1. n. [Formation Evaluation]

Related to a log of the resistivity of the flushed zone recorded by a wireline electrode device. The device is mounted on a pad and pressed against the borehole wall. Several designs exist, for example microlog, microlaterolog, proximity log, microspherical log, and microcylindrical log. The microlog, being unfocused, is a more qualitative measurement. The other measurements are focused. They try to minimize the effect of mudcake and rugose hole while reading as short a distance as possible into the formation to remain unaffected by the undisturbed zone. They are usually combined with a laterolog or induction log to correct the latter for the effects of invasion and for saturation determination in quick-look ratio methods. The logs are presented on a logarithmic scale from, for example 0.2 to 2000 ohm-m.

See related terms: electrode resistivity,  flushed zone,  microcylindrical log,  microspherical log,  proximity log,  spherical focusing,  undisturbed zone