Natural-gas processing

Natural-gas processing is a range of industrial processes designed to purify raw natural gas by removing contaminants such as solids, water, carbon dioxide (CO₂), hydrogen sulfide (H₂S), mercury and higher molecular mass hydrocarbons (condensate) to produce pipeline quality dry natural gas^[1] for pipeline distribution and final use.^[2] Some of the substances which contaminate natural gas have economic value and are further processed or sold. Hydrocarbons that are liquid at ambient conditions: temperature and pressure (i.e., pentane and heavier) are called natural-gas condensate (sometimes also called natural gasoline or simply condensate).

Raw natural gas comes primarily from three types of wells: crude oil wells, gas wells, and condensate wells. Crude oil and natural gas are often found together in the same reservoir. Natural gas produced in wells with crude oil is generally classified as associated-dissolved gas as the gas had been associated with or dissolved in crude oil. Natural gas production not associated with crude oil is classified as “non-associated.” In 2009, 89 percent of U.S. wellhead production of natural gas was non-associated.^[3] Non-associated gas wells producing a dry gas in terms of condensate and water can send the dry gas directly to a pipeline or gas plant without undergoing any separation processIng allowing immediate use.^[4]

Natural-gas processing begins underground or at the well-head. In a crude oil well, natural gas processing begins as the fluid loses pressure and flows through the reservoir rocks until it reaches the well tubing.^[5] In other wells, processing begins at the wellhead which extracts the composition of natural gas according to the type, depth, and location of the underground deposit and the geology of the area.^[2]

Natural gas when relatively free of hydrogen sulfide is called sweet gas; natural gas that contains elevated hydrogen sulfide levels is called sour gas; natural gas, or any other gas mixture, containing significant quantities of hydrogen sulfide or carbon dioxide or similar acidic gases, is called acid gas.

^ "PHMSA: Stakeholder Communications - NG Processing Plants". primis.phmsa.dot.gov. Retrieved 9 April 2018.
^ ^a ^b Speight, James G. (2015). Handbook of Petroleum Product Analysis, Second Edition. Hoboken, NJ: John Wiley & Sons. p. 71. ISBN 978-1-118-36926-5.
^ "Archived copy" (PDF). Archived from the original (PDF) on 2016-03-05. Retrieved 2014-09-21.{{cite web}}: CS1 maint: archived copy as title (link)
^ Kidnay, Arthur J.; Parrish, William R.; McCartney, Daniel G. (2019). Fundamentals of Natural Gas Processing, Third Edition. Boca Raton, FL: CRC Press. p. 165. ISBN 978-0-429-87715-5.
^ Agency, United States Central Intelligence (1977). Natural Gas. Washington, D.C.: U.S. Central Intelligence Agency. p. 25.

[1] "PHMSA: Stakeholder Communications - NG Processing Plants". primis.phmsa.dot.gov. Retrieved 9 April 2018.

[:3-2] Speight, James G. (2015). Handbook of Petroleum Product Analysis, Second Edition. Hoboken, NJ: John Wiley & Sons. p. 71. ISBN 978-1-118-36926-5.

[3] "Archived copy" (PDF). Archived from the original (PDF) on 2016-03-05. Retrieved 2014-09-21.{{cite web}}: CS1 maint: archived copy as title (link)

[4] Kidnay, Arthur J.; Parrish, William R.; McCartney, Daniel G. (2019). Fundamentals of Natural Gas Processing, Third Edition. Boca Raton, FL: CRC Press. p. 165. ISBN 978-0-429-87715-5.

[5] Agency, United States Central Intelligence (1977). Natural Gas. Washington, D.C.: U.S. Central Intelligence Agency. p. 25.

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