Page 39 - Practical Well Planning and Drilling Manual

Section 1 revised 11/00/bc 1/17/01 2:55 PM Page 15

1.1.2
Preliminary Work for the Well Design [ ]

Differential sticking is not probable in the Abu Roash formation.
On trips out of the hole (through hole drilled since the last trip) the
shales can give quite high overpulls. Backreaming is not necessary or
helpful, just take the time to work up carefully without setting off the
jar. Make sure you can come up about 3 m extra before setting the slips
to break off a stand, otherwise you may not be able to go down enough
to free the pipe if you pull straight into tight hole after racking the
stand. Once you have wiped through it, you will probably not see sig-
nificant overpull again at the same depth.

In summary, keep a very tight handle on the mud properties.
Ensure that solids control equipment is kept functioning at top effi-
ciency and check this personally several times a day. Do not rely on
the crews to spot equipment problems. A centrifuge is worthwhile.
Dump the sand trap and dilute as necessary. Avoid swab/surge that
will increase shale instability and possibly induce losses. If losses
occur it will be quicker and easier to cure with cuttings and care than
pumping LCM and waiting. Run large nozzles, since maximizing
hydraulic horsepower (HHP) does not seem to have a measurable ben-
eficial effect; optimize impact force if optimization is preferred. Good
bit runs have been obtained with Hughes ATM05 and Smith F1 in a
12 /4 12º in hole. Be willing to use maximum WOB. General type of
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bit: journal bearing, good gauge protection with diamond-coated heel
row and gauge inserts, and a 4-1-7 or 4-2-7 type cutting structure.
Also use locked bottom hole assemblies (BHAs) where possible. Ream
before connections. Work carefully through high overpulls when trip-
ping out, it may add a couple of hours to the trip, but you should not
get into trouble.

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