Using Higher Order Harmonics to Determine Acoustic Impedance of Material Behind Borehole Casings
AssigneeSchlumberger Technology Corporation
InventorsBenoit Froelich, Andrew J. Hayman, Kenneth K. Liang
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Abstract
An acoustic logging tool emits a wideband acoustic pulse toward an inside surface of a borehole casing and an acoustic response is received. The acoustic response is analyzed at one or more higher order harmonics of the thickness mode resonance of the casing to determine the acoustic impedance of the material behind the casing.
Claims20
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;
- and
- analyzing the acoustic response at the at least one second or higher order harmonic to determine the acoustic impedance of the material.
A method of determining a 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 by analyzing the acoustic response;
- determining an acoustic impedance of the material by analyzing the acoustic response at the at least one second or higher order harmonic;
- and
- determining a corrected acoustic impedance of the material by applying a correction to the acoustic impedance of the material.
A system for determining an acoustic impedance of a material behind a casing, the system comprising:
- an ultrasonic-imaging (USI) tool having an acoustic transducer that emits a wideband acoustic pulse toward the casing and receives an acoustic response thereto;
- and
- a computing device including a processor and a computer-readable medium having computer-executable instructions embodied thereon that, when executed by the processor, causes the computing device to determine an acoustic impedance of the material, the computer-executable instructions comprising a multi-harmonic inversion component that identifies at least one second or higher order harmonic of a thickness mode resonance frequency associated with the casing by analyzing the acoustic response, wherein the multi-harmonic inversion component analyzes the acoustic response at the at least one second or higher order harmonic to determine the acoustic impedance of the material.
Dependencies are inferred from the claim text.