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Density, SG, and °API in Crude Oil
Density, specific gravity (SG) and API gravity* values are used to monitor quality during the production of crude oil, and to establish its price in trading. This application describes the fully automatic measurement of density, SG, and oAPI of light crude oil at 15 °C and heavy crude oil at 90 °C and 50 °C.
Background
Depending on their origin, crude oils can differ substantially as to the chain lengths of the constituent hydrocarbons and additional components (such as sulfur) and are therefore grouped into two categories, light and heavy:
i) Light crudes normally have a low density (e.g. below 900 kg/m3), and API gravity of 30° or more.
ii) Heavy crudes, by contrast, usually have densities above 1000 kg/m3 and API gravity of less than 20°.
These oils show considerable differences in their chemical and physical properties, requiring different methodological approaches for their testing. To comply with ASTM D5002, light crudes can be readily measured without heating treatment directly on a density meter; measurements can be undertaken between 15 and 35 °C, and the integrated temperature compensation according to API tables transforms the density or specific gravity to either 15 °C or 60 °F. To comply with the same standard, heavy crudes typically require heating before measurement.
*oAPI, which refers to the weight of the oil relative to water
Related Applications:
Trouble Free Density Measurement of Bitumen
Temperature-Compensated Density with Portable Density Meters
