Kick Tolerance Calculator: MAASP and Maximum Kick Volume

Kick tolerance answers a question every drilling engineer needs answered before drilling ahead past a casing shoe. How large a kick can this well take and still be circulated out safely, without breaking down the formation at the shoe and losing control of the well entirely. Use the calculator above to work through the pressure margin, maximum kick height, and kick tolerance volume for your own well.

The Logic Behind Kick Tolerance

When a kick enters the wellbore, it displaces heavier mud with lighter formation fluid, typically gas, reducing the hydrostatic pressure holding the well in check. As you circulate the kick out, pressure at the weakest point in the open hole, almost always the casing shoe, has to stay below the formation fracture pressure there. If it does not, the formation breaks down, mud is lost into it, and the well can underground blow out. Kick tolerance is the maximum influx volume the well can take while keeping shoe pressure below that fracture limit.

The Calculation

The first step is the pressure margin available at the shoe, commonly called MAASP, the maximum allowable annular surface pressure:

MAASP = (fracture gradient – mud weight) x 0.052 x shoe TVD

That pressure margin is then converted into a maximum kick height using the density contrast between the mud and the kick fluid, and finally into a kick tolerance volume using the annular capacity between the open hole and the drill string:

Kick height = MAASP / (0.052 x (mud weight – kick gradient)), kick tolerance volume = kick height x annular capacity

Worked Example

With a 10 ppg mud, a 14 ppg fracture gradient at an 8000 ft shoe, a 2 ppg gas kick gradient, an 8.5 inch open hole, and 5 inch drill pipe, the MAASP works out to 1664 psi. That converts to a maximum kick height of 4000 feet in the annulus, and with an annular capacity of about 0.0459 barrels per foot, a kick tolerance volume of roughly 184 barrels. Anything larger than that, taken all at once, risks exceeding the fracture gradient at the shoe once circulation begins.

Why This Number Matters

• It sets the maximum safe trip margin and influx size before drilling ahead into a new hole section
• A low kick tolerance signals the need for a shallower casing point, a heavier mud weight, or tighter kick detection
• It directly informs well control planning and choke procedures during an actual shut in
• This simplified method assumes the kick stays in open hole annulus and ignores some real world complications like migration and temperature effects

Related Calculator and Reference

For the fracture gradient values used in this calculation, see the Fracture Gradient Calculator. The kick tolerance methodology used here follows the standard well control approach described in the Wikipedia entry on well control.