Coring Trouble Shooting Guide

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When any of these symptoms arise, come out of the hole immediately as damage may occur to bit and barrel.

Check pump strokes hourly or if pressure changes to determine if the pump is a problem or washout has occurred. When drilling, core pressure will fluctuate by c.200lbs. over and c. 200 lbs. under normal conditions.

SYMPTOMS POSSIBLE PROBLEM
Sudden pressure increase
  1. Groove (O-ring) cut in bit due to diamond damage or wear.
  2. Foreign material plugging core barrel.
  3. Inner barrel backed off and dropped on bit.
Gradual Pressure Increase Core bit damaged. Pressure caused by groove (O-ring) starting on face of bit and gradually deepening, cutting off the fluid courses. Torque will also increase as waterways plug off.
Pressure Fluctuation Indication of jammed inner barrel. Pressure fluctuation due to the jammed core taking weight causing the bit to drill off and drill up the core. Torque will also be erratic.
Pressure Decrease Indication of jammed core barrel. Core cannot enter inner barrel causing the bit to drill off and stop penetration.
Gradual Pressure Decrease Hole in drill pipe or washout in pin & box connection of pipe or core barrel.

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