Interferometric imaging of a salt flank using walkaway VSP data

Abstract

VSP has long been a tool for investigating the location of salt flanks. Traditionally a salt proximity survey has been used to estimate the location of salt boundaries relative to a wellbore; however, this technique depends on accurate knowledge of the shape of the salt and the local sediment velocities. In addition, this method does not work well with complicated 3D salt structure. Beyond the traditional salt proximity survey, many researchers have developed various methods and strategies for improving the locating and/or imaging of salt flanks (O'Brien et al., 2002; Brandsberg-Dahl et al., 2003; Zhao et al., 2006). With these methods, the quality of the resultant image depends on a prior knowledge of the (possibly anisotropic) overburden velocity field for very long offsets and also is concerned with multi-pathing through salt invalidating a 2D assumption. In looking for a simpler approach to this problem, a single-well imaging concept may be attractive. Using downhole sources and receivers, it is possi...