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The three most quoted oil products are North America's West Texas Intermediate crude (WTI), North Sea Brent Crude, and the UAE Dubai Crude, and their pricing is used as a barometer for the entire petroleum industry, although, in total, there are 46 key oil exporting countries. Brent Crude is typically priced at about $2 over the WTI Spot price ...
where U is the oil's kinematic viscosity at 40 °C (104 °F), Y is the oil's kinematic viscosity at 100 °C (212 °F), and L and H are the viscosities at 40 °C for two hypothetical oils of VI 0 and 100 respectively, having the same viscosity at 100 °C as the oil whose VI we are trying to determine.
For example, the viscosity of Venezuela's Orinoco extra-heavy crude oil lies in the range 1000–5000 cP (1–5 Pa·s), while Canadian extra-heavy crude has a viscosity in the range 5000–10,000 cP (5–10 Pa·s), about the same as molasses, and higher (up to 100,000 cP or 100 Pa·s for the most viscous commercially exploitable deposits). [2]
Crude oil is classified as light, medium, or heavy according to its measured API gravity. Light crude oil has an API gravity higher than 31.1° (i.e., less than 870 kg/m 3) Medium oil has an API gravity between 22.3 and 31.1° (i.e., 870 to 920 kg/m 3) Heavy crude oil has an API gravity below 22.3° (i.e., 920 to 1000 kg/m 3)
Consequently, if a liquid has dynamic viscosity of n centiPoise, and its density is not too different from that of water, then its kinematic viscosity is around n centiStokes. For gas, the dynamic viscosity is usually in the range of 10 to 20 microPascal-seconds, or 0.01 to 0.02 centiPoise. The density is usually on the order of 0.5 to 5 kg/m^3.
Extensional viscosity can be measured with various rheometers that apply extensional stress. Volume viscosity can be measured with an acoustic rheometer. Apparent viscosity is a calculation derived from tests performed on drilling fluid used in oil or gas well development. These calculations and tests help engineers develop and maintain the ...
If the viscosity, density, relative density (specific gravity) and refractive index [7] for a mineral oil is determined, the viscosity-gravity constant (VGC) and refractivity intercept (ri) can be calculated. Using the given values, the percent carbons (%CA, %CN, %CP) can be derived from a correlation chart, the ASTM D2140 method. [8]
The clear cut definition of light and heavy crude varies because the classification is based more on practical grounds than theoretical. The New York Mercantile Exchange (NYMEX) defines light crude oil for domestic U.S. oil as having an API gravity between 37° API (840 kg/m 3) and 42° API (816 kg/m 3), while it defines light crude oil for non-U.S. oil as being between 32° API (865 kg/m 3 ...