User:Milton Beychok/Sandbox: Difference between revisions

From Citizendium
Jump to navigation Jump to search
imported>Milton Beychok
imported>Milton Beychok
No edit summary
Line 1: Line 1:
'''Natural gas condensate''' is a [[Boiling point|low-boiling mixture]] of [[hydrocarbon]] liquids that are present as gaseous components in the raw [[natural gas]] produced from many natural [[gas field]]s.<ref name=Manning>{{cite book|author=Francis S. Manning and Richard E. Thompson|title=Oilfield Processing of Petroleum (Volume One:Natural Gas)|edition=|publisher=Pennwell Books|year=1991|id=ISBN 0-87814-343-2}}</ref> If the raw [[gas]] [[temperature]] is reduced to below its  [[hydrocarbon dew point]], the liquids begin to [[Condensation|condense]] out of the gas. The resulting 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:<ref>[http://www.eia.doe.gov/emeu/iea/glossary.html#L International Energy Glossary] (a page from the website of the [[Energy Information Administration]])</ref><ref>[http://www.eia.doe.gov/pub/oil_gas/natural_gas/feature_articles/2006/ngprocess/ngprocess.pdf Natural gas processing] (a page from the website of the [[Energy Information Administration]])</ref>
*Crude [[oil well]]s – Raw natural gas that comes from [[Petroleum crude oil|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 [[Natural gas well|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 low-boiling hydrocarbon liquids.  Such gas is also ''non-associated'' gas and often referred to as ''wet 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 gravity]] ranging from 0.5 to 0.8 and may contain:<ref name=Manning/><ref>[http://www.kindermorgan.com/public_awareness/common_files/MaterialSafetyDataSheets/NaturalGas_Condensate.pdf Natural Gas Condensate]  [[Kinder-Morgan]] [[MSDS]]</ref><ref>[http://www.marathonpetroleum.com/msds/0245MAR001.pdf Natural Gas Condensate] [[Marathon Oil Company]] MSDS</ref><ref>[http://www.hess.com/ehs/msds/7838NaturalGasCondensateSour.pdf  Natural Gas Condensate (Sour)] [[Amerada Hess Corporation]] MSDS</ref>
*[[Hydrogen sulfide]] (H<sub>2</sub>S}
*[[Thiol]]s traditionally also called [[mercaptan]]s (denoted as RSH, where R is an organic group such as methyl, ethyl, etc.)
*[[Carbon dioxide]] (CO<sub>2</sub>) 
*[[Alkane|Straight-chain alkanes]] having from 2 to 12 [[carbon]] atoms (denoted as C<sub>2</sub> to C<sub>12</sub>)
*[[Cyclohexane]] and perhaps other [[naphthene]]s
*[[Aromatics]] ([[benzene]], [[toluene]], [[xylenes]] and [[ethylbenzene]])
==Separating the condensate from the raw natural gas==
[[Image:Natural Gas Condensate.png|right|thumb|298px|{{#ifexist:Template:Natural Gas Condensate.png/credit|{{Natural Gas Condensate.png/credit}}<br/>|}}Schematic flow diagram of a typical facility for separating and recovering liquid condensate from raw natural gas.]]
There are many different equipment configurations for the processing required to separate natural gas condensate from a raw natural gas. The [[Process flow diagram|schematic flow diagram]] to the right depicts just one of the possible configurations.<ref>[http://www.mse.co.uk/pdf/papers/tp01.pdf Simplified Process Flow Diagram]</ref>
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. That condenses a good part of the gas condensate hydrocarbons. The resulting 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 liquid 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 evaporation|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|pipeline transportation]] 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 [[Gas dehydration process|dehydrated]] and [[acid gas]]es and other impurities will be removed from the gas. Then the  [[ethane]] (C<sub>2</sub>), propane (C<sub>3</sub>), butanes (C<sub>4</sub>) and C<sub>5</sub>  plus higher [[molecular weight]] hydrocarbons (referred to as C<sub>5</sub>+) 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 [[Natural gas reservoir|gas reservoir]] pressures.
==Characterizing the amount of condensate in natural gas==
In the [[United States]], the hydrocarbon dewpoint of [[Natural gas processing|''processed, pipelined natural gas'']] is related to and characterized by the term ''GPM'', meaning [[U.S. customary units|gallons]] of liquifiable hydrocarbons per million (10<sup>6</sup>) [[U.S. customary units| cubic feet]] of natural gas at a stated temperature and pressure. When the liquifiable hydrocarbons are characterized as being [[hexane]] or higher [[molecular weight]] components, they are reported as ''GPM (C6+)'' meaning hydrocarbons with 6 carbon atoms or more.<ref name=NGC>[http://www.naesb.org/pdf/update011905w9.pdf White Paper on Liquid Hydrocarbon Drop Out in Natural Gas Infrastructure] (NGC+ Liquid Hydrocarbon Dropout Task Group, October 15, 2004)</ref><ref name=NGC2>[http://www.beg.utexas.edu/energyecon/lng/documents/NGC_HDP_Paper.pdf White Paper on Liquid Hydrocarbon Drop Out in Natural Gas Infrastructure] (NGC+ Liquid Hydrocarbon Dropout Task Group, September 28, 2005)</ref>
However, it should be noted that the quality of ''[[Natural gas|raw produced natural gas]]'' (before it is purified by processing) is also often characterized by the term ''GPM'', meaning the gallons of liquifiable hydrocarbons contained in a thousand (10<sup>3</sup>)  cubic feet of the raw natural gas. In such cases, when the liquifiable hydrocarbons in the raw natural gas are characterized as being [[ethane]] or higher molecular weight components, they are reported as''GPM (C2+)''. Similarly, when characterized as being [[propane]] or higher molecular weight components, they are reported as''GPM (C3+)''.<ref name=NGC/><ref name=NGC2/>
Care must be taken not to confuse the two different definitions of the term GPM.
==References==
{{reflist}}

Revision as of 14:43, 5 September 2008

Retrieved from "https://citizendium.org/wiki/index.php?title=User:Milton_Beychok/Sandbox&oldid=385260"