Casing resonant radial flexural modes in cement bond evaluation

摘要

A method useful for evaluating the presence and/or the quality of the cement bond (44) of a downhole tubular (36). The method involves measuring radial resonance modes of the tubular (36), and comparing those measured values to the unbound tubular resonant values of a calibration ring. For a well bonded tubular (36), the measured radial resonance should be greater than that of the unbound tubular calibration ring. In regions where a fluid, such as water surrounds the outside of the tubular (36), or the cement (44) is otherwise not bonded to the outer surface of the tubular (36), the measured response should be less than the calibrated response. The calibration ring should have the same diameter, wall thickness, and be made of the same material as the tubular (36).