In petroleum production gas is often burnt as gas flare. The World Bank estimates that over 150 cubic kilometers of natural gas are flared or vented annually.
Before natural gas can be used as a fuel, most, but not all, natural gas processing to remove impurities, including water, to meet the specifications of marketable natural gas. The by-products of this processing include: ethane, propane, butanes, pentanes, and higher molecular weight hydrocarbons, hydrogen sulfide (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. However, it is not to be confused with gasoline, especially in North America, where the term gasoline is often shortened in colloquial usage to ''gas''.
Natural gas was discovered accidentally in ancient China, as it resulted from the drilling for Brine (solution)
. Natural gas was first used by the Chinese in about 500 BC (possibly even 1000 BC
). They discovered a way to transport gas seeping from the ground in crude pipelines of bamboo to where it was used to boil salt water to Salt in Chinese history
By 2009, 66 000 km³ (or 8%) had been used out of the total 850 000 km³ of estimated remaining recoverable reserves of natural gas.
In the 19th century, natural gas was usually obtained as a by-product of Oil well, since the small, light gas carbon chains came out of solution as the extracted fluids underwent pressure reduction from the Petroleum reservoir to the surface, similar to uncapping a soft drink bottle 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 prohibitively expensive to pipe to the end user.
In the 19th century and early 20th century, unwanted gas was usually Gas flare. Today, unwanted gas (or stranded gas reserve 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), Pipeline transport are constructed when it is economically feasible to transport gas from a wellsite to an end consumer.
In addition to transporting gas via pipelines for use in power generation, other end uses for natural gas include export as LNG (LNG) or conversion of natural gas into other liquid products via gas to liquids (GTL) technologies. GTL technologies can convert natural gas into liquids products such as gasoline, diesel or jet fuel. A variety of GTL technologies have been developed, including Fischer–Tropsch (F–T), methanol to gasoline (MTG) and syngas to gasoline plus (STG+). F–T produces a synthetic crude that can be further refined into finished products, while MTG can produce synthetic gasoline from natural gas. STG+ can produce drop-in gasoline, diesel, jet fuel and aromatic chemicals directly from natural gas via a single-loop process.
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 a significant amount 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.
Natural gas extracted from oil wells is called casinghead gas (whether or not truly produced up the annulus and through a casinghead outlet) or associated gas. The natural gas industry is extracting an increasing quantity of gas from challenging History of the petroleum industry in Canada (natural gas)#Unconventional gas: sour gas, tight gas, shale gas, and coalbed methane.
There is some disagreement on which country has the largest proven gas reserves. Sources that consider that Russia has by far the largest proven reserves include the US CIA (47 600 km³),
the US Energy Information Administration (47 800 km³), [US Energy Information Administration, International statistics, accessed 1 Dec. 2013.] and OPEC (48 700 km³). which would place it in second place, slightly behind Iran (33 100 to 33 800 km³, depending on the source). With Gazprom, Russia is frequently the world's largest natural gas extractor. Major proven resources (in cubic kilometers) are world 187 300 (2013), Iran 33 600 (2013), Russia 32 900 (2013), Qatar 25 100 (2013), Turkmenistan 17 500 (2013) and the United States 8500 (2013).
It is estimated that there are about 900 000 km³ of "unconventional" gas such as shale gas, of which 180 000 km³ may be recoverable.
[ of Natural-gas condensate.]
Because natural gas is not a pure product, as the reservoir pressure drops when non-associated gas is extracted from a field under Supercritical fluid (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 depleted. 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 Natural gas processing is to collect this condensate. The resulting liquid is called natural gas liquid (NGL) and has commercial value.
Town gas is a flammable gaseous fuel made by the destructive distillation of coal. It contains a variety of calorific gases including hydrogen, carbon monoxide, methane, and other volatile hydrocarbons, together with small quantities of non-calorific gases such as carbon dioxide and nitrogen, and is used in a similar way to natural gas. This is a historical technology and is not usually economically competitive with other sources of fuel gas today.
