Crude Oil, Crude Oil Grades, Varieties of Crude Oil

By: EconomyWatch   Date: 30 June 2010

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Crude oil has withstood the test of time, with its oldest oil bearing rocks dating back to over 600 million years. Its chemical composition and usage are varied.

Its main characteristics are:

  • It is highly inflammable dark, dense fluid that consists of hydrocarbon molecules.

  • It has been found in natural underground reservoirs.

  • It produces petroleum products and accounts for nearly 40% of the world’s primary energy consumption.

  • When processed, it yields natural gas and chemical residue, which are also fuels.

  • It is classified on the basis of viscosity and the extent of impurities (like sulfur) present in it.
  • Classification of Crude Oil: Viscosity

    Viscosity of crude oil is the internal friction of a liquid. Its evaluation involves assessing the thickness of the substance. Based on its viscosity, crude oil is classified as:

    • Light crude oil: It has low wax content.

    • Heavy crude oil: This type of crude oil has higher wax ratio as compared to light crude oil. Due to high density, it does not flow as freely as the light crude oil.

    The density of crude oil is very important, which is why the oil industry uses the API (American Petrochemical Institute) gravity as its measurement.

    Oil Grades

    Here are various grades of crude oil, based on API gravity measurements:

    • Light crude oil: It has API gravity more than 31.1. °

    • Medium crude oil: It has API gravity between 22.3° and 31.1.°

    • Heavy crude oil: It has API gravity lower than 22.3.°

    Classification of Crude Oil: Sulfur Content

    Based on its sulfur content, crude oil is classified as follows:

    Sweet crude oil:

    • It has very little sulfur content (less than 0.5%) with diminutive amounts of hydrogen sulfide and carbon dioxide.

    • Due to low percentage of wax, it has low viscosity which facilitates easy pumping and transportation of oil.

    • It reduces the chances of oil clogging while processing.

    • It can be used to process gasoline, kerosene and high quality diesel.

    • Light sweet crude oil demands the highest price in the market.

    Sour crude oil:

    • It has a high percentage of sulfur impurities (more than 0.5%).

    • Refining is highly necessary so that it can be processed into gasoline or kerosene.

    • It is usually processed into fuel oil and diesel instead of gasoline.

    Crude oil varieties are in great demand and highly priced. To stay updated about crude oil prices, follow the prices of benchmark varieties such as the OPEC basket price, Brent and Dubai crude.

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