BAKER HUGHES - Drilling Fluids Reference Manual

GLOSSARY OF TERMS
Hydrostatic Head - The pressure exerted by a column of fluid, usually expressed as pounds per
square inch. To determine the hydrostatic head in psi at a given depth, multiply the depth in feet by
the density in pounds per gallon by 0.052.
Hydroxide - A designation that is given for basic compounds containing the OH = radical. When
these substances are dissolved in water, they increase the pH of the solution. See Base.
Hygroscopic - The property of a substance enabling it to absorb water from the air.
Indicator - Substances in acid-base titrations which, in solution, change color or become colorless as
the hydrogen ion concentration reaches a definite value, these values varying with the indicator. In
other titration such as chloride, hardness, and other determinations, these substances change color at
the end of the reaction. Common indicators are phenolphthalein, potassium chromate, etc.
Inhibited Fluid - A drilling fluid having an aqueous phase with a chemical composition that tends to
retard and even prevent (inhibit) appreciable hydration (swelling) or dispersion of formation clays
and shale through chemical and/or physical means. See Inhibitor (Fluid).
Inhibitor (Corrosion) - Any agent which, when added to a system, slows down or prevents a
chemical reaction or corrosion. Corrosion inhibitors are used widely in drilling and producing
operations to prevent corrosion of metal equipment exposed to hydrogen sulfide, carbon dioxide,
oxygen, saltwater, etc. Common inhibitors added to drilling fluids are filming amines, chromates,
and lime.
Inhibitor (Fluid) - Substances generally regarded as drilling fluid contaminants, such as salt and
calcium sulfate, are called inhibitors when purposely added to fluid so that the filtrate from the
drilling fluid will prevent or retard the hydration of formation clays and shales.
Initial Gel - See Gel Strength, Initial.
Interfacial Tension - The force required to break the surface between two immiscible liquids. The
lower the interfacial tension between the two phases of an emulsion, the greater the ease of
emulsification. When the values approach zero, emulsion formation is spontaneous. See Surface
Tension.
Interstitial Water - Water contained in the interstices or voids of formations.
Invert Oil-Emulsion Fluid - An invert emulsion is a water-in-oil emulsion where fresh or saltwater
is the dispersed phase and diesel, crude, or some other oil is the continuous phase. Water increases
the viscosity and oil reduces the viscosity.
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 15-26