Prediction ahead of the bit by using drill‐bit pilot signals and reverse vertical seismic profiling (RVSP)

Abstract

Surface drillstring axial pilot signals are used to predict reflections ahead of the drill bit. We show that part of the drill‐bit signal propagates downward in the formation, reflects upward by a seismic interface, and is then transmitted to the drillstring and the surface pilot sensors. 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. These while‐drilling results are integrated with conventional drill‐bit RVSP measurements and compared with other geophysical and well results.