Most town "gashouses" located in the eastern US in the late 19th and early 20th centuries were simple by-product coke (fuel) ovens that 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 waterproofing purposes, and when mixed with sand and gravel was used for paving streets.
Some live in symbiotic relationships with other life forms, including termite
s, and cultivated crops. Other sources of methane
, the principal component of natural gas, include landfill gas
, biogas, and methane hydrate
. When methane-rich gases are produced by the anaerobic decay
of organic compound
), these are referred to as biogas (or natural biogas). Sources of biogas include swamp
es, and landfill
s, as well as agricultural waste
materials such as sewage sludge
by way of anaerobic digester
Crystallized natural gas — hydrates
Huge quantities of natural gas (primarily methane) exist in the form of methane clathrate
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.
In 2010, the cost of extracting natural gas from crystallized natural gas was estimated to be as much as twice the cost of extracting natural gas from conventional sources, and even higher from offshore deposits.
In 2013, Japan Oil, Gas and Metals National Corporation (JOGMEC) announced that they had recovered commercially relevant quantities of natural gas from methane hydrate.
The image below is a schematic Process 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 +).
It reached 24.1 million cubic feet in 1973, followed by a decline, and reached 24.5 million cubic feet in 2001. After a brief drop, withdrawals have been increasing nearly every year since 2006, with 2017 production at 33.4 million cubic feet.
Storage and transport
Because of its low density, it is not easy to store natural gas or to transport it by vehicle. Natural gas pipeline transport are impractical across oceans, since the gas needs to be cooled down and compressed, as the friction in the pipeline causes the gas to heat up. Many List of natural gas pipelines#North America are close to reaching their capacity, prompting some politicians representing northern states to speak of potential shortages. The large trade cost implies that natural gas markets are globally much less integrated, causing significant price differences across countries. In Western Europe, the gas pipeline network is already dense.
[. Usually sales quality gas that has been Natural-gas processing is traded on a "dry gas" basis and is required to be commercially free from objectionable odours, materials, and dust or other solid or liquid matter, waxes, gums and gum forming constituents, which might damage or adversely affect operation of equipment downstream of the custody transfer point.]
LNG carriers transport liquefied natural gas (LNG) across oceans, while tank trucks can carry liquefied or compressed natural gas (CNG) over shorter distances.
[. 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 gas flare. Flaring is now illegal in many countries.
Additionally, higher demand in the last 20–30 years has made production of gas associated with oil economically viable. As a further option, the gas is now sometimes re-wikt:inject into the formation for enhanced oil recovery by pressure maintenance as well as miscible or immiscible flooding. Conservation, re-injection, or flaring of natural gas associated with oil is primarily dependent on proximity to markets (pipelines), and regulatory restrictions.
Natural gas can be indirectly exported through the absorption in other physical output. A recent study suggests that the expansion of shale gas production in the US has caused prices to drop relative to other countries. This has caused a boom in energy intensive manufacturing sector exports, whereby the average dollar unit of US manufacturing exports has almost tripled its energy content between 1996 and 2012.
[ [https://www.ngdc.noaa.gov/ National Geophysical Data Center (NGDC)]]
Floating liquefied natural gasFloating liquefied natural gas
(FLNG) is an innovative technology designed to enable the development of offshore gas resources that would otherwise remain untapped 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.
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.
Many gas and oil companies are considering the economic and environmental benefits of floating liquefied natural gas (FLNG). There are currently projects underway to construct five FLNG facilities. Petronas is close to completion on their FLNG-1
The Browse LNG project will commence Front-end loading in 2019.
Natural gas is primarily used in the northern hemisphere. North America and Europe are major consumers.
