STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

MWD and LWD 953
Solution
1. a. 6,255 psia
b. 8,740 psia
c, 7,664 psia
2. Free fluid velocity:
Surface: 4,168.6 ft/s
Bottom: 4,356 ft/s
Velocity in drillpipe:
Surface: 4,044 ft/s
Bottom: 4,215 ft/s
Average velocity in pipe: 4,130 ft/s
3.
Table 4-1 27
Amplitudes at Surface for a 10,000-ft Well, 200-psi
Downhole Pulses, for Various Frequencies
0.2 Hz 12 Hz 24 Hz
L 83,357 ft 10,761 ft 7,609 ft
D 57,766 ft 7,457 ft 5,273 ft
B 191,971 ft 24,782 ft 17,523 ft
Attenuation 0.104 dBll,000 ft 0.807 dB11,OOO ft 1.141 dB/1,000 ft
Pulse p-p amplitude at surface 177.4 psi 78.96 psi 53.73 DSi
Example 11 : Mud Pulse Telemetry-Fluidic
Pulser Calculations
We have built a fluidic pulser system that can generate approximately 100 psi
peak to peak with 500 gal/min mud flowrate. It is to be used down to 15,000 ft.
The surface detector needs a 5-psi peak to peak sine wave for proper phase
detection. The following oil-base mud is used:
density: 12 lb/gal
viscosity: 25 cp
pressure wave velocity in the drill pipe: 3685 ft/s
drillpipe diameter: 4.5 in. OD, 3.64 in. ID.
The system transmits 5 bits/s with a phase-shift-keying system. Four sine waves
are necessary to define the phase with a negligible chance of error. Assume a
perfect pipe, drill collar ID same as the drill pipe and no wave reflections at
the drill pipe ends.
1. What frequency(s) should be used?
2. What peak-to-peak amplitude (psi) of the pressure wave is necessary at
bottom to get the required peak to peak value at surface? Is our pulsing
device suited for this job?
3. The pump noise frequency is varying around 8 Hz with a peak-to-peak
amplitude of 20 psi. Can the signal still be detected? Explain.
4. If we generate a 12-Hz wave at surface to transmit instructions downhole
to the instrument package, what amplitude should it have at surface to
reach bottom with 5 psi peak to peak?
5. Can both channels work simultaneously with proper filtering? Explain.