Well Control Formulas

These are some well control formulas that I have learned from my well control school and I would like to share with you guys. Please feel free to comments or give me suggestions.

Pressure (P) - psi

Pressure (psi) = Force (lb) / Area in Square Inch (in ²)

Pressure Gradient (G) - psi/ft

Mud Gradient ( Psi/ft ) = Mud weight ( PPG) x 0.052


Hydrostatic Pressure (HP) - psi

Hydrostatic Pressure (HP) = Mud weight (PPG) x 0.052 x TVD (ft)

You may have seen this triangle before but I need to emphasize on this because it will let you see all relationship of the hydrostatic pressure.

If you want to solve for MW or TVD, fill in the known information in these equations below;

Bottom Hole Pressure (BHP) - psi

Under static condition

Bottom Hole Pressure (BHP) = Hydrostatic Pressure (HP) + Surface Pressure (SP)

Under dynamic condition, use the following equation.

Bottom Hole Pressure (BHP) = Hydrostatic Pressure (HP) + Surface Pressure (SP) + Frictional Pressure (FrP)

Note: Frictional pressure acts opposite way of flow direction.

Formation Pressure (FP) - psi

After get Shut In Drill Pipe Pressure, you can calculate the formation pressure from this following relationship;

Formation Pressure (FP) = Hydrostatic Pressure (HP) + Shut-In Drill Pipe Pressure (SIDPP)

Equivalent Circulating Density (ECD) , ppg

Equivalent Circulating Density (ECD) ,ppg = (annular pressure loss, psi) ÷ 0.052 ÷ true vertical depth (TVD), ft + (current mud weight, ppg)

Leak-off Test Equivalent Mud Weight (LOT), ppg

Leak off test (ppg) = (Leak off test pressure in psi) ÷ 0.052 ÷ (Casing Shoe TVD in ft) + (Mud Weight used for LOT in ppg)

Maximum Initial Shut-In Casing Pressure (MISICP), psi

This calculation is based on shoe fracture which is equal to Leak Off Test Pressure.

MISICP (psi) = [LOT (ppg) – Current Mud Weight (ppg)] x 0.052 x Shoe TVD (ft)

Kill Mud Weight to Balance Formation (KMW), ppg

KWM (ppg) = [Shut In Drill Pipe Pressure (SIDP), psi ÷ (0.052x True Vertical Depth (TVD) of the well, ft)] + Original Mud Weight (ppg)

Slow Circulation Rate (SCR), psi


SCR (psi) = Initial Circulating Pressure (psi) – Shut In Drill Pipe Pressure (psi)

Annulus Capacity Factor (ACF),bbl/ft



Final Circulating Pressure (FCP), psi




Surface To Bit Strokes, strokes





Circulating Time, mins




Capacity Factor (CF), bbl/ft





Opened End Pipe Displacement, bbl/ft





Closed end pipe displacement, bbl/ft

Height of Influx, ft




Approximate gas migration rate, ft/hr




Sacks of Barite Required For Weight-up, sx




Volume Gain From Slug, bbl




Triplex Pump Output (volume), bbl/stroke



Pump Output, bbl/min




New Pump Pressure With New Pump Strokes, psi




Boyle’s Law - Gas Pressure and Volume Relationship



Mud Increment for Volumetric Method (MI), bbl




Lube Increment for Lubricate and Bleed Method (LI), bbl





Bottle Capacity Required, gal




Volume of Usable Fluid, gal