Convert specific gravity to mud weight (ppg and lb/ft3) and pressure gradient (psi/ft)

Referring to the previous post, Calculate Specific Gravity (SG) in oilfield unit , you get specific gravity (SG) from mud weight (ppg and lb/ft3) and pressure gradient (psi/ft) but you may need to reverse calculation from specific gravity (SG) to mud weight or pressure gradient (psi/ft). So you will learn how to how to convert specific gravity to mud weight (ppg and lb/ft3) and pressure gradient (psi/ft) by using simple formulas as follows:

1. Convert specific gravity to mud weight in pounds per gallon (ppg)


Convert specific gravity formula: Mud weight in ppg = specific gravity (SG) x 8.33

Example: specific gravity = 1.50
mud wt, ppg = 1.50 x 8.33
mud wt = 12.5 ppg

2. Convert specific gravity to mud weight in lb/ft3


Convert specific gravity formula: Mud weight in lb/ft3 = specific gravity x 62.4

Example: specific gravity = 1.50
Mud weight in lb/ft3 = 1.50 x 62.4 lb/ft3
Mud weight in lb/ft3 = 93.6 lb/ft3

3. Convert specific gravity to pressure gradient in psi/ft


Convert specific gravity formula: Pressure gradient in psi/ft = specific gravity (SG) x 0.433

Example: specific gravity = 1.5
Pressure gradient in psi/ft  = 1.5 x 0.433
Pressure gradient in psi/ft = 0.650 psi/ft

Please also find the Excel sheet regarding how to convert specific gravity (SG)

Ref books: Lapeyrouse, N.J., 2002. Formulas and calculations for drilling, production and workover, Boston: Gulf Professional publishing.

Bourgoyne, A.J.T., Chenevert , M.E. & Millheim, K.K., 1986. SPE Textbook Series, Volume 2: Applied Drilling Engineering, Society of Petroleum Engineers.

Mitchell, R.F., Miska, S. & Aadny, B.S., 2011. Fundamentals of drilling engineering, Richardson, TX: Society of Petroleum Engineers.

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