Patent ID: 8767506
Filing Date: 2014-07-01
Classification: E21B,G01V

Abstract:
1. A method of determining an acoustic impedance of a material behind a casing, the method comprising: emitting a wideband acoustic pulse toward an inside surface of the casing; receiving an acoustic response corresponding to the emitted acoustic pulse; identifying at least one second or higher order harmonic of a thickness mode resonance frequency associated with the casing, wherein the at least one second or higher order harmonic comprises a second order harmonic, a third order harmonic, a higher order harmonic, or combinations thereof; analyzing the acoustic response at the at least one second or higher order harmonic to determine the acoustic impedance of the material identifying the thickness mode resonance frequency associated with the casing; analyzing the acoustic response at the thickness mode resonance frequency and at each of the at least one second or higher order harmonic to determine the acoustic impedance of the material and to generate a set of acoustic-impedance estimates; and performing a comparison of the set of acoustic-impedance estimates and determining the acoustic impedance based on the comparison.