Heavy crude oil

Heavy crude oil

Heavy crude oil or Extra Heavy oil is any type of crude oil which does not flow easily. It is referred to as "heavy" because its density or specific gravity is higher than of light crude oil. Heavy crude oil has been defined as any liquid petroleum with an API gravity less than 20°,cite conference
first = M.B.
last = Dusseault
authorlink =
coauthors =
title = Comparing Venezuelan and Canadian Heavy Oil and Tar Sands
booktitle =
pages =
publisher = Canadian International Petroleum Conference
date = June 12-14, 2001
location = Calgary, Canada
url = http://www.energy.gov.ab.ca/OilSands/pdfs/RPT_Chops_app3.pdf
doi =
id =
accessdate = 2008-05-05
] meaning that its specific gravity is greater than 0.933.

Production, transportation, and refining of heavy crude oil present special challenges compared to light crude oil. The largest reserves of heavy oil in the world are located north of the Orinoco river in Venezuela [Energy Information Administration (2001) "Venezuela Offers Full Market Value to Encourage Foreign Investment in Oil" [http://www.eia.doe.gov/emeu/finance/usi&to/upstream/venezuela.html] ] , the same amount as the conventional oil reserves of Saudi Arabia [M. Talwani, "The Orinoco heavy oil belt in Venezuela (Or heavy oil to the rescue?)" [http://cohesion.rice.edu/naturalsciences/earthscience/research.cfm?doc_id=2819] ] , but 30 or more countries are known to have reserves. Heavy crude oil is closely related to tar sands, the main difference being that tar sands generally do not flow at all. Canada has large reserves of tar sands, located north and northeast of Edmonton, Alberta.

Physical properties that distinguish heavy crudes from lighter ones include higher viscosity and specific gravity, as well as heavier molecular composition. Extra heavy oil from the Orinoco region has a viscosity of over 10,000 centipoiseFact|date=April 2008 and 10° API gravity [Rodriguez H. A., Vaca P., Gonzalez O., and De Mirabal M. C., "Integrated study of a heavy oil reservoir in the Orinoco Belt : A field case simulation" [http://cat.inist.fr/?aModele=afficheN&cpsidt=6242344] ] . Generally a diluent is added at regular distances in a pipeline carrying heavy crude to facilitate its flow.

Some petroleum geologists categorize bitumen from tar sands as extra heavy oil although bitumen does not flow at ambient conditions.


Heavy crude oils provide an interesting situation for the economics of petroleum development. The Resources of Heavy oil in the world are more than twice of those conventional light crude oil. On one hand, due to increased refining costs and high sulfur content, heavy crudes are often priced at a discount to lighter ones. The increased viscosity and density also makes production more difficult (see: reservoir engineering). On the other hand, large quantities of heavy crudes have been discovered in the Americas including Canada, Venezuela and Northern California. The relatively shallow depth of heavy oil fieldsFact|date=April 2008 (often less than 3000 feet) contributes to lower drilling costs.

Chemical properties

Heavy oil is asphaltic. It is "heavy" (dense and viscous) due to the high ratio of naphthenes to paraffin (linear alkanes). Heavy oil has over 60 carbon atoms and hence a high boiling point and molecular weight. For example, the viscosity of Venezuela's Orinoco extra-heavy crude oil lies in the range 1000-5000 cP, while Canadian extra-heavy crude has a viscosity in the range 5000-10,000 cP, about the same as molasses, and higher (up to 100,000 cP for the most viscous commercially exploitable deposits).A definition from the Chevron Phillips Chemical company is as follows:

The "heaviness" of heavy oil is primarily the result of a relatively high proportion of a mixed bag of complex, high molecular weight, non-paraffinic compounds and a low proportion of volatile, low molecular weight compounds. Heavy oils typically contain very little paraffin and may or may not contain high levels of asphaltenes. [ [http://www.cpchem.com/enu/docs_drilling/heavyoils.pdf "What causes heavy oil if they don't have asphaltene or paraffin problems?"] - Chevron Phillips Chemical]

Environmental impact

As a rule, heavy crudes have a more severe environmental impact than light ones. With more difficult production comes the employment of a variety of enhanced oil recovery techniques, including steam flooding and tighter well spacing, often as close as one well per acre. Heavy crudes also carry contaminants. For example, Orinoco extra heavy oil contains 3.5% sulfur as well as vanadium and nickel. [http://www.worldenergy.org/wec-geis/publications/default/tech_papers/17th_congress/3_1_04.asp] Heavy crude oils contain more carbon in relation to hydrogen, thus releasing more carbon dioxide (a greenhouse gas) per amount of usable energy when burned.

Advanced technologies are mitigating the environmental impact via horizontal wells and increased energy efficiency, but, barrel for barrel, heavy crudes will likely always be more environmentally damaging than light crudes.


Most geologists agree that crude becomes "heavy" as a result of biodegradation, in which lighter ends are preferentially consumed by bacterial activity in the reservoir, leaving heavier hydrocarbons behind. This hypothesis leans heavily on the techniques of petroleum geochemistry.


See also

*Oil shale
*Tar sands
*Steam injection (oil industry)

External links

* [http://www.lloydminsterheavyoil.com OTS Heavy Oil Science Centre]
* [http://www.heavyoilinfo.com/blog-posts/worldwide-heavy-oil-reserves-by-country/ Schlumberger map of global heavy oil resources]
* [http://www.uic.edu/~mansoori/HOD_html Molecular Basis of Heavy Organics in Petroleum and Heavy Oil]

Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать реферат

Look at other dictionaries:

  • Light crude oil — is liquid petroleum that has a low density and flows freely at room temperature.[1] It has a low viscosity, low specific gravity and high API gravity due to the presence of a high proportion of light hydrocarbon fractions.[2] It generally has a… …   Wikipedia

  • Sour crude oil — is crude oil containing the impurity sulfur. It is common to find crude oil containing some impurities. When the total sulfur level in the oil is > 0.5 % the oil is called sour . [cite web|url=http://www.spe.org/spe/jsp/basic/0,,1104… …   Wikipedia

  • List of crude oil products — In the international petroleum industry, crude oil products are traded on various oil bourses based on established chemical profiles, delivery locations, and financial terms. The chemical profiles, or crude oil assays, specify important… …   Wikipedia

  • Crude — can refer to: Petroleum in its unprocessed form ( crude oil ), including: Brent crude oil Heavy crude oil Light crude oil Sweet crude oil Pennsylvania Grade Crude Oil, a type of sweet crude Synthetic crude oil Crude jokes Documentary films: Crude …   Wikipedia

  • Components of crude oil — Crude oil is essentially a mixture of many different hydrocarbons, all of varying lengths and complexities. In order to separate the individual components that make up the raw natural resource, the crude oil must be fractionally distillated so… …   Wikipedia

  • Manure-derived synthetic crude oil — is a synthetic crude oil chemically engineered (converted) from animal or human manure. Research into the production of manure derived synthetic crude oil began with pig manure in 1996 at the University of Illinois at Urbana Champaign by the… …   Wikipedia

  • Oil depletion — per major producing country. This model assumes world oil depletion remains constant at the 2004 level of 80 million barrels per day.[1] However, world oil depletion is currently (as of 2008) at 85 million barrels per day …   Wikipedia

  • Heavy oil — may refer to:*Fuel oil that contains residual oil left over from distillation. *Heavy crude oil, viscous crude oil. *Coal tar creosote, a wood preservative and waterproofing agent.Please join our discussion group on HEAVY OIL at:… …   Wikipedia

  • Oil and Natural Gas Corporation — Limited Type State owned enterprise Public Traded as NSE:  …   Wikipedia

  • Oil & Gas UK — Abbreviation (former UKOOA) Motto The Voice of the Offshore Industry Formation April 2007 Legal status Non profit company Purpose/focus Offshore oil …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”