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296 SHALE SHAKERS AND DRILLING FLUID SYSTEMS
Emulsion A substantially permanent heterogeneous mixture of two or more liquids
that do not normally dissolve in each other, but which are held in a dis-
persed state, one within the other. This dispersion is accomplished by the
combination of mechanical agitation, fine solids, and/or emulsifiers.
Emulsions may be mechanical, chemical, or a combination of both.
Emulsions may be either oil-in-water or water-in-oil. See.- Interfacial Ten-
sion, Surface Tension.
Emulsoid Colloidal particle that takes up water.
Encapsulation A process of enclosing a material in a covering. Used to describe the pro-
cess of totally enclosing electrical parts or circuits with a polymeric
material (usually epoxy); or coating drilled solids with a polymer.
End Point Indicates the end of a chemical testing operation when a clear and defi-
nite change is observed in the test sample. In titration, this change is
frequently in color of an indicator or marker, which has been added to
the solution or the disappearance of a colored reactant.
Enriching The process of increasing the concentration of a flammable gas or va-
por to a point where the atmosphere has a concentration of that flam-
mable gas or vapor above its upper flammable or explosive limit.
EP Additive See.- Extreme Pressure Lubricant.
EPL See.- Extreme Pressure Lubricant.
Epm See/ Equivalents Per Million, Parts Per Million.
Equalizer An opening for flow between compartments in a surface fluid holding
system.
Equivalent Circulating The effective drilling fluid weight at any point in the annulus of the well-
Density bore during fluid circulation. ECD includes drilling fluid density, cuttings
in the annulus, and annular pressure loss. See.- Annular Pressure Loss, ECD.
Equivalent Spherical The theoretical dimension usually referred to when the sizes of irregu-
Diameter larly shaped, small particles are discussed. These dimensions can be de-
termined by several methods such as settling velocity, electrical resis-
tance, and light reflection. See.- ESD, Particle Size.
Equivalent Weight The atomic weight or formula weight of an element, compound, or ion di-
vided by its valence. Elements entering into combination always do so in
quantities proportional to their equivalent weights. See: Combining Weight.
Equivalents Per Million Unit chemical weight of solute per million unit weights of solution. The
epm of a solute in solution is equal to the ppm (parts per million) di-
vided by the equivalent weight. See: Parts Per Million.
ESD See: Equivalent Spherical Diameter, Particle Size.
Extreme Pressure Lubricant Additives which, when added to the drilling fluid, impart lubrication to
bearing surfaces when subjected to extreme pressure conditions. See: EPL.
Fault Geological term denoting a formation break across the trend of a sub-
surface strata. Faults can significantly affect the drilling fluid and casing
programs due to possibilities for lost circulation, sloughing hole, or kicks.
