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Kick - Definition
A kick occurs when formation fluid flows in to the
wellbore due to insufficient mud hydrostatic
pressure
Mud
hydrostatic
pressure
Pf Pf
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Causes of Kicks
1. Tripping
2. Drilling into an overpressured zone
3. Failure to fill hole
4. Inadequate mud weight
5. Gas cut mud
6. Lost circulation
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Kick Detection
Increase in flow rate out of the hole
Increase in surface mud volume ( pit
volume)
Action : Driller has to close the
Blowout Preventer ASAP
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Pdp = Pf- mud hydrostatic
Mud
hydrostatic
pressure
Pf
Pressure Changes During A Kick
During a kick the
reverse
happens…downhole
pressure is seen at
surface
Formation pressure = mud hydrostatic pressure + Pdp
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Migration ( percolation ) rate ( Ft/hr)
= Pressure increase per hour ( Psi/hr) / Mud gradient ( Psi/ft )
New MAASP ( Psi)
= [ Max allowable mud wt (PPG) - mud wt (PPG)] x 0.052 x Casing TVD (ft)
Barite required to raise mud weight ( Lbs/bbl.)
= [1500 x ( Kill mud wt (PPG) - Old mud wt (PPG)] / [ 35.8 - Kill weight mud
(PPG)]
Shut in casing pressure ( Psi)
= Formation pressure (Psi) - [Mud grad x height + Influx
grad x Influx height ]
Where Gradients = Psi/ft , Heights = (ft).
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Example
Well Depth 7560' MD 7050' TVD.
13 3/8” casing shoe at 6000' MD 5820' TVD.
Bit Size 12 ¼”
Drill pipe 5” 19.5 lb/ft.
Drill Collars 8” x 2 13/16”~ x 530'
Well is shut in with the following data
SIDPP 550 psi
SICP 680 psi
Kick Volume 25 bbls
Mud Weight in use is 11.0 ppg.
Slow Circulating Rate Pressure is 500 psi at 30 spm
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1. What is the formation pressure ?
2. What is the kill mud weight required to balance formation
pressure?
3. What is the initial circulating pressure?
4. What is the final circulating pressure, once the kill mud has
reached the bit?
5. What is the gradient of the influx?
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Well Control
SLOW
CIRCULATING
RATES (SCR)
Wells should be killed using Slow
Circulating Rates for the
following reasons:
1: To allow for a smooth
weight-up of the mud and
degassing of mud.
2: To maintain pressures at
the bottom of the hole to a
minimum.
3: To allow the choke operator
time to make choke
adjustments.
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Well Control
SLOW
CIRCULATING
RATES SCR
Wells should be killed using
Slow Circulating Rates for the
following reasons:
4: To allow controlled disposal of the
formation fluids at surface.
5: The handling capacity of the
choke may be limited.
6: To reduce annular velocity in the
wellbore in the event that slight
losses are encountered.
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Slow
Circulation Rate SCR
Slow Circulation Rates should be
recorded:
1: On the drillpipe pressure
gauge at the remote choke
panel.
2: On the drillpipe pressure
gauge on the Drillers console,
for verification and in the event
of remote choke gauge failure.
3: With the bit as close to bottom
as possible.
4: When the mud is at the correct
temperature.
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Well Control
SLOW
CIRCULATING
RATES SCR
Slow Circulation Rates
should be taken:
1: At the beginning of every tour.
2: Any time the mud weight is
changed.
3: Any time the bit nozzle
configuration is changed.
4: After bit or BHA changes.
5: After a leak off test.
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Well Control
SLOW
CIRCULATING
RATES SCR
Slow Circulation Rates
should be taken:
6: Only after the mud in
the well is in optimum
condition.
7: If any repairs have been
carried out on the mud
pumps.
8: On each mud pump,
with at least two
different pump speeds.
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Well Control
SLOW
CIRCULATING
RATES SCR
Slow Circulation Rates
should be taken:
9: For floating drilling units SCR’s
should be recorded up the riser
and up the choke line at the
same rate to establish the
chokeline friction. This
operation should be carried out
prior to drilling out the casing
shoe, in case of excessive
chokeline friction. The
pressures recorded can then be
adjusted for increases in mud
weight as the well is drilled
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Well Control
SLOW
CIRCULATING
RATES SCR
Slow Circulation Rates
should be taken:
10: If the mud properties
change
significantly.
