D-exponent method

Jordan and Shirley (1966) approximated a solution to Bingham's equation for a single unknown, the d-exponent, by eliminating variable K (assuming it to be constant as in a uniform shale). They also inserted constants in the equation to in-corporate American oilfield units of measurement.
        (2) where: R = penetration rate, ft/hr N = rotary speed, rpm
W = weight on bit, lb
D = diameter of bit, inches

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