Page 321 - Drilling Technology in Nontechnical Language

312 Drilling Technology in Nontechnical Language Second Edition

5. Pump mud behind the cement. The volume of mud pumped
should be some barrels less than the total drillpipe capacity
so that a bit of cement is left in the pipe (about 5 bbl). If mud
returns to the surface during this part of the job, it indicates that

the fibers are plugging off the channels leaving the wellbore
(a good sign).
6. Pull out about 200 ft of the drillpipe without putting any mud
into the hole. Normally, mud is pumped into the annulus when
pipe is pulled out to ensure primary well control is maintained (as
described in chapter 11). While pulling out, the cement remaining
in the drillpipe will drop out of the bottom.
7. Pull out another 300 ft or so of pipe. Pump a measured amount

of fluid into the annulus while pulling out, but no more than is
needed to replace the volume of steel removed. It is better to
pump too little than too much so as to avoid chasing cement away
from the near-wellbore zone.

8. Wait until the cement should be hard, and then top up the well
with mud. Pull out the drillpipe, run in with a drilling assembly,
and drill out the cement. While the procedure will vary a little
depending on the actual situation, this procedure gives a high

probability of success the first time. Cement floods the spaces

around the well and is allowed to stay there and set.

Stuck Pipe

The drillstring can be said to be stuck when it cannot be pulled all the
way out of the hole without exceeding the maximum allowable pull on the

pipe. Within that definition, it may or may not be possible to circulate; pipe
movement downwards below the stuck point may or may not be possible,
and pipe rotation also might or might not be possible.
Most cases of stuck pipe (over 90%) are avoidable with good
supervision. Pipe rarely gets stuck with no advance warning signs. If the
conditions are present to make stuck pipe possible, the drilling supervisor
and drillers must stay on the ball and take suitable precautions to prevent
it from occurring.

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