The document provides guidance on troubleshooting issues that may arise while drilling and maintaining the drilling fluid system. It discusses four key properties (density, viscosity, gel strength, filtration) that must be adequately monitored and controlled. Issues covered include contamination, abnormal pressure, lost circulation, fluid characteristics like high viscosity or fluid loss. For each problem, the summary lists typical symptoms and recommends solutions such as changing the mud weight or viscosity, adding lost circulation materials, or using solids control equipment.

1. 2
DRILLING FLUID - TROUBLE-SHOOTING
All the drilling fluid problems can be attributed mainly to four physical properties:
• Density (Mud Gravity)
• Viscosity (Plastic viscosity & yield point)
• Gel strength ( Gel0
and Gel10
)
• Filtration (Fluid loss in down hole)
The adequate monitoring and control of the properties should be the primary
concern for maintaining drilling fluid in good condition. Sp. gr. of mud provides
hydrostatic pressure to the well bore. It is easily controlled by addition of weighing
materials like barite, CaCO3
, Hematite, and Galena etc. or by dilution with water or
oil. Mud wt. can be increased by using the following formula -
Kgs of weighting material 1000 S.G.WM
(SG2
-SG1
)
=
M3
of fluid (SGWM
-SG2
)
Where,
SG2
- final specific gravity
SG1
- initial specific gravity
SGWM
- Sp. gravity of weighting material

2. 2
Similarly desired weight reduction can be calculated by using the following
formula:
V1
(SG1
- SG2
)
V2
=
SG2
-SG
Where,
V2
- volume of diluting fluid
V1
- volume of original fluid to be diluted
SG1
- original specific gravity
SG2
- final specific gravity
SG - Sp. gravity of diluting fluid
Viscosity indicates the initial resistance of a drilling fluid. It comprises of two parts
i.e. plastic viscosity (PV) & yield point (YP). Using good solid control equipment,
by dilution or by selective flocculation where as YP can be controlled by addition of
chemicals can control PV. Addition of clays, bentonite extenders, polymers etc.,
increases the YP and addition of thinners and dispersants like CLS, cutch etc,
reduces the YP.
The control of filtration loss helps in minimizing the thickness of filter cake in
addition to less formation destabilisation, which minimises many down hole
problems.
The control of gelation helps in minimising the swabs and surge problems.
Solids in drilling fluid are to be maintained in correct range, as they are very vital
for many drilling fluid properties, ROP etc. In drilling fluid we have two types of
solids: -

3. 2
Reactive (clays)
Low gravity solids
Non reactive (sand, silt, limestone)
High gravity solids weighted materials
If not controlled properly, they can lead to many problems viz, mud viscosity
& treatment related problems, gelation, differential sticking, mud loss, drag
and torque etc.,
Drilling Fluid Trouble Shooting:
Problems Symptoms Solution

4. 2
Contamination
High Drilled Solids
Abrasion
Salt Rock
Salt Water
High viscosity and gel
strength. Slow drilling rate.
Reduced temperature
stability. Mud does not
respond to chemical
treatment.
Premature bit failure and
excessive wear of swabs,
liners and valve seats.
High viscosity and high gel
strengths, increase in water
loss and salt content. Grainy
appearance to mud.
Same as salt – rock except
increase in pit volume and a
reduction in mud weight.
Reduce drilled solids by
water dilution, use of
selective flocculants and
mechanical separation.
Use Desander to hold sand
content to a minimum.
Adjust mud properties with
lime and organic thinners and
water loss control agents, or
convert to saturated salt
system.
Raise weight to overcome
salt water flow. Adjust mud
properties with loss control
agents. If only stringers are
encountered dilute with
water.
Problems Symptoms Solution
Abnormal
Pressure
Lost circulation
Low pressure
Partial to complete loss of
returns
Pull up in casing and wait for
fracture to close. Adjust flow
properties to afford minimum
flow resistance and
equivalent circulating density.
Reduce mud weight, if
possible. For low weight
muds add flake or fibrous
materials to avoid increasing
mud weight from material
additions. In high weight
muds, add fine flake or
granular lost circulation
material for partial loss of

5. 2
Formation Gas or
water influx
Gas Cutting
Differential sticking
of drill pipe.
High Pressure
Increased pit volume
possibly preceded or
accompanied by gas or salt
water cut mud. Mud
continues to flow when
pumps are shut off.
Normally shows up as gas-
cut mud after trips but
dissipates rapidly. If
encountered while drilling,
gas cutting or kicking will
occur in heads. Possible
change in chloride content.
Normally occurs when drill
pipe is not in motion. Cause
in excessive pressure
differential between well
bore and porous formation
Full or partial circulation
while stuck. Probably high
fluid loss and high solids
content mud.
returns.
Shut in well. Record drill pipe
and casing pressure.
Circulate out gas or water
influx and separate at
surface. Using data obtained
calculate necessary mud
weight, mix mud and circulate
to kill well.
Raise weight only as
necessary. Keep gel
strengths as low as possible.
Continue to circulate and
avoid use of blowout
preventers if possible. Use
degasser as necessary to
clear gas from mud.
If possible reduce mud
weight, Use spotting fluid. For
prevention measure reduce
fluid loss at static. Bottom
hole temperature at 500 psi
differential pressure and use
minimum safe mud weight.
Problems Symptoms Solution
Corrosion

