Reduction of energy losses: a key to improved rock drilling?

The viscous power losses of a rotary-vibratory drilling system are estimated in this study. Rotational and pure vibratory losses are considered separately. This analysis indicates that considerable power is dissipated into the drilling fluid. Pure vibratory power losses of over 3,728 W (5 hp) are expected at frequencies equal to the first mode maximum response point for a drill column that is 152.4 m (500 ft) long. This is a frequency slightly less than the first undamped natural frequency of the drill column.

For the same column, viscous rotational power losses of over 74.56 W ( 0.1 hp) are expected at rotational speeds of 10.47 rad/s (100 rpm). Rotational and vibratory losses increase with increases in the length of the column, fluid viscosity, and operating frequency.