Petroleum—or crude oil—is a fossil fuel that is found in naturally occurring large in quantities beneath the Earth's surface in many countries worldwide and is often used as a fuel or raw material in the chemical industry. It is Crude oil is often referred as “Black Gold” because when crude oil is extracted from beneath the earth it is black in color and gold because of its oils and value. It primarily consists of hydrogen, carbon and oxygen. Oils contain high amounts of carbon and hydrogen content making them highly flammable. An "oil field'' is referred to as a region with plenty of oil wells extracting petroleum (crude oil) from beneath the ground. Since the oil reservoirs are typically spread over a large area, possibly several hundred kilometers across, full exploitation results in multiple wells scattered all over the area. Oil drilling is oftentimes referred as a complicated process that involves the drilling and pumping of oil from underground wells.