Oil & Gas Terms in Category N



A passageway through jet bits that causes the drilling fluid to be ejected from the bit at high velocity.

The jet of mud clears the bottom of the hole.

Nozzles come in different sizes that can be interchanged on the bit to adjust the velocity with which the mud exits the bit.


The part of the fuel system of an engine that has small holes in it to permit fuel to enter the cylinder.

Properly known as a fuel-injection nozzle, but also called a spray valve.

The needle valve is directly above the nozzle.

No-go nipple

A special nipple made up in the tubing, casing, or drill pipe string the configuration of which is such that a tool contacting it can pass through only if the tool is in the proper position or configuration.

Non-associated gas

Natural gas which is in reservoirs that do not contain significant quantities of crude oil.


A short, threaded tubular coupling used for making connections between pipe joints and other tools.

Nipple up

In drilling, to assemble the blowout preventer stack on the wellhead at the surface.

Newtonian flow

See newtonian fluid.

Normal butane

In commercial transactions, a product meeting gpa specification for commercial butane and, in addition, containing a minimum of 95 liquid volume percent normal butane.

Chemically, normal butane is an aliphatic compound of the paraffin series.

Normal circulation

The smooth, uninterrupted circulation of drilling fluid down the drill stem, out the bit, up the annular space between the pipe and the hole, and back to the surface.

Compare reverse circulation.

Newtonian fluid

A fluid in which the viscosity remains constant for all rates of shear if constant conditions of temperature and pressure are maintained.

Most drilling fluids behave as non-newtonian fluids, as their viscosity is not constant but varies with the rate of shear.


Term to describe the passage entry of seal assemblies into a packer seal bore not locking into place.


A gauge run downhole to verify dimensions.

Nail pin

A pin shaped like a carpenter’s nail and placed in a pressure relief valve.

When the pin shears, it opens the valve to relieve pressure inside a vessel.


Position of the rig’s weight indicator where hook load is zero.


The tendency of a metal bar or pipe to taper to a reduced diameter at some point when subjected to excessive longitudinal stress.

See bottleneck.

Needle valve

A globe valve that contains a sharp, pointed, needle-like plug that is driven into and out of a cone-shaped seat to control accurately a relatively small rate of fluid flow.

In a fuel injector, the fuel pressure forces the needle valve off its seat to allow injection.