If we consider the composition of natural gas, we see that it is a hydrocarbon that mainly consists of methane, although it usually also contains a variable proportion of nitrogen, ethane, CO2, H2O, butane, propane, mercaptanes and traces of heavier hydrocarbons. This proportion varies depending on the fields in which the gas is found and whether or not other substances are in those field. The formula for methane is CH4 and it may constitute up to 97% of natural gas.
Millions of years ago, layers of organic material were gradually deposited among the sediments on estuary and reservoir beds, in a very oxygen-poor environment. When these sediments are mixed with sandy or clay-like particles and the remains of vegetation, the pressure and temperature rise and natural gas is formed.
The natural gas that is formed, whose proportions depend on the temperature and the pressure that it is submitted to, then pushes to rise through the layers of permeable rock that we now call fields or reserves and which are now being discovered. Natural gas fields are, thus, an accumulation of hydrocarbons that may be discovered saturating the pores and cracks of the rocks in which they are found.
The natural gas extraction proves is very similar to that used for oil and its transportation is effectuated using gas pipelines to the point of use.