VSP imaging using free-surface multiples: A case study from the Gulf of Mexico

Abstract

Vertical seismic profile surveys (VSP) provide a unique opportunity to obtain high-quality seismic images of the subsurface. Placing receivers downhole mitigates many near-surface and overburden challenges associated with surface seismic imaging and results in improved image quality. Unfortunately, these benefits are restricted by the limited area illuminated by the primary P-wave reflection wavefield (typically a relatively narrow cone that underlies the geophone array). The free-surface multiple wavefield recorded in a VSP survey illuminates a significantly larger area, both vertically and laterally, and so can provide an expanded imaging capability (Jiang et al, 2005; Jiang et al, 2007; Lou et al 2007). Subsurface imaging using the multiple wavefield has been demonstrated and is commonly used for imaging deep-water 3D node surveys, which are typically acquired using a sparse distribution of receivers. However, no case studies have been published yet, which present a critical analysis of the images provided by this technology when applied to VSP surveys.