What is gas?
Natural gas is a made up of a mixture of hydrocarbons. The main hydrocarbon in natural gas is methane, but there are also small amounts of ethane, propane and butane.
Natural gas originates from organic matter like plants and tiny sea creatures that lived millions of years ago. As the organic matter decayed it was covered with layers of silt and clay which over time turned into rock.
Over millions of years, the heat of the earth and the pressure from the weight of rocks above transformed some of the organic matter into the fossil fuels coal, oil and natural gas.
The movement of water, and pressures within the earth's crust, caused the oil and natural gas to move. Some of the oil and gas accumulated in traps or reservoirs (formed by porous rocks, covered by non-porous rocks) within the earth's crust.