Abstract

CARA, LUIS  and  BOSCH, MIGUEL. Inversion of variable offset seismic amplitudes using Monte Carlo techniques. Rev. Fac. Ing. UCV [online]. 2007, vol.22, n.4, pp.69-75. ISSN 0798-4065.

We describe a method for the estimation of the elastic parameters (slowness P, slowness S and mass density) in a stratified medium by inverting variable offset seismic amplitudes with Monte Carlo techniques. The observed data are the seismic amplitudes in time for different source-receiver offsets. For the simulation of the seismic data we convolve a source waveletwith the reflectivity series obtained with ray tracing and the exact solution of the Zoeppritz equations; we also include in the inversion scheme prior information of the statistics of the elastic medium parameters. We invert the seismic data using a sampling Markov Chain Monte Carlo technique that generates a long chain of the stratified model realizations, all probable in terms of the geophysical and prior statistical information, and convergent to the posterior probability density. In this technique we combine the Gibbs and the Metropolis algorithms. We validate the method with numerical tests, using elastic models simulated on the basis of the statistics of real well-logged data, including mean property values, standard deviations and correlation across the elastic properties. With this method we produce a complete description of the uncertainties of the model parameters.

Keywords : Elastic inversion; Seismic data; Variable offset; Statistics; Seismic velocity; Density.