Casing Inspection - Cased-Hole Log Analysis and Reservoir Performance Monitoring - page 221

13

Casing Inspection

Inspection of the mechanical state of the completion string is an important aspect of
production logging. Many production (or injection) problems can be traced back to
mechanical damage to, or corrosion of, the completion string. A number of inspec-
tion methods are available, including:

￿ Multi-fi ngered caliper logs

￿ Electrical-potential logs

￿ Electromagnetic inspection devices

￿ Borehole video cameras

Of these, the majority measure the extent to which corrosion has taken place.
Only the electrical-potential log may indicate where corrosion is currently taking
place. With the exception of the caliper logs, all the devices require that the tubing
be pulled before running the survey, since (1) most are designed to inspect casing
rather than tubing and (2) most are large-diameter tools.

Caliper Logs

Various arrangements of caliper mechanisms are available to gauge the internal
shape of a casing or tubing string. Figure 13.1 illustrates three such tools. Table 13.1
lists the various sizes available (Dia-Log), their respective number of feelers, and
the appropriate casing size.

Tubing Profiles

Tubing-profi le calipers will determine the extent of wear and corrosion, and will detect
holes in the tubing string—all in a single run into the well. The large number of feelers