pits are examples of areas that petroleum affects without man’s involvement. Regardless of source, petroleum’s effects when released into the environment are similar.

Global warming

When burned, petroleum releases carbon dioxide; a greenhouse gas. Along with the burning of coal, petroleum combustion is the largest contributor to the increase in atmospheric CO₂. Atmospheric CO₂ has risen steadily since the industrial revolution to current levels of over 380ppmv, from the 180 – 300ppmv of the prior 800 thousand years, driving global warming.^[51][52][53] The unbridled use of petroleum could potentially cause a runaway greenhouse effect on Earth.^{[citation needed]}

Extraction

Oil extraction is simply the removal of oil from the reservoir (oil pool). Oil is often recovered as a water-in-oil emulsion, and specialty chemicals called demulsifiers are used to separate the oil from water. 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.^[54]

Oil spills

Crude oil and refined fuel spills from tanker ship accidents have damaged natural ecosystems in Alaska, the Gulf of Mexico, 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., Deepwater Horizon Oil Spill, 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;^[55] modern techniques would include pumping the oil from the wreck, like in the Prestige oil spill or the Erika oil spill.^[56]

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.^[57]

Degradation of underground tanks located at gas stations may also occur, significantly affecting soil and groundwater. In these instances of the biological degradation of petroleum hydrocarbons, solutions such as bioremediation may be used.^{[citation needed]}

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.^[58][59] 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,^[60][61] and tarballs themselves may be dispersed over long distances by deep sea currents.^[59] They are slowly decomposed by bacteria, including Chromobacterium violaceum, Cladosporium resinae, Bacillus submarinus, Micrococcus varians, Pseudomonas aeruginosa, Candida marina and Saccharomyces estuari.^[58]

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.^[62]

Alternatives to petroleum

In the United States in 2007 about 70% of petroleum was used for transportation (e.g. petrol, diesel, jet fuel), 24% by industry (e.g. production of plastics), 5% for residential and commercial uses, and 2% for electricity production.^[63] Outside of the US, a higher proportion of petroleum tends to be used for electricity.^[64]

Alternatives to petroleum-based vehicle fuels

Alternative fuel vehicles refers to both:

• vehicles that use alternative fuels used in standard or modified internal combustion engines such as natural gas vehicles, neat ethanol vehicles, flexible-fuel vehicles, biodiesel-powered vehicles, and hydrogen vehicles.
• vehicles with advanced propulsion systems that reduce or substitute petroleum use such as battery electric vehicles, plug-in hybrid electric vehicles, hybrid electric vehicles, and hydrogen fuel cell vehicles.

Alternatives to using oil in industry

This section requires expansion.

Biological feedstocks do exist for industrial uses such as Bioplastic production.^[65]

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 and twenty-first centuries has been abundantly pushed by automobile growth; the 1985–2003 oil glut even fuelled the sales of low economy vehicles 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.^[66] 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 oil sales, and both OPEC and EIA kept lowering their 2020 consumption estimates during the past 5 years.^[67] 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^[68] ) will continue to play a major role in increasing the world’s recoverable oil.

Peak oil

Peak Oil is the scientific projection 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.^[69]

Hubbert applied his theory to accurately 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 world peak oil in “half a century” after his publication, which would be 2006.^[70]

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.^[71] The scientist and researchers from Oxford University argue that official figures are inflated because OPEC members over-reported reserves in the 1980s when competing for global market share.^[72] 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.^{[original research?]}

The International Energy Agency (IEA) says production of conventional crude oil peaked in 2006.^[73][74] Since virtually all economic sectors rely heavily on petroleum, peak oil could lead to a “partial or complete failure of markets.”^[75]

See also

Wikinews has news related to: Energy

• Barrel of oil equivalent
• Gas oil ratio
• Gross domestic product per barrel
• Hydrocarbon
• List of countries by proven oil reserves
• List of oil fields
• List of petroleum companies
• Manure-derived synthetic crude oil
• Oil burden
• Petroleum geology
• Thermal depolymerization
• Total petroleum hydrocarbon
• Waste oil
• Tar Sands

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) (in (Latin)). De Natura Fossilium.  translated 1955
• Hyne, Norman J. (2001). Nontechnical Guide to Petroleum Geology, Exploration, Drilling, and Production. PennWell Corporation. ISBN 0-87814-823-X. 
• Mabro, Robert; Organization of Petroleum Exporting Countries (2006). Oil in the 21st century: issues, challenges and opportunities. Oxford Press. ISBN 0-19-920738-0, 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 0-8247-0217-4. 
• Vassiliou, Marius (2009). Historical Dictionary of the Petroleum Industry. Scarecrow Press (Rowman & Littlefield). ISBN 0-8108-5993-9. 

