STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

Drilling Muds and Completion Fluids 699
Problem Symptoms Treatment
Salt rock
Salt water
Overtreatment with soda
ash or calcium
bicarbonate
3. High Pressure Zones
Gaslwater influx
Gas cutting
4. Lost circulation
High viscosity, high gel
strength increased water
loss, filtrate chlorides
Same as salt rock; increase
in pit volume; reduction
in mud
Excessive viscosity and
yield point. YP cannot be
lowered with thinner.
Increase in 10 min gel
strength. Methyl Orange
alkalinity M, > 5
Increase in pit volume. Gas
or salt water cut mud.
Mud flows when pumps
are shut off.
Normally shows up as gascut
mud after trips. If
encountered while drilling,
it is usually accompanied
by rapid change in filtrate
chlorides.
Chemical treatment:
(1) thinners-to reduce
apparent viscosity, gel
strength and yield point;
(2) caustic soda-to
adjust pH; (3) CMC,
filtration control agent. If
massive salt is to be
drilled-convert to
saturated salt water mud.
Weight-up to overcome salt
water flow. Chemical
treatment as for salt rock.
Run alkalinity test and
calculate CO, and HCO,
ions concentration.
Calculate lime required:
to remove CO
lime, ppb = 0.001 3 x
epm CO,
to remove HCO,
lime, ppb = 0.026 x epm
HCO,
Shut in well. Record drill
pipe and casing pressure.
Circulate out gas or water
influx and separate on
surface. Calculate mud
weight necessary to
balance formation
pressure. Kill the well.
Add weighting material to
rise density. Thin mud with
water and thinners. Use
degasser to clear gas
from mud. Continue to
circulate and avoid use of
blowout preventers if
possible.
Keep mud weight as low as
possible. Maintain
minimum flow resistance
of mud. Consider air
drilling or foam drilling.