Cement Bond Logging - Cased-Hole Log Analysis and Reservoir Performance Monitoring - page 203

Figure 12.17 shows a section of log in a deviated hole where the tool was not
properly centralized. Note that where

t decreases so does the amplitude. The cure
is to insist that the tool be centralized top, middle, and bottom with either rubber fi ns
or spring centralizers.

∆

Fig. 12.17 CBL run in
deviated hole. Courtesy
Schlumberger

Interpretation

Cement Compressive Strength

For a given casing size and weight, the amplitude of the transmitted wave, measured
in millivolts, may be converted to a cement compressive strength value in psi. This
is conveniently achieved using the nomogram in Fig. 12.18 . The required inputs are:
(1) amplitude in mV from the log (2) casing size and (3) casing thickness (requires
knowledge of casing weight).