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Natural-gas condensate, also called natural gas liquids, is a low-density mixture of hydrocarbon liquids that are present as gaseous components in the raw
natural gas Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbon di ...
produced from many natural gas fields. Some gas species within the raw natural gas will condense to a liquid state if the temperature is reduced to below the
hydrocarbon dew point The hydrocarbon dew point is the temperature (at a given pressure) at which the hydrocarbon components of any hydrocarbon-rich gas mixture, such as natural gas, will start to condense out of the gaseous phase. It is often also referred to as the ...
temperature at a set pressure. The natural gas condensate is also called condensate, or gas condensate, or sometimes natural gasoline because it contains hydrocarbons within the gasoline boiling range, and is also referred to by the shortened name condy by many workers on gas installations. Raw natural gas may come from any one of three types of gas wells: * Crude oil wells: Raw natural gas that comes from crude oil wells is called ''associated gas''. This gas can exist separate from the crude oil in the underground formation, or be dissolved in the crude oil. Condensate produced from oil wells is often referred to as ''lease condensate''. * Dry gas wells: These wells typically produce only raw natural gas that contains no hydrocarbon liquids. Such gas is called ''non-associated'' gas. Condensate from dry gas is extracted at gas processing plants and is often called ''plant condensate''. * Condensate wells: These wells produce raw natural gas along with natural gas liquid. Such gas is also called ''associated'' gas and often referred to as wet gas.


Composition

There are many condensate sources, and each has its own unique gas condensate composition. In general, gas condensate has a specific gravity ranging from 0.5 to 0.8, and is composed of hydrocarbons such as propane,
butane Butane () or ''n''-butane is an alkane with the formula C4H10. Butane is a gas at room temperature and atmospheric pressure. Butane is a highly flammable, colorless, easily liquefied gas that quickly vaporizes at room temperature. The name bu ...
, pentane, and
hexane Hexane () is an organic compound, a straight-chain alkane with six carbon atoms and has the molecular formula C6H14. It is a colorless liquid, odorless when pure, and with boiling points approximately . It is widely used as a cheap, relatively ...
. Natural gas compounds with more than two carbon atoms exist as liquids at ambient temperatures. Propane,
butane Butane () or ''n''-butane is an alkane with the formula C4H10. Butane is a gas at room temperature and atmospheric pressure. Butane is a highly flammable, colorless, easily liquefied gas that quickly vaporizes at room temperature. The name bu ...
, and isobutane are liquid at normal temperatures only under pressure. Additionally, condensate may contain: *Heavier straight-chain alkanes having from 7 to 12 carbon atoms (denoted as to ) * Hydrogen sulfide () *
Thiol In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl grou ...
s traditionally also called mercaptans (denoted as RSH, where R is an organic group such as methyl, ethyl, etc.) * Carbon dioxide () * Cyclohexane and perhaps other
naphthenes In organic chemistry, the cycloalkanes (also called naphthenes, but distinct from naphthalene) are the monocyclic saturated hydrocarbons. In other words, a cycloalkane consists only of hydrogen and carbon atoms arranged in a structure containing ...
* BTX (chemistry) (
Aromatics Aromatic compounds, also known as "mono- and polycyclic aromatic hydrocarbons", are organic compounds containing one or more aromatic rings. The parent member of aromatic compounds is benzene. The word "aromatic" originates from the past grouping ...
such as
benzene Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms ...
, toluene,
xylenes In organic chemistry, xylene or xylol (; IUPAC name: dimethylbenzene) are any of three organic compounds with the formula . They are derived from the substitution of two hydrogen atoms with methyl groups in a benzene ring; which hydrogens are su ...
, and
ethylbenzene Ethylbenzene is an organic compound with the formula . It is a highly flammable, colorless liquid with an odor similar to that of gasoline. This monocyclic aromatic hydrocarbon is important in the petrochemical industry as an reaction intermediat ...
)


