There are basically three sources of raw natural gas that are used for extracting the natural gas including petroleum crude oil wells, condensate wells and gas wells.

The raw natural gas that is extracted from petroleum crude oil wells the associated gas that exists separately from the crude oil in the underground formation, or dissolved in the crude oil.

The raw natural gas from gas wells and condensate wells do not have crude oil and is termed as non-associated gas. The gas wells produce raw natural gas while the condensate wells produce raw natural gas in addition to natural gas condensate.

The methane-rich gas occurs in the methane deposits in form of pores of coal seams and called as coal- bed gas. It is called as sweet gas as it is free of hydrogen sulphide. It primarily consists of methane with small quantities of nitrogen, ethane, and carbon dioxide. It does not contain butanes, pentanes, propane, or condensate.

Natural gas hydrate or methane hydrate is a solid structure that traps the methane within the crystal structure of ice. The significant deposits of methane clathrate are found under the sediments on the ocean floors and in the arctic regions. The amount of the worldwide methane reserves are not known significantly.

As per the recent estimates, the range of methane is from 1 to 5 × 1015 m3. It amounts to six to twenty nine times of the worldwide natural gas reserves that amounts to 175.4 × 1012 m3 from the conventional sources.  The technology for economically exploiting and extracting the methane from the hydrate reservoirs is not available.

Here m3 are defined at the conditions of temperature 0 °C and 1 atm (101.325 kPa) of absolute pressure.

Other types of gases such as landfill gas, town Gas, Biogas, and synthetic gas, are not natural gases as they are man-made fuels.