Cement Bond Logging - Cased-Hole Log Analysis and Reservoir Performance Monitoring - page 211

If a microannulus is suspected in the zone of interest, rerun the log with 500-
1,000 psi at the casing head. The service company should come equipped with the
appropriate pressure-control equipment to do the job safely. If the CBL amplitude
is lower on the rerun under pressure, then there is no need to squeeze. No case has
ever been documented where communication existed across a microannulus zone.
If the CBL does not improve, channeling may be suspected and a squeeze should be
attempted. Figure 12.25 documents a microannulus case.
Figure 12.26 is a useful reference for determining the pressure required to expand
a given casing by a given amount. Normal microannuli are between 0.005 and
0.01 in..

Fig. 12.25 Microannulus case. Courtesy Schlumberger