BAKER HUGHES - Drilling Fluids Reference Manual

GLOSSARY OF TERMS
Oil-In-Water Emulsion Fluid - Commonly called "emulsion fluid." Any conventional or special
water-base fluid to which oil has been added. The oil becomes the dispersed phase and may be
emulsified into the fluid either mechanically or chemically.
Oil-Wet - Pertaining to the preference of a solid to be in contact with an oil phase rather than a water
or gas phase. Oil-wet rocks preferentially imbibe oil. Generally, polar compounds or asphaltenes
deposited from the crude oil onto mineral surfaces cause the oil-wet condition. Similar compounds
in oil-base mud also can cause a previously water-wet rock to become partially or totally oil-wet.
Solids in an oil mud must be oil-wet for the mud to remain stable. Water-wet solids in an oil mud
will create an unstable system with the solids agglomerating and either being removed by the shale
shaker, or sticking to and building up on tubulars such as the drill pipe. This situation is aggravated
by high shear, i.e. inside the drill pipe or drill collars where the solids will build up and cause
undesirable increases in pump pressure.
Packer Fluid - Any fluid placed in the annulus between the tubing and casing above a packer. Along
with other functions, the hydrostatic pressure of the packer fluid is utilized to reduce the pressure
differentials between the formation and the inside of the casing and across the packer itself.
Particle - A minute unit of matter, usually a single crystal, of regular shape with a specific gravity
approximating that of a single crystal.
Parts-Per Million - See-ppm.
Parallel Flow - See Laminar Flow.
Pay Zone or “Pay” - The formation drilled that contains oil and/or gas in commercial quantities.
Penetration, Rate of - The rate in feet per hour at which the drill proceeds to deepen the well bore
and is commonly referred to as Rate of Penetration (ROP).
Peptization - An increased dispersion due to the addition of electrolytes or other chemical
substances. See Deflocculation and Dispersion.
eptizing Agent - A product that enhances dispersion of a substance (such as clay) into colloidal
form. Peptizing agents for drilling-mud clays are sodium carbonate, sodium metaphosphates,
sodium polyacrylates, sodium hydroxide and other water-soluble compounds, even common table
salt, NaCl, if added at low concentration.
Peptized Clay - A clay to which a chemical agent has been added to increase its initial yield. For
example, soda ash is frequently added to calcium montmorillonite clay.
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 15-34