11: If more than 500 ft is
drilled in a tour.
12: Before returning to
drilling after a well control
situation.
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Well Control
SLOW
CIRCULATING
RATES SCR
Note:
Slow Circulating Rates (SCR),
are only as good as when they
are taken. Slow Circulating
Rates, are not written in stone,
any changes to the above
parameters will alter the Slow
Circulating Rates pressure,
gauge accuracy and human error
are common reasons for different
Slow Circulating Rates
pressures.
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1. The Drillers method is a two
circulation method.
2. On the first circulation the
influx is circulated out of the
hole with the existing mud
weight using the choke to
maintain the required
pressure differential.
3. the well is circulated with
original weight mud to
remove the influx while kill
mud is being prepared.
Drillers Method
Formation
fluid
Mud
Mud Mud
Shut-in
casing
pressure
Shut-in
drill pipe
pressure
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4. After completing one
complete circulation,
pressure on DP and
annulus are the same.
5. On the second circulation,
kill weight mud is circulated
round the hole.
6. kill mud is circulated around
to kill the well - well is dead
Drillers Method
SICP
SIDPP
Mud
Gas
Pf
TD
CSD
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DPSIP + Pc1
Pc2
DPSIP 1
2
3 4
6
5
0
Volume of drill pipe Volume of annulus
Start
Kill mud
at drill pipe
Kill mud
arrives at
bit
Shut-in
period
No. of barrels pumped (or time)
Drillpipe
4. After completing one complete circulation, pressure on DP
and annulus are the same.
5. On the second circulation, kill weight mud is circulated round
the hole.
6. kill mud is circulated around to kill the well - well is dead
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DPSIP + Pc1
CSIP
Light mud
Gas
(1)
Pc2
Casing
pressure
Kill mud
Gas
Light mud
(2)
Pc2
Casing
pressure
Light mud
Kill mud
(3)
Light mud
Kill mud
Pc2
(4)
Casing
pressure
Pc2
Kill mud
(5)
0
Pressure
1
2
3
4
5
CSIP
Kill mud
fills drill pipe
Gas arrives at
the choke
Volume pumped Extra pressure on casing due to
U-tubing effect from kill mud in drill pipe
on the mixed mud in annulus
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Dynamic bottomhole pressure
Static bottomhole pressure
Well is
dead
Annular
pressure loss
Pressure, psi
Time
(b)
Time
(a)
DPSIP
(DPSIP + Pc1)
Pressure, psi
Pc
2
Kick
detected
Shut-in
well
Slowly bring
pump to speed
keeping DPSIP
constant
Gas (or influx
fluids) arrives
at surface
Gas out
of well
Kill mud
is now
circulated
in drill pipe
Kill mud
arrives at
bit
(DPSIP=0)
Kill mud
arrives at
surface
(well is
dead)
EVENTS
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“Wait and Weight” Method
1. The well is kept closed in while the surface mud
weight is increased.
2. kill mud is circulated around the well in one
circulation.
3. one circulation removes the influx and kills the
well.
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DPSIP + Pc1
Pc2
DPSIP 1
2
3 4
6
5
0
Volume of drill pipe Volume of annulus
Start
Kill mud
at drill pipe
Kill mud
arrives at
bit
Shut-in
period
No. of barrels pumped (or time)
Drillpipe : Weight and Wait
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Kill mud arrives
at bit
3
2
1
Initial CSIP
Shut-in
period
4
Kill mud arrives
at surface
Casing: Weight and Wait
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1. Wellbore and surface pressures are generally lower
with the Wait-and-Weight method, particularly if the
influx contains gas.
2. The maximum pressure exerted on the last casing
shoe, which is assumed to be the weakest point in
the hole, is lower with the Wait-and-Weight method
as long as the open hole annular volume is larger
than the drillstring capacity,
3. The well is under pressure for the least time and
there is less time circulating through the choke.
Features of The Wait & Weight Method
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1. It requires the longest waiting time prior to circulation
2. If the annulus was full of cuttings at the time the kick
was taken there may be a danger of packing off.
3. Gas migration may become a problem while waiting
for the mud to be weighted up.
