VSP imaging using all multiples: Full wavefield migration approach

Abstract

One of the values of VSP (Vertical Seismic Profiling) data is its potential to provide high-resolution details for the reservoir area. However, VSP imaging is challenging because of the poor illumination from the primary-only data. In the past, some approaches were suggested to enhance the illumination away from the well trajectory using the downgoing surface multiples. Here, we are proposing a full wavefield migration (FWM) approach to image the VSP data. Full wavefield migration aims at estimating the true angle-dependent reflectivity of the subsurface utilizing the primaries, surface multiples and internal multiples. The reflectivity estimation process is performed as a constrained least-squares inversion scheme, which is recursive in depth and incorporates the nonlinear transmission effect at each depth level. During the inversion scheme in FWM the upand downgoing wavefields is updated at each depth level. The use of the full wavefield in imaging the VSP data could further enhance illumination as well as the image reliability. In this paper we propose this method and illustrate its potential via some simple synthetic VSP data examples.