Page 484 - Practical Well Planning and Drilling Manual

Appendix NEW! revised 11/00/bc 1/30/01 3:30 PM Page 460

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Glossary

A, Area. Usually given in square inches (eg TFA = Total Flow Area,
area of bit nozzle configuration in square inches).

Absorption. The penetration or apparent disappearance of molecules
or ions of one or more substances into the interior of a solid or liq-
uid. For example in hydrated bentonite, the planar water that is held
between the mica-like layers is the result of absorption.

Acidity. The relative acid strength of liquids as measured by pH. A
pH value below 7. See pH.

Adaptive Electromagnetic Propagation Tool. Schlumberger wireline
tool that measures phase shift and attenuation of a 1100 MHz wave.
Used for Hydrocarbon identification independent of formation water
salinity, thin bed detection, Hydrocarbon saturation and mobility and
to evaluate invaded zones.

Adhesion. The force which holds together unlike molecules.

Adsorption. A surface phenomenon exhibited by a solid (adsorbent)
to hold or concentrate gases, liquids or dissolved substances (adsorp-
tive) upon its surface, due to adhesion. For example, water held to
the outside surface of hydrated bentonite is adsorbed water.

Aeration. The technique of injecting air or gas in varying amounts
into a drilling fluid for the purpose of reducing hydrostatic head. See
also Air Cutting.

Aggregate. A group of two or more individual particles held together
by strong forces. Aggregates are stable to normal stirring, shaking or
handling as powder or a suspension. They may be broken by drastic
treatment such as ball milling a powder or by shearing a suspension.

Air Cutting. The inadvertent mechanical incorporation and disper-
sion of air into a drilling fluid system. See also Aeration.

Alkalinity. The combining power of a base measured by the maxi-
mum number of equivalents of an acid with which it can react to

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