Page 382 - Practical Well Planning and Drilling Manual

Section 3 revised 11/00/bc 1/17/01 12:00 PM Page 358

[ ] Practical Wellsite Operations
3.3.1

to slump off the wall. Differentially stuck pipe comes free going down
more often than by overpulling. If torque can also be applied, this is
even better. Pull up to about 30,000-40,000 lbs above the up-drag
weight and, if not free, then repeat several times. If unsuccessful start
to jar up and bump down. This is one of the few situations where
working the pipe both ways will not make the sticking problem worse.
If the stuck point depth is unknown, use stretch data to determine
the approximate depth.
If not free within 10 minutes of working the pipe, continue to work
the pipe while preparing a Pipelax or similar pill. These pills work by
shrinking the wall cake, thus reducing the contact area between the
pipe and hole. Make enough to cover the BHA (if stuck at the BHA)
and to leave about 10 barrels inside the string.
Displace out the pill sufficient to cover the BHA, leaving the excess
inside the bit. Pump about one-quarter barrel every 10 or 15 minutes
while working the pipe.
In some cases the well has been displaced to oil-based mud to free
the pipe. This would have to be fully discussed with the drilling office
and would probably take a few days to organize logistically.
The sticking force will be roughly proportional to the overbalance
at the stuck point. If the mud density were reduced then the sticking
force would also reduce. This can be done as follows:

Displace the complete well to lower density mud. If the annulus is
loaded with cuttings at the time the pipe stuck, then circulating clean
would reduce overbalance. Otherwise the mud can be conditioned to a
lower weight, possibly over several circulations to ensure that well con-
trol is not compromised.

Some company policies prohibit the following method but it is
worth considering as long as a float is not in the string and well control
can be maintained.
Displace some of the drillstring to water, diesel, base oil, or some
suitable lightweight fluid. Allow to U-tube out so that the level in the
annulus drops and the bottomhole pressure decreases. Have the kelly
or top drive on (bleed off on the standpipe manifold) and pull/jar to
maximum. Full hydrostatic is restored by pumping in enough mud to
replace the backflowed fluid; the remaining light fluid can be circulat-
ed out either conventionally or reverse as appropriate to the situation.

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