Interferometric correlogram-space analysis

Abstract

Seismic interferometry is a method of obtaining a virtual shot gather from a collection of physical shot gathers. The set of traces corresponding to two common receiver gathers from many physical shots is used to synthesize a virtual shot located at one of the receivers and a virtual receiver at the other. An estimate of a Green's function between these two receivers is obtained by first cross-correlating corresponding pairs of traces from each of the shots and then stacking the resulting cross-correlograms. In this paper, we study the structure of cross-correlograms obtained from a VSP acquisition geometry using surface sources and down-hole receivers. The model is purely acoustic and contains flat or dipping layers and/or point inclusions that act as di ffractors. Results of a semblance-based moveout scan of the cross-correlograms are used to identify the potential geometry of the reflectors. This new information allows improvements in the quality of the trace at the virtual receiver by either rejecting those moveouts or enhancing them before the stack is performed.