Well Control Equations
By Drillingformulas.com © 2012
1|Page
Table of Contents Introduction ................................................................................................................................................................ 4 Well Control Quiz Kindle Book from Drillingformulas.com................................................................... 5 Pressure (P) – psi ..................................................................................................................................................... 6 Pressure Gradient (G) – psi/ft ............................................................................................................................ 6
Hydrostatic Pressure (HP) – psi......................................................................................................................... 6
Bottom Hole Pressure (BHP) – psi .................................................................................................................... 7 Under static condition........................................................................................................................................ 7
Under dynamic condition ................................................................................................................................. 7
Formation Pressure (FP) – psi ............................................................................................................................ 7
Equivalent Circulating Density (ECD) , ppg .................................................................................................. 7
Leak-off Test Equivalent Mud Weight (LOT), ppg ...................................................................................... 7 Maximum Initial Shut-In Casing Pressure (MISICP), psi ......................................................................... 8 Kill Mud Weight to Balance Formation (KMW), ppg ................................................................................. 8 Slow Circulation Rate (SCR), psi ........................................................................................................................ 8
Annulus Capacity Factor (ACF),bbl/ft ............................................................................................................. 8
Final Circulating Pressure (FCP), psi ............................................................................................................... 8 Surface To Bit Strokes, strokes ........................................................................................................................... 8 Circulating Time, minutes..................................................................................................................................... 9 Capacity Factor (CF), bbl/ft.................................................................................................................................. 9
Opened End Pipe Displacement, bbl/ft ........................................................................................................... 9
Closed end pipe displacement, bbl/ft .............................................................................................................. 9 Height of Influx, ft ..................................................................................................................................................... 9 Approximate gas migration rate, ft/hr............................................................................................................ 9
Sacks of Barite Required For Weight-up, sx .............................................................................................. 10
Volume Gain From Slug, bbl .............................................................................................................................. 10
Triplex Pump Output (volume), bbl/stroke .............................................................................................. 10
Pump Output, bbl/min ........................................................................................................................................ 10 New Pump Pressure With New Pump Strokes, psi ................................................................................. 10
Boyle’s Law – Gas Pressure and Volume Relationship.......................................................................... 10 Mud Increment for Volumetric Method (MI), bbl.................................................................................... 11 2|Page
Lube Increment for Lubricate and Bleed Method (LI), bbl ................................................................. 11 Bottle Capacity Required, gal ........................................................................................................................... 11
Volume of Usable Fluid, gal ............................................................................................................................... 11
Snubbing force for snubbing operation ....................................................................................................... 11
Buoyed Weight of Open Ended Tubular (Wb),lb ..................................................................................... 12 Buoyed Weight of Closed Ended Tubular without fluid in the pipe (Wb),lb ............................... 12
Buoyed Weight of Closed Ended Tubular after filling the pipe (Wb),lb -> in this case, there is different fluid weight in pipe and annular ............................................................................................. 12 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. ............................................................... 13 This is the second case for balance point calculation. The Balance Point for closed ended pipe and the pipe is filled with fluid. .............................................................................................. 13
Maximum Down Force on Jacks ...................................................................................................................... 13
3|Page
Introduction Well control is one of the important subjects that personnel in drilling should know. Because of importance of well control, drillingformulas.com creates this ebook “Well Control Equations” to help people solve problems in well control easily. We wish you would have advantageous from our ebook.
4|Page
Well Control Quiz Kindle Book from Drillingformulas.com
Well Control Quiz Book: Basic Concept of Well Control
Well Control Quiz Book: Basic Pressure In Well Control
Well Control Quiz Book: Kick Detection (Warning Sign) and Shut in
Well Control Quiz Book: Basic Well Control Calculations
Well Control Quiz Book: Well Control Method
Well Control Quiz Book: Tricky Questions and Well Control Equipment
5|Page
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)
6|Page
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) 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)
7|Page
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
8|Page
Circulating Time, minutes
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
9|Page
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
10 | P a g e
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
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.
11 | P a g e
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.
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
12 | P a g e
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
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
13 | P a g e
