Abstract:

Based on anisotropic theory, the authors considered fractured reservoir with the horizontal axis of symmetry and high-angle equivalent of HTI media. First of all, by analysis of P wave reflection coefficient formula, it studied the characterization about amplitude versus offset and azimuth, and explored the pre-stack estimation method for anisotropic elastic and anisotropic parameters. Secondly, in order to estimate the elastic parameters of the medium: longitudinal wave impedance, I_P, shear wave impedance, I_S, and anisotropic gradient Γ better, the study made a simplification of the reflection coefficient, and analyzed the accuracy of the simplified formula. Finally, it selected 2D overthrust model to test azimuth AVO prestack inversion method. The authors used the convolution formula to produce synthetic seismic gathers in different directions, added random noise to synthetic seismic gather (signal to noise ratio is 2∶1), and applied it to the azimuth AVO pre-stack inversion algorithm test. The results showed that the value which estimated by using the azimuth AVO pre-stack inversion method, longitudinal wave impedance, shear wave impedance and anisotropic gradient, was consistent with the true value of the overthrust model basically, and the estimation value could more accurately describe the stratigraphic features of original model, and it verified the applicability accuracy of the azimuth AVO pre-stack inversion algorithm.

Key words: fracture, anisotropy, azimuth angle dataset, AVOZ, overthrust model, pre-stack inversion