Page 401 - Practical Well Planning and Drilling Manual

Section 3 revised 11/00/bc 1/17/01 12:00 PM Page 377

Drilling Problems [ ]
3.3.9

Underground blowout situation. In this situation, it is more like-
ly that you will leave the string in place after setting the plug. Moving
the pipe up out of the plug may mean stripping out and is likely to dis-
turb the plug (which should be set around the outside of the drill-
string). If the pipe becomes stuck higher up, subsequent barite plugs
will be spotted higher and will be less effective.
The drillstring should be positioned below the loss zone if possi-
ble. However, if this would mean making up an inside BOP and strip-
ping in (i.e., no float and pressure on the string), then the string will
have to be left where it is since the inside BOP will prevent running a
temperature log. If the bit is above the loss zone, a larger plug will have
to be used (to give the desired length in open hole instead of around
the drillstring), and hopefully the plug will move down and bridge off
below the loss zone or inside it.

1. Mix, pump, and displace the barite plug slurry right out of the
drillstring. Overdisplace by 5-10 barrels.
2. Wait about 6 hours for temperatures to stabilize. Meanwhile
pump a few strokes every 15 minutes through the drillstring to
keep it clear, unless there is still pressure on the string from the
kicking formation.
3. Run a temperature survey through the drillstring (pressure equip-
ment will be needed on the string). The loss zone should appear
hotter than normal.
4. Wait another 4-6 hours and run another temperature survey. If the
underground blowout has stopped, the temperature in the loss
zone will have decreased. If the blowout is still going, set another
(larger) plug.
5. If the plug has worked, bullhead cement below it. If the pumping
or casing pressure fluctuates significantly, it may indicate that the
barite plug has not held. Under-displace the cement to plug the
drillstring to the theoretical top of the barite plug.
6. Wait on cement; pressure test inside the drillstring. Bleed off and
check for backflow.
7. Perforate the drillstring, using the pressure lubricator in case flow
starts.
8. Attempt to circulate. If possible to circulate, displace out any for-
mation fluids with a mud density that will stop the losses. Then

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