BAKER HUGHES - Drilling Fluids Reference Manual

GLOSSARY OF TERMS
and uses whole mud samples, whereas the water-base mud procedure tests filtrate. The GGT unit is
a clear, plastic block that contains three interconnected chambers. A carrier gas is used to flow an
inert gas through the chambers. The sample is placed in chamber #1 and is acidified to release
sulfides as H 2 S and carbonates as CO 2 . The appropriate Dräger tube is used to measure the effluent
gas that is evolved from the sample.
Gas Cut - Gas entrained by a drilling fluid. See Air Cutting.
Gas Hydrate - A crystalline solid consisting of water with gas molecules in an ice-like cage
structure. Water molecules form a lattice structure into which many types of gas molecules can fit.
Most gases, except hydrogen and helium, can form hydrates. C 1 to n C 5 hydrocarbons, H 2 S and CO 2
readily form hydrates at low temperature and high pressure. Gas-cut muds can form hydrates in
deepwater drilling operations, plugging BOP lines, risers and subsea wellheads, causing a
well-control risk.. Gas hydrates are thermodynamically suppressed by adding antifreeze materials
such as salts or glycols. Gas hydrates are found in nature, on the bottom cold seas and in arctic
permafrost regions.
Gel - A term used to identify highly colloidal, high yielding, viscosity- building commercial clays,
such as bentonite and attapulgite clays.
Gelation - Association of particles to form a continuous structure of charged clays, the state of which
can be face to face, face to edge, and edge to edge forming a continuous network structure held
together by electronic charges.
Gel Cement - Cement having a small to moderate percentage of bentonite added as filler and/or to
reduce the slurry weight. See Gunk Plug.
Gelled - A state of a colloidal suspension in which shearing stresses below a certain finite value fail
to produce permanent deformation. The minimum shearing stress that will produce permanent
deformation is known as-the shear or-gel-strength of the gel. Gels commonly occur when the
dispersed colloidal particles have a great affinity for the dispersing medium, i.e., are lypophilic.
Thus, gels commonly occur with bentonite in water. For their measurement, see Gel Strength,
Initial and Gel Strength, 10-Minute.
Gelled Up - Oil-field jargon usually referring to any fluid with high gel strength and/or highly
viscous properties, often a state of severe flocculation.
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 15-20