MAMW Calculator
Maximum Allowable Mud Weight restates your shoe's LOT/FIT limit as an equivalent mud weight, then uses it to work out the new MAASP once a kill mud weight is set.
The Formulas Used
Where This Fits
MAMW and MAASP come from the same LOT/FIT test and describe the identical shoe limit, just in different units — one as an equivalent mud weight, one as a live surface pressure. Once a kick is confirmed and a kill mud weight is chosen on the kill sheet calculator, the second box here answers the real operational question: is that kill mud weight actually safe for this shoe, and if not, how much surface pressure is left before it isn't? A negative or very small New MAASP means the planned kill mud weight is close to or past the shoe's real limit, which calls for the well control supervisor's attention before pumping starts, not after.
Frequently Asked Questions
How is MAMW different from MAASP?
They express the same shoe limit in two different units. MAASP restates the limit as a live surface pressure in psi at today's mud weight. MAMW restates it as an equivalent mud weight in ppg — the heaviest mud the shoe could take with zero surface pressure showing. Converted to the same units, both should agree.
Why does New MAASP need the kill mud weight, not the current mud weight?
Once a kill is underway, the mud weight in the hole is changing on purpose, and the shoe cares about whatever mud weight will actually be in the annulus once the kill mud weight is circulated — not the mud weight that was in the hole when the kick was taken. Recalculating MAASP against the kill mud weight, not the original mud weight, is what tells you whether the planned kill mud weight itself is safe for the shoe.