Transient Constant Area Surface and Downhole Wave Models - Measurement While Drilling Signal Analysis, Optimization and Design - page 117

4.3.5 Run 3. Very, very noisy environment.
Here we increase the noise level significantly to determine how well the
method continues to work. The time delay between transducers is 0.01 sec or 10
ms, as before. Here, a S/N of approximately 1/8 is assumed, and from our Figure
4.3f, the blue curve again replicates the black pulse very successfully.
FUNCTION SIGNAL(T)
C MWD upward wave signal function
C Train of pulses, 0.5 sec width, 0.5 sec separation
C CASE 2. NARROW PULSE WIDTH (Considered in single xducer
method)
C Clearly see interference between upgoing and reflected pulses
A = 10.0
R = 100.0
SIGNAL = A*(TANH(R*(T-0.100))-TANH(R*(T-0.101)))/2.
RETURN
END
FUNCTION XNOISE(T)
C Mud pump noise function may also include reflected MWD signal,
C but it is not necessary to add the wave reflection to the
C total noise to demonstrate directional filtering.
C FRQPMP = Hertz freq of pump noise, propagates downward
PI = 3.14159
FRQPMP = 15.
C AMP = 0.25
AMP = 2.
XNOISE = AMP*SIN(2.*PI*FRQPMP*T) + 0.0*SIGNAL(T)
RETURN
END
Figure 4.3d . Very, very noisy environment.