Natural gas condensate
Encyclopedia
Natural-gas condensate is a low-density mixture of hydrocarbon
liquids that are present as gaseous components in the raw natural gas
produced from many natural gas fields.
It condenses
out of the raw gas if the temperature is reduced to below the hydrocarbon dew point
temperature of the raw gas.
The natural gas condensate is also referred to as simply condensate, or gas condensate, or sometimes natural gasoline
because it contains hydrocarbons within the gasoline boiling range. Raw natural gas may come from any one of three types of gas wells:
ranging from 0.5 to 0.8 and may contain:
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
at the feedstock pressure and that condenses a good 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. The raw natural gas from the high pressure separator is sent to the main gas compressor
.
The gas condensate from the high pressure separator flows through a throttling control valve to a low pressure separator. The reduction in pressure across the control valve causes the condensate to undergo a partial vaporization referred to as a flash vaporization
. The raw natural gas from the low pressure separator is sent to a "booster" compressor which raises the gas pressure and sends it through a cooler and on to the main gas compressor. The main gas compressor raises the pressure of the gases from the high and low pressure separators to whatever pressure is required for the pipeline transport
ation of the gas to the raw natural gas processing
plant. The main gas compressor discharge pressure will depend upon the distance to the raw natural gas processing plant and it may require that a multi-stage compressor be used.
At the raw natural gas processing plant, the gas will be dehydrated
and acid gas
es and other impurities will be removed from the gas. Then, the ethane
, propane
, butanes , and pentanes —plus higher molecular weight hydrocarbons referred to as C5+—will also be removed and recovered as byproducts.
The water removed from both the high and low pressure separators will probably need to be processed to remove hydrogen sulfide before the water can be disposed of or reused in some fashion.
Some of the raw natural gas may be re-injected into the gas wells to help maintain the gas reservoir pressures.
found near many oil and natural gas wells, in natural gas pipelines, and 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 has industrial uses as a cleaner and solvent
, as a lantern and stove fuel, and as a denaturing additive for fuel alcohol
.
—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
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."
Woody Guthrie
'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 Badlands
, the Terrence Malick movie.
It was sold commercially at gas stations and hardware stores in North America until the early 1950's. The White gas
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, high heat of combustion and lack of additives. It has a distinctive smell when used as a fuel, which allowed police to catch people using drip gas illegally.
, drip gas consists of butane
, pentane
, and hexane
hydrocarbon
s. Within set ranges of distillation, drip gas may be extracted and used to denature fuel alcohol.
Hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....
liquids that are present as gaseous components in the raw natural gas
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...
produced from many natural gas fields.
It condenses
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
out of the raw gas if the temperature is reduced to below the hydrocarbon dew point
Hydrocarbon dew point
The hydrocarbon dew point is the temperature 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 HDP or the HCDP. The maximum temperature at which such condensation takes...
temperature of the raw gas.
The natural gas condensate is also referred to as simply condensate, or gas condensate, or sometimes natural gasoline
Natural gasoline
Natural gasoline is a natural gas liquid with a vapor pressure intermediate between natural gas condensate and liquefied petroleum gas and has a boiling point within the range of gasoline. The typical gravity of natural gasoline is around 80 API....
because it contains hydrocarbons within the gasoline boiling range. Raw natural gas may come from any one of three types of gas wells:
- Crude oil wellOil wellAn oil well is a general term for any boring through the earth's surface that is designed to find and acquire petroleum oil hydrocarbons. Usually some natural gas is produced along with the oil. A well that is designed to produce mainly or only gas may be termed a gas well.-History:The earliest...
s—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 dissolved in the crude oil.
- Dry gas wells—These wells typically produce only raw natural gas that does not contain any hydrocarbon liquids. Such gas is called non-associated gas.
- Condensate wells—These wells produce raw natural gas along with natural gas liquid. Such gas is also non-associated gas and often referred to as wet gasWet gasA wet gas is any gas with a small amount of liquid present. The term "wet gas" has been used to describe a range of conditions ranging from a humid gas which is gas saturated with liquid vapour to a multiphase flow with a 90% volume of gas...
.
Composition of natural-gas condensate
There are hundreds of wet gas fields worldwide and each has its own unique gas condensate composition. However, in general, gas condensate has a specific gravitySpecific gravity
Specific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...
ranging from 0.5 to 0.8 and may contain:
- Hydrogen sulfideHydrogen sulfideHydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...
