## D Exponent

The "d" exponent is derived from the general drilling equation: R — N = a (Wd - D)

where R = penetration rate d = exponent in general drilling equation, dimensionless

N = rotary speed, rpm a = a constant, dimensionless

"d" exponent equation: "d" = log (R - 60N) - log (12W - 1000D)

where d = d exponent, dimensionless R = penetration rate, ft/hr N = rotary speed, rpm W = weight on bit, 1,000 lb

Example: R = 30 ft/hr N = 120 rpm W = 35,000 lb D = 8.5 in.

Solution: d = log [30 - (60 x 120)] - log [(12 x 35) (1000 x 8.5)] d = log (30 - 7200) - log (420 - 8500) d = log 0.0042 - log 0.0494 d = — 2.377 - — 1.306 d = 1.82

Corrected "d" exponent:

The "d" exponent is influenced by mud weight variations, so modifications have to be made to correct for changes in mud weight:

where dc = corrected "d" exponent MWi = normal mud weight — 9.0 ppg MW2 = actual mud weight, ppg

+5 -2

### Responses

• Bonacata
What is corrected d exponent?
7 years ago
• mike
What is the d drilling exponent for?
2 years ago