Joint migration of primary and multiple reflections in RVSP data

Seismic imaging for RVSP or drill-bit data recorded for deviated or horizontal wells is a challenging task. Conventional filtering methods such as dip-filtering will fail to separate the primary and multiple (or ghost) reflections because the drill path generates primary and multiple reflections with similar moveout and the same polarity. In this paper, I present a migration method that uses both primary and free-surface related multiple reflections to image the reflectors below the source. The merit of this method is that it does not require the separation of the primary and multiple reflections. This joint imaging is implemented using the autocorrelogram imaging condition because it can produce a subsurface image without knowing the pilot signal. Additionally, it is also capable of suppressing the static errors at the source or/and receiver positions. Test results on synthetic data and field data show that the joint imaging method is capable of suppressing spurious interferences and also performs robustly when seismic data are distorted by statics shifts at the source and receiver locations. In the field data example, the joint imaging approach produces a better ”look-ahead” image compared with the primary-reflection autocorrelogram images.