Frequency-dependent analysis of seismic data is gaining more and more attention in the seismic industry and academia, simply because it opens potential opportunities not only for indicating hydrocarbon anomalies, but also for estimating fluid mobility properties of underground reservoirs. While there has been significant advanced in the interpretation of seismic amplitude-versus-offset (AVO) anomalies, there is a lack of theory to guide the interpretation of frequency-dependent analysis. In this paper, based on White''s patchy saturation model, we analytically examined the characteristics of the reflection amplitude variations as a function of frequency at an interface between a non-dispersive medium and a dispersive medium. And then, numerical modeling based on Biot''s poroelastic wave theory was conducted on three selected reservoir models. The numerical modeling results confirmed our analytical analysis. Then, similar to AVO classification, the amplitude-versus-frequency curves are generally divided into three classes. This classification provides a guide to frequency-dependent interpretations.
The modern use of spectral decomposition has shown that reflection events are virtually always frequency dependent. Here we describe Wolf''s theory of a linear velocity transition zone (termed a Wolf ramp) and how it leads to frequency-dependent reflectivity.