VSP While Drilling For Geosteering Applications

Summary Drilling-related problems cost the oil industry large amounts of money. Drill-bit seismic data can be used to detect drilling hazzards in sections drilled with rollercone bits and at relatively small water depths. An interesting alternative is VSP data acquired while drilling. Using a drill string equipped with receivers and a repeatable surface source, zero-offset and offset VSP data can be used to put the drill bit on the surface seismic section, and to compute the distance to reflectors ahead of the bit. Walkaway data have a potential both for structural imaging and for detection of overpressured sediments ahead of the bit. We discuss some potential application of VSP while drilling data. The applications are illustrated with simple numerical examples.