Science, Tech, Math › Science Chemical Composition of Petroleum Petroleum Composition Share Flipboard Email Print bashta/Getty Images Science Chemistry Chemical Laws Basics Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated December 06, 2019 Petroleum or crude oil is a complex mixture of hydrocarbons and other chemicals. The composition varies widely depending on where and how the petroleum was formed. In fact, chemical analysis can be used to fingerprint the source of petroleum. However, raw petroleum or crude oil has characteristic properties and composition. Hydrocarbons in Crude Oil There are four main types of hydrocarbons found in crude oil. paraffins (15-60%)naphthenes (30-60%)aromatics (3-30%)asphaltics (remainder) The hydrocarbons primarily are alkanes, cycloalkanes, and aromatic hydrocarbons. Elemental Composition of Petroleum Although there is considerable variation between the ratios of organic molecules, the elemental composition of petroleum is well-defined: Carbon - 83 to 87%Hydrogen - 10 to 14%Nitrogen - 0.1 to 2%Oxygen - 0.05 to 1.5%Sulfur - 0.05 to 6.0%Metals - < 0.1% The most common metals are iron, nickel, copper, and vanadium. Petroleum Color and Viscosity The color and viscosity of petroleum vary markedly from one place to another. Most petroleum is dark brown or blackish in color, but it also occurs in green, red, or yellow. Sources Norman, J. Hyne (2001). Nontechnical guide to petroleum geology, exploration, drilling, and production (2nd ed.). Tulsa, OK: Penn Well Corp. ISBN 978-0-87814-823-3. Ollivier, Bernard; Magot, Michel (January 1, 2005). Petroleum Microbiology. Washington, DC: American Society of Microbiology. doi:10.1128/9781555817589. ISBN 978-1-55581-758-9.Speight, James G. (1999). The Chemistry and Technology of Petroleum (3rd ed.). New York: Marcel Dekker. ISBN 978-0-8247-0217-5.