Viscosity of Crude Oil
Description and Classification Overview
Crude oil is a complex mixture of various components. Depending on its geographic origin, its chemical composition and consistency vary. The different types of crude oil need to be classified for further treatment. Both a crude oil's viscosity and its API (American Petroleum Institute) degree are important parameters for classification. Crude oil's viscosity can vary from a low-viscosity liquid to up to tar-like, nearly solid form.
Classification according to the API degree:
- Light crude oil: API gravity higher than 31.1 °API (less than 870 kg/m³)
- Medium crude oil: API gravity from 31.1 °API to 22.3 °API (870 to 920 kg/m³)
- Heavy crude oil: API gravity from 22.3 °API to 10 °API (920 to 1000 kg/m³)
- Extra-heavy crude oil: API gravity below 10 °API (higher than 1000 kg/m³)
The API degrees indicate whether a crude oil floats on water or sinks. Light crude oils flow easily and contain more volatile components, while extra-heavy crude oils are highly viscous to nearly tar-like and show a higher density. Intermediate oils are between these extremes.
According to the sulfur content, it can be distinguished between:
- Sweet crude: sulfur content up to 1 % *
- Sour crude: sulfur content higher than 1 %
*Different sources state a different maximum percentage of sulfur content for sweet crudes (between 0.42 % up to 1 %).
The tables below show examples for different crude oils and their typical values for kinematic viscosity and °API.
Viscosity Table – Measurement data
Crude oils - viscosity and °API
Typical values obtained from producer's data sheets.
|Crude Oil||Kin. Viscosity [mm²/s] at Temp.||API Gravity °API|
|Arabian Light||10.7 at 20 °C||34.2|
|Brent||2.86 at 50 °C||37.9 ... 38.2|
|Bonny Light||2.90 at 50 °C||35.4 ... 35.8|
|Boscan||11233 at 100 °F||10.1|
|Escalante||307 at 38 °C||39.6|
|Kutubu||2.1 at 20 °C||44|
|Tia Juana Light||8.8 at 100 °F||31.9|
|Tia Juana Heavy||88.6 at 100 °F||12.3|
|West Texas Intermediate||4.9 at 20 °C||39|
U.S. Energy Information Administration
Genesis Group, USA
Chevron Crude Oil Marketing
AMSA-Australian Maritime Safety Authority
|Reference||U.S. Energy Information Administration, Genesis Group, USA, Chevron Crude Oil Marketing, Exxon Mobil, AMSA-Australian Maritime Safety Authority|
|Related||Crude oil, heavy crude, sweet crude, sour crude, light crude oil, petroleum, viscosity, API gravity, °API|