Aniline Point
The aniline point of a petroleum product is the minimum equilibrium solution temperature with an equal volume of freshly distilled aniline
Annulus
annular space between drill string and casing or borehole.
Anomaly
a divergence from the background levels of physical or chemical properties of an area under survey
Anticlinal Trap
an Anticline that contains a top seal and a reservoir under the top seal
Anticline
an upfold in rock strata producing an arch or dome structure that closes in four directions. One of the most common hydrocarbon traps