A naturally occurring mixture of hydrocarbon gases that is highly compressible and expansible. Natural gas is often found in association with crude petroleum. 

The portions of gas from a reservoir that are liquified at the surface in separators, field facilities, or gas processing plants. NGL from gas processing plants is also called liquified petroleum gas (LPG). Natural gas liquids include propane, butane, pentane, hexane and heptane, but not methane and ethane, since these hydrocarbons need refrigeration to be liquefied. 

This is a well in which the formation pressure is sufficient to produce oil at a commercial rate without requiring a pump.

This is a chemical reaction between an acid and a base to form a salt and water. The process involves removing acidic contaminants from muds and formation of emulsifiers in oil mud. 

Natural gas produced from a reservoir that does not contain significant quantities of crude oil.