Geology Reference
In-Depth Information
Sirens in series.
In the same way that multiple conversations are carried
along modern phone lines, the drilling telemetry channel supports multiple
transmissions provided each is relegated to its own narrow frequency band.
“Measurement-While-Drilling System and Method,” U.S. Patent No. 5,583,827,
awarded on December 10, 1996 to the lead author, describes this mode of
operation, noting that “the pulse generation system preferably includes a
plurality of mud sirens in tandem to further enhance signal level and to provide
multiple amplitude levels to increase data transmission rate.”
Multiple sirens can also be operated at the same frequency to augment
amplitude, e.g., two sirens each with larger rotor-stator gaps may be better than
a single siren with a tight gap from an erosion perspective. The two need not
operate all the time - one might “kick in” only when needed, say, under
attenuative circumstances in deep wells or cold environments. Figure 9.22,
duplicated from U.S. Patent No. 5,583,827, shows one possible configuration.
Figure 9.23 shows two “turbosirens” with different lobe numbers in tandem;
these self-spinning sirens rotate without motor drive, drawing upon the energy
of the mud flow, and would be modulated by controlled mechanical braking.
Their telemetry characteristics, first tested in the long wind tunnel, were later
confirmed by mud loop testing using the metal model shown.
Figure 9.22.
Multiple mud sirens in series (U.S. Patent No. 5,583,827).
Figure 9.23.
Turbosirens in series (U.S. Patent 5,831,177).
9.5.4
Erosion testing.
Here we address the important subject of erosion evaluation. Although we
have described how wind tunnel analysis can provide useful clues related to
wear, e.g., streamline convergence indicates locally high sand convection
speeds, it does not provide complete information. Short of detailed testing in
which actual muds and metal specimens are used to obtain wear patterns and life
Search WWH ::
Custom Search