Well Control Euqations Drilling Formulas PDF

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Well Control Equations 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)

Bottom Hole Pressure (BHP) – psi Under static condition Bottom Hole Pressure (BHP) = Hydrostatic Pressure (HP) + Surface Pressure (SP)

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

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Note: Frictional pressure acts opposite way of flow direction.

Formation Pressure (FP) – psi 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)

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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, minutes

Capacity Factor (CF), bbl/ft

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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

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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

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Bottle Capacity Required, gal

Volume of Usable Fluid, gal

Snubbing force for snubbing operation Snubbing Force (SF) = Force at wellhead (Fp) + Frictional Force – Buoyed weight of string (Wb) Total force to overcome pressure at wellbore is a summation of force at wellhead and frictional force minus buoyed weight of string. Force at wellhead (Fp) can be determined by one of following equations.

OR

Buoyed Weight of Open Ended Tubular (Wb),lb For this formula, you just use the buoyancy factor and multiply it with weight of pipe in the air.

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Buoyed Weight of Closed Ended Tubular without fluid in the pipe (Wb),lb This formula below is different from the 1st formula because it is used for the closed ended pipe. Weight in the air will be subtracted with buoyancy weight of pipe ran in hole. Note: 24.5 is conversion factor to make the unit in gallon.

Buoyed Weight of Closed Ended Tubular after filling the pipe (Wb),lb -> in this case, there is different fluid weight in pipe and annular

The Balance Point for closed ended and unfilled pipe is the point where the weight of pipe in the fluid equates to force created by wellhead pressure.

Note:

OR

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This is the second case for balance point calculation. The Balance Point for closed ended pipe and the pipe is filled with fluid.

Maximum Down Force on Jacks

Effective Area of Snubbing Jacks, square inch

Hydraulic Pressure to Snub, psi

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