UNRAVEL THE OLIGOCENE-MIOCENE DEPOSITIONAL ARCHITECTURES TN THE NORTH MADURA PLATFORM USING SEISMIC STRATAL VOLUME

摘要

Various works on depositional setting and paleogeography of the Oligocene-Miocene sediments in East Java Basin have been done by previous authors using outcrop, well, and seismic data. The recent development in seismic technology has allow us to image the geomorphology or depositional features preserved in the stratigraphy record. An initiative has been taken to further understand the depositional architectures of the Oligocene-Miocene sediments in North Madura Platform using stratal volume method. Detail horizon interpretations were conducted in the Oligocene-Miocene interval using the new reprocessed 3D seismic data in the study area. These horizons, given the definition of discordant or concordant surfaces, have been cross-checked and refined in the first pass of stratal volume, where distinct breaks and vertical shifts were observed due to cycle skip in initial interpretation. The intention for stratal slicing was to pick a depositional surface (geologic-time surface) so that any seismic attribute extracted on the particular surface could represent a genetic paleo-depositional unit, which result is 3D spatial transform of seismic volume into a 3D chronostratigraphic chart or Wheeler volume; an extension of concept for chronostratigraphic sequence analysis. This transformation considered the effects of 3D structure, different sediment deposition rates, horizon dip, and unconformity. Five main intervals in the Oligocene-Miocene section were identified in this study. The stratal volume slice from these intervals able to show detailed geomorphic features such as fluvial channels and deltas. The interpretation of stratal slices was carried out to the five intervals by integrating all available geological and geophysical data, and using modern depositional and geomorphic models to guide the interpretation of depositional patterns in seismic-attribute slices.