Mid-stream natural gas
Often well head gases require removal of various hydrocarbon molecules contained within the gas. Some of these gases include heptane
and other hydrocarbons with molecular weights above methane
(). The natural gas transmission lines extend to the natural gas processing plant or unit which removes the higher molecular weighted hydrocarbons to produce natural gas with energy content between and for alimenting Load profile
power stations functioning in tandem with hydroelectric
plants. Most grid peaking power plant
s and some off-grid engine-generator
s 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 fuels, such as oil and coal. Because burning natural gas produces both water and carbon dioxide, it produces less carbon dioxide per unit of energy released than coal, which produces mostly carbon dioxide. Burning natural gas produces only about half the carbon dioxide per kilowatt-hour
(kWh) that coal
[ For transportation, burning natural gas produces about 30% less carbon dioxide than burning petroleum. The US Energy Information Administration reports the following emissions in million Tonne of carbon dioxide in the world for 2012:] Because of this higher carbon efficiency of natural gas generation, as the fuel mix in the United States has changed to reduce coal and increase natural gas generation, carbon dioxide emissions have unexpectedly fallen. Those measured in the first quarter of 2012 were the lowest of any recorded for the first quarter of any year since 1992.
Combined cycle power generation using natural gas is currently the cleanest available source of power using hydrocarbon fuels, and this technology is widely and increasingly used as natural gas can be obtained at increasingly reasonable costs. Fuel cell technology may eventually provide cleaner options for converting natural gas into electricity, but as yet it is not Natural gas prices. Locally produced electricity and heat using natural gas powered Combined Heat and Power plant (CHP or Cogeneration plant) is considered energy efficient and a rapid way to cut carbon emissions.
[ making it a powerful domestic cooking and heating fuel.] In much of the developed world it is supplied through pipes to homes, where it is used for many purposes including ranges and ovens, gas-heated clothes dryers, HVAC/air conditioning, and central heating. Heaters in homes and other buildings may include boilers, furnaces, and water heaters. Both North America and Europe are major consumers of natural gas.
Domestic appliances, furnaces, and boilers use low pressure, usually 6 to 7 inch of water (6" to 7" WC), which is about 0.25 psig. The pressures in the supply lines vary, either utilization pressure (UP, the aforementioned 6" to 7" WC) or elevated pressure (EP), which may be anywhere from 1 psig to 120 psig. Systems using EP have a pressure regulator at the service entrance to step down the pressure to UP.
In the US compressed natural gas (CNG) is used in rural homes without connections to plumbing-in public utility services, or with portable Grill (cooking). Natural gas is also supplied by independent natural gas suppliers through Natural Gas Choice programs throughout the United States. However, as CNG costs more than LPG (liquefied petroleum gas), LPG is the dominant source of rural gas.
CNG is a cleaner and also cheaper alternative to other automobile fuels such as gasoline (petrol) and Diesel fuel. By the end of 2014 there were over 20 million natural gas vehicles worldwide, led by Iran (3.5 million), China (3.3 million), Pakistan (2.8 million), Argentina (2.5 million), India (1.8 million), and Brazil (1.8 million).
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. The program has been running since the mid-1970s, and seeks to develop LNG and hydrogen variants of the Tupolev Tu-204 and Tupolev Tu-334 passenger aircraft, and also the Tupolev Tu-330 cargo aircraft. Depending on the current market price for jet fuel and LNG, fuel for an LNG-powered aircraft could cost 5,000 Russian ruble (US$100) less per tonne, roughly 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.
Natural gas is a major feedstock for the production of ammonia, via the Haber process, for use in fertilizer production.
an approximate value).
) formed in the troposphere or stratosphere, giving the overall chemical reaction (2009 est).
