Petroleum is recovered mostly through oil drilling. This comes after the studies of structural geology , sedimentary basin analysis, reservoir characterization. It is refined and separated, most easily by boiling point, into a large number of consumer products, from gasoline (petrol) and kerosene to asphalt and chemical reagents used to make plastics and pharmaceuticals. Petroleum is used in manufacturing a wide variety of materials.
Petroleum is found in vast underground reservoirs where ancient seas were located. Petroleum reservoirs can be found beneath land or the ocean floor. Their crude oil is extracted with giant drilling machines.
Crude oil is usually black or dark brown, but can also be yellowish, reddish, tan, or even greenish. Variations in color indicate the distinct chemical compositions of different supplies of crude oil. Petroleum that has few metals or sulfur, for instance, tends to be lighter (sometimes nearly clear).