Kill Mud Weight Calculator

After a kick is shut in, the first number the crew needs is the mud weight that will balance formation pressure. The kill mud weight calculator takes your SIDPP, current mud weight and true vertical depth and gives you KMW, initial circulating pressure (ICP), final circulating pressure (FCP) and MAASP at the shoe.

Formulas

Kill mud weightKMW = MW + SIDPP / (0.052 × TVD)

Initial circulating pressureICP = SIDPP + SCR

Final circulating pressureFCP = SCR × KMW / MW

MAASPMAASP = (LOT EMW − MW) × 0.052 × Shoe TVD

Worked example

GIVEN

SIDPP = 520 psi
Current MW = 10.2 ppg
TVD = 10,000 ft
Slow circulating rate (SCR) = 600 psi

WORKING

KMW = 10.2 + 520 / (0.052 × 10,000) = 10.2 + 1.0
ICP = 520 + 600
FCP = 600 × 11.2 / 10.2

KMW = 11.2 ppg · ICP = 1,120 psi · FCP ≈ 659 psi

FAQ

Should I add a safety margin to kill mud weight?

Many operators add a trip margin of 0.1–0.3 ppg, but this raises shoe pressure. RIGCALC lets you enter an optional safety factor so you can see its effect before committing.

Why use TVD and not measured depth?

Hydrostatic pressure depends only on vertical height of the fluid column, so all well-control weight calculations use TVD.

What is 0.052?

It converts ppg to a pressure gradient in psi/ft (1 ppg × 0.052 = 0.052 psi/ft).

Run it with your well data

Field & Metric units, works offline, save and share results with your crew.

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Reference only. Always verify against your company procedures and well-control certification.