External links

Wikimedia Commons has media related to: Petroleum

• 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 and Gas Industry Learning Center – information on oil and gas processes
• U.S. National Library of Medicine: Hazardous Substances Databank – Crude Oil

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Natural gas is a naturally occurring hydrocarbon gas mixture consisting primarily of methane, with up to 20 %^[1] of other hydrocarbons as well as impurities in varying amounts such as carbon dioxide. Natural gas is widely used as an important energy source in many applications including heating buildings, generating electricity, providing heat and power to industry, as fuel for vehicles and as a chemical feedstock in the manufacture of products such as plastics and other commercially important organic chemicals.

Natural gas is found in deep underground natural rock formations or associated with other hydrocarbon reservoirs, in coal beds, and as methane clathrates. Oil is also another resource found near and with natural gas. Most natural gas was created over time by two mechanisms: biogenic and thermogenic. Biogenic gas is created by methanogenic organisms in marshes, bogs, landfills, and shallow sediments. Deeper in the earth, at greater temperature and pressure, thermogenic gas is created from buried organic material.^[2][3]

Before natural gas can be used as a fuel, it must undergo processing to clean the gas and remove impurities including water in order to meet the specifications of marketable natural gas. The by-products of processing include ethane, propane, butanes, pentanes, and higher molecular weight hydrocarbons, hydrogen sulphide (which may be converted into pure sulfur), carbon dioxide, water vapor, and sometimes helium and nitrogen.

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

Contents 1 Sources 1.1 Natural gas 1.2 Town gas 1.3 Biogas 1.4 Crystallized natural gas — hydrates 2 Natural gas processing 3 Depletion 4 Uses 4.1 Power generation 4.2 Domestic use 4.3 Transportation 4.4 Fertilizers 4.5 Aviation 4.6 Hydrogen 4.7 Other 5 Storage and transport 6 Environmental effects 6.1 CO2 emissions 6.2 Other pollutants 6.3 Extraction 7 Safety concerns 7.1 Production 7.2 Use 8 Energy content, statistics, and pricing 8.1 European Union 8.2 United States 8.3 Canada 8.4 Elsewhere 9 See also 10 References

Sources

Natural gas

In the 19th century, natural gas was usually obtained as a byproduct of producing oil, since the small, light gas carbon chains came out of solution as the extracted fluids underwent pressure reduction from the reservoir to the surface, similar to uncapping a bottle of soda pop where the carbon dioxide effervesces. Unwanted natural gas was a disposal problem in the active oil fields. If there was not a market for natural gas near the wellhead it was virtually valueless since it had to be piped to the end user. In the 19th century and early 20th century, such unwanted gas was usually burned off in the oil fields. Today, unwanted gas (or stranded gas without a market) associated with oil extraction often is returned to the reservoir with ‘injection’ wells while awaiting a possible future market or to repressurize the formation, which can enhance extraction rates from other wells. In regions with a high natural gas demand (such as the US), pipelines are constructed when economically feasible to move the gas from the wellsite to the end consumer.

Another possibility is to export the natural gas as a liquid. Gas-to-liquids (GTL) is a developing technology that converts stranded natural gas into synthetic gasoline, diesel, or jet fuel through the Fischer-Tropsch process developed during World War II by Germany. Such fuel can be transported to users through conventional pipelines and tankers. Proponents claim GTL burns cleaner than comparable petroleum fuels. Most major international oil companies are in an advanced stage of GTL production. A world-scale (140,000 barrels (22,000 m³) a day) GTL plant in Qatar went into production in 2011.

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 amounts of ethane, propane, butane, and pentane—heavier hydrocarbons removed for commercial use prior to the methane being sold as a consumer fuel or chemical plant feedstock. Non-hydrocarbons such as carbon dioxide, nitrogen, helium (rarely), and hydrogen sulfide must also be removed before the natural gas can be transported.^[4]

Natural gas is commercially extracted from oil fields and natural gas fields. Gas extracted from oil wells is called casinghead gas or associated gas. The natural gas industry is extracting 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 (1.68×10¹⁵ cubic feet). With the Gazprom company, Russia is frequently the world’s largest natural gas extractor. Major proven resources (in billion cubic meters) 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 about 900 trillion cubic meters of “unconventional” gas such as shale gas, of which 180 trillion may be recoverable.^[5] In turn, many studies from MIT, Black & Veatch and the DOE — see natural gas — will account for a larger portion of electricity generation and heat in the future.^[6]

The world’s largest gas field is Qatar‘s offshore North Field, estimated to have 25 trillion cubic meters^[7] (9.0×10¹⁴cubic feet) of gas in place—enough to last more than 420 years^{[citation needed]} at optimum extraction levels. The second largest natural gas field is the South Pars Gas Field in Iranian waters in the Persian Gulf. Located next to Qatar’s North Field, it has an estimated reserve of 8 to 14 trillion cubic meters^[8] (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 liquid thus formed may get trapped as the pores of the gas reservoir get deposited. One method to deal with this problem is to re-inject dried gas free of condensate to maintain the underground pressure and to allow re-evaporation and extraction of condensates. More frequently, the liquid condenses at the surface, and one of the tasks of the gas plant is to collect this condensate. The resulting liquid is called natural gas liquid (NGL) and has commercial value.

