Temperature Logging - Cased-Hole Log Analysis and Reservoir Performance Monitoring - page 107

Fig. 8.4 Determination of static formation temperature. Reprinted with permission of the SPE-
AIME from Dowdle and Cobb ( 1975 )
Cement-Top Evaluation
Although no longer widely used for finding cement tops in recently cemented wells,
the temperature log may be used for this purpose—its advantage being that it is
cheap and demands less rig time. Its disadvantage is that it gives no indication of the
cement quality or the ability of the cement job to make a hydraulic seal. The prin-
ciple involved is the exothermic chemical reaction that takes place while cement is
curing. The heat given off raises the temperature in and around the borehole at those
places where cement is placed. Thus, a marked drop in temperature may be expected
at the cement top. Figure 8.5 shows a temperature log run in a recently cemented
well and the corresponding pick for the cement top.