top of page

What is Kick Tolerance - Formula, Examples & practice problems

kick tolerance

Kick tolerance is one of the most important well control calculations in drilling. It tells us how much influx (kick) can safely enter the wellbore before fracturing the formation at the weakest point. If the influx exceeds this tolerance, the well could lose circulation, leading to severe well control issues or even a blowout.



This blog explains:

  • What kick tolerance means

  • The formula step-by-step

  • A worked-out example

  • Practice problems you can try


What is Kick Tolerance?

Kick tolerance is defined as the maximum influx volume (kick) that can be safely shut in and circulated out without breaking down the weakest formation in the well.

It’s usually expressed in:

  • Barrels (bbls)

  • Cubic meters (m³)

  • Or as an equivalent height in feet/meters of influx in the annulus


The Formula

The simplified formula is:


KICK formulat learntodrill

Where:

  • Fracture Pressure Gradient (FPG) = pressure at which the formation fractures (psi/ft or ppg)

  • Mud Weight Gradient (MWG) = hydrostatic pressure of the mud (psi/ft or ppg)

  • TVD = true vertical depth (ft)

  • Kick Intensity Gradient (KIG) = difference between influx gradient and mud gradient



Worked Example

Problem:

  • Mud weight = 12.0 ppg

  • Fracture pressure gradient at casing shoe = 15.0 ppg

  • Influx gradient (gas) = 0.1 ppg

  • True Vertical Depth (TVD) = 10,000 ft

Step 1: Convert gradients to psi/ft

  • 1 ppg = 0.052 × psi/ft

  • MWG = 12 × 0.052 = 0.624 psi/ft

  • FPG = 15 × 0.052 = 0.78 psi/ft

  • Influx gradient = 0.1 × 0.052 = 0.0052 psi/ft

Step 2: Calculate allowable overbalance

kick step 1

Step 3: Kick intensity gradient

step 2 kick

Step 4: Kick tolerance height

kick 3 step

Step 5: Convert to barrels Annular capacity at casing shoe = 0.1 bbl/ft

kick step 4

✅ Kick tolerance = 252 bbl at the casing shoe.


Practice Problems

  1. Mud weight = 10.5 ppg, fracture gradient = 13.8 ppg, TVD = 9,000 ft, influx = saltwater (1.05 SG). What is the kick tolerance?

  2. TVD = 11,000 ft, MW = 11.8 ppg, fracture gradient = 14.5 ppg, influx gradient = 0.2 ppg. Calculate the maximum safe influx volume if annular capacity = 0.12 bbl/ft.

  3. At 8,500 ft, mud = 9.5 ppg, FPG = 12.2 ppg, influx gas = 0.1 ppg. Find kick tolerance in both feet and barrels.

Want to master well control with hands-on simulator?  Join our IWCF & IADC accredited courses at LearnToDrill.com.

 
 
 
bottom of page