BAKER HUGHES - Drilling Fluids Reference Manual

GLOSSARY OF TERMS
Homogeneous - Of uniform or similar nature throughout; or a substance or fluid that has at all points
the same property or composition.
Hopper, Jet - A device to facilitate the addition of drilling fluid additives to the system.
Horizontal Drilling - A subset of the more general term “directional drilling,” is used where the
departure of the wellbore from vertical exceeds about 80 degrees. Note that some horizontal wells are
designed such that after reaching true 90-degree horizontal, the wellbore may actually start drilling
upward. In such cases, the angle past 90 degrees is continued, as in 95 degrees, rather than reporting
it as deviation from vertical. Because a horizontal well typically penetrates a greater length of the
reservoir, it can offer significant production improvement over a vertical well.
Humic Acid - Organic acids of indefinite composition in naturally occurring leonardite lignite. The
humic acids are the most valuable constituent. See Lignin.
Hydrate - A substance containing water combined in the molecular form (such as CaSO 4 x 2H 2 0), a
crystalline substance containing water of crystallization.
Hydration - The act of a substance to take up water by means of absorption and/or adsorption.
Hydrogen Ion Concentration - A measure of the acidity or alkalinity of a solution, normally
expressed as pH. See pH.
Hydrogen Embrittlement - The process whereby steel components become less resistant to
breakage and generally much weaker in tensile strength. While embrittlement has many causes, in
the oil field it is usually the result of exposure to gaseous or liquid hydrogen sulfide (H 2 S). On a
molecular level, hydrogen ions work their way between the grain boundaries of the steel, where
hydrogen ions recombine into molecular hydrogen (H 2 ), taking up more space and weakening the
bonds between the grains. The formation of molecular hydrogen can cause sudden metal failure due
to cracking when the metal is subject to tensile stress.
Hydrolysis - Hydrolysis is the reaction of a salt with water to form an acid and base. For example,
soda ash (Na 2 CO 3 ) hydrolyzes basically, and hydrolysis is responsible for the increase in the pH of
water when soda ash is added.
Hydrometer - A floating instrument for determining the specific gravity or density of liquids,
solutions, and slurries. A common example is the fluid weight hydrometer used to determine the
density of fluid.
Hydrophile - A substance usually in the colloidal state or an emulsion, which is wetted .by water, i.e.
it attracts water or water adheres to it.
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 15-23