**D exponent Method – **Drilling Calculator

**D exponent** is an extrapolation of drilling parameters to get a trend while drilling into over-pressured zones. Usually, mud logger will correct all data, calculate d-exponent and plot the d exponent valve on the curve. The d-exponent can be utilized to detect transition from normal pressure regime to abnormal formation pressure. While drilling, if the change of trend is observed, rig supervisors must be cautious about this situation because this is one of the possible well control indications.

The “d” exponent method has been described from the equation below:

**Formula d = log (R ÷ 60N) ÷ log (12W ÷ 1000D)**

**Where; **

R = penetration rate in feet per hour

d = exponent in drilling equation, dimensionless

N = rotary speed in rpm

W = weight on bit in kilo pound

D = bit size in inch

**IMPORTANT Note: this equation is is valid for constant drilling fluid weight.**

### Example:

### Determine the d-exponent from following information.

Rate of penetration (R) = 90 ft/hr

Rotary drilling speed (N) = 110 rpm

Weight on bit (W) = 20 klb

Bit Diameter (D) = 8.5 in.

**Solution: **d = log [90÷ (60 x 110)] ÷ log [(12 x 20) ÷ (1000 x 8.5)] d = 1.20

#### NOW YOU PEOPLE MAY USE THIS CALCULATOR FOR YOUR PURPOSE

## d exponent Calculator

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