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Spectral decomposition and amplitude decomposition to detect hydrocarbons: Comparison and application


Hydrocarbon-saturated hydrocarbon formations are proved to have their own characteristic frequency at which they preferentially show up in seismic data. This is because of their unique solid and fluid properties discriminating them from their surroundings. This has provided great support to interpretation of spectral decomposition methods and led to great success in detecting hydrocarbons in different parts of the world. Likewise, early works in Amplitude Variation with Offset (AVO) proved that these geological formations have their own amplitude with which they respond to seismic excitation; these seismic responses are controlled by their lithology type, pore space, and fluid content. This in turn has provided supportive interpretation to strong amplitude anomalies observed at top of hydrocarbon-saturated reservoirs and led to the success of AVO in worldwide basins. In this study spectral decomposition approaches are used to decompose the spectra of seismic traces into individual frequencies; whereas, AVO equations are invoked to decompose seismic amplitude in stack sections into its constituent components recorded at different offsets. From the angle gathers or from intercept and gradient amplitude, sections are produced at different angles. Results demonstrated that decomposing amplitude and frequency of seismic data into their constituent components can help in the discrimination of different lithologies and fluid types. Furthermore, the decomposition showed that if the intercept and gradient are properly scaled, they can help predict amplitude responses at offsets where the data is not of good presence (very near offset) or poor quality (very-far offsets) or in case only angle-stacks are available.