Editing Petroleum (section)

== Classification ==
{{globalize|date=January 2024}}
{{See also|Benchmark (crude oil)}}
[[File:Crudes.PNG|thumb|Some [[Benchmark (crude oil)|marker crudes]] with their [[sulfur]] content (horizontal) and [[API gravity]] (vertical) and relative production quantity.{{citation needed|date=March 2020|reason=Brent shown as sweeter than WTI, yet most sources claim the opposite. That and other claims in image probably need checking and sourcing. Example: http://www.petroleum.co.uk/benchmarks}}]]
The [[petroleum industry]] generally classifies crude oil by the geographic location it is produced in (e.g., [[West Texas Intermediate]], [[Brent oilfield|Brent]], or [[DME Oman Crude Oil Futures Contract|Oman]]), its [[API gravity]] (an oil industry measure of density), and its sulfur content. Crude oil may be considered ''[[Light crude oil|light]]'' if it has low density, ''[[Heavy crude oil|heavy]]'' if it has high density, or ''medium'' if it has a density between that of ''light'' and ''heavy''.<ref>{{Cite web |date=2009 |title=Glossary |url=http://www.capp.ca/library/glossary/Pages/default.aspx#l |archive-url=https://web.archive.org/web/20090827031218/http://www.capp.ca/library/glossary/Pages/default.aspx#l |archive-date=August 27, 2009 |access-date=November 29, 2020 |publisher=Canadian Association of Petroleum Producers}}</ref> Additionally, it may be referred to as ''[[sweet crude oil|sweet]]'' if it contains relatively little sulfur or ''[[sour crude oil|sour]]'' if it contains substantial amounts of sulfur.<ref>{{Cite web |title=Heavy Sour Crude Oil, A Challenge For Refiners |url=http://www.commodity-trading-today.com/sour-crude-oil.html |archive-url=https://web.archive.org/web/20081121001856/http://www.commodity-trading-today.com/sour-crude-oil.html |archive-date=November 21, 2008 |access-date=November 29, 2020}}</ref>

The geographic location is important because it affects transportation costs to the refinery. ''Light'' crude oil is more desirable than ''heavy'' oil since it produces a higher yield of gasoline, while ''sweet'' oil commands a higher price than ''sour'' oil because it has fewer environmental problems and requires less refining to meet sulfur standards imposed on fuels in consuming countries. Each crude oil has unique molecular characteristics which are revealed by the use of [[crude oil assay]] analysis in petroleum laboratories.<ref>{{Cite journal |last=Rhodes |first=Christopher J. |year=2008 |title=The Oil Question: Nature and Prognosis |journal=Science Progress |volume=91 |issue=4 |pages=317–375 |doi=10.3184/003685008X395201 |pmc=10367496 |pmid=19192735 |s2cid=31407897}}</ref>

