Petroleum is a complex of hydrocarbons, mostly alkanes and cycloalkanes. It occurs deep below earth's crust entrapped under rocky strata.
It is taken out by drilling wells. The natural oil thus derived is a viscous black liquid. In its taken out by drilling wells Petroleum ( Latin, petra = rock; oleum= oil) or Crude oil. There occurs invariably a gas in naturally from oil wells is referred to as Natural gas. Natural gas is primarily a mixture of methane and ethane, along with small amounts of propane.
Petroleum and natural gas are generally considered to be formed by the decomposition of plants and microscopic animals. When buried under earth, these are converted to petroleum and natural gas under geological conditions of high temperature and pressure in absence of oxygen.
Since the emergy for plant growth comes from the sun, petroleum and natural gas can be regarded stored form of solar energy. It seems prabable that petroleum and natural gas are being formed at the present times.
However, the rate at which these natural resources are being used up is very much greater than the rate at which they are formed.
Petroleum constitutes the principal energy sources for our modern industrial society. It is the major source for most of the chemicals used to form the synthetics' fibres, plastics, film, drugs, food additions and pesticides.
Industry agriculture, communication and means of transportation in the present- day world depend largely upon 'black gold'. In fact, it is the most valuable material for nations in peace and war. A statesman has observed, " The nation that has petroleum dominates world politics".
