Reverse Time Migration in Determining AVA Function

Abstract

One of the main objectives of seismic imaging is to generate maps of the Earth's reflectivity function, which can be inferred about the physical properties of rocks in their locations. The amount of energy that is reflected on an interface depends on the incident’s wave field angle, called AVA (Amplitude vs. Angle) function. In the methodology proposed in this work, the seismic data recorded on the surface is extrapolated to a region just above the datum of the exploratory interest. This redatum is achieved by a generalization of the concept of reverse time migration in which common focus point gathers are extrapolated. The synthesis’ operators and extrapolations of the direct and reverse fields are made for solutions of acoustic complete wave equation by finite differences method. It was proposed a new imaging condition based on the sum of modules of amplitudes around the wavelet of maximum amplitude. As a result of this methodology, we have obtained graphs of reflectivity, i.e., amplitude based on incidence’s angle, corrected from effects of propagation (specifically, spherical divergence, transmission and conversion).