Drill-Bit Seismic While Drilling by Downhole Wired Pipe Telemetry

Drill-bit seismic while drilling provides reverse VSP, makes it possible to predict the formation changes ahead of the bit, and to image 2D and 3D structures without interference with drilling activity. When the pilot signals used for crosscorrelation with the seismic signals are recorded at the surface, an issue in the application of this methodology may be the loss of the drill-bit-vibration signal during its propagation from the bottom to the surface through the drill string. With PDC bits, as well as during drilling by sliding condition without pipe rotation, and in highly deviated or horizontal wells, the pilot signal recorded at the surface may be weak and consequently the SWD results poor. A solution is to use near-bit downhole tools to get good-quality measurements of the pilot signal. Literature reports examples of SWD with the use of downhole memory systems, from which the data are downloaded after the bit retrieval at the surface. In this paper we present the new results obtained using a drill pipe equipped with a wireline communication system from bottom hole to the surface. The results demonstrate the applicability of this method providing good-quality RVSP data, in terms of S/N and frequency content.