Town gas

Town gas, a synthetically produced mixture of methane and other gases, mainly the highly toxic carbon monoxide, is used in a similar way to natural gas and can be produced by treating coal chemically. This is an historical technology, not usually economically competitive with other sources of fuel gas today. But there are still some specific cases where it is the best option and it may be so into the future.

Most town “gashouses” located in the eastern US in the late 19th and early 20th 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 networks of pipes to residences and other buildings where it was used for cooking and lighting. (Gas heating did not come into widespread use until the last half of the 20th century.) The coal tar (or asphalt) that collected in the bottoms of the gashouse ovens was often used for roofing and other water-proofing purposes, and when mixed with sand and gravel was used for paving 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^[9] 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 of 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.^[10] 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 (230,000 m³) of gas per day to generate power^[11] New York City utilizes gas to run equipment in the sewage plants, to generate electricity, and in boilers.^[12] Using sewage gas to make electricity is not limited to large cities. The city of Bakersfield, California, uses cogeneration at its sewer plants.^[13] 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.^[14]

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. This 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 yet to extract natural gas economically from hydrates.

In 2010, using current technology, the cost of extracting natural gas from crystallized natural gas is estimated to 100–200% the cost of extracting natural gas from conventional sources, and even higher from offshore deposits.^[16]

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 +).^{[17][18][19][20][21]}

Depletion

See main article, Gas depletion

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 hydrocarbon fuels, such as oil and coal, and produces less carbon dioxide per unit of 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.^[22] Combined cycle power generation using natural gas is thus the cleanest source of power available using hydrocarbon 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. (December 2010)

Natural gas dispensed from a simple stovetop can generate heat in excess of 2000°F (1093°C) making it a powerful domestic cooking and heating fuel.^[23] In much of the developed world it is supplied to homes via pipes where it is used for many purposes including 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. Compressed natural gas (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

CNG 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).^[24][25] 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.^[26]

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.^[27] 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 many applications: it is a primary feedstock for the chemical industry, a hydrogenating agent, an important commodity for oil refineries, and the 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 store natural gas or transport by vehicle. Natural gas pipelines are impractical across oceans. Many existing pipelines in 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.^[28] 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.^[29] 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^[30] and venting^[31] are still practiced in some gas-extracting 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 extraction, access to natural gas has become an important issue in international politics, and countries vie for control of pipelines.^[32] In the first decade of the 21st century, Gazprom, the state-owned energy company in Russia, engaged in disputes with Ukraine and Belarus over the price of natural gas, which have created concerns that gas deliveries to parts of Europe could be cut off for political reasons.^[33]

Floating Liquefied Natural Gas (FLNG) is an innovative technology designed to enable the development of offshore gas resources that would otherwise remain untapped because due to environmental or economic factors it is nonviable to develop them via a land-based LNG operation. FLNG technology also provides a number of environmental and economic advantages:

• Environmental – Because all processing is done at the gas field, there is no requirement for long pipelines to shore, compression units to pump the gas to shore, dredging and jetty construction, and onshore construction of an LNG processing plant, which significantly reduces the environmental footprint.^[34] Avoiding construction also helps preserve marine and coastal environments. In addition, environmental disturbance will be minimised during decommissioning because the facility can easily be disconnected and removed before being refurbished and re-deployed elsewhere.

• Economic – Where pumping gas to shore can be prohibitively expensive, FLNG makes development economically viable. As a result, it will open up new business opportunities for countries to develop offshore gas fields that would otherwise remain stranded, such as those offshore East Africa.^[35]

Many gas and oil companies are considering the economic and environmental benefits of Floating Liquefied Natural Gas (FLNG). However, for the time being, the only FLNG facility now in development is being built by Shell,^[36] due for completion around 2017.^[37]

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^[22] and far fewer pollutants than other hydrocarbon fuels^{[citation needed]}. 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 because demand is increasing 1.9% a year.^[38] (Total global emissions for 2004 were estimated at over 27,200 million tons.)

