Oil & Gas Terms in Category G

Gel strength

A measure of the ability of a colloidal dispersion to develop and retain a gel form, based on its resistance to shear.

The gel, or shear, strength of a drilling mud determines its ability to hold solids in suspension.

Sometimes bentonite and other colloidal clays are added to drilling fluid to increase its gel strength.

Galvanic corrosion

A type of corrosion that occurs when a small electric current flows from one piece of metal equipment to another.

It is particularly prevalent when two dissimilar metals are present in an environment in which electricity can flow (as two dissimilar joints of tubing in an oil or gas well).

Gunk plug

A slurry in crude or diesel oil containing any of the following materials or combinations: bentonite, cement, attapulgite, and guar gum (never with cement).

Used primarily in combating lost circulation.

Gas lift valve

A device installed on a gas lift mandrel, which in turn is put on the tubing string of a gas lift well.

Tubing and casing pressures cause the valve to open and close, thus allowing gas to be injected into the fluid in the tubing to cause the fluid to rise to the surface.

Gravity drainage

The movement of fluids in a reservoir resulting from the force of gravity.

In the absence of an effective water or gas drive, gravity drainage is an important source of energy to produce oil, and it may also supplement other types of natural drive.

Also called segregation drive.

Guyed-tower platform rig

A compliant offshore drilling platform used to drill development wells.

The foundation of the platform is a relatively lightweight jacket upon which all equipment is placed.

A system of guy wires anchored by clump weights helps secure the jacket to the seafloor and allows it to move with wind and wave forces.

See platform rig.

Go in the hole

To lower the drill stem, tubing, casing, or sucker rods in to the wellbore.


(slang) gypsum

Gas sand

A stratum of sand or porous sandstone from which natural gas is obtained.

Guy line

A wireline attached to a mast, derrick, or offshore platform to stabilize it.

See wind guy line.

Gunk squeeze

A bentonite and diesel oil mixture that is pumped down the drill pipe and into the annulus to mix with drilling mud.

The stiff, putty-like material is squeezed into lost circulation zones to seal them.

Guar gum

A naturally occurring hydrophilic polysaccharide derived from the seed of the guar plant.

The gum is chemically classified as a galactomannan.

Guar gum slurries made up in clear fresh or brine water possess pseudoplastic flow properties.

Gas processing plant

A facility designed:


To achieve the recovery of natural gas liquids from the stream of natural gas which may or may not have been processed through lease separators and field facilities, and


To control the quality of the natural gas to be marketed.

Greasing out

When water-insoluble greasy materials (e.g., emulsifiers, lubricants) separate out of drilling fluids.

Gone to water

Describes a well in which water production is increasing.