Investigation of the phase-components-amplitude-variation-with-angle.

What is it about?

Phase decomposition provides a new way of interpreting seismic data. Thin beds, subtle fluid responses and changes in lithology, otherwise hidden in seismic waveforms, can be amplified on specific phase components. Assuming zero-phase, normal polarity seismic data, seismically thin layers that are high impedance relative to overlying and underlying half-spaces are seen on the +90o phase component, while a relatively low-impedance thin layer will appear on the -90o phase component. In this study, we applied phase decomposition to pre-stack data across gas-bearing channel sand. The results showed that the amplitude-variation-with-angle is magnified on the -90o phase component allowing for a better delineation of the lateral extent of the reservoir when compared to a traditional AVO analysis. These results are corroborated by phase decomposition of fluid-substituted synthetic gathers which shows for the gas-case the same phase component relationships for near and far angle stacks as are observed on the real data. A comparison between the brine-case and the gas-case shows that no amplitude variation is observed on the -90o phase component for the brine-case, while for the gas-case, a strong amplitude-variation-with-angle response is observed for this same component.

Featured Image

Photo by Christopher Burns on Unsplash

Photo by Christopher Burns on Unsplash

Why is it important?

In a seismically thin layer scenario, where the tuning effect can either lead to a pitfall or masking the gas response, the phase component amplitude-variation-with-angle can be a used as a tool to de-risk prospects and as a direct hydrocarbon indicator. It also can provide a better volumetric estimate of hydrocarbon in place.

Perspectives