Natural gas

Natural gas is commercially produced from oil fields and natural gas fields. Gas produced from oil wells is called casinghead gas or associated gas. The natural gas industry is producing gas from increasingly more challenging resource types: sour gas, tight gas, shale gas and coalbed methane.The world's largest gas field by far is Qatar's offshore North Field, estimated to have 25 trillion cubic metres[15] (900 trillion cubic feet) of gas in place — enough to last more than 200 years at optimum production levels. The second largest natural gas field is the South Pars Gas Field in Iranian waters in the Persian Gulf. Connected to Qatar's North Field, it has estimated reserves of 8 to 14 trillion cubic metres[16] (280-500 trillion cubic feet) of gas; see List of natural gas fields

Compressed Natural Gas (CNG) is a substitute for gasoline (petrol), diesel, or propane fuel. It is considered to be an environmentally "clean" alternative to those fuels and it is much safer than other motor fuels in the event of a fuel spill: natural gas is lighter than air, so it disperses quickly when leaked or spilled. It is made by compressing natural gas (which is mainly composed of methane (CH4)), by about 75%. It is stored and distributed in hard containers, at a normal pressure of 200–220 bar (20–22 MPa), usually in cylindrical or spherical shapes to maintain equal pressure on the walls of the containers.

Liquefied natural gas or LNG is natural gas that has been converted to liquid form for ease of storage or transport. Liquified natural gas takes up about 1/600th the volume of natural gas at a stove burner tip. It is odorless, colorless, non-corrosive, and non-toxic. When vaporized, it burns only in concentrations of 5% to 15% when mixed with air. Neither LNG, nor its vapor, can explode in an unconfined environment.

LNG is principally used for transporting natural gas to markets, where it is regasified and distributed as pipeline natural gas. LNG offers an energy density comparable to petrol and diesel fuels and produces less pollution, but its relatively high cost of production and the need to store it in expensive cryogenic tanks have prevented its widespread use in commercial applications. It can be used in natural gas vehicles, although these are more commonly designed to use compressed natural gas.