Equivalent offset migration for vertical receiver arrays

John C. Bancroft and Yong Xu

ABSTRACT

The equivalent offset method of prestack migration is extended to include data that is acquired with vertical receiver arrays. Summing of input data directly to the vertical-array common scatterpoint gather (VCSP) is maintained with a single time shift (static) for each input trace.

Seismic reflection energy is usually recorded with horizontal arrays of sources and receiververtical seismic profile (VSP) where the receivers are placed at various depths in a borehole (see Wuenschel 1976 for an early review). More recently, vertical arrays of hypdrophones have been used in marine acquisition to acquire high quality seismic data (Hunter and Pullan 1990, Krail 1994). The large elevation difference between the sources and receivers requires special attention. In surface seismic, small elevation changes are compensated by vertical time shifts of the seismic trace. Large elevation changes may be addressed by some form of wave-equation datuming, or by algorithms that migrate from surface. Kirchhoff migrations are particularly adaptable for this purpose as the travel times for the source and receiver ray paths may be computed to the actual surface locations.

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