1. n. [Well Testing]

A tool run on an electric logging cable that pushes a probe into the formation, which then allows production into a small closed chamber. The tool is primarily used to obtain formation pressures at chosen locations in an interval, and, with an accurate quartz gauge, permeability estimates may be obtained. Modern variations on this tool have been developed to acquire formation-fluid samples.

Synonyms: fluid tester

See: formation pressure,  wireline