BAKER HUGHES - Drilling Fluids Reference Manual

GLOSSARY OF TERMS
Geochemical anomalies at the surface of the Earth can also indicate an accumulation of
hydrocarbons at depth. Geophysical anomalies, such as amplitude anomalies in seismic data and
magnetic anomalies in the Earth's crust, can also be associated with hydrocarbon accumulations.
API - Abbreviation for American Petroleum Institute, a trade association founded in 1919 with
offices in Washington, DC, USA. The API is sponsored by the oil and gas industry and is recognized
worldwide. Among its long-term endeavors is the development of standardized testing procedures
for drilling equipment, drilling fluids and cements, called API Recommended Practices ("RPs"). The
API licenses the use of its monogram (logo), monitors supplier quality assurance methods and sets
minimum standards for materials used in drilling and completion operations, called API
Specifications ("Specs"). The API works in conjunction with the International Standards
Organization (ISO).
API Gravity - The gravity (weight per unit volume) of crude oil or other related fluids as measured
by a system recommended by the American Petroleum Institute. It is related to specific gravity by the
following formula:
Deg API
=
141.5
−131.5
Specific Gravity
Apparent Viscosity - The viscosity (shear stress) a fluid appears to have on a given instrument at a
stated rate of shear (shear stress/shear rate relationship) . It is a function of the Bingham properties
of plastic viscosity and yield point. The apparent viscosity in centipoises, as determined by the
direct-indicating viscometer, which is equal to 1/2 of the 600-rpm Fann Viscometer reading. See also
Viscosity, Plastic Viscosity, and Yield Point. In a Newtonian fluid, the apparent viscosity is
numerically equal to the plastic viscosity.
Asphalt - A natural or mechanical mixture of solid or viscous bitumens found in natural beds or
obtained as a residue from petroleum. Asphalt, blends containing asphalt, and altered asphaltic
materials (e.g., air-blown, chemically modified, etc.) have been added to certain drilling fluids for
such varied purposes as a component in oil-base fluids, lost-circulation material, emulsifier,
fluid-loss-control agent, wall-plastering agent, etc.
Asphaltenes - Organic materials consisting of aromatic and naphthenic ring compounds containing
nitrogen, sulfur and oxygen molecules. The asphaltene fraction of crude is defined as the organic part
of the oil that is not soluble in straight-chain solvents such as pentane or heptane. Asphaltenes exist
as a colloidal suspension stabilized by resin molecules (aromatic ring systems) in the oil. The
stability of asphaltic dispersions depends on the ratio of resin to asphaltene molecules. The
determination of the quantity of resin is important in estimating the potential damage created by
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 15-4