Extended Elastic Impedance and Its Relation to AVO Crossplotting and Vp/Vs

Extended Elastic Impedance (EEI) has proved to be a highly convenient framework for seismic AVO studies. EEI logs can be directly related to the petrophysical properties of interest and seismic EEI reflectivity volumes can be obtained directly from the prestack data via linear projection in sin2theta. The directness of the EEI method is one of its strengths, making it unnecessary to perform intermediate steps such as examining conventional AVO attributes (e.g., intercepts and gradients). Consequently it can be difficult for those more familiar with the conventional AVO analysis to understand the parallels between the two methods. Once these parallels are understood we show how they can be exploited to provide new AVO attributes for background Vs/Vp ratio and AVO class based on the EEI seismic projection method.