Geology Reference
In-Depth Information
5.2.3
Run 2. Phase-shift-keying, 24 Hz carrier wave.
Figure 5.2b
. Phase-shift-keying, 24 Hz carrier wave.
5.2.4
Run 3. Phase-shift-keying, 96 Hz carrier wave.
Figure 5.2c
. Phase-shift-keying, 96 Hz carrier wave.
5.2.5 Run 4. Short rectangular pulse with rounded edges.
This run is quite interesting. As noted, the recovery is excellent - the
green 'p(t) curve is a well-defined rectangle and the computed recovered black
curve is identical. The red curve is completely different, bearing little
resemblance to the green, due to the assumed solid reflector condition at the
drillbit which reverses the sign of the wave and causes destructive interference.
MWD engineers cannot explain this, claiming only that “the drilling channel
differentiates the signal.” It is true that the spikes resemble spatial derivatives at
the edges of the rectangular pulse, but the conventional explanation is wrong.
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