1. n. [Heavy Oil]

A mixture of crude oils, blended in the pipeline to create a crude with specific physical properties. Because heavy and extraheavy crudes or bitumens cannot flow from the field to the refinery in their original state and at normal surface temperatures, they are blended with lighter crude oils primarily to reduce viscosity, thereby enabling transportation to a refinery. A secondary objective may be to provide a blended crude oil that has significantly higher value than the raw heavy crude. The blend is usually constructed so that the value of the overall blended volume is greater than the summed value of the initial volumes of individual heavy and light crudes.

See: bitumen,  heavy oil,  light crude oil,  raw crude oil