Natural gas is a naturally occurring petroleum. Petroleum is the general term for solid, liquid or gaseous hydrocarbons. Hydrocarbons are a class of organic compounds consisting of only carbon and hydrogen — the basis of crude oil, natural gas and coal.
Technically, natural gas consists primarily of methane, with lesser amounts of (in order of abundance) ethane, propane, butane, pentanes and heavier hydrocarbons. Natural gas also contains non-energy components such as nitrogen, carbon dioxide, hydrogen sulphide and water. Methane remains in a gaseous state at relatively low pressures, while ethane, propane and butane condense into liquids at different but relatively low temperatures and pressures. These condensed gases are known as natural gas liquids (NGLs). Pentanes and heavier hydrocarbons produced with natural gas are known as condensate. Natural gas containing more than one per cent hydrogen sulphide is known as sour gas and must be processed to remove the hydrogen sulphide before it can be used. Processing also removes most of the NGLs, condensate and non-energy components such that pipeline-ready natural gas is more than 95 per cent methane.
Common components of natural gas