Well and Field Monitoring - Cased-Hole Log Analysis and Reservoir Performance Monitoring - page 252

Figure 14.14 shows the flow pattern at and above the gas lift valve. Rising gas
bubbles are shown as it takes 3 min from the valve to surface with a delay of 100 s.
Another application of DAS is for seismic surveys. Since DAS can pick up pas-
sive noises from a distance it has a bright future with applications in the fields of
seismic and MSM. Figure 14.15a, b show the deployment of DAS fibers as well as
seismic geophones for the purpose of vertical seismic profiling (VSP). This exam-
ple is from a carbon capture and sequestration project in Canada. As shown in
Fig. 14.15a , the DAS recordings are comparable to the geophone recordings. The
noise level of DAS is higher than that of the geophones but doubtless will be low-
ered in future versions.
Figure 14.15b shows a comparison between a sonic log recording of sound
velocity (made with a sonic log run on the borehole) and both the geophone and
DAS recordings.
Fig. 14.15 ( a ) Left : VSP recorded using a geophone array. Right : VSP recorded using the DAS
array. ( b ) Comparison of velocity profiles obtained from (borehole) sonic log ( green ), geophones
( blue ), and DAS ( red ). Courtesy SPE 150203