Page 278 - Practical Well Planning and Drilling Manual

Section 2 revised 11/00/bc 1/17/01 12:04 PM Page 254

[ ] Well Programming
2.6.2

for the casing and cement job. The mud should be conditioned before
pulling out of the hole for low gels and YP for lower surge pressures
while running casing. Minimizing the MBT and low gravity solids will
also be worthwhile considering the possibility of differential sticking.
Optimizing rheology will improve mud displacement and minimize
ECD during cementing (reducing the chance of inducing losses).
If the rig tank capacity permits, consider having a tank of clean,
rheology-optimized mud standing by so that after circulating clean, the
optimal mud can be displaced into the open hole prior to pulling out
for logging/casing. This will save rig time compared to making several
circulations while conditioning the mud. Only the open hole mud
needs to be displaced.
If any fill is likely, then spotting 200-300 ft of viscous pill on bot-
tom after getting the conditioned mud in the hole will help to keep the
fill off bottom.
Normally on the last trip out before casing, a survey tool (Totco or
single shot) will be dropped as a check and the drillpipe will be mea-
sured with a steel tape to confirm the tally.
Most operators throw in a “traditional” wiper trip before running
casing, especially if logging is done. Wiper trips cost money and are
often more detrimental than beneficial to the wellbore. Refer to the
notes on wiper trips in Section 2.9.1, “Wellbore Stability.” In practice,
if the wellbore is stable, no mobile formations are squeezing in, and no
problems are seen while tripping or logging, then a wiper trip is unlike-
ly to be necessary.
Once on bottom, circulate 110% of casing contents while monitor-
ing for losses to ensure that nothing in the casing can plug the float.
The casing should be filled and circulated with conditional mud. If
possible, use a cement head which allows all of the programmed plugs
to be loaded in advance so that circulation can be maintained until the
slurry is ready to displace and periods of no circulation are minimized.
The casing program needs to include precautions or procedures
required for possible problem areas.

2.6.2. Addressing Potential Casing Problems in the Drilling Program

If the casing should become stuck while running, the two likeliest
causes are differential or geometry related (high DLS or a ledge). Some

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