In addition, natural gas itself is a greenhouse gas more potent than carbon dioxide. Although natural gas is released into the atmosphere in much smaller quantities, methane is oxidized in the atmosphere, and hence natural gas affects the atmosphere for approximately 12 years, compared to CO₂, which is already oxidized, and has effect for 100 to 500 years. Natural gas is composed mainly 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 as much radiation as 20 tons of carbon dioxide; however, it remains in the atmosphere for 8–40 times less time. Carbon dioxide still receives the lion’s share of attention concerning 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. (Coal methane not captured by coal bed methane extraction techniques is simply lost into the atmosphere. Current estimates by the EPA place global emissions of methane at 3 trillion cubic feet (85 km³) annually,^[39] or 3.2% of global production.^[40] Direct emissions of methane represented 14.3% of all global anthropogenic greenhouse gas emissions in 2004.^[41]

Other pollutants

Natural gas produces far lower amounts of sulfur dioxide and nitrous oxides than any other hydrocarbon fuel (fossil fuels).^[42] Carbon dioxide produced is 117,000 ppm vs 208,000 for burning coal. Carbon monoxide produced is 40 ppm vs 208 for burning coal^{[citation needed]}. Nitrogen oxides produced is 92 ppm vs 457 for burning coal. Sulfur dioxide is 1 ppm vs 2,591 for burning coal. Mercury is 0 vs .016 for burning coal.^[43] Particulates are also a major contribution to global warming. Natural gas has 7ppm vs coal’s 2,744ppm.^[44] Natural gas also has Radon, from 5 to 200,000 Becquerels per cubic meter. ^[45]

Extraction

According to Business Week, scientists at the National Oceanic and Atmospheric Administration (NOAA), which conducts much of the government’s climate science, then surprised nearly everyone in February when they revealed that air samples from an area of Colorado with a lot of wells contained twice the amount of methane the EPA estimated came from that production method.^[46]

The practice of hydraulic fracturing, the process of using a combination of chemicals ranging from harmless to toxic to force natural gas to the surface from reservoirs with low permeability, has come under scrutiny internationally due to concerns about environmental and health safety, and has been suspended or banned in some countries.

Safety concerns

Production

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

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.^[47]

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

Another ecosystem effect results from the noise of the process. This can change the composition of animal life in the area, and have consequences for plants as well in that animals disperse seeds and pollen.

Releasing the gas from low-permeability reservoirs is accomplished by a process called hydraulic fracturing or “hydrofracking”. To allow the natural gas to flow out of the shale, oil operators force 1 to 9 million US gallons (34,000 m³) of water mixed with a variety of chemicals through the wellbore casing into the shale. The high pressure water breaks up or “fracks” the shale, which releases the trapped gas. Sand is added to the water as a proppant to keep the fractures in the shale open, thus enabling the gas to flow into the casing and then to the surface. The chemicals are added to the frack fluid to reduce friction and combat corrosion. During the extracting life of a gas well, other low concentrations of other chemical substances may be used, such as biocides to eliminate fouling, scale and corrosion inhibitors, oxygen scavengers to remove a source of corrosion, and acids to clean the perforations in the pipe.

Dealing with fracking fluid can be a challenge. Along with the gas, 30% to 70% of the chemically-laced frack fluid, or flow back, returns to the surface. Additionally, a significant amount of salt and other minerals, once a part of the rock layers that were under prehistoric seas, may be incorporated in the flow back as they dissolve in the frack fluid.

Use

In order to assist in detecting leaks, a minute amount of odorant is added to the otherwise colorless and almost odorless gas used by consumers. The odor has been compared to the smell of rotten eggs, due to the added tert-Butylthiol or t-butyl mercaptan. Sometimes a related compound, thiophane may be used in the mixture. Situations in which an odorant that is added to natural gas can be detected by analytical instrumentation, but cannot be properly detected by an observer with a normal sense of smell, have occurred in the natural gas industry. This is caused by odor masking, when one odorant overpowers the sensation of another. As of 2011, the industry is conducting research on the causes of odor masking. ^[48]

Explosions caused by natural gas leaks occur a few times each year. Individual homes, small businesses and other structures 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 flow rates are high enough. However, considering the tens of millions of structures that use the fuel, the individual risk of using natural gas is very low.

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).^{[citation needed]}

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).^[49] 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).^[50] 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.

European Union

As one of the world’s largest importers of natural gas, the EU is a major player on the international gas market.

Gas prices for end users vary greatly across the EU.^[51] 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.^[52]

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. Gas sales to domestic consumers may be in units of 100 standard cubic feet (Ccf).

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.^[53]

Canada

Canada uses metric measure for internal trade of petrochemical products. Consequently, natural gas is sold by the Gigajoule, a measure approximately equal to 1/2 of a barrel (250lbs) of oil, or 1 million BTUs, or 1000 cu ft of gas, or 28cu metres of gas.

Elsewhere

In the rest of the world, natural gas is sold in Gigajoule retail units. LNG (liquefied natural gas) and LPG (liquefied petroleum gas) are traded in metric tons or mmBTU as spot deliveries. Long term natural gas distribution contracts are signed in cubic metres, and LNG contracts are in metric tonnes (1,000kg). 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.

In the Russian Federation, Gazprom sold approximately 250 billion cubic metres of natural gas in 2008.

See also

References