- ThiolThiolIn organic chemistry, a thiol is an organosulfur compound that contains a carbon-bonded sulfhydryl group...
s traditionally also called mercaptans (denoted as RSH, where R is an organic group such as methyl, ethyl, etc.) - Carbon dioxideCarbon dioxideCarbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
- Straight-chain alkanesAlkaneAlkanes are chemical compounds that consist only of hydrogen and carbon atoms and are bonded exclusively by single bonds without any cycles...
having from 2 to 12 carbonCarbonCarbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
atoms (denoted as to ) - CyclohexaneCyclohexaneCyclohexane is a cycloalkane with the molecular formula C6H12. Cyclohexane is used as a nonpolar solvent for the chemical industry, and also as a raw material for the industrial production of adipic acid and caprolactam, both of which being intermediates used in the production of nylon...
and perhaps other naphthenes - Aromatics (benzeneBenzeneBenzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....
, tolueneTolueneToluene, formerly known as toluol, is a clear, water-insoluble liquid with the typical smell of paint thinners. It is a mono-substituted benzene derivative, i.e., one in which a single hydrogen atom from the benzene molecule has been replaced by a univalent group, in this case CH3.It is an aromatic...
, xylenes, and ethylbenzeneEthylbenzeneEthylbenzene is an organic compound with the formula C6H5CH2CH3. This aromatic hydrocarbon is important in the petrochemical industry as an intermediate in the production of styrene, which in turn is used for making polystyrene, a common plastic material....
)
Separating the condensate from the raw natural gas
There are literally hundreds of different equipment configurations for the processing required to separate natural gas condensate from a raw natural gas. The schematic flow diagramProcess Flow diagram
A process flow diagram is a diagram commonly used in engineering to indicate the general flow of plant processes and equipment.The PFD displays the relationship between major equipment of a plant facility and does not show minor details such as piping details and designations...
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
Hydrocarbon dew point
The hydrocarbon dew point is the temperature 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 HDP or the HCDP. The maximum temperature at which such condensation takes...
at the feedstock pressure and that condenses a good 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. The raw natural gas from the high pressure separator is sent to the main gas compressor
Gas compressor
A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume.Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a gas...
.
The gas condensate from the high pressure separator flows through a throttling control valve to a low pressure separator. The reduction in pressure across the control valve causes the condensate to undergo a partial vaporization referred to as a flash vaporization
Flash evaporation
Flash evaporation is the partial vapor that occurs when a saturated liquid stream undergoes a reduction in pressure by passing through a throttling valve or other throttling device. This process is one of the simplest unit operations...
. The raw natural gas from the low pressure separator is sent to a "booster" compressor which raises the gas pressure and sends it through a cooler and on to the main gas compressor. The main gas compressor raises the pressure of the gases from the high and low pressure separators to whatever pressure is required for the pipeline transport
Pipeline transport
Pipeline transport is the transportation of goods through a pipe. Most commonly, liquids and gases are sent, but pneumatic tubes that transport solid capsules using compressed air are also used....
ation of the gas to the raw natural gas processing
Natural gas processing
Natural-gas processing is a complex industrial process designed to clean raw natural gas by separating impurities and various non-methane hydrocarbons and fluids to produce what is known as pipeline quality dry natural gas.-Background:...
plant. The main gas compressor discharge pressure will depend upon the distance to the raw natural gas processing plant and it may require that a multi-stage compressor be used.
At the raw natural gas processing plant, the gas will be dehydrated
Dehydration
In physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...
and acid gas
Acid gas
Acid gas is natural gas or any other gas mixture which contains significant amounts of hydrogen sulfide , carbon dioxide , or similar contaminants. The terms acid gas and sour gas are often incorrectly treated as synonyms...
es and other impurities will be removed from the gas. Then, the ethane
Ethane
Ethane is a chemical compound with chemical formula C2H6. It is the only two-carbon alkane that is an aliphatic hydrocarbon. At standard temperature and pressure, ethane is a colorless, odorless gas....
, propane
Propane
Propane is a three-carbon alkane with the molecular formula , normally a gas, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used as a fuel for engines, oxy-gas torches, barbecues, portable stoves, and residential central...
, butanes , and pentanes —plus higher molecular weight hydrocarbons referred to as C5+—will also be removed and recovered as byproducts.
The water removed from both the high and low pressure separators will probably need to be processed to remove hydrogen sulfide before the water can be disposed of or reused in some fashion.
Some of the raw natural gas may be re-injected into the gas wells to help maintain the gas reservoir pressures.
Drip gas
Drip gas is natural gas condensate, a naturally occurring form of gasolineGasoline
Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...
found near many oil and natural gas wells, in natural gas pipelines, and 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 has industrial uses as a cleaner and solvent
Solvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...
