Cement acoustic properties from ultrasonic signal amplitude dispersions in cased wells

摘要

Apparatus and methods for characterizing the physical state of a barrier installed in a borehole traversing a formation including locating an ultrasonic tool with a plurality of spaced receivers and a transmitter at a location in the borehole, activating the ultrasonic tool to form ultrasonic waveforms, wherein the spaced receivers record the ultrasonic waveforms, aligning the transmitter and the spaced receivers, wherein the ultrasonic waveforms comprise propagated Lamb modes, processing the ultrasonic waveforms to obtain a first amplitude dispersion plot of attenuation as a function of frequency and first phase dispersion plot of phase velocity as a function of frequency, processing attenuation dispersions to identify discontinuities, and relating the discontinuities to barrier wavespeeds.

主权项

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.