Natural gas: physical properties and combustion features

The majority of natural gases are mixtures of saturated hydrocarbons where methane prevails; they come from underground accumulations of gases alone or gases associated with oil. There are thus as many compositions of natural gases as exploited hydrocarbon layers. Apart from the methane which is the prevailing element, the crude natural gas usually contains decreasing volumetric percentages of ethane, propane, butane, pentane, etc. The ultimate analysis of a natural gas thus includes/understands the molar fraction of hydrocarbons in CH4, C2H6, C3H8, C4H10 and the remainder of heavier hydrocarbons is generally indicated under the term C5+. Table 1 gives typical compositions. Apart from these hydrocarbons, one often finds one or more minor elements, or impurities, quoted hereafter: