Patent ID: 9732607
Date: 2017-08-15
CPC Classifications: E21B,G01V

Claim:
1. A method of evaluating an annulus between a borehole casing and a formation for a solid substance, comprising: (a) obtaining waveform indications from at least one ultrasonic receiver that has received signals originating from at least one ultrasonic transmitter both located in fluid within the borehole casing, said waveform indications including waveform indications from a plurality of different transmitter-receiver axial distances; (b) processing said waveform indications to generate a velocity-frequency dispersion; (c) analyzing said velocity-frequency dispersion to determine the presence or absence of a non-dispersive headwave at a velocity other than at a velocity of a borehole fluid; and (d) determining the presence or absence of a solid substance in the annulus based on said presence or absence of a non-dispersive headwave at a velocity other than at the velocity of the borehole fluid.