Petroleum

Petroleum is a term that includes a wide variety of liquid hydrocarbons. Many scientists also include natural gas in their definition of petroleum. The most familiar types of petroleum are tar, oil, and natural gas. Petroleum forms through the accumulation, burial, and transformation of organic material, such as the remains of plants and animals, by chemical reactions over long periods of time. After petroleum has been generated, it migrates upward through the earth, seeping out at the surface of the earth if it is not trapped below the surface. Petroleum accumulates when it migrates into a porous rock called a reservoir that has a non-porous seal or cap rock that prevents the oil from migrating further. To fully understand how petroleum forms and accumulates requires considerable knowledge of geology, including sedimentary rocks, geological structures (faults and domes, for example), and forms of life that have been fossilized or transformed into petroleum throughout the earth's long history.

Tremendous petroleum reserves have been produced from areas all over the world. In the United States, the states of Alaska, California, Louisiana, Michigan, Oklahoma, Texas, and Wyoming are among the most important sources of petroleum. Other countries that produce great amounts of petroleum include Saudi Arabia, Iran, Iraq, Kuwait, Algeria, Libya, Nigeria, Indonesia, the former Soviet Union, Mexico, and Venezuela.

Petroleum products have been in use for many years. Primitive man might have used torches made from pieces of wood dipped in oil for lighting as early as 20,000 B.C. At around 5000 B.C., the Chinese apparently found oil when they were digging underground. Widespread use of petroleum probably began in the Middle East by the Mesopotamians, perhaps by 3000 B.C., and probably in other areas where oil seeps were visible at the surface of the earth. Exploration for petroleum in the United States began in 1853, when George Bissell, a lawyer, recognized the potential use of oil as a source of lamp fuel. Bissell also recognized that boring or drilling into the earth, as was done to recover salt, might provide access to greater supplies of petroleum than surface seeps. In 1857, Bissell hired Edwin Drake, often called "Colonel" Drake despite having worked as a railroad conductor, to begin drilling the first successful oil well, in Titusville, Pennsylvania. The well was drilled in 1859. Once the usefulness of oil as a fuel was widely recognized, exploration for oil increased. By 1885, oil was discovered in Sumatra, Indonesia. The famous "gusher" in the Spindletop field in eastern Texas was drilled in 1901. The discoveries of giant oil fields in the Middle East began in 1908 when the company now known as British Petroleum drilled a well in Persia (now Iran). During World Wars I and II, oil became a critical factor in the ability to successfully wage war.

Currently, petroleum is among our most important natural resources. We use gasoline, jet fuel, and diesel fuel to run cars, trucks, aircraft, ships, and other vehicles. Home heat sources include oil, natural gas, and electricity, which in many areas is generated by burning natural gas. Petroleum and petroleum-based chemicals are important in manufacturing plastic, wax, fertilizers, lubricants, and many other goods. Thus, petroleum is an important part of many human activities.