Heavy crude oil or extra heavy crude oil is any type of crude oil which does not flow easily. It is referred to as "heavy" because its density or specific gravity is higher than that of light crude oil. Heavy crude oil has been defined as any liquid petroleum with an API gravity less than 20°. Physical properties that differ between heavy crudes lighter grades include higher viscosity and specific gravity, as well as heavier molecular composition. Extra heavy oil is defined with a gravity of less than 10° API (i.e. with density greater than 1000 kg/m3 or, equivalently, a specific gravity greater than 1) and a reservoir viscosity of no more than 10,000 centipoises. With a specific gravity of greater than 1, extra heavy crude is present as a dense non-aqueous phase liquid in ambient conditions.
Heavy crude oil is closely related to natural bitumen from oil sands. Some petroleum geologists categorize bitumen from oil sands as extra heavy crude oil due to the density of less than 10 °API. Other classifications label this as bitumen differing it from extra-heavy oil. They differ in the degree by which they have been degraded from the original crude oil by bacteria and erosion. Often, bitumen is present as a solid and does not flow at ambient conditions.
The largest reserves of heavy crude oil in the world are located north of the Orinoco river in Venezuela, the same amount as the conventional oil reserves of Saudi Arabia, but 30 or more countries are known to have reserves.
Production, transportation, and refining of heavy crude oil present special challenges compared to light crude oil. Generally, a diluent is added at regular distances in a pipeline carrying heavy crude to facilitate its flow.
Read more about Heavy Crude Oil: Economics, Extraction, Environmental Impact, Geological Origin, Chemical Properties
Famous quotes containing the words heavy, crude and/or oil:
“A valiant man, Sire, fears no enemy, but the righteous anger of noble women weighs upon him as a heavy burden.”
—Franz Grillparzer (17911872)
“The idealism of Berkeley is only a crude statement of the idealism of Jesus, and that again is a crude statement of the fact that all nature is the rapid efflux of goodness executing and organizing itself.”
—Ralph Waldo Emerson (18031882)
“As artists theyre rot, but as providers theyre oil wells; they gush. Norris said she never wrote a story unless it was fun to do. I understand Ferber whistles at her typewriter. And there was that poor sucker Flaubert rolling around on his floor for three days looking for the right word.”
—Dorothy Parker (18931967)