Prediction ahead of the bit by using drill-bit pilot signals and reverse vertical seismic profiling(RVSP0

摘要

Surface drillstring axial pilot signals are used to pre- dict reflections ahead of the drill bit. We show that part of the drill-bit signal propagates downward in the forma- tion, reflects upward by a seismic interface, and is then transmitted to the drill string and the surface pilot sen- sors. These reflections are interpreted in drill-bit pilot signals by means of a numerical model of the drillstring coupled to the formation at the bit-rock contact. The result is an additional, low-cost, reverse VSP(RVSP) in the zero-offset approximation.