3 1 well control

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Basic Well Control

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Basic Well Control
• Lecture Contents;
– Lecture Objectives,
– Introduction,
– Primary Control,
– Warning Signs of Kicks,
– Secondary Control,
– Well Killing Procedures,
– Kill Sheet.
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Basic Well Control
• Lecture Objectives
– At the end of this lecture YOU will be able to:
• Define the term “kick”,

• State warning signs of a kick,
• Describe the drawback of uncontrolled kicks,
• State primary and secondary control procedures,
• List well killing procedures and the various calculation to
fill-up the well control work sheet.

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Basic Well Control
• Introduction;
– In simple terms, kick occur when the formation pressure
exceeds the mud hydrostatic pressure,
– The resultant negative differential pressure is forced into
the wellbore,
– If the flow of the kick is controlled then the well is killed,
– Blow-out occurs when the kick (influx) is uncontrolled,
– The rig crew must be alert all times in order to take
immediate action to bring the well under control.
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Basic Well Control
• Introduction;
– Uncontrolled Kick !

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Basic Well Control
• Introduction;
– And result result !

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Basic Well Control
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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Basic Well Control
A study of 55 blowouts during a 10-year period
lists the following primary causes of blowouts:

Cause

% of Total

Failure to keep hole full

42

Insufficient Mud weight

15

Lost Circulation

22

Swabbing

16

Other

5

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Basic Well Control
Mud
hydrostatic
pressure

Pf

Pressure Changes During A Kick
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Basic Well Control
Mud
hydrostatic
pressure

New
heavy
mud

Pf

Pressure Changes During A Kick
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Basic Well Control
Imagine we applied a
surface pressure of
Mud
hydrostatic
pressure

100
psi

Pf

Pf – hydrostatic = say
100 psi on surface

Bottomhole
pressure changes
by same amount

Pressure Changes During A Kick
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Basic Well Control
Pdp = Pf- mud hydrostatic
Mud
hydrostatic
pressure

During a kick the
reverse happens…
downhole pressure is
seen at surface

Pf
Formation pressure = mud hydrostatic pressure + Pdp
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Basic Well Control
– Kick due to Overpressured Zone:

Depth
Mud Pressure

Normal Pressure

Formation Pressure

Overpressure
Pressure
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Basic Well Control
– Reduction in hydrostatic pressure due to fluid level drop
in borehole:
Depth

Mud Pressure

Pore Pressure

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Pressure
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Basic Well Control
DPSIP

Well Shut-in
Before circulation

Pa

Mud

Gas

Yf

Pf

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Basic Well Control

Remedy
Before normal operations ca resume:
1.

The influx has to be removed from the
annulus

2.

Mud hydrostatic has to balance the
formation

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Basic Well Control
• Primary Control;
– The aim of primary control is to prevent the influx of
formation fluids into the wellbore by keeping sufficient
hydrostatic pressure,
– There are two ways in which primary control can be lost:
• Low mud weight,
• Reduction of the mud column.

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Basic Well Control
• Primary Control;
– Low Mud Weight:
• The mud weight maybe too low for the following reason:
– Drilling through an overpressured zone that required a
heavier mud,
– Inaccurate measurement of fluid density,
– Excessive dilution of the mud,
– Gas cut of the mud,
– Solids removal.

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Basic Well Control

• Primary Control;
– Reduction of the Mud Column:
• This is due to the following scenarios:
– Swabbing:
» This is the process by which the drillpipe acts as a
piston upward,
– Lost circulation:
» This occurs when a fractured formation is being drilled,
it can be either natural or induced fractures.

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Basic Well Control
• Warning Signs of Kicks;
– Primary Indicators:
• Flowrate increase:
– While the mud pumps are circulating at a constant rate, there
should be a constant flowrate of mud returns to surface,
– If the flowrate increases, this will be an indication that
formation fluids are fed into the wellbore.

• Pit Volume Increase:
– When active pit level increases. This will be a sign that an

influx has been entered the wellbore,
– The influx volume is equal to the pit gain and should be
noted for later calculations.

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Basic Well Control
• Warning Signs of Kicks;
– Primary Indicators:

• Flowing Well with Pumps Shut-off:
– When rig pumps are not operating, there should be no returns,
– If the well flows, a flow check must be carried-out to verify
whether it is due to either thermal expansion, U-tube affect, or an
influx.

• Improper Hole Fill-Up During Trips:
– The hole should be filled when the pipe is tripped-out,
– If the pipe displacement volume has not been replaced, then this
will indicate that the mud has been displaced by the formation
fluids.

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Basic Well Control
• Warning Signs of Kicks;
– Secondary Indicators:
• Change in Pump Pressure & Flowrate:
– An entry of an influx to the wellbore will reduce the mud
hydrostatic pressure and hence the pump flowrate will
increase.

• Drilling Break:
– A sudden increase in the rate of penetration could indicate an
entrance to an overpressured zone (bearing in mind
formation change, or change in drilling parameters)

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Basic Well Control
Once Kick is Detected by;


Increase in flow rate out of the
hole



Increase in surface mud
volume ( pit volume)
Driller has to close Blowout Preventer
ASAP

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Basic Well Control
• Secondary Control;
– Shut-in procedure:
• For a kick detected while drilling:
– Raise kelly above rotary table until tool joint appears,
– Stop mud pumps,
– Close Annular Preventer (or Pipe Rams),

– Record SIDPP, SICP and Pit Gain.

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Basic Well Control
In the 55-well study referred to earlier, evidence
showed that after the wells kicked, 62% were not
controlled for the following reasons:

Cause

% of Total

Insufficient Blowout Equipment

29

Improperly designed Blowout Equipment

5

Improper Installation

11

Improper Surface Fittings

6

Improper well, casing and cementing
program

11

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