[[barrel (unit)|Barrels]] from an area in which the crude oil's molecular characteristics have been determined and the oil has been classified are used as pricing [[Benchmark (crude oil)|references]] throughout the world. Some of the common reference crudes are:<ref>{{cite web |language=en |access-date=16 December 2024 |website=Fuel Logic |title=How US Gas Prices Affect the Overall Economy |date=September 12, 2024 |url=https://www.fuellogic.net/how-us-gas-prices-affect-the-overall-economy/}}</ref>
* [[West Texas Intermediate]] (WTI), a very high-quality, sweet, light oil delivered at [[Cushing, Oklahoma]] for North American oil
* [[Brent Blend]], consisting of 15 oils from fields in the [[Brent oilfield|Brent]] and [[Ninian Central Platform|Ninian]] systems in the [[East Shetland Basin]] of the [[North Sea]]. The oil landed at [[Sullom Voe]] terminal in [[Shetland]]. Oil production from Europe, Africa and Middle Eastern oil flowing West tends to be priced off this oil, which forms a [[Benchmark (crude oil)|benchmark]]
* [[Dubai Crude|Dubai-Oman]], used as a benchmark for the Middle East sour crude oil flowing to the Asia-Pacific region
* [[Tapis crude|Tapis]] (from [[Malaysia]], used as a reference for light Far East oil)
* Minas (from [[Indonesia]], used as a reference for heavy Far East oil)
* The [[OPEC Reference Basket]], a weighted average of oil blends from various [[OPEC]] (Organization of the Petroleum Exporting Countries) countries
* [[Midway-Sunset Oil Field|Midway Sunset]] Heavy, by which heavy oil in California is priced<ref>{{Cite web |date=May 1, 2007 |title=Chevron Crude Oil Marketing – North America Posted Pricing – California |url=http://crudemarketing.chevron.com/posted_pricing_daily_california.asp |url-status=live |archive-url=https://web.archive.org/web/20100607035625/http://crudemarketing.chevron.com/posted_pricing_daily_california.asp |archive-date=June 7, 2010 |access-date=August 29, 2010 |publisher=Crudemarketing.chevron.com}}</ref>{{Failed verification|date=March 2018}}
* [[Western Canadian Select]] the benchmark crude oil for emerging heavy, high TAN (acidic) crudes.<ref name="NRCPetroleumProducts">{{Cite report |url=http://www.nrcan.gc.ca/sites/www.nrcan.gc.ca.energy/files/pdf/eneene/sources/crubru/revrev/pdf/revrev-09-eng.pdf |title=Canadian Crude Oil, Natural Gas and Petroleum Products: Review of 2009 & Outlook to 2030 |last=Natural Resources Canada |date=May 2011 |publisher=Government of Canada |location=Ottawa |page=9 |isbn=978-1-100-16436-6 |archive-url=https://web.archive.org/web/20131003093310/http://www.nrcan.gc.ca/sites/www.nrcan.gc.ca.energy/files/pdf/eneene/sources/crubru/revrev/pdf/revrev-09-eng.pdf |archive-date=October 3, 2013}}</ref>

There are declining amounts of these benchmark oils being produced each year, so other oils are more commonly what is actually delivered. While the reference price may be for West Texas Intermediate delivered at Cushing, the actual oil being traded may be a discounted Canadian heavy oil – Western Canadian Select – delivered at [[Hardisty, Alberta|Hardisty]], [[Alberta]], and for a Brent Blend delivered at Shetland, it may be a discounted Russian Export Blend delivered at the port of [[Primorsk, Leningrad Oblast|Primorsk]].<ref>{{Cite web |year=2006 |title=Light Sweet Crude Oil |url=http://www.nymex.com/lsco_fut_descri.aspx |archive-url=https://web.archive.org/web/20080314074204/http://www.nymex.com/lsco_fut_descri.aspx |archive-date=March 14, 2008 |access-date=April 21, 2008 |website=About the Exchange |publisher=New York Mercantile Exchange (NYMEX)}}</ref>

Once extracted, oil is refined and separated, most easily by [[Continuous distillation#Continuous distillation of crude oil|distillation]], into numerous products for direct use or use in manufacturing, such as [[gasoline]] (petrol), [[diesel fuel|diesel]] and [[kerosene]] to [[Bitumen|asphalt]] and chemical [[reagent]]s ([[ethylene]], [[propylene]], [[butene]], [[acrylic acid]],  [[para-xylene]]<ref>{{Cite journal |last1=Li |first1=Guixian |last2=Wu |first2=Chao |last3=Ji |first3=Dong |last4=Dong |first4=Peng |last5=Zhang |first5=Yongfu |last6=Yang |first6=Yong |date=April 1, 2020 |title=Acidity and catalyst performance of two shape-selective HZSM-5 catalysts for alkylation of toluene with methanol |journal=Reaction Kinetics, Mechanisms and Catalysis |language=en |volume=129 |issue=2 |pages=963–974 |doi=10.1007/s11144-020-01732-9 |issn=1878-5204 |s2cid=213601465}}</ref>) used to make [[plastic]]s, [[pesticide]]s and [[pharmaceuticals]].<ref name="Dixie State College">{{Cite web |title=Organic Hydrocarbons: Compounds made from carbon and hydrogen |url=http://cactus.dixie.edu/smblack/chem1010/lecture_notes/2B.htm |archive-url=https://web.archive.org/web/20110719184614/http://cactus.dixie.edu/smblack/chem1010/lecture_notes/2B.htm |archive-date=July 19, 2011}}</ref>