Patent ID: 7689362

Claim:
A method for estimating an impedance of a material behind a casing wall in a borehole, the method comprising the steps of: exciting the casing wall with an acoustic pulse, measuring by means of a transducer an experimental acoustic waveform (W) reflected from the casing wall, initializing an impedance parameter (Zin), computing an inverse casing response (R cas −1 ) as a function of the impedance parameter (Zin) and a casing thickness parameter (Cas in ), deconvoluting the experimental acoustic waveform with the inverse casing response to obtain a transducer response (T), performing an iterative loop comprising the computing of an inverse casing response and the deconvoluting of the experimental acoustic waveform by varying the impedance parameter until the transducer response becomes compact in the time domain, and obtaining the estimated impedance (Zcem) from the impedance parameter when the transducer response is compact.