<p>The present invention provides an apparatus an methods for detecting the behavior of perforations in a wellbore casing, the apparatus including a sensor array (10) movable within the internal diameter of the casing, the sensor array having one or more sensors (16) located proximate the internal surface of the casing with the sensors being located or oriented such that properties of flow from a proximate perforation can be distinguished from properties of a main flow through the wellbore.</p>
