If any tight hole is experienced when drilling with water the followint actions should be taken to prevent stuck pipe:
- With kelly: Immediately pull the string back to above the tight spot (after having spotted a viscous slug) and ream the complete interval until no more overpull is experienced.
- With top drive: Backream out of the hole, and ream into the hole until the drag has disappeared.
When heavy overpulls are experienced, and the above precautions have been taken, but the weight indicator regularly indicate a drop-off in overpulls and then an increase again, do not pull more than 6 m and work the string down again. Ensure the pipe is completely free before continuing to pull out the next 6 m interval. If necessary, use the kelly and circulate to come out of the hole. Do not pump at excessively high rates as this may cause the formation below or around the tight spot to break.
If the pipe should become stuck then proceed as follows:
1. If circulation is still possible, change from water to mud, work the pipe and circulate clean. If there is no result, relax the string, stop the pump and wait for 2 to 3 hours. Bleed off any drill pipe pressure. Work the pipe again.
2. If no circulation is possible then immediately relax the string and bleed off any drill pipe pressure to ensure that no fluid is pumped or squeezed into the formation. Work the pipe, and occasionally pump a few strokes and try to regain circulation. If circulation is still not possible then bleed off through the drill pipe.
If there is a float in the string, then it will not be possible to bleed off any pressure trapped between the float sub and a restriction in the annulus.