Importance

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Abstract

A method and apparatus for acoustically investigating a casing in a borehole are described. An electronically scannable acoustic transducer is formed on a planar circular surface and is oriented on a tool so as to direct circumferentially scannable beams of acoustic energy initially in an axial direction and subsequently in a radial direction onto the casing. Acoustic reflections from casing wall segments are detected and the frequencies of the casing reverberations present in the reflections are measured. One frequency measuring technique employs a reiterative technique whereby a previously measured frequency of a reflection attributable to one wall segment is used to generate a subsequent pulsed acoustic beam at the same wall segment. The number of reiterations may vary and is selected to accurately determine the thickness resonance of the casing. The scanning speed of the array and the number of transducers are selected so that the casing segments onto which the beams are incident circumferentially overlap.

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First Claim