Use of dual waves for the elimination of reverberations in drill strings

Drill-string waves can be used to transmit acoustic and seismic information from the bottom hole to the surface. Because the drill string is a heterogeneous assembly, the investigated signal is disturbed by reverberations. Removal of the reverberations generated in the drill string is obtained by measuring acceleration and strain, which have opposite reflection coefficients and are used as dual waves. Addition of the dual waves makes it possible to remove part of the drill-string reflections and improve the signal-to-noise ratio. (C) 2002 Acoustical Society of America.