Temperature Logging - Cased-Hole Log Analysis and Reservoir Performance Monitoring - page 113

Fig. 8.10 Gas-injection temperature profiles. Courtesy Schlumberger
Logging Techniques
Several special logging techniques can improve interpretation of temperature pro-
files. These include:
1. Shut-in temperature surveys
2. Differential-temperature logs
3. Radial differential-temperature logs
Shut-In Temperature Surveys
If more than one zone is taking water in an injection well, it is sometimes difficult to
judge from the flowing temperature profile which zone is taking what percentage of the
injected total. Two techniques are offered here. The first simply relates the ∆ T value to
the volumetric flow. Figure 8.11 illustrates the concept. In the figure, T G is the undis-
turbed formation temperature and T h is the temperature observed in the borehole.
A second useful technique is to stop injection altogether and repeat the tempera-
ture profile several times at various time intervals, such as at 3, 6, 12, and 24 h. Or,
depending on the local conditions, at 12, 24, and 48 h. Zones that were taking rela-
tively cool injection water will remain cooler than surrounding formations for a
relatively long time and will be visible on the repeat profiles. Figure 8.12 shows
such an example.