The Baker Hughes Acoustic Cement Bond Log™ (CBL™) is a valuable source of data about the effectiveness of the cement sheath surrounding the casing. This data is obtained by evaluating the effect of the casing, the cement sheath, and the formation on an acoustic wave emanating from the CBL instrument. The amplitude curve of the reflected acoustic wave is maximum in unsupported casing and minimum in those sections in which the cement is well-bonded to the casing and the formation.
Part of the log presentation is a recording of the reflected acoustic waveform either as a half-wave or full-wave signature or a variable-density display. These waveforms are used to identify the wave path and confirm the interpretation of the amplitude curve. When complete bonding is indicated, the through-the-formation wave is identifiable and can be used similarly to the openhole acoustic log.