Casing Inspection - Cased-Hole Log Analysis and Reservoir Performance Monitoring - page 234

larger for deep but small-diameter defects. Pad overlap effects apparent on both eddy-
current and fl ux-leakage tests. Defect at 2158 ft does not show on fl ux-leakage (total
wall) test and therefore is minor, <1 mm deep. Defect at 2164 ft shows larger on eddy-
current than fl ux-leakage test, therefore shallow ID pit.

Fig. 13.15 Splits. Courtesy Schlumberger

Comments
Split from 2105 to 2115 ft is ragged. Note dramatic response to eddy-current (inner-
surface) and fl ux-leakage (total wall) tests. ETT phase shift drops dramatically at
split from 2105 to 2115 ft. Split from 2142 to 2159 ft cannot be determined with
certainty using only the PAT. Since fl ux path leaks into wellbore only at ends of
split, PAT indicates only point anomalies at 2142 and 2159 ft. Split from 2142 to
2159 ft shows up dramatically on ETT. With both ETT and PAT, this anomaly could
easily be identifi ed as a split seam in the casing.

Fig. 13.16 Inner- and outer-wall corrosion. Courtesy Schlumberger