Fluid Identification of Caved Carbonate Reservoir Based on Prestack Inversion

For three-parameter AVO inversion it may be important to use large incidence angles close to the critical angle, where spherical wave effects become important. For the amplitude of a spherical wave reflected from a fluid-fluid interface, Brekhovskikh and Godin (1997) developed an analytical approximation, which is accurate at all angles. For the amplitude of a spherical wave reflected from a solid/solid interface, we propose a formula which combines this analytical approximation with a standard linearised plane-wave AVO equation of Thomsen (1990). The proposed approximation shows reasonable agreement with numerical simulations for a range of frequencies. Using this solution, we constructed a two-layer three-parameter least-squares inversion algorithm. Application of this algorithm to synthetic data for a single interface shows promising results.