Page 380 - Practical Well Planning and Drilling Manual

Section 3 revised 11/00/bc 1/17/01 12:00 PM Page 356

[ ] Practical Wellsite Operations
3.3.1

be optimized with a good mud program. Of particular concern is devel-
opment drilling through a depleted reservoir because the overbalance
can be very high. Additives can be used to make the cake thinner and
less sticky or oil mud will form very little cake.
Keep all the solids control equipment running at full efficiency to
minimize low gravity solids buildup. Use a centrifuge if possible. Walk
around and check the solids control equipment several times a day.
Dump the sand trap and dilute, if necessary, to achieve LG solids con-
trol. MBT level should be kept as low as possible, preferably below 8
ppb equivalent.
Static overbalance is the second of the four conditions. Use the
minimum safe mud weight to minimize the static overbalance on the
formation. Condition the mud carefully before running casing to the
minimum safe density.
Keep the hole clean to minimize loading up the annulus with cut-
tings. Watch rheology and pump rate to achieve this.
Wall contact is the third of the four conditions. Use a well stabi-
lized BHA. Spiral or square drill collars have less contact area than
round ones. Run HWDP in compression to reduce the length of drill
collars. Use a bit that requires less WOB and, therefore, less BHA (PDC,
diamond) if the formation is suitable and the rig cost justifies it. Wall
contact will be greater as inclination increases. Centralize casing well
where it is run past the problem zone.
A stationary string is the last of the four conditions. Minimize pro-
grammed directional surveys, especially if run on wireline. Top drive is
an advantage since fewer connections are required. When POH make
the initial flowcheck brief, pull out above the potential sticking zone,
then carry out a full flowcheck.
If differential pressure is causing the pipe to start getting stuck
when in the slips for connections or pulling out of the hole, try the fol-
lowing procedure. Ensure the crews are properly briefed to carry this
out safely first.
Land in the slips, break the connection keeping about 30,000-
40,000 lbs pull over block weight. Leave on the breakout tong, rotate
out slowly, and leave the table rotating slowly. When ready to stab the
next connection or latch the elevator, stop the rotary, ensure no torque
is left on the table, make up connection, or latch elevator, and careful-
ly pick out of the slips. Once the slips are out, move the string down

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