Anisotropic seismic reservoir characterization: Practical applications

Abstract

Seismic AVO (amplitude variation with offset) analysis is an important element in reservoir characterization. AVO information carries important information regarding lithology and fluid content, and AVO inversion and AVO projections are widely used in industry. However, traditional AVO studies ignore the impact of anisotropy contrasts on the AVO response, making it difficult to use far offset data effectively in some cases. This is due to the fact that nonnegligible differences in the anisotropy parameters between the various lithologies make the seismic data far offset response completely different from the isotropic response. In this case, it is very difficult to invert for density consistent with well-log data and AVO projections including far offset data may lead to unexpected results. Anisotropic AVO studies are conducted using data from an offshore Western Australia filed. A good understanding of anisotropy parameters makes it possible to use far offset data effectively through AVO inversion and AVO projections. Bayesian linearized AVO inversion using pseudoisotropic elastic properties and the extended elastic impedance (EEI) inversion based on anisotropic three-term (3T) AVO projections will be demonstrated. Results show the benefit of including far offset data for lithofacies identification; utilization of inverted density or curvature term gave better results than those without these information.