Kick tolerance is the maximum kick volume that can be taken into the well and circulated out without causing formation damage. Kick tolerance is a function of formation pressure and formation breakdown pressure. On floating rigs increased water depths and the inclusion of riser margins reduce kick tolerance.
Kick Tolerance, Fixed Rig, Simple Method.
- Maximum kick length, or Volume at shut-in
= (MAASP – SIDPP) ÷ (Mud gradient – Influx gradient)
= Length of influx at shut-in. now, Convert to a volume in barrels.
- Convert the length calculated in a) above into the volume at the annulus section below the casing shoe. Volume in barrels.
- Use Boyles gas law to convert this to a volume in downhole conditions.
Where; P1 = Formation breakdown pressure at shoe.
V1 = Volume calculated in b).
P2 = Formation pressure.
V2 = Kick volume.
Kick tolerance will be the smaller of the two volumes calculated in steps
a) and b).
Depth = 10000 ft TVD
Shoe = 5000ft
Mud = 10 ppg
Frac. Gradient = 0.72 psi/ft
Breakdown pressure at shoe = 0.72 x 5000 ft = 3600 psi
DC/OH Capacity = 0.0291 bbls/ft (800 ft Collars)
DP/OH Capacity = 0.0459 bbls/ft
MAASP = (0.72 – 0.52) x 5000 ft =1000 psi
Assume SIDPP = 500 psi
Influx gas = 0.12 psi/ft
Formation pressure = 500 + (10000 ft x 10 x 0.052) = 5700 psi
(1000 – 500) ÷ (0.52 – 0.12)
1250 ft This will cover the collars and 450 ft of pipe.
Collars = 23.28 bbls
Around the pipe = 450 ft x 0.0459 = 20.655 bbls
Total length 1250 ft Total volume 43.935 bbls
1250 ft converted to a volume below the shoe.
1250 x 0.0459 = 57.375 bbls
Step C Converting the above volume to downhole conditions.
(3600 x 57.375) ÷ 5700 = 36.236 bbls
The kick volume is the smaller of the volumes calculated in the steps A) and C).
Kick Tolerance = 36.236 bbls
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