1. n. [Formation Evaluation]

An electrode device with small spacings from which the current flow, and hence the measurement, is focused a short distance into the formation. The microcylindrical log measures the resistivity of the flushed zone with minimum influence from the mudcake or the undisturbed zone. The electrodes are mounted on a pad that is pressed against the borehole wall. The current is focused both parallel and perpendicular to the tool axis. Three measurements are made, each with a different depth of investigation. These measurements are combined to solve for the mudcake and flushed-zone resistivity.

See related terms: electrode resistivity,  flushed zone,  microresistivity