Energy balance of a drill-bit seismic source, part 1: Rotary energy and radiation properties

An issue in seismic-while-drilling (SWD) technology is to characterize the dynamic and radiation properties of the drill-bit source working under different operational conditions. The energy requirements, power losses, local crack effects, radiation, and near-field effects associated with rotary drilling are analyzed to quantify the waves produced by an SWD vertical force acting in bounded and unbounded media. Results are expressed in terms of a complex integrated impedance and the equations for rotary drilling. The calculations — extended to the waves in the drill string — are used in part 2 of this paper (Poletto, 2005, this issue) to quantify the performance of actual drill-bit sources.