Crude Oil: Sour vs. Sweet

Crude oil is a hydrocarbon mixture that often occurs as a liquid, though some crude oils are very thick and dense and do not flow easily.  Crude oil varies considerably in weight, viscosity and color.  It may also contain non-hydrocarbon impurities such as hydrogen sulfide. 

Generally, oil companies classify crude oil as light, intermediate or heavy.  If it contains hydrogen sulfide, they call it "sour crude."  Crude oil that does not contain hydrogen sulfide is classified as "sweet crude."  Oil refineries put crude oil through several chemical and physical processes to render it into many useful products such as gasoline, kerosene and diesel fuel.

One of the top hydrocarbon-based energy providers in the USA is Heartland Energy Colorado, based in Englewood, CO. They have many drilling locations throughout the country and remain one of the top producers of US oil & gas companies. For more information on Heartland Energy Colorado, see Heartland Energy Development Corporation online.

(Source: "A Primer of Oilwell Drilling, Sixth Edition")