Resolving Small-Scale Heterogeneities with Dense Non-Hyperbolic Seismic Tomography

The main goal of 3D CRS (Common Reflection Surface) stack is the improvement of the image with respect to NMO/DMO processing route. However, also the set of parameters defining the CRS stacking surface are a precious source of information on subsurface properties. In 3D, the CRS second order traveltime trajectory is defined by eight parameters, that can be divided into three groups: KN, KNIP (each one is a 2x2 matrix with three independent parameters) and angles (azimuth and emergence). KN are mainly related to the subsurface reflectors geometry, KNIP to velocity; angles describe the normal ray emergence. The NIP-wave tomography method described in Duvenek, 2004 uses KNIP and angles to reconstruct a smooth velocity model in depth, suited for a PSDM and/or for petrophysical studies . In this paper, the first application to a real 3D data-set (from West Africa) of the method is presented. The comparison among common image gathers obtained from a reference velocity model and the ones coming out using NIP-wave tomography shows that a reliable velocity model can be reconstructed in a very cost-effective way directly from CRS processing.