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

1.4 Specific Gravity

Specific gravity using mud weight, ppg

SG = mud weight, ppg ÷ 8.33

Example: 15.0 ppg fluid
SG = 15.0 ppg ÷ 8.33
SG = 1.8

Specific gravity using pressure gradient, psi/ft

SG = pressure gradient, psi/ft ÷ 0.433

Example: pressure gradient = 0.624 psi/ft
SG = 0.624 psi/ft ÷ 0.433
SG = 1.44

Specific gravity using mud weight, lb/ft3

SG = mud weight, lb/ft3 ÷ 62.4

Example: mud weight = 120 lb/ft3
SG = 120 lb/ft3 ÷ 62.4
SG = 1.92

Convert specific gravity to mud weight, ppg

mud weight, ppg = specific gravity × 8.33

Example: specific gravity = 1.80
mud weight, ppg = 1.80 × 8.33
mud weight = 15.0 ppg

Convert specific gravity to pressure gradient, psi/ft

psi/ft = specific gravity × 0.433

Example: specific gravity = 1.44
psi/ft = 1.44 × 0.433
psi/ft = 0.624

Convert specific gravity to mud weight, lb/ft3

lb/ft3 = specific gravity × 62.4

Example: specific gravity = 1.92
lb/ft3 = 1.92 × 62.4
lb/ft3 = 120