This study was criticized later for its over-estimation of methane leakage values. Preliminary results of some air sampling from airplanes done by the National Oceanic and Atmospheric Administration indicated higher-than-estimated methane releases by gas wells in some areas,
Carbon dioxide emissions
Natural gas is often described as the cleanest fossil fuel. It produces 25–30% and 40–45% less carbon dioxide per joule delivered than oil and coal respectively,
[ and potentially fewer pollutants than other hydrocarbon fuels.] The production of natural gas from hydraulically fractured wells has utilized the technological developments of directional and horizontal drilling, which improved access to natural gas in tight rock formations. However, in absolute terms, it comprises a substantial percentage of human carbon emissions, and this contribution is projected to grow. According to the IPCC Fourth Assessment Report, in 2004, natural gas produced about 5.3 billion tons a year of
|class="wikitable sortable"||+ Comparison of emissions from natural gas, oil and coal burning|
[!! NG !! Oil !! Coal]
Natural gas extraction also produces radioactive isotopes of polonium (Po-210), lead (Pb-210) and radon (Rn-220). Radon is a gas with initial activity from 5 to 200,000 becquerels per cubic meter of gas. It decays rapidly to Pb-210 which can build up as a thin film in gas extraction equipment.
Some gas fields yield sour gas containing hydrogen sulfide (). 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.
Extraction of natural gas (or oil) leads to decrease in pressure in the oil 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.
[Fitzgerald, Timothy. "Frackonomics: Some Economics of Hydraulic Fracturing." Case Western Reserve Law Review 63.4 (2013). Web. 1 Sept. 2015.] Strong growth in the production of unconventional gas from hydraulically fractured wells occurred between 2000–2012. [Chojna, J., Losoncz, M., & Suni, P. (2013, November). Shale Energy Shapes Global Energy Markets. National Institute Economic Review.]
In hydraulic fracturing, well operators force water mixed with a variety of chemicals through the wellbore casing into the rock. The high pressure water breaks up or "fracks" the rock, which releases gas from the rock formation. Sand and other particles are added to the water as a proppant to keep the fractures in the rock open, thus enabling the gas to flow into the casing and then to the surface. Chemicals are added to the fluid to perform such functions as reducing friction and inhibiting corrosion. After the "frack," oil or gas is extracted and 30–70% of the frack fluid, i.e. the mixture of water, chemicals, sand, etc., flows back to the surface. Many gas-bearing formations also contain water, which will flow up the wellbore to the surface along with the gas, in both hydraulically fractured and non-hydraulically fractured wells. This produced water often has a high content of salt and other dissolved minerals that occur in the formation.
The decades in development of drilling technology for conventional and unconventional oil and gas production has not only improved access to natural gas in low-permeability reservoir rocks, but also posed significant adverse impacts on environmental and public health.
The US EPA has acknowledged that toxic, carcinogenic chemicals, i.e. benzene and ethylbenzene, have been used as gelling agents in water and chemical mixtures for high volume horizontal fracturing (HVHF).
In order to assist in detecting leaks, an odorizer 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 (t-butyl mercaptan). Sometimes a related compound, tetrahydrothiophene, 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.
Risk of explosion
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 is powerful 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.
Risk of carbon monoxide inhalation
Natural gas heating systems may cause carbon monoxide poisoning if unvented or poorly vented. In 2011, natural gas furnaces, space heaters, water heaters and stoves were blamed for 11 carbon monoxide deaths in the US. Another 22 deaths were attributed to appliances running on liquified petroleum gas, and 17 deaths on gas of unspecified type. Improvements in natural gas furnace designs have greatly reduced CO poisoning concerns. Carbon monoxide detector are also available that warn of carbon monoxide and/or explosive gas (methane, propane, etc.).
[US Consumer Product Safety Commission, [http://www.cpsc.gov/Global/Research-and-Statistics/Injury-Statistics/Carbon-Monoxide-Posioning/NonFireCarbonMonoxideDeathsAssociatedwiththeUseofConsumerProducts2011AnnualEstimatesSept2014.pdf Non-Fire Carbon Monoxide Deaths, 2011 Annual Estimate], September 2014.]