, as a lantern and stove fuel, and as a denaturing additive for fuel alcohol
Alcohol fuel
Although fossil fuels have become the dominant energy resource for the modern world, alcohol has been used as a fuel throughout history. The first four aliphatic alcohols are of interest as fuels because they can be synthesized chemically or biologically, and they have characteristics which allow...
.
Historical use in vehicles
Some very early internal combustion enginesInternal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...
—such as the first types made by Karl Benz
Karl Benz
Karl Friedrich Benz, was a German engine designer and car engineer, generally regarded as the inventor of the gasoline-powered car, and together with Bertha Benz pioneering founder of the automobile manufacturer Mercedes-Benz...
, and early Wright brothers
Wright brothers
The Wright brothers, Orville and Wilbur , were two Americans credited with inventing and building the world's first successful airplane and making the first controlled, powered and sustained heavier-than-air human flight, on December 17, 1903...
aircraft engines—used natural gasoline
Natural gasoline
Natural gasoline is a natural gas liquid with a vapor pressure intermediate between natural gas condensate and liquefied petroleum gas and has a boiling point within the range of gasoline. The typical gravity of natural gasoline is around 80 API....
, which could be either drip gas or a similar range of hydrocarbons distilled from crude oil. Natural gasoline has an octane rating
Octane rating
Octane rating or octane number is a standard measure of the anti-knock properties of a motor or aviation fuel. The higher the octane number, the more compression the fuel can withstand before detonating...
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
Engine knocking
Knocking in spark-ignition internal combustion engines occurs when combustion of the air/fuel mixture in the cylinder starts off correctly in response to ignition by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front.The...
or detonation.
Beginning in the Great Depression
Great Depression
The Great Depression was a severe worldwide economic depression in the decade preceding World War II. The timing of the Great Depression varied across nations, but in most countries it started in about 1929 and lasted until the late 1930s or early 1940s...
, 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."
Woody Guthrie
Woody Guthrie
Woodrow Wilson "Woody" Guthrie is best known as an American singer-songwriter and folk musician, whose musical legacy includes hundreds of political, traditional and children's songs, ballads and improvised works. He frequently performed with the slogan This Machine Kills Fascists displayed on his...
'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 Badlands
Badlands (film)
Badlands is a 1973 American crime drama film written and directed by Terrence Malick, starring Martin Sheen and Sissy Spacek. Warren Oates and Ramon Bieri are also featured. Malick has a small speaking part although he does not receive an acting credit...
, the Terrence Malick movie.
It was sold commercially at gas stations and hardware stores in North America until the early 1950's. The White gas
White gas
White gas is a common name for two flammable substances. In its most common modern usage, it is used as a generic name for camp stove and lantern fuel, usually naphtha....
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, high heat of combustion and lack of additives. It has a distinctive smell when used as a fuel, which allowed police to catch people using drip gas illegally.
Composition
Under the United States Code of Federal RegulationsCode of Federal Regulations
The Code of Federal Regulations is the codification of the general and permanent rules and regulations published in the Federal Register by the executive departments and agencies of the Federal Government of the United States.The CFR is published by the Office of the Federal Register, an agency...
, drip gas consists of butane
Butane
Butane is a gas with the formula C4H10 that is an alkane with four carbon atoms. The term may refer to any of two structural isomers, or to a mixture of them: in the IUPAC nomenclature, however, butane refers only to the unbranched n-butane isomer; the other one being called "methylpropane" or...
, pentane
Pentane
Pentane is an organic compound with the formula C5H12 — that is, an alkane with five carbon atoms. The term may refer to any of three structural isomers, or to a mixture of them: in the IUPAC nomenclature, however, pentane means exclusively the n-pentane isomer; the other two being called...
, and hexane
Hexane
Hexane is a hydrocarbon with the chemical formula C6H14; that is, an alkane with six carbon atoms.The term may refer to any of four other structural isomers with that formula, or to a mixture of them. In the IUPAC nomenclature, however, hexane is the unbranched isomer ; the other four structures...
hydrocarbon
Hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....
s. Within set ranges of distillation, drip gas may be extracted and used to denature fuel alcohol.
External links
- Processing raw natural gas
- Preparing raw natural gas for sales
- Natural Gas Processing (part of the US EPA's AP-42 publicationAP 42 Compilation of Air Pollutant Emission FactorsThe AP 42 Compilation of Air Pollutant Emission Factors, was first published by the U.S. Public Health Service in 1968. In 1972, it was revised and issued as the second edition by the U.S. Environmental Protection Agency . In 1985, the subsequent fourth edition was split into two volumes...
and includes a schematic diagram)