Page 326 - Practical Well Planning and Drilling Manual

Section 2 revised 11/00/bc 1/17/01 12:04 PM Page 302

[ ] Well Programming
2.9.2

shale instability that may be present in the well.
Ensure that the mud system is correctly maintained.
Gather all available information. Analyze it carefully so that root
causes are identified and can be addressed on the next well.

2.9.2. Stuck Pipe

Some years ago, I worked on the BP Stuck Pipe Task Force. We did
a lot of research work on instances of stuck pipe, looking at causes.
One of the conclusions from this work was that most cases of stuck
pipe—well over 90%—are avoidable with good planning and listening
to the hole. There are rare cases when this is not so. Sticking can occur
when drilling in highly mobile salts or into a stressed fault, even while
drilling ahead.
Two of the key factors in stuck pipe prevention are training and
crew awareness. This explains how the well program should be used as
a tool in stuck pipe prevention. Section 3.3.1, “Stuck Pipe,” covers the
practical rig site aspects of preventing and curing stuck pipe.
Sticking mechanisms summary. Causes of stuck pipe can be clas-
sified into three basic categories.
Geometry is related to dimensional problems. Circulation is usual-
ly possible—the problem will be seen with the string moving and only
in one direction.
Solids are related to solid particles in the hole. Circulation may be
restricted or impossible and hole cleaning may have been inadequate.
Usually occurs when pulling out of the hole.
Differential sticking is related to differential pressure between for-
mation and hole. Four conditions are identified that must all be present
for differential sticking: the presence of a permeable zone covered with
wall cake, a static overbalance on the formation, contact between the
wall and drillstring, and a stationary string.
Stuck pipe: geometry related problems.
Undergauge hole. Ream tight spots when tripping in. Ream to bot-
tom after tripping if dictated by hole conditions or if the bit laid out
was undergauge.
Keyseating. Keyseating can occur if a dogleg section is followed by
a long tangent section before running casing. For this reason, high
doglegs should be avoided high up in the hole. Drillpipe fatigue and
wear will also be accelerated by high dogleg severities.

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