Patent ID: 9534487
Date: 2017-01-03
CPC Classifications: E21B,G01V

Claim:
1. A method for characterizing the physical state of a barrier comprising a casing and an annular fill installed in a borehole traversing a formation, the method comprising: locating an ultrasonic tool at a location in the borehole, wherein the ultrasonic tool comprises a plurality of receivers and at least one transmitter; activating the ultrasonic tool to form ultrasonic waveforms that comprise propagated Lamb modes within the casing, wherein the spaced receivers record the ultrasonic waveforms; processing the ultrasonic waveforms to obtain (i) an amplitude attenuation dispersion plot of attenuation as a function of frequency and (ii) a phase dispersion plot of phase velocity as a function of frequency; identifying discontinuities within the amplitude attenuation dispersion plot; and determining barrier wavespeeds by relating the discontinuities to barrier wavespeeds using the phase dispersion plot.