Oil is found in geological formations at variable depths in the earth’s crust. The presence of oil is usually identified by visible features such as gas oozes, oil seeps and crater formations due to gas leakage. Typically, oil is found trapped within layers of porous sandstone, which lies in the bed of non-porous sediments. Natural gas is present below the non-porous layer and just above the oil surface. Also, at times oil tends to break the layer crust to reveal its presence.
Once the initial geological studies confirm the presence of oil, sophisticated technology is employed to determine the quantity and depth. The branch of science that deals with the study of oil exploration is called ‘exploration geophysics.’ The possible location of oil exploration is subjected to various geology surveys such as magnetic survey, seismic reflection survey and gravity survey. At a higher stage, elaborate seismic surveys are conducted to measure the time taken by sound waves to travel through matter. If the presence of oil is confirmed, the site is transferred to an oil exploration company.
Oil extraction requires the deployment of heavy machines and the drilling of oil wells. First, natural gas is extracted through pipes and later crude oil.
Oil fields are scattered across the globe. Some of the biggest oil exploration sites are: