# Formulas for Wait and Weight Well Control Method

There are some well control formulas that you need to know for wait and weight method.

1. Kill Weight Mud

KWM = OMW + [SIDPP ÷ (0.052 x TVD)]

Where;

KWM is kill weight mud in ppg.

OMW is original mud weight in ppg.

SIDPP is shut in drill pipe pressure in psi.

TVD is true vertical depth of the well in ft.

2. Determine barite required to wait up to KWM

Where;

Barite Require is in sack.

Total Mud Volume is in bbl.

KWM is kill weight mud in ppg.

OMW is original mud weight in ppg.

3. Slow Circulating Rate (SCR)

SCR = ICP – SIDPP

Where;

SCR is slow circulating rate in psi.

ICP is initial circulating pressure in psi.

SIDPP is shut in drill pipe pressure in psi.

4. Final Circulating Pressure (FCP)

FCP = SCR x KWM ÷ OMW

Where;

FCP is final circulating pressure in psi.

SCR is slow circulating rate in psi.

KWM is kill weight mud in ppg.

OMW is original mud weight in ppg.

5. Drill string volume (strokes)

Drill string volume = Drill pipe capacity x TD ÷ Pump output

Where;

Drill string volume is in strokes.

Drill pipe capacity is in bbl/ft.

TD is well measured depth in ft.

Pump output in bbl/stroke.

Note: read more about pipe capacity and pump output >> Inner Capacity of Pipe and Pump Output

6. Drill pipe schedule for a vertical and non taper-string

Drillpipe pressure drop/stroke increment = (ICP – FCP) x increment strokes ÷ surface to bit (strokes)

Where;

ICP is initial circulating pressure in psi.

FCP is final circulating pressure in psi.

Increment strokes are how many strokes for pressure drop certain psi.

surface to bit (stokes) is stokes require from surface to bit.

The detailed calculation can be find in the following topics:

Drill Pipe Pressure Schedule Calculation for Wait and Weight Well Control Method

Pressure Profile of Drillpipe and Casing Pressure while killing a well with wait and weight method

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