Spectral decomposition and AVO-based Amplitude decomposition: A comparative study and application

Scismic data are very rich in information about rocks and fluids saturating their pores. As a result of their unique mineralogical compositions and fluid properties that discriminate them from their surroundings, hydrocarbon-saturated formations have proved to have their own characteristic frequencies at which they preferentially show up in seismic data. This has provided considerable support to interpretations of spectral decomposition methods and led to great success in detecting hydrocarbons in many basins of the world. Early works in Amplitude Variation with Offset (AVO) proved that geological formations containing hydrocarbons have also their own amplitude expressions with which they respond to seismic excitations. These seismic responses are controlled by their lithology type, pore space, and fluid content. This in turn has supported interpretations of strong amplitude anomalies observed at top of hydrocarbon-saturated reservoirs and led to the success of AVO in many areas around the globe. In this study, AVO-based amplitude decomposition is introduced as a new way to look at seismic amplitudes from AVO. The amplitude decomposition is compared with the decomposition of frequencies concept and methods. Both decompositions are examined over a gas-saturated sandstone from Alberta, Canada. Results demonstrated that decomposing both amplitude and frequency of seismic data into their constituent components can help detect more reliable expressions from fluid-saturated formations. The study shows that the Intercept and Gradient can be used to reproduce partial stacks and also gathers and suggests that the two attributes can be thought of as alternative products to partial stacks.