You may need to calculate specific gravity from different density or pressure gradient units. This post demonstrates you about specific gravity calculation and specific gravity formulas frequently used in oilfield business.
1. Calculate specific gravity using mud weight in PPG
Specific gravity formula : SG = mud weight in ppg ÷ 8.33
Example: Fluid = 13.0 ppg
SG = 13.0 ppg ÷ 8.33
SG = 1.56
2. Calculate specific gravity using pressure gradient in psi/ft
Specific gravity formula : SG = pressure gradient in psi/ft ÷ 0.433
Example: pressure gradient = 0.50 psi/ft
SG = 0.50 psi/ft ÷ 0.433
SG = 1.15
3. Calculate specific gravity using mud weight in lb/ft3
Specific gravity formula : SG = mud weight in lb/ft3 ÷ 62.4
Example: Mud weight = 90 lb/ft3
SG = 90 lb/ft3÷ 62.4
SG = 1.44
Please also find the Excel Sheet: Specific Gravity Calculation Sheet
Ref book: Formulas and Calculations for drill, production and workover by Norton J. Lapeyrouse
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