The disadvantages of the Wait-and-
Weight method are:
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Differences between Methods
Wait & Weight Drillers Method
1. Completed in one circulation. Completed in two
circulations.
2. Lower pressures on the wellbore. Higher pressures on
casing shoe
3. Takes less time overall Must be used in
HPHT wells
4. The preferred method in most cases.
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Example
Well Depth 7560' MD7050' TVD.
13 3/8” casing shoe at 6000' MD5820' TVD.
A leak-off test was carried out at the 13 3/8” shoe using a mud weight of 10.0 ppg. A
surface pressure of 1400 psi was recorded.
Bit Size 12 ¼”
Drill pipe 5” 19.5 lb/ft. capacity=0.01776 bbl/ft
Drill Collars 8” x 2 13/16”~ x 530' capacity=0.0080 bbl/ft
Drill pipe / Casing annulus capacity=0.1293 bbl/ft
Drill pipe / Open hole annulus capacity=0.1215 bbl/ft
Drill Collar / Open hole annulus capacity=0.0836 bbl/ft
Well is shut in with the following data
SIDPP 550 psi
SIC 680 psi
Kick Volume 25 bbls
Mud Weight in use is 11.0 ppg.
Pump is a National 12-?-160, using 6 ½” liners.
Pump output is 0.119 bbl/stroke.
Slow Circulating Rate Pressure is 500 psi at 30 spm.
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Bit Size 12 ¼”
Drill pip Drillpipe 19.5 lb/ft.
capacity=0.01776 bbl/ft
Drill Collars 8” x 2 13/16”~ x 530' capacity=0.0080 bbl/ft
Drill pipe / Casing annulus capacity=0.1293 bbl/ft
Drill pipe / Open hole annulus capacity=0.1215 bbl/ft
Drill Collar / Open hole annulus capacity=0.0836 bbl/ft
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(1) What is the kill mud weight required to balance formation pressure?
ANSWER ppg.
(2) How many strokes will be required to pump kill mud from the surface to the
bit?
ANSWER ___ ___ strokes.
(3) How many strokes are required to pump from the bit to the casing shoe?
ANSWER ___________ strokes.
(4) What is the total annular volume? ANSWER : ______ barrels.
(5) What is the MAASP at the time the well is shut in?
ANSWER ________psi.
(6) What is the new MAASP once the kill mud has been circulated around the
well?
ANSWER ________psi
(7) What is the initial circulating pressure? ANSWER ___ psi
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(8) What is the final circulating pressure, once the kill mud has reached
the bit?
ANSWER ____ psi
(9) What is the gradient of the influx? ANSWER -______ psi/ft.
(10) Approximately how long will it take to circulate around the well at 30
spm?
ANSWER _________ minutes.
(11) The well is shut in. What is the drillpipe pressure drop
per 100 strokes as kill mud is being pumped to the bit?
ANSWER ______ psi/100 stroke
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Imagine two equal quantities of gas injected into two
tubes full of mud. One tube is open to the atmosphere
and one is closed
Open
Gas
Closed
Gas
?
One bbl of gas
0
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When the tube is closed , gas rises up the tube
without expansion carrying its pressure with it all the
way up the tube.
Gas
Gas
Mud hydrostatic = 5000 psi
Gas pressure = 5000 psi
Gas
Closed
Mud = 9.6 ppg
Depth= 10000’
0 5000
?
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Bottom Hole Pressure (Igore gas head)
BHP= surface pressure + Hydrostatic
heads= 0 +5000 = 5000 psi
Gas
5000
0
Gas
Closed
Mud = 9.6 ppg
Depth= 10000’ Gas
?
BHP= surface pressure + Hydrostatic
heads=5000 +5000 = 10,000 psi
In a real well, the hole will
fracture when gas is at surface
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Gas
Gas
Hence gas expansion must be allowed to reduce
wellbore pressures. This is the basis of well kill
methods.
Gas expansion is carried out in a controlled manner by
manipulating the choke at surface
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Annular Gas Expansion: Conclusions
• Gas expands as it rises (Boyle’s Law)
• Gas Pressure reduces as it rises
• Gas height increases, mud height decreases
• Pan must rise to compensate if BHP stays the
same.
