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Origin and Natural Occurrence
Exploration and Drilling of Wells
Composition and Refining of Petroleum
The physical properties and exact chemical composition of crude oil varies from one locality to another. The different hydrocarbon components of petroleum are dissolved natural gas, gasoline, benzine, naphtha, kerosene, diesel fuel and light heating oils, heavy heating oils, and finally tars of various weights (see tar and pitch). The crude oil is usually sent from a well to a refinery in pipelines (see under pipe) or tanker ships.
The hydrocarbon components are separated from each other by various refining processes. In a process called fractional distillation petroleum is heated and sent into a tower. The vapors of the different components condense on collectors at different heights in the tower. The separated fractions are then drawn from the collectors and further processed into various petroleum products. One of the many products of crude oil is a light substance with little color that is rich in gasoline. Another is a black tarry substance that is rich in asphalt.
As the lighter fractions, especially gasoline, are in the greatest demand, so-called cracking processes have been developed in which heat, pressure, and certain catalysts are used to break up the large molecules of heavy hydrocarbons into small molecules of light hydrocarbons. Some of the heavier fractions find eventual use as lubricating oils, paraffins, and highly refined medicinal substances such as petrolatum.
See also petrochemicals.
History and Development of Petroleum
Petroleum has been known throughout historical time. It was used in mortar, for coating walls and boat hulls, and as a fire weapon in defensive warfare. Native Americans used it in magic and medicine and in making paints. Pioneers bought it from the Native Americans for medicinal use and called it Seneca oil and Genesee oil. In Europe it was scooped from streams or holes in the ground, and in the early 19th cent. small quantities were made from shale. In 1815 several streets in Prague were lighted with petroleum lamps.
The modern petroleum industry began in 1859, when the American oil pioneer E. L. Drake drilled a producing well on Oil Creek in Pennsylvania at a place that later became Titusville. Many wells were drilled in the region. Kerosene was the chief finished product, and kerosene lamps soon replaced whale oil lamps and candles in general use. Little use other than as lamp fuel was made of petroleum until the development of the gasoline engine and its application to automobiles, trucks, tractors, and airplanes. Today the world is heavily dependent on petroleum for motive power, lubrication, fuel, dyes, drugs, and many synthetics. The widespread use of petroleum has created serious environmental problems. The great quantities that are burned as fuels generate most of the air pollution in industrialized countries, and oil spilled from tankers and offshore wells has polluted oceans and coastlines.
See K. K. Landes, Petroleum Geology of the United States (1970); S. Schackne and N. D. Drake, Oil for the World (2d ed. 1960); L. Mosley, Power Play: Oil in the Middle East (1973).