Interpretive advantages of 90°-phase wavelets:: Part 2 -: Seismic applications

We examine field seismic data to test the benefits of 90 degrees-phase wavelets in thin-bed interpretation that are predicted by seismic modeling in part 1 of this paper. In an interbedded sandstone-shale Miocene succession in the Gulf of Mexico basin, a 90 degrees-phase shift of nearly zero-phase seismic data significantly improves lithologic and stratigraphic interpretation. A match between seismic and acoustic impedance (AI) profiles results in a better tie between seismic amplitude traces and lithology-indicative logs. Better geometric imaging of AI units that does not use dual-polarity seismic events results in easier and more accurate reservoir delineation. Less amplitude distortion and the stratigraphy-independent nature of thin-bed interference significantly improves stratigraphic resolution and seismic stratigraphic profiling. For a Ricker-like wavelet having small side lobes, stratigraphic resolution of 90 degrees-phase data is considerably higher than that of zero-phase data. In this specific case, stratigraphic resolution of 90-phase data is lambda/4 (lambda =wavelength), compared with lambda/2 for its zero-phase counterpart. Stratal slices made from 90 degrees-phase data show geomorphologic patterns of depositional systems with less noise and fewer interference fingerprints. A Permian Basin field provides a real-world example of porous zones in thin, high-frequency carbonate sequences that are better visualized with 90-phase seismic data than with zero-phase data.