Noise Logging - Cased-Hole Log Analysis and Reservoir Performance Monitoring - page 127

The green temperature line shows the geothermal gradient. The blue trace shows
the fl owing condition temperature distribution and the red trace the distribution
after extended shut-in. Multiple computer modeling iterations can match expected
profi les to the observed ones by varying the relative fl ow rates from the two produc-
ing intervals.

Noise and Flowmeter Combinations

Noise spectral analysis can also provide useful complementary data when analyzing
fl owmeter logs. An example is given in Fig. 9.9 where a fl uid entry point in the well,
as seen by the fl owmeter alone, fails to detect that in fact fl ow from the formation is
more extensive and that there is cross-fl ow behind pipe before it reaches the entry
point in to the wellbore. The wellbore-noise, reservoir-matrix-noise, and the fl ow-
through-perforation-noise can be nicely discriminated by the color coded frequency/
amplitude track on the right-hand side of the fi gure. A possible explanation for such
fl ow behavior could be plugged perforations. In such a case re-perforating the inter-
val could well result in increased fl ow rate.

Fig. 9.9 Cross-fl ow detected by spinner and noise log. Courtesy TGT

Fiber Optic Sensors

The use of fi ber optics to continuously measure temperature and sound energy along
the entire completion string is covered in Chap. 14 . Commonly referred to as
Distributed Audio System (DAS) and Distributed Temperature System (DTS) these
high tech permanent gauges open up an entirely new way of production monitoring.