Target-oriented interferometry – Imaging with internal multiples from subsalt VSP data

Seismic interferometry has become a technology of growing interest for imaging from borehole seismic data. We demonstrate that interferometry of internal multiples can be used to image targets above a borehole receiver array. We use an interferometry technique that targets the reconstruction of specific primary reflections from multiply reflected waves. In this target-oriented interferometry approach, we rely on shot-domain wavenumber separation to select the directions of waves arriving at a given receiver. We provide a description of this method along with two conceptual applications, and compare it to other approaches to seismic interferometry. Using a numerical walkaway VSP experiment recorded by a subsalt borehole receiver array in the Sigsbee salt model, we use the interference of internal multiples to image the salt structure from below. In this numerical example, the interferometric image that targets internal multiples reconstructs the bottom and top salt reflectors above the receiver array, as well as subsalt sediment structure between the array and the salt.