Hydraulic Considerations

The drilling fluid system introduces noise during pump operation which can make MWD surface equipment struggle to decode the tool signal from down-hole. MWD performance can be improved by careful attention to the mud system.

  • Keep the pump rate as high as possible for the required flow rates. Mud pump pressure pulses at increased pump frequency are filtered out by MWD surface gear. This reduces the effect of pump noise on the MWD signal.
  • Make sure the pump liners are in good condition. Damaged liners cause so much noise they may even have an identifiable signature on the surface pressure record. If the MWD engineer mentions a bad liner signature - at least check it out.
  • Keep the pulsation dampeners fully charged. The ideal mud flow would be at constant pressure, the only changes in system pressure being those of the MWD pulser. Properly charged dampeners go a long way towards this ideal condition.
  • Maintain as constant weight on bit as possible, particularly when drilling with mud motors. Changes in motor torque will themselves cause changes in standpipe pressure. By keeping these to a minimum, reliability of signal decoding will be improved.
  • Mud additives should be mixed as uniformly as possible. Changes in viscosity and suspended solids concentration can attenuate the MWD signal more than usual. Slugged additives can also clog the tools.
  • Avoid duplex mud pumps if possible. Their noise is particularly difficult to filter.

The mud column is the mud pulse MWD tool communication line to the surface. Keeping this system clean, uniform and as free as possible of induced noise can materially improve the quality of the MWD job.

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