Estimation of pore pressure by AVO inversion

Seismic velocities, anisotropy coefficients and rock densities are estimated from the variation of the reflection coefficient versus incidence angle. The data (CDP gathers) are processed to obtain true amplitudes at each receiver position, and the AVO inversion is performed by a leastsquares method using the exact reflection coefficient for transversely isotropic and viscoelastic media (the algorithm assumes that P- and S- quality factors are known). The inversion can be performed for the upper and lower properties at once, or be a layer stripping technique. We suggest a method for reducing the number of parameters and perform a sensitivity analysis to determine the reliability of the inversion. An application to real data is shown.