Flowmeters - Cased-Hole Log Analysis and Reservoir Performance Monitoring - page 72

Flow measurement alone is not sufficient to completely describe both the flow
rate of each phase and whether its position within the cross section is of the quasi-
horizontal or highly deviated pipe string. Of assistance in this task is a sister tool
that uses a circumferential array of capacitance sensors that can distinguish between
water and hydrocarbons that have different dielectric properties. Figure 5.17 illus-
trates such a capacitance array tool.
Fig. 5.17 Capacitance array tool (CAT) sensors. Courtesy GE Oil & Gas, 2014
Other sensors are also available to help distinguish which fluid phase is traveling
in which direction in what sector of the pipe being studied and by combining such
multiple measurements, 3-D “maps” of fluid type and flow can be constructed and
the results visualized as shown in Fig. 5.18 . More will be discussed on this topic in
Chap. 10 .
Fig. 5.18 Visualization of fluid phase and flow rate using MAP view software. Courtesy GE Oil
& Gas, 2014
Oxygen Activation Logging
Pulsed neutron logging is covered in Chap. 11 in detail. The normal use of tools that
rely on pulsed neutron capture (PNC) is for the determination of the captured cross
section, sigma (Σ), of the materials surrounding the logging tool. In a cased-hole
environment these materials include both the borehole fluids inside the casing and
the formation outside the casing. A correctly compensated PNC measurement can
then indicate the water saturation in the formation surrounding the casing.