Horizon slices of bandwidth-extended seismic data: optimizing thin bed interpretation from spectral decomposition

Abstract

Fourth-order sequences in the northern central Miocene Gulf of Mexico are typically at or below seismic resolution and embedded in deformed strata with lateral thickness variations, making it difficult to image the corresponding paleo-depositional surfaces. Stratal or proportional slicing, involving proportionally slicing between two bounding reference horizons, can overcome these difficulties. However, if the target horizon can be readily interpreted, its horizon slice can provide the most accurate image. In this study, we first improved the resolution of the seismic data from the northern central Gulf of Mexico by bandwidth extension. Then, we autotracked a Miocene fourth-order sequence (M4) through the 50-Hz isofrequency volume obtained by the generalized spectral decomposition of the bandwidth-exteneded data. The horizon slice along M4 through the bandwidth-extended data provides a better image for incised-fluvial valleys and distributary channels compared with the stratal slice of the original data reported by earlier work. The corendered image of the variance and amplitude horizon slices further highlights the depositional features of M4. The horizon slice of M4 through the acoustic impedance volume, computed from inversion, shows that the incised-fluvial-valley fill is characterized by low impedance, suggesting good reservoir quality and that the distributary-channel fill is characterized by low to moderate impedance, suggesting fair to good reservoir quality. The definition of the horizon slice includes both the slice along the target horizon and those parallel to the reference horizon. We propose to call the slice along the target horizon a “horizon slice” and to use the term “horizon-parallel slices” for any slices parallel to an interpreted horizon.