Signal Processor Design and Additional Noise Models - Measurement While Drilling Signal Analysis, Optimization and Design - page 167

Figure 6.3d . Example non-Newtonian attenuation results.
In Figure 6.3d, the bottom box indicates that 69.29% of the signal will
remain after 5,280 feet (1 mile). Also, for information purposes, the effective
viscosity in centipoise is shown in the shaded box. If further calculations are
required in either Newtonian or non-Newtonian modes, simply edit the data in
the white text boxes and click “Find” again.
Finally note that a complementary wave attenuation model has been
developed that predicts the “critical frequency” above which MWD signals are
damped, given fluid properties, drillpipe geometry and length, source signal
strength and transducer sensitivity. Refer to the discussion for Figure 10-7 on
the math model underlying MWDFreq.vbp and datarate*.for.
6.4 Drillpipe Attenuation and Mudpump Reflection (software
reference, PSURF-1.FOR).
This model assumes that the signal entering the drillpipe at the top of the
MWD drill collar - that is, the complicated waveform containing initially
upgoing waves at the pulser, downgoing waves that reflect at the drillbit and
travel upward, plus the complete reverberant field associated with an acoustic
impedance mismatch at the drill collar and drillpipe junction - is known from
the models developed in Chapters 2, 3, 4 and 5. The Newtonian or non-
Newtonian attenuation models in the foregoing section are applied to this signal
as it travels along the length of the very long drillpipe.