BAKER HUGHES - Drilling Fluids Reference Manual

GLOSSARY OF TERMS
Gel Strength - The ability or the measure of the ability of a colloid to form gels. Gel strength is a
pressure unit usually reported in lbs/100 sq ft. It is a measure of the same inter-particle forces of a
fluid as determined by the yield point except that gel strength is measured under static conditions,
yield point under dynamic conditions. The common gel-strength measurements are initial and
ten-minute gels. See also Shear and Thixotropy.
Gel Strength, Initial - The measured initial gel strength of a fluid is the maximum reading
(deflection) taken from a direct-reading viscometer after the fluid has been quiescent for 10 sec. It is
reported in lbs/100 sq ft. See API RP 13B for details of test procedure.
Gel Strength, 10 Minute – The measured to-minute gel strength of a fluid is the maximum reading
(deflection) taken from a direct-reading viscometer after the fluid has been quiescent for l0 min, The
reading is reported in lbs/l00 sq ft. See API RP 13B for details of test procedure.
Geothermal Gradient - The rate of increase in temperature per unit depth in the earth. Although the
geothermal gradient varies from place to place, it averages 25 to 30ºC/km (15ºF/1000 ft). It is
particularly important to know the geothermal gradient in an area when designing the drilling mud
program for a deep well. The downhole temperature can be estimated by adding the surface
temperature to the product of the depth and the geothermal gradient.
Gpg or Grains per Gallon - ppm equals gpg x 17.1.
Gravity, Specific – The ratio of the mass of a body to the mass of an equal volume of water at 4ºC.
For example, 1 mL of water weighs 1 gm at 4ºC (i.e. the density is 1 gm/mL). One mL of barite
weighs 4.2 g (it’s density is 4.2 gm/mL). The ratio of the two equal volumes of material is 4.2g/1g
and the specific gravity is 4.2.
Grains per Gallon - Equal to the number of grains of a given substance in one U.S. gallon of water.
One grain = 1/7,000 pound and one U.S. gallon of water weighs 8.33 pounds. Hardness can be
expressed in terms of ppm (parts per million). Conversion of parts per million or milligrams per liter
into grains per gallon is accomplished by dividing the parts per million (or milligrams per liter) by
17.1 to convert to grains per gallon.
Greasing Out - Certain organic substances, usually fatty-acid derivatives, which are added to
drilling fluids as emulsifiers, extreme pressure (EP) lubricants, etc., may react with such ions as
calcium and magnesium that are in, or will subsequently come into the system. An essentially
water-insoluble greasy material separates out.
Gum - Any hydrophilic plant polysaccharides or other derivatives which when dispersed in water,
swell to produce a viscous dispersion or solution. Unlike resins, they are soluble in water and
insoluble in alcohol.
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 15-21