Petroleum

Petroleum products, such as gasoline, kerosene, home heating oil, residual fuel oil and lubricating oils, come from one source-crude oil found below the earth’s surface, as well as under large bodies of water, from a few hundred feet below the surface to as deep as 25,000 feet into the earth’s interior. Sometimes crude oil is secured by drilling a hole into the earth, but more dry holes are drilled than those producing oil. Either pressure at the source or pumping forces crude oil to the surface.

Crude oil wells flow at varying rates, from about ten to thousands of  barrels per hour. Petroleum products are always measured in forty-two-gallon barrels.

Petroleum products vary greatly in physical appearance: thin, thick, transparent, or opaque but regardless, their chemical composition is made up of only two elements: carbon and hydrogen, which form compounds called hydrocarbons. Other chemical elements found in union with the hydrocarbons are few and classified as impurities. Trace elements are also found, but in such minute quantities that they are disregarded. The combination of carbon and hydrogen forms many thousands of compounds which are possible because of the various positions and unions of these two atoms in the hydrocarbon molecule.

The various petroleum products are refined by heating crude oil and then condensing the vapors. These products are the so-called light oils, such as gasoline, kerosene and distillate oil. The residue remaining after the light oils are distilled is known as heavy or residual fuel oil and is used mostly for burning under boilers. Additional complicated refining processes rearrange the chemical structure of the hydrocarbons to produce other products, some of which are used to upgrade and increase the octane rating of various types of gasoline.