An oil field is a tract of land used for extracting petroleum – otherwise known as crude oil – from the ground. Although some contest the exact origin of oil, most consider petroleum a fossil fuel created from dead organic material often found in ancient sea beds thousands of meters below the surface of the earth.
An oil refinery or petroleum refinery is an industrial process plant where crude oil is transformed and refined into more useful products such as petroleum naphtha, gasoline, diesel fuel, asphalt base, heating oil, kerosene, liquefied petroleum gas, jet fuel and fuel oils.