well control for drilling engineers
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WELL CONTROL
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Introduction to Drilling Well Control
Describe primary and secondary well control
Explain the mechanism of a kick List causes of kicks
Explain shut-in procedure
Explain the two well control methods commonly used
Describe the working of annular and ram preventers
Describe the layout of the choke manifold and control panel
Explain the function of the closing unit
Identify mud/gas separator
Learning Objectives
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Introduction to Drilling Well Control
Primary Control
Vertical depth = 10,000’
Mud weight10 ppg
Hydrostatic pressure on bottom of hole10 x 0.052 x 10,000 = 5,200 psi
Overbalance = 5,200 – 5,000 = 200 psi
Formation pressure = 5,000 psi
Hydrostatic pressure
of the mud column
prevents flow of
formation fluid into
the wellbore if it is
equal to or greater
than the formation
pressure
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Introduction to Drilling Well Control
A kick is an influx of
formation fluid into
the wellbore whenthe formation
pressure exceeds
the hydrostatic
pressure of the mud
column. The
intruding fluid could
be liquid or gas.
Formation pressure = 5,500 psi
Influx enters wellbore(Kick is taken)
Hydrostatic pressure on bottom of hole10 x 0.052 x 10,000 = 5,200 psi
Overbalance = 5,200 – 5,500 = -300 psi
Well is shut-in to prevent a blow out
Drill string is still full of 10.0 ppg mudDrill pipe pressure represents magnitudeof underbalance.Mud weight required to just balance the
formation pressure:
Old MW + 300/(10,000 x 0.052) = 10.0 + 0.6
Vertical depth = 10,000’
A Kick
300 psi 500 psiShut-in drillpipe pressure
Shut-in casing pressureHigher than SIDPP due toinflux in part of the annulus
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Introduction to Drilling Well Control
Calculation of Kill Mud Weight
)(0.052)(TD
SIDPPOMWKMW
TVD +=
325
0.052 x 8,000 = 12.28, say 12.3 ppg
Add trip margin of 0.5 ppg
New Mud Weight for drilling = 12.3 + 0.5 = 12.8 ppg
)(0.052)(TD
SIDPPOMWKMW
TVD +=
Example:
True Vertical Depth (TD)= 8,000 feetOld Mud Weight (OMW) = 11.5 ppg
Shut In Drill Pipe Pressure (SIDPP) = 325 psi
Kill Mud Weight (MW) = 11.5 +
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Introduction to Drilling Well Control
Causes of Kicks
Failure to keep the hole full while tripping out
Unexpected formation pressure
Low density fluid
Lost circulation
Swabbing
Mechanical failure
Human error
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Shut-In Procedure
Kick detected while drilling Space out
Stop pumps
Close uppermost applicable BOP
Record SIDPP, SICP, pit gain, time
Kick detected while tripping
Stab full opening safety valve, close same
Space out
Close uppermost applicable BOP
Record SICP, pit gain, time
Prepare to strip to bottom
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Well Control Methods
Driller’s Method:
The influx (kick) is circulated out of the hole
immediately after the well is shut in. Kill weight
mud is pumped in the second circulation
Wait & Weight Method:
With the influx in the well, kill weight mud is
prepared at the surface and pumped in to circulate
out the kick and kill the well in one circulation
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Driller’s Method -Example
500
SHUT-IN
700
500
SHUT-IN
500
1500
START
PUMP
700
1500
1800
1500
CIRCULATE INFLUX OUT
800
First Circulation
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500
500
1500
START
PUMP
500
1100
500
1100
0
0
KWM TO
BIT
KWM TO
SURFACESHUT-IN
SHUT DOWN
0
Driller’s Method -Example
Second Circulation
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500
SHUT-IN
700
KWM TO
BIT
1500
START
PUMP
700
1400
705
1200
715
1100
720
200
STROKES
600
STROKES
Wait & Weight Method -Example
Kill Weight Mud to Bit
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1100
KWM TOBIT
720
SHUT
DOWN
1100
GAS TO
SURFACE
1500
1100
100
1100
0
0
0
GAS OUT KWM TO
SURFACE
Wait & Weight Method -Example
Kill Weight Mud to Surface
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Pipe Ram
Pipe Ram
Blind Ram
Annular
Surface Application
Main considerations:
• Size – inside diameter• Pressure rating
• Ram sizes
Typical Blow Out Preventer (BOP) Stack
To Choke
ManifoldKill Line
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Introduction to Drilling Well Control
Typical Blow Out Preventer (BOP) Stack
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Introduction to Drilling Well Control
Hydril GK – Annular Preventer
• 1200 psi normaloperating pressure
• 1500 psi maximumoperating pressure
• Highly wellboreassisted
Piston
Indicator
Hole
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Introduction to Drilling Well Control
Cameron type “U” Ram Preventer
Manual Locking Screw
Bonnet Bolt
Operating Piston
Intermediate Flange(Larger for shear rams)
Bonnet
Ram Change Piston
Ram Assembly
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Introduction to Drilling Well Control
Choke Manifold
O Normally Open
C Normally Closed
Master
C O
C
C
C
O
O
C C
O
C C
C
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Pipe Ram
Pipe Ram
Blind Ram
Annular
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Introduction to Drilling Well Control
Typical Mud/Gas Separator
Outlet of the choke manifold is
connected to a mud/gas separator
The mud/gas separator is designed
to provide effective separation of
the mud and gas circulated fromthe well by venting the gas and
returning the mud to the mud pits
via gravity feed
Small amounts of entrained gas may
remain in the mud and can beremoved by the degasser located at
the mud pits
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Introduction to Drilling Well Control
Remote Choke Control Panel
Manualhydraulicpumpandhandle
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Introduction to Drilling Well Control
BOP Operating Unit
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Introduction to Drilling Well Control
Remote Operating Station
API RP 53 2nd Edition
Minimum of one remote control
panel should be provided along
with the main hydraulic control
manifold.
The controls should be clearly
marked
One station should be locatednear the Driller’s console and the
other should be located a safe
distance from the wellbore nearan escape route
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Introduction to Drilling Well Control
Jackup Drilling Rig
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Introduction to Drilling Well Control
After a Blowout
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Introduction to Drilling Well Control24
After a Blowout
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Introduction to Drilling Well Control
Barge Rig Blowout
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