Method for determining the thickness of a casing in a wellbore by signal processing pulse-echo data from an acoustic pulse-echo imaging tool

摘要

The invention is a method of determining the thickness of a casing in a wellbore penetrating an earth formation using group delay determined casing resonance extracted from processed reflection signals from an acoustic pulse-echo imaging tool. A first Fourier transform coefficient series is calculated from the digitized reflection signal. Individual samples of the reflection signal are multiplied by their sample index values to obtain a modified digitized data string. A second Fourier transform coefficient series is calculated from the modified digitized data. The complex group delay function is calculated directly from the first and second Fourier coefficient series.