Natural Gas

**Definition:** A combustible, gaseous mixture of low-molecular weight PARAFFIN hydrocarbons, generated below the surface of the earth. It contains mostly METHANE and ETHANE with small amounts of PROPANE; BUTANES; and higher hydrocarbons, and sometimes NITROGEN; CARBON DIOXIDE; HYDROGEN SULFIDE; and HELIUM. (from McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)

**Tree numbers:** - D20.345.369 - N06.230.132.258.369

**Synonyms:** - Shale Gas - Gas, Natural