Energy content, statistics, and pricing
Quantities of natural gas are measured in normal cubic meters (cubic meter of gas at "normal" temperature ) or Standard cubic foot (cubic foot of gas at "standard" temperature ),
Gas prices for end users vary greatly across the European Union.
In United States customary units, . The actual heating value when the water formed does not condense is the lower heating value and can be as much as 10% less.
[[https://www.webcitation.org/5nhzCic1h?url=http://www.energy.wsu.edu/documents/distributed/03_025_CHP_glossary_fct.pdf Heat value definitions]. WSU website. Retrieved 2008-05-19.]
In the United States, retail sales are often in units of therms (th); 1 therm = 100,000 BTU. Gas sales to domestic consumers are often in units of 100 standard cubic feet (scf). 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. The typical annual consumption of a single family residence is 1,000 therms or one Residential Customer Equivalent (RCE). Wholesale transactions are generally done in decatherms (Dth), thousand decatherms (MDth), or million decatherms (MMDth). A million decatherms is a trillion BTU, roughly a billion cubic feet of natural gas.
The price of natural gas varies greatly depending on location and type of consumer. In 2007, a price of $7 per 1000 cubic feet () was typical in the United States. The typical caloric value of natural gas is roughly 1,000 BTU per cubic foot, depending on gas composition. This corresponds to around $7 per million BTU or around $7 per gigajoule (GJ). In April 2008, the wholesale price was $10 per 1000 cubic feet ($10/MMBTU).
[).] [. Thus, if the price of gas is $10/MMBTU on the NYMEX, the contract is worth $100,000.]
Canada uses metric units measure for internal trade of petrochemical products. Consequently, natural gas is sold by the gigajoule (GJ), cubic meter (m3) or thousand cubic meters (E3m3). Distribution infrastructure and meters almost always meter volume (cubic foot or cubic meter). Some jurisdictions, such as Saskatchewan, sell gas by volume only. Other jurisdictions, such as Alberta, gas is sold by the energy content (GJ). In these areas, almost all meters for residential and small commercial customers measure volume (m3 or ft3), and billing statements include a multiplier to convert the volume to energy content of the local gas supply.
A gigajoule (GJ) is a measure approximately equal to half a barrel (250 lbs) of oil, or 1 million BTUs, or depending on gas supply and processing between the wellhead and the customer.
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 tonnes (1,000 kg) or MMBTU as spot deliveries. Long term natural gas distribution contracts are signed in cubic meters, and LNG contracts are in metric tonnes. The LNG and LPG is transported by specialized LNG carrier, 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
Natural gas as an asset class for institutional investors
Research conducted by the :fr: Forum Mondial des Fonds de Pension
Adsorbed natural gas (ANG)
Another way to store natural gas is adsorbing it to the porous solids called sorbents. The best condition for methane storage is at room temperature and atmospheric pressure. The used pressure can be up to 4 MPa (about 40 times atmospheric pressure) for having more storage capacity. The most common sorbent used for ANG is activated carbon (AC). Three main types of activated carbons for ANG are: Activated Carbon Fiber (ACF), Powdered Activated Carbon (PAC), activated carbon monolith.
- [http://mitei.mit.edu/publications/reports-studies/future-natural-gas The future of Natural Gas MIT study]
- [http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2341738 A Comparison between Shale Gas in China and Unconventional Fuel Development in the United States: Health, Water and Environmental Risks] by Paolo Farah and Riccardo Tremolada. This is a paper presented at the Colloquium on Environmental Scholarship 2013 hosted by Vermont Law School (11 October 2013)
- [http://rto.american-environmental.us/BTU_Reduction_and_Gas_Conditioning_System.html New Technology For High BTU Natural Gas Fuel Conditioning]
- GA Mansoori, N Enayati, LB Agyarko (2016), [http://www.worldscientific.com/worldscibooks/10.1142/9699 Energy: Sources, Utilization, Legislation, Sustainability, Illinois as Model State], World Sci. Pub. Co.,