Noise Logging - Cased-Hole Log Analysis and Reservoir Performance Monitoring - page 125

For example the log shown in Fig. 9.7 records the noise level above the 600 Hz
fi lter. The cube of the fl ow rate may be related to the recorded noise and inversely
proportional to the density of the fl uid fl owing.

Fig. 9.7 Noise log over a gas producing interval

Sounds carry great distances in cased wells. Any surface noise should be
eliminated before attempting a noise survey. Pump jacks, motors, etc., can generate
noise unrelated to fl uid fl ow in the well and confuse interpretation of noise logs.
Two general rules apply:

1. Changes in noise level indicate a change in volumetric fl ow rate.
2. Changes in the relative noise levels in different frequency bands indicate changes
in the phase make-up of the fl uid mixture.