Natural gas
Natural gas is usually found together with oil but the proportion of oil to gas varies and either may be the main product of a field. This is why boe is used as a measure of volume.
Like crude oil, it is a mixture of hydrocarbon compounds, mostly methane. Methane (CH4) is colourless, flammable, and odourless (which causes some safety problems). It is a greenhouse gas.
Natural gas is sold in the form of various extracts such as dry natural gas and LPG.