Seismic sedimentology is a very effective tool for mapping high-frequency sequence and depositional systems, and plays an important role in the exploration of thin sandstone reservoirs.

Five types of depositional systems were identified in the study area (Gaoyou depression, Subei Basin, China): fan delta and nearshore subaqueous fan in the south steep slope belt, delta in the north gentle slope belt, and turbidite fan and lacustine in the deep sag zone. Almost 80 wells were drilled in both the steep and gentle slope belts, but only two exploration wells were drilled in the deep sag zone, and the wire-line log data from these two wells proved the existence of oil-bearing sandstone reservoir. Also, here is about 240 km² high-quality 3D seismic data in the deep sag zone where faults are not developed. Guided by third-order sequence-stratigraphic correlations from seismic and wire-line log data, in this study, stratal slices were prepared from a three-dimensional seismic volume to reveal sand-body distribution in the deep sag zone and to map the associated depositional systems distributions in slopes of the depression. Basic steps include well-to-seismic tie, wavelet-phase adjustment, picking of geologