Natural gas is typically found 1 to 2 miles underneath the surface of the earth where it becomes trapped by large formations of porous sedimentary rock. Deposits of natural gas, known as reservoirs, are typically dome-shaped and require industrial drilling operations in order to harvest. Natural gas reservoirs exist in multiple locations all over the world, with the largest known deposits located in the Middle East, Europe, Asia and Africa.
Natural gas is a fossil fuel created from the remains of biological organisms that lived millions of years ago. The most widely accepted theory regarding the formation process of fossil fuels states that natural gas, oil and coal form through the compression of organic matter that is subjected to intense heat and pressure over millions of years. The pressure and high temperature found deep below the surface of the earth breaks down the carbon bonds of organic matter which produces methane and other types of fossil fuels.
Natural gas may also be formed by microorganisms that transform organic matter into biogenic methane. Deposits of biogetic methane are typically found much closer to the surface of the earth. Natural gas is also found in waste-containing landfills. The decomposing waste materials found in landfills produce methane which is then harvested.