6. 2
General, salt muds
etc.
Aerated Mud
Sulphide stress
corrosion
Formation
Bit Balling
Bentonite Swelling.
Running, sloughing,
caving shales.
Plastic salt
Internal and external pitting,
more pronounced internally
in uncoated pipe
Severe pitting of drill pipe
more pronounced internally.
Severe brittle, flat fractures
of susceptible materials,
either tool joints and / or
pipes.
Little, or no progress in
footage. Balled up bit and
drill string. Swabbing on
trips and connections. Bit
generally comes out in good
condition, showing little
wear, but heavily packed
with cuttings.
Increase in viscosity, gel
strength and solids content.
Tight places in hole, slow
drilling. Mud difficult to
control
Hole fill-up after trip.
Excessive cuttings over
shaker. Tight connections.
Tight connections. Even
with saturated or oil based
mud pipe may become
stuck.
Add corrosion inhibitors, Use
oxygen scavengers.
Extremely difficult to control.
Use corrosion inhibitors and
oxygen scavengers.
Maintain sufficient weights to
avoid influx of formation
fluids. Add sulphide
scavengers.
Add lubricants, surfactants,
etc. or oil slowly at suction.
Maintain low viscosity and gel
strength to keep hole clean.
Utilise available horsepower
for most efficient hydraulics.
Do not emulsify for best
results.
Keep viscosity and gel
strength low to prevent
swabbing. Use an emulsion
mud to keep bit and drill
string clean. Use an inhibitive
mud. Raise mud weight to
hold bore hole open
Raise weight, increase,
viscosity, decrease fluid loss
and maintain mud in laminar
flow. Use inhibitive mud.
Increase mud weight. Ream
through tight spots. If stuck,
spot fresh water then
increase mud weight.
Problems Symptoms Solution
Mud
characteristics

7. 2
Foam, surface.
Foam, internal
High fluid loss
High fluid loss
High viscosity
High viscosity
Increase of surface
mud weight.
Unstable Mud.
Foam on surface of mud
pits. (Not that while
converting mud)
Reduction in mud weight,
increased viscosity, fluffy
appearance. Pumps run
rough or hammer and pump
pressure falls off.
Normal viscosity but high
fluid loss.
Filter cake spongy, soft and
too thick. There is sufficient
fluid loss agent in system.
High funnel viscosity, plastic
viscosity, yield point, gels
and solids. Sometimes
normal gel and / or solids.
High funnel viscosity, yield
point and gels and normal
plastic viscosity and solids.
High viscosity.
Barite settles out.
Not serious unless mud
weight reduced by internal
foam. Keep guns submerged.
Use fine spray of water or oil
to break foam. Use defoamer
if foam persists. In salt or low
solids mud, bentonite will be
helpful.
Eliminate all mechanical
causes of foam. Maintain low
viscosity and gel strength.
Use defoamers, if necessary.
Add fluid loss agent through
hopper.
Add bentonite to system (run
Methylene Blue test)
Run mechanical solids
removal equipment to discard
drill solids and fine barite
particles. Water dilution also
required. Thinner may be
used later.
Add dispersant. Run
mechanical solids removal
equipment. Check mud for
contamination.
Run mechanical solids
removal equipment and add
water.
Add viscosifier to increase
viscosity.
Problems Symptoms Solution

8. 2
Slow Drilling Rate
See ‘Bit Balling’ under Formation and ‘High Drill Solids’ under Contamination.
High temperature
High temperature
Gelation.
Bearing Failure
Locked Cones
Difficult to break circulation.
Inability to run tools to
bottom. High viscosity and
gel strengths of mud off
bottom. Decrease in
alkalinity, increased water
loss and increase insoluble
calcium.
Cones locked or bearings
loose with teeth structure
still on cones
Reduce solids concentration
by water dilution and add
bentonite. Increase thinner
concentration. To any mud
spot a slurry or mud treated
with 1 – 2 lb/bbl sodium
chromate in that portion of
hole subjected to high
temperature.
Reduce drilled solids by water
dilution, mechanical
separation and use selective
flocculants. Use sealed
bearing bits.
Abnormal Pressure Formations:
Occurrence Warning Signs Causes Action Of Take

9. 2
When Drilling
When Making Trip
Increase in pump
speed or decrease
in pump pressure
Drill break
Hole fails to take
mud when filling
up
Drilling mud too
light or hole in drill
pipe
Drilled into porous
formation
Swabbing
Observe mud pit
level. If increase is
observed close
blowout preventor
and increase mud
weight. If no
increase in mud pit
level, check for
hole in drill pipe.
Observe mud pit
level. If increase is
obtained. Close
blowout preventer
and increase mud
weight. Circulate
returns up from
bottom mud and ,
if showing of gas,
oil, or saltwater is
of sufficient
intensity, increase
the mud weight.
Attempt to run drill
pipe as near back
to bottom as time
will permit.
Circulate and
condition mud.
Close blowout
preventer and put
through choke, if
necessary.
Increase mud
weight only if
necessary.
Occurrence Warning Signs Causes Action Of Take
When Making Trip Well begins to flow Swabbing and / or Attempt to get drill

10. 2
When Out of Hole
back, increase in
mud pit level.
Loss of circulation;
unable to fill hole
Well begins to flow
back; increase in
mud pit level
failure to fill hole.
Running drill pipe
is too fast,
spudding drill pipe.
Swabbing and / or
failure to fill hole
pipe as near back
to bottom, as
safety and time will
permit. Close
blowout preventor.
Circulate and
condition mud;
increase mud
weight only if
necessary.
Attempt to keep
annulus full using
water, if
necessary. Watch
annulus and
should well kick,
close blowout
preventer. Add lost
circulation material
to mud system and
regain returns.
Increase mud
weight only if
necessary.
Attempt to run drill
pipe as near back
to bottom as safety
and time will
permit. Circulate
and condition mud.
Close blowout
preventer and put
through choke, if
necessary.
Increase mud
weight only if
necessary.