These Natural Gas Liquids are also called Condensates and refer to the non-methane hydrocarbon gas such as Ethane, Propane, Benzene, Butane or Pentane which stand at liquid state within the reservoir at underground pressure.
These NGLs are valuable natural gas by-products as they find many applications in the petrochemical industry.
That is the purpose of the Natural gas processing plant to perform the NGL fractionation to separate the NGLs from the Natural gas.
After that treatment the natural gas becomes available for transportation, that is the so called pipeline quality dry natural gas while the separated NGLs are then called the Condensates.
If the Natural gas is produced out of a crude oil field it is considered as associated gas, if it comes from a gas field production it is named non-associated gas as reference to the oil still.
The Natural gas may also be extracted from coal as coalbed methane, in that case the methane represents about 90% of Natural gas and 10% carbon dioxide .