How Seismic Anisotropy Improves the Reliability of Exploration DHI (AVO)

The role of seismic anisotropy has dramatically increased over the past two decades due to advances in parameter estimation. Many seismic processing and inversion methods take into account anisotropy. The inadequacy of isotropic velocity models has been emphasized in prestack depth migration, which is highly sensitive to the accuracy of the velocity field. At the same time this study demonstrates how amplitude variation with offset analyses are sensitive to anisotropy. The correct integration between different seismic processing steps that incorporate anisotropic models represents a valid support for the identification of explorative targets. A new integrated workflow has been developed in terms of anisotropic Thomsen parameters estimation, velocity and AVO models. We present interesting results of modelling for special cases of exploration interest, highlighting the anisotropic effects for gas sands encased in shales. The analysis has been also performed on a real dataset, confirming the relevance of models that account for the seismic anisotropy. This could explain the inability of elastic synthetics to match the prestack amplitudes of field data in some cases. This considerations lead to more realistic reservoir models and hopefully answer some of the unexplained pitfalls in AVO interpretation.