Separating the condensate from the raw natural gas

There are hundreds of different equipment configurations to separate natural gas condensate from raw natural gas. The schematic flow diagram to the right depicts just one of the possible configurations. The raw natural gas feedstock from a gas well or a group of wells is cooled to lower the gas temperature to below its
hydrocarbon dew point The hydrocarbon dew point is the temperature (at a given pressure) at which the hydrocarbon components of any hydrocarbon-rich gas mixture, such as natural gas, will start to condense out of the gaseous phase. It is often also referred to as the ...
at the feedstock pressure. This condenses a large part of the gas condensate hydrocarbons. The feedstock mixture of gas, liquid condensate and water is then routed to a high pressure separator vessel where the water and the raw natural gas are separated and removed. If a pressure boost is required, the raw natural gas from the high pressure separator is sent to the main
gas compressor A compressor is a mechanical device that increases the pressure of a gas by reducing its volume. An air compressor is a specific type of gas compressor. Compressors are similar to pumps: both increase the pressure on a fluid and both can tran ...
, which raises the pressure of the gases to whatever pressure is required for the
pipeline transport Pipeline transport is the long-distance transportation of a liquid or gas through a system of Pipe (fluid conveyance), pipes—a pipeline—typically to a market area for consumption. The latest data from 2014 gives a total of slightly less than ...
ation of the gas to the raw natural gas processing plant. The main gas compressor discharge pressure will depend upon the operating pressure of and the distance to the raw natural gas processing plant and may require a multi-stage compressor. The gas condensate from the high pressure separator flows through a throttling
control valve A control valve is a valve used to control fluid flow by varying the size of the flow passage as directed by a signal from a controller. This enables the direct control of flow rate and the consequential control of process quantities such as press ...
to a low pressure separator. The reduction in pressure across the control valve causes the condensate to undergo a partial vaporization referred to as flash vaporization. The raw natural gas from the low pressure separator is sent to a "booster" compressor that raises the gas pressure and sends it through a cooler, and then to the main gas compressor. At the raw natural gas processing plant, the gas will be
dehydrated In physiology, dehydration is a lack of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mil ...
and acid gases and other impurities will be removed from the gas. Then, the ethane (), propane (), butanes (), and pentanes ()—plus higher
molecular weight A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioche ...
hydrocarbons referred to as C5+—will also be removed and recovered as byproducts. The water removed from both the high and low pressure separators may need to be processed to remove hydrogen sulfide () before the water can be disposed of underground or reused in some fashion. Some of the raw natural gas may be re-injected into the producing formation to help maintain the reservoir pressure, or for storage pending later installation of a pipeline.


Dangers

Natural gas condensate is generally more flammable and explosive than normal crude oil. Operating in areas where condensate has escaped is dangerous for crew due to the danger of explosions, oxygen displacement and the threat of asphyxiating and anaesthetizing, which can occur within a few human breaths.


Drip gas

Drip gas, so named because it can be drawn off the bottom of small chambers (called ''drips'') sometimes installed in pipelines from gas wells, is another name for natural-gas condensate, a naturally occurring form of gasoline obtained as a byproduct of natural gas extraction. It is also known as "condensate", "natural gasoline", "casing head gas", "raw gas", "white gas" and "liquid gold". Drip gas is defined in the United States
Code of Federal Regulations In the law of the United States, the ''Code of Federal Regulations'' (''CFR'') is the codification of the general and permanent regulations promulgated by the executive departments and agencies of the federal government of the United States. ...
as consisting of
butane Butane () or ''n''-butane is an alkane with the formula C4H10. Butane is a gas at room temperature and atmospheric pressure. Butane is a highly flammable, colorless, easily liquefied gas that quickly vaporizes at room temperature. The name bu ...
, pentane, and
hexane Hexane () is an organic compound, a straight-chain alkane with six carbon atoms and has the molecular formula C6H14. It is a colorless liquid, odorless when pure, and with boiling points approximately . It is widely used as a cheap, relatively ...
hydrocarbons. Within set ranges of
distill Distillation, or classical distillation, is the process of separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distillation is the heating ...
ation, drip gas may be extracted and used to denature fuel alcohol. Drip gas is also used as a cleaner and solvent as well as a lantern and stove fuel.


Use as a diluent in heavy oil production

Because condensate is typically liquid in ambient conditions and also has very low viscosity, condensate is often used to dilute highly viscous heavier oils that cannot otherwise be efficiently transported via pipelines. In particular, condensate is frequently mixed with
bitumen Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term a ...
from oil sands to create dilbit. The increased use of condensate as diluent significantly increased its price during 2013 in certain regions.


