BAKER HUGHES - Drilling Fluids Reference Manual

GLOSSARY OF TERMS
Streaming Potential - The electrokinetic portion of the spontaneous potential (SP) electric-log
curve which can be significantly influenced by the characteristics of the filtrate and fluid cake of the
drilling fluid that was used to drill the well.
Streamline Flow - See Laminar Flow.
Stearate - Salt of stearic acid, which is saturated, 18 carbon fatty acid. Certain compounds, such as
aluminum stearate, calcium stearate, zinc stearate, have been used in drilling fluids for one or more
of the following purposes: defoamer, lubrication, air drilling in which a small amount of water is
encountered, etc.
Stuck - A condition whereby the drillpipe, casing, or other devices inadvertently become lodged in
the hole. Can be the result of numerous conditions including but not limited to; sloughing (caving) of
the well bore, formation swelling, salt flow (migration), differential pressure sticking, key seating,
junk in the hole, dogleg, etc.
Sulfide Scavenger - A chemical that removes all three soluble sulfide species, H 2 S, S -2 and HS - , and
forms a reaction product that is irreversible by chemical reaction, nonhazardous and noncorrosive.
Zinc compounds are commonly used to precipitate ZnS and decrease the concentration of all three
sulfides that are in equilibrium in a solution to a very low concentration. For water mud, zinc basic
carbonate, and for oil mud, zinc oxide, are recognized to be effective sulfide scavengers. Oxidation
of sulfides to form other types of sulfur compounds will remove sulfides from a mud, but slowly and
with less certainty.
Supersaturation - If a solution contains a higher concentration of a solute in a solvent that would
normally correspond to its solubility at a given temperature, this constitutes supersaturation. This is
an unstable condition, as the excess solute separates when the solution is needed by introducing a
crystal of the solute. The term "supersaturation" is frequently used erroneously for hot salt fluids.
Surface-Active Materials - See Surfactant.
Surfactant - A material which tends to concentrate at an interface. Used in drilling fluids to control
the degree of emulsification, aggregation, dispersion, interfacial tension, foaming, defoaming,
wetting, etc.
Surfactant Fluid - A drilling fluid which contains a surfactant. Usually refers to a drilling fluid
containing surfactant material to effect control over degree of aggregation and dispersion or
emulsification.
Surface Tension - Generally the force acting within the interface between a liquid and its own vapor
which tends to maintain the area of the surface at a minimum and is expressed in dynes per
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 15-45