Fluid Identification - Cased-Hole Log Analysis and Reservoir Performance Monitoring - page 91

Fig. 7.6 A fluid density log. Courtesy Baker Atlas
The advantages of this type of tool over the gradiomanometer are that (a) its
measurement is not affected by the wellbore deviation angle, or by friction effects.
However, since it is a tool relying on a statistical radioactive decay, the readings are
subject to statistical variations. It should also be noted that the measured quantity is
the average density of the flowing mixture and thus subject to the same holdup
effects as the gradiomanometer.
A variation employs the detection of back scattered gamma rays rather than their
adsorption by the wellbore fluids. Figure 7.7 illustrates one embodiment of this
principle.