Natural gas is a mixture of small organic molecules that are all gasses at normal temperatures. Methane is the most abundant constituent of natural gas, while ethane, propane, and helium are also present.Natural gas also includes trace amounts of other organic gases.ost of the natural gas that we use is called dry.. It generally consists of 95% methane, 3% ethane, propane, and butane, and 2% non-hydrocarbon gases such as carbon dioxide, nitrogen, or helium (EPA 2010).