1. n. [Formation Evaluation]

The condition in which cement flows in a channel only on some sides of the casing or borehole annulus, and thus does not provide adequate hydraulic isolation in all radial azimuths. The channel frequently manifests itself as an intermediate amplitude signal on a cement bond log. Pulse-echo tools are able to detect a channel because they measure the cement bond at different azimuths.

See: azimuth