Historical use in vehicles

Some early internal combustion engines—such as the first types made by Karl Benz, and early Wright brothers aircraft engines—used natural gasoline, which could be either drip gas or a similar range of hydrocarbons distilled from crude oil. Natural gasoline has an
octane rating An octane rating, or octane number, is a standard measure of a fuel's ability to withstand compression in an internal combustion engine without detonating. The higher the octane number, the more compression the fuel can withstand before detonatin ...
of about 30 to 50, sufficient for the low-compression engines of the early 20th century. By 1930, improved engines and higher compression ratios required higher-octane, refined gasolines to produce power without knocking or detonation. Beginning in the Great Depression, drip gas was used as a replacement for commercial gasoline by people in oil-producing areas. "In the days of simple engines in automobiles and farm tractors it was not uncommon for anyone having access to a condensate well to fill his tank with 'drip,'" according to the Oklahoma Historical Society. Sometimes it worked fine. "At other times it might cause thundering backfires and clouds of foul-smelling smoke." Certain manufacturers such as John Deere made farm tractors specifically designed to run on heavy, low-octane fuels which were commonly called "distillate" or "tractor fuel". Other names were
tractor vaporising oil Tractor vaporising oil (TVO) is a fuel for petrol-paraffin engines. It is seldom made or used today. In the United Kingdom and Australia, after the Second World War, it was commonly used for tractors until diesel engines became commonplace, e ...
(United Kingdom) and "power kerosene" (Australia). Often the tractors were referred to as "all-fuel". The most important factor in burning heavy fuels in a spark-ignition engine is proper fuel vaporization. Tractors designed to run on those fuels usually used a "hot" intake air manifold that allowed exhaust heat to warm the manifold and carburetor to aid vaporization. Given the poor vaporization at low temperatures, all-fuel tractors were started on gasoline, then switched to the heavy fuel. They were equipped with a small gasoline tank and a large fuel tank, both of which fed into a common valve supplying the fuel to the carburetor. The engine would be started on gasoline and the tractor would then be worked until the engine was sufficiently warm to change over. At that point, the fuel valve would be turned to switch the fuel supply from the gasoline tank to the fuel tank and the heavy fuel would flow to the carburetor. Shutters or curtains were typically used to restrict airflow to the radiator, keeping the engine sufficiently hot for efficient operation. Coolant temperatures in the 200 degree F range were normal. John Deere two-cylinder all-fuel tractors worked well on heavy fuel, as their long piston strokes, slow engine speeds and low compression ratios allowed for effective use of the fuel. Most were also equipped with thermosiphon cooling systems that used no water pumps. Natural convection allowed the water to flow up and out of the engine block and into the top of the radiator, where it cooled and dropped and fell to continue the cycle.
Woody Guthrie Woodrow Wilson Guthrie (; July 14, 1912 – October 3, 1967) was an American singer-songwriter, one of the most significant figures in American folk music. His work focused on themes of American Left, American socialism and anti-fascism. He ...
's autobiographical novel ''Seeds of Man'' begins with Woody and his uncle Jeff tapping a natural gas pipeline for drip gas. The gas also has a mention in Terrence Malick's movie ''
Badlands Badlands are a type of dry terrain where softer sedimentary rocks and clay-rich soils have been extensively eroded."Badlands" in ''Chambers's Encyclopædia''. London: George Newnes, 1961, Vol. 2, p. 47. They are characterized by steep slopes, mi ...
''. It was sold commercially at gas stations and hardware stores in North America until the early 1950s. The
white gas Coleman fuel, also generically sold as white gas, is a petroleum naphtha product marketed by the Coleman Company. Contents Historically called ''white gas'', it is a liquid petroleum fuel (100% light hydrotreated distillate), composed of cyclohe ...
sold today is a similar product but is produced at refineries with the benzene removed. In 1975, the New Mexico State Police's drip gas detail – three men in pickup trucks – began patrolling oil and gas fields, catching thieves and recovering barrels of stolen gas. The detail stopped its work in 1987. The use of drip gas in cars and trucks is now illegal in many states. It is also harmful to modern engines due to its low octane rating, much higher combustion temperature than that of gasoline, and lack of additives. It has a distinctive smell when used as a fuel, which allowed police to sometimes catch people using drip gas illegally."Drip Gas Was A Real Gas for Me As A Kid"
by Jack Cawthon, June 9, 2004.

in Horntown, Oklahoma, by Clayton Adair.


See also

*


References


External links


Processing raw natural gas



Natural Gas Processing
(part of the US EPA's AP-42 publication and includes a schematic diagram) {{DEFAULTSORT:Natural Gas Condensate Natural gas