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Quick Tips About Drilling Problems

Below general good practice steps to avoid general drilling problems encountered during drilling operations   

Inadvertent Side-tracking (in soft formation)

  • Wash through obstruction without rotating with the drilling Bottom Hole Assemply BHA.
  • Use bullnose (with centre jet plugged) on all hole opener and Underreamer runs.
  • When reaming a dogleg, lower the Drill String at a rate greater than the Penetration Rate RPM at which the section was drilled.

Gumbo (sticky shale)   

  • Use seawater native clay mud for sticky formation.
  • Control drill to at; 600 ft/hr.
  • Maintain circulation velocity at 200 ft/min.
  • If hole condition permits, drill the section with seawater and dump returns overboard.

Hole Cleaning

  • Maintain high annular velocity (+800 gpm for 12-1/4″€ WBM hole and +1000 gpm for 12-1/4″ OBM hole sections).
  • Control drilling to at; 600 ft/hr.
  • Conduct frequent wiper trips (check also tripping pipe procedures).
  • Space out Stabilisers every 5 – 10 stands in the Drill String.
  • Pump in and out of hole – rotate if necessary.
  • Use low rheology fluid.

Borehole Instability (brittle shale)

  • Increase mud weight if possible.
  • After drilling each stand, wipe the full Drill Pipe stand at least twice with pumps on. If wiping a full stand causes directional problems, wipe with 2 singles at least twice.
  • Monitor drill cuttings for any sign of caving. If the cutting amount is suspicious, sweep hole with Hi-Vis pill and consider a wiper trip.
  • Use non-Water Based Mud for brittle shale.

Lost Circulation (common in drilling carbonate formations)

  • Control drill so as not to overload the annulus with cutting.
  • Drill with maximum pump rate to clean the hole.
  • Ensure lost circulation material is adequately stocked on board
  • When sweeping hole with Hi-Vis pill, ensure the first pill is out of the hole prior to pumping another.

Swelling Shale                 

  • Minimise the openhole expose times.
  • Control the fluid loss from the drilling fluid to the formation.