Joint Imaging of Primary and Multiple Reflections for Rvsp: Real Data Example

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 (upgoing) and multiple (downgoing) reflections because the drill path generates primary and multiple reflections with similar moveout and the same polarity. In this paper, I present a new migration method using both primary and free-surface reflections to image the reflectors below the drill bit. 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. I test the sensitivity of joint autocorrelogram migration to velocity and statics shift errors using synthetic data for a 5-layer synthetic model and a source in a horizontal well. Test results on synthetic data show that our 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 better ”look-ahead” image compared with primary autocorrelogram images.