Page 232 - Standard Handbook Petroleum Natural Gas Engineering VOLUME2
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Formation Evaluation 201
Figure 5-124. CBL-VDL log showing effects of microannulus and the change
in signal strength on VDL in pressured and nonspressured pipe [220].
2. Microannulus tends to occur over long intervals of the log; channeling is
a localized phenomena. This is a result of microannulus being directly
related to pipe expansion during cementing operations.
Once the log has been interpreted, remedial measures can be applied as
necessary.
Multifingered Caliper Logs. These logs incorporate up to 64 feelers or scratchers
to examine pipe conditions inside the casing. Specifically, they can be combined
with other logs to check
1. Casing collar locations.
2. Corroded sections of pipe.
3. Casing wear.
4. Casing cracks or burstings.
5. Collapsed or crushed casing.
6. Perforations.
7. Miscellaneous breaks.
The number of feelers is a function of pipe diameter; smaller diameter pipe
requires fewer feelers on the tool.
Electromagnetic Inspection Logs. This device induces a magnetic field into the
casing and measures the returning magnetic flux. In general any disturbance
in the flux from readings in normal pipe can be used to find:
