Establish A Bottom Hole Pattern

  • Rotate the bit and circulate mud when approaching bottom. This will prevent plugged nozzles and clear out fill.
  • Lightly tag bottom with low RPM.
  • Gradually increase RPM.
  • Gradually increase weight.

USE A DRILL-OFF TEST TO SELECT BEST WEIGHT AND RPM (WR)

  • Select RPM.
  • Select bit weight. Depending on bit selected, refer to appropriate page and chart in this catalog for recommended maximum RPM's and weights.
  • Lock brake.
  • Record drill-off time for 5,000 lb, increments of weight indicator decrease.
  • Repeat this procedure for different RPM.
  • Drill at weight and RPM giving fastest drill-of time.

THE BIT ISN'T ALWAYS TO BLAME FOR LOW RATE OF PENETRATION

  • Mud weight may be too high with respect to formation pressure.
  • Mud solids may need to be controlled.
  • Pump pressure or pump volume may be too low.
  • Formation hardness may have increased.
  • RPM and weight may not be the best for bit type and formation — use drill-off test.
  • Bit not stabilized.
  • The bit used may be too hard for the formation.

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