Маг техн англ: Petroleum

Petroleum

Petroleum usually refers just to crude oil, but the term can also apply to natural gas and shale oil. Crude oil and natural gas are found in commercial quantities in more than 50 countries in all parts of the world. The largest deposits are in the Middle East, which contains more than half the known oil reserves and almost one-third of the known natural-gas reserves. In contrast, the U.S. contains only about 2 percent of the known oil and 3 percent of the known gas reserves.

Geologists and other scientists have developed techniques that indicate the possibility of oil or gas deep in the ground. These techniques include aerial photography of special surface features, shock waves sent through the earth and reflected back into instruments, and meters to measure the earth’s gravity and magnetic field. Nevertheless, the only method by which oil or gas can be found is by drilling a hole into the reservoir. In some cases oil companies spend many millions of dollars drilling in promising areas, only to find dry holes. For a long time, most wells were drilled on land, but after World War II, drilling commenced in water from platforms supported by legs that rested on the sea bottom. Later, floating platforms were developed that could drill at water depths of 1000 m or more. Large oil and gas fields have been found offshore in the United States, mainly off the Gulf Coast, in Europe, primarily in the North Sea, in Russia in the Barents Sea and Kara Sea, and off Brazil. Most major finds in the future may be offshore.