Crude Oil Qualities

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Density

Oil density is generally expressed in degrees using an API scale. This is a specific gravity scale developed by the American Petroleum Institute (API), designed to measure the relative density of various petroleum liquids. The measure is expressed in degrees and most values fall between 10° and 70° API gravity.[1] The specific gravity of oil is its relative density to water at 60° Farenheit.[2]

Light Oil

Otherwise known as "conventional oil", light oil has an API gravity of 22° or over.[3]

For example, Saudi Arabia's new blend of super light crude has an API gravity of 44°.[4] The oil produced from Libyan fields is also typically very "light" and the country's nine export grades have API gravities that range from 26 - 43.3°.[5]

Heavy Oil

Heavy oil is a dense, viscous oil with low API gravity. Definitions vary, but it is generally accepted that the upper limit for heavy oils is 22° API. In Venezuela for example, the Bachaquero Heavy Crude Oil has an API gravity of 17º.[6]

Heavy oils are usually not recoverable in their natural state through a well or using ordinary production methods. Most need to be heated or diluted so that they can flow into a well or through a pipeline.[7]

Extra Heavy Oil

Extra heavy oil has an API gravity of less than 10°.[8]

Bitumen

Otherwise known as "oil sands", bitumen shares many attributes of heavy oil but is even more dense and viscous.[9]

Sulphur Content

Crude oil can also be measured in terms of sulphur content (ranging from "sweet" to "sour"). "Sweet" crude is usually defined as oil with a sulphur content below 0.5 percent, while "sour" crude has a sulphur content of 0.5 percent or over.[10]

Impact on Refining

The density and "sourness" of crude oil feedstocks affects the amount of processing and conversion necessary to achieve what is known as an optimal mix of products. Light, sweet crude demands a higher price than heavier, sourer crude as it requires less processing and produces a greater percentage of value-added products, such as gasoline, diesel and aviation fuel. Heavier grades of fuel generally require additional processing to producer lighter products.[11]

Crude oil blends

Blended crude is a mixture of crude oils, blended in the pipeline to create a crude with specific physical properties. This may be to reduce viscosity and ease transportation, or alternatively to create added value compared to the raw crude.[12]

Oil producing countries, particularly those with a many different qualities of crude from their fields, must decide which brand they will put on the international market. There are around 160 crude grades marketed globally as of 2012. In order to optimise investments in pipelines and storage facilities, countries tend to reduce the number of marketable streams by blending different oil grades. For example, the 'Brent blend' in fact comes from the blending of 15 different grades of oil from the North Sea.[13]

Crude oil qualities around the globe

Egypt

Main article: Crude Oil Qualities in Egypt

Iran

Main article: Crude Oil Qualities in Iran

Iraq

Main article: Crude Oil Qualities in Iraq

Libya

Main article: Crude Oil Qualities in Libya

South Sudan

Main article: Crude Oil Qualities in South Sudan

Syria

Main article: Crude Oil Qualities in Syria

Uganda

Main article: Crude Oil Qualities in Uganda

Kenya

Main article: Crude Oil Qualities in Kenya

References

  1. API GravitySchlumberger Oil Glossary, retrieved 22 January 2012.
  2. Tech Talk - Venezuela, heavy crudes, API gravity and refinery gainsThe Oil Drum, 9 January 2011.
  3. What is Heavy Oil and How is it Formed?Rigzone, retrieved 22 January 2012.
  4. What is Heavy Oil and How is it Formed?Wall Street Journal, retrieved 22 January 2012.
  5. Saudi's New Super Light Crude Blend To Hit Market In April -SourceIEA, 31 March 2011.
  6. Crude Oil TypesA Barrel Full, 31 March 2011.
  7. What is Heavy Oil and How is it Formed?Rigzone, retrieved 22 January 2012.
  8. What is Heavy Oil and How is it Formed?Rigzone, retrieved 22 January 2012.
  9. What is Heavy Oil and How is it Formed?Rigzone, retrieved 22 January 2012.
  10. Types of Crude OilNeste Oil, retrieved 23 January 2012.
  11. Types of Crude OilNeste Oil, retrieved 23 January 2012.
  12. "Blended Crude" Schlumberger OIl Glossary', retrieved 29 November 2012.
  13. "Iraq oil: The crude oil quality dilemma" Gulf News', 11 November 2012.