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Naphthene-base crude oil	Hydrocarbon liquid with an API gravity less than 25° API. Crude oil containing asphaltic materials but very little or no paraffin wax. This type of oil is suitable for making gasoline, lubricating oil and asphalt. It is also called asphalt-base crude.

Natural gas	A naturally occurring mixture of hydrocarbon gases that is highly compressible and expansible. Methane (CH4) is the chief constituent of most natural gas (constituting as much as 85% of some natural gases), with lesser amounts of ethane (C2H6), propane (C3H8), butane (C4H10) and pentane (C5H12). Impurities can also be present in large proportions, including carbon dioxide, helium, nitrogen and hydrogen sulfide.

Natural gas liquids (NGL)	Components of natural gas are liquid at surface in field facilities or in gas-processing plants. Natural gas liquids can be classified according to their vapor pressures as low (condensate), intermediate (natural gasoline) and high (liquefied petroleum gas) vapor pressure.

Naturally flowing well	A well in which the formation pressure is sufficient to produce oil at a commercial rate without requiring a pump. Most reservoirs are initially at pressures high enough to allow a well to flow naturally.

Net gas production	The volume of gas produced less gas injected.

Net oil production	The volume of oil produced less oil injected. In hydraulic pumping, the oil injected is known as power oil.

Neutron log	A porosity log whose response is primarily related to the hydrogen content of the formation (hydrogen index). Neurons emitted from the logging tool are scattered off formation nuclei, and the porosity is determined from either counting the neutrons themselves or the gamma rays produced when the neutrons are absorbed by nuclei. Used with other porosity information, the neutron log is used to ascertain the presence of gas, determine mineralogy, and quantify shaliness.

NMDC: Non-Magnetic Drill-Collars	NMDC's – also called top collars – are non-magnetic drillstring components used to avoid adverse effects on measurements (in particular of the azimuth).

Non-associated gas	Wells which typically only produce natural gas without any hydrocarbon liquids. See also associated-gas.

Non-magnetic Steel	Non-magnetizable steel characterized by high material-strength and corrosion resistance. Special processes – such as cold-forging or surface treatment – generate, in particular, high resistance to stress corrosion.