Abstract

In an on-going effort to produce more thorough and meaningful descriptions of the formations, as well as borehole features, a new generation of imaging devices has been developed. Among these is the Circumferential Acoustic Scanning Tool (CAST) which operates on the principle of acoustic reflectivity. While the tool concept is not new, image enhancement and three-dimensional presentations are important innovations, which provide the flexibility to clarify geological and drilling related features.

The identification and description of natural fractures is an obvious application. Examples of simple and complex fracture patterns are presented. While planar layering of small dimensions may be illustrated by several tools, the depiction of curved bedding can be property accomplished only by a device which scans the full 360° of the borehole wall. Textural differences and fault intersections may be revealed. Core photographs and dipmeter Images provide interesting comparisons.

Additional applications are found in the description of borehole features such as induced fractures and tool artifacts. In cased holes, accurate mapping of perforations and casing damage is achieved. CAST imaging is an important addition in the quest for increasing detail and precision of wireline logging techniques.