The drilling exponent (d), the exponent corrected for [[mud]] density (dc), and the exponent corrected for mud density and [[bit]] wear (dcs) are used to detect undercompacted shaly formations and associated high-pressure zones.

(1)	d	=	uncorrected drilling exponent

{{ :terms:p31f1.gif }}


when:\\
R = drilling rate (ft/hr)\\
K = rock drillability (~ 1 for shales)\\
N = rotary speed (rpm)\\
W = weight on bit (lb)\\
D = bit diameter (in.)

(2)	dc	=	 drilling exponent corrected for mud density

{{ :terms:p31f2.gif }}

where:\\
d<sub>1</sub> = equivalent mud density of normal pore pressure gradient\\
d<sub>2</sub> = equivalent mud density of actual pore pressure gradient

(3)	dcs	=	drilling exponent corrected for nmud density and bit wear.

Same as "dc" except that instead of R (drilling rate at time t) the drilling rate R<sub>o</sub> (corrected for bit wear) is used.