CAUSES OF KICKS

• You have to consider the vertical height or depth of the fluid column, the shape of the hole doesn’t matter.

T.V.D. – True Vertical Depth

Height TVD

The Driller must know true vertical depth (TVD) measurements.

Pressure Hydrostatic, Ph = Mud wt. x 0.052 x TVD

Hydrostatic Pressure

6240 psi 7800 psi 5616 psi 6058 psi

6100 psi Pf

WHY do we lose the Primary Well Control ?

• Failure to Fill The Hole Properly While Tripping

• Swabbing / Surging ‐Mud properties, Pulling speed, Annulus Clearance …

• Drilling into zones of known pressure with Mud Weight too low

• Drilling into unexpected abnormal formation pressure

• Lost Circulation

• Insufficient Mud Weight ‐ enough to drill, but not to trip

• Accidental dilution of drilling fluids

• Weighting material (barite) settling out

Because the pressure in the wellbore becomes less than the pressure in the formation, due to:

WELL CONTROL

Keep the Bottom Hole Pressure (BHP)slightly higher than Pore Pressure in order to have the full 

control of the well.

The main rule of Well Control Game

Well Control can be defined under 2 main categories:

• Primary Well Control: is the use of the fluid to prevent the influx of formation fluid into the well bore.

• Secondary Well Control: is the use of the BOP and Kill Mud to control the well, if Primary WC cannot be maintained. 

Well Control Principles

No Fill‐Up Exercise

Well Data:

TVD 10000 ftHole diameter 8 1/2 "Mud Weight 12,6 ppgFormation Gradient 0,64 psi/ftDrill Pipe Diameter 5 "Drill Pipe Stand Length 90 ftCasing Diameter 9 5/8 "CapacitiesDrill Pipe Total Displaceme 0,02538bbl/ftDrill Pipe Capacity 0,01745bbl/ftOpen Hole Capacity 0,07030bbl/ftCasing Capacity 0,07340bbl/ft

1

22

345

Consequence of no filling-up while triping out

How many stands of dry DP can you POOH, before the overbalance is lost ? (no fill-up)

10

Well Data: coef 0,052pouce 25,4mm

TVD 10000ft TVD 3048m pound0,4536Hole diameter8 1/2" Hole diameter8,5" bar 1,019367992kgfMud Weight12,6ppg Mud Weight1,5098SG bbl 158,984lFormation Gradient0,64psi/ft Formation Gradient0,1448bar/m ft 0,3048mDrill Pipe Diameter5" Drill Pipe Diameter5" psi 0,070308141kgf/cm2Drill Pipe Stand Length90ft Drill Pipe Stand Length27,432m ppg 0,119828816SGCasing Diameter9 5/8" Casing Diameter9,625" psi/ft0,226287027bar/mCapacities Capacities bbl/ft521,6010499l/mDrill Pip0,02538bbl/ft Drill Pi13,238l/m gal 3,7854lDrill Pipe Capacity0,01745bbl/ft Drill Pipe Capacity9,1019l/m SecondaireOpen Hole Capacity0,07030bbl/ft Open Hole Capacity36,669l/m psi 0,068972286barCasing Capacity0,07340bbl/ft Casing Capacity13,238l/m psi/ft0,230669753kgf/cm2/m

1

2

2

3 DP Metal Displacement0,00793bbl/ft DP M 4,1363l/m 4,13634 Pore pressure6400psi Pore pressure441,42bar 441,425 Bottom Hole pressure6552psi Bottom451,18bar 451,916 OverBalance152psi OverBalance9,754bar 10,6877 Equiv 232ft Equiv 65,9m 70,7118 Empty Volume15,2bbl Empty Volume2144l 2414,79 Lengt 1915ft Length of Drill Pipe518m

10 Number of stand18,9stand

ANSW

The hydrostatThe missing mOverBalance p

Consequence

Num21sta

How many standoverbalance is lo

We can write from the well

an

How many stands of dry DP can you POOH, before the overbalance is lost ?

(no fill-up) Well Data:

- TVD: 10,000 ft

- Mud Weight: 12.6 ppg

- Formation Gradient: 0.64 psi/ft

- 5” DP close end Displacement: 0.02538 bbl/ft

- 5” DP Capacity : 0.01745 bbl/ft

- 1 stand: 90 ft

- 8 1/2 Open Hole Capacity: 0.0703 bbl/ft

- 9 5/8 Casing Capacity: 0.0734 bbl/ft

We can write : pipe metal of drill pipe removed from the well = Empty volume in the well

andThe hydrostatic pressure loss corresponding to The missing mud in the well represents the OverBalance prevailing before tripping.

DP Metal Displacement = 0,00793 bbls / ft

Pore Pressure = 6400 psi

Bottom Hole Pressure = 6552 psi

Bottom Hole Margin = 152 psi

Equivalent Mud Height = 232 ft

Empty Volume = 15,2 bbl

Length of Drill Pipe = 1915 ft

Stands of Drill Pipe = 21,3 stands