Oil & Gas Terms in Category G

Gas well

A well that primarily produces gas.

Legal definitions vary among the states.


Lead sulfide (pbs).

Technical grades (specific gravity about 7) are used for increasing the density of drilling fluids to points impractical or impossible with barite.


A scientist who gathers and interprets data pertaining to the rocks of the earth’s crust.

Guy line anchor

A buried weight or anchor to which a guy line is attached.

See deadman.

Glass disk

A sub with a glass blockage in the bore, used to isolate a surge chamber in gravel packing or perforation cleaning operations.

Gas-cut mud

A drilling mud that contains entrained formation gas, giving the mud a characteristically fluffy texture.

Then entrained gas in not released before the fluid returns to the well, the weight or density of the fluid column is reduced.

Because a large amount of gas in mud lowers its density, gas-cut mud must be treated to reduce the chance of a kick.


A compressible fluid that fills any container in which it is confined.

Technically, a gas will not condense when it is compressed and cooled, because a gas can exist only above the critical temperature for its particular composition.

Below the critical temperature, this form of matter is known as a vapor, because liquid can exist and condensation can occur.

Sometimes the terms “gas” and”vapor” are used interchangeably.

The latter, however, should be used for those streams in which condensation can occur and that originate form, or are in equilibrium with, a liquid phase.


A process in which gas becomes entrained in a liquid.


A semisolid, jelly-like state assumed by some colloidal dispersions at rest.

When agitated, the gel converts to a fluid state.

Also a nickname for bentonite.

Gaging nipple

A small section of pipe in the top of a tank through which a tank may be gaged.

Guide shoe


A short, heavy, cylindrical section of steel filled with concrete and rounded at the bottom, which is placed at the end of the casing string.

It prevents the casing from snagging on irregularities in the borehole as it is lowered.

A passage through the center of the shoe allow drilling fluid to pass up into the casing while it is being lowered and allows cement to pass out during cementing operations.

Also called casing shoe.


A device, similar to a casing shoe, placed at the end of other tubular goods.


To place a slotted or perforated liner in a well and surround it with gravel


The science of the physical history of the earth and its life, especially as recorded in the rocks of the crust.



General gas law

Any law relating to the pressure, temperature, or volume of a gas.