Crude Oil Qualities

=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. The specific gravity of oil is its relative density to water at 60° Farenheit.

Light Oil
Otherwise known as "conventional oil", light oil has an API gravity of 22° or over. For example, Saudi Arabia's new blend of super light crude has an API gravity of 44°. 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°.

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.

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.

Extra Heavy Oil
Extra heavy oil has an API gravity of less than 10°.

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

=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.

=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.

=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.

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.

=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=