Well Control Formulas
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 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 Pip e Displacement Disp lacement , 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, 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
