A naturally occurring yellow-to-black liquid which is found beneath the Earth's surface and commonly refined into various types of fuels is known as petroleum. Petroleum consists of hydrocarbons of various molecular weights and other organic compounds. Petroleum is a fossil fuel which is formed when large quantities of dead organisms are buried underneath sedimentary rock and subjected to intense heat and pressure.
Petroleum is obtained in form of crude oil from ground. It is composed of hydrocarbons. Other elements such as nitrogen, sulphur, oxygen and metals such as iron, nickel, and copper can also be mixed in with the hydrocarbons in small amounts.
An industrial process plant where crude oil is processed and refined into more useful products such as petroleum naphtha, gasoline, diesel fuel, heating oil, kerosene, and liquefied petroleum gas. It is an essential part of the downstream side of the petroleum industry.