1. Basic Formulas

Table of Content

  1. Pressure Gradient
  2. Hydrostatic Pressure
  3. Converting Pressure into Mud Weight
  4. Specific Gravity
  5. Equivalent Circulation Density
  6. Maximum Allowable Mud Weight
  7. Pump Output
  8. Annular Velocity
  9. Capacity Formulas
  10. Control Drilling
  11. Buoyancy Factor
  12. Hydrostatic Pressure Decrease POOH
  13. Loss of Overbalance Due to Falling Mud Level
  14. Formation Temperature
  15. Hydraulic Horsepower
  16. Drill Pipe, Drill Collar Calculation
  17. Pump Pressure, Pump Strokes
  18. Cost Per Foot
  19. Temperature Conversion Formulas

1.1 Pressure Gradient

Pressure gradient, psi/ft, using mud weight, ppg

psi/ft = mud weight, ppg × 0.052

Example: 12.0 ppg fluid
psi/ft = 12.0 ppg × 0.052
psi/ft = 0.624

Pressure gradient, psi/ft, using mud weight, lb/ft3

psi/ft = mud weight, lb/ft3 × 0.006944

Example: 100 lb/ft3 fluid
psi/ft = 100 lb/ft3 × 0.006944
psi/ft = 0.6944

OR

psi/ft = mud weight, lb/ft3 ÷ 144

Example: 100 lb/ft3 fluid
psi/ft = 100 lb/ft3 ÷ 144
psi/ft = 0.6944

Pressure gradient, psi/ft, using mud weight, specific gravity (SG)

psi/ft = mud weight, SG × 0.433

Example: 1.0 SG fluid
psi/ft = 1.0 SG × 0.433
psi/ft = 0.433

Convert pressure gradient, psi/ft, to mud weight, ppg

ppg = pressure gradient, psi/ft ÷ 0.052

Example: 0.4992 psi/ft
ppg = 0.4992 psi/ft ÷ 0.052
ppg = 9.6

Convert pressure gradient, psi/ft, to mud weight, lb/ft3

lb/ft3 = pressure gradient, psi/ft ÷ 0.00694

Example: 0.6944 psi/ft
lb/ft3 = 0.6944 psi/ft ÷ 0.006944
lb/ft3 = 100

Convert pressure gradient, psi/ft, to mud weight, SG

SG = pressure gradient, psi/ft ÷ 0.433

Example: 0.433 psi/ft
SG = 0.433 psi/ft ÷ 0.433
SG = 1.0

⬆ Table of Content