Natural gas is a mixture of light hydrocarbons found underground, in which the percentage of methane is over 70% by volume.
Natural gas is found underground, in accumulations in porous rocks, isolated from the outside by impermeable rocks. It is the result of the degradation of organic matter in an anaerobic way, originating from extraordinary quantities of micro-organisms; organic matter that degraded away from contact with air, at high temperatures and under strong pressures.
The composition of natural gas can vary depending on the field in which the gas is produced, the production process, conditioning, processing and transportation.
Generally, it has a density less than 1 (lighter than air) and a high calorific value between 8,000 and 10,000 kcal/m³, depending on the heavy content, in particular ethane and propane, and inert materials, such as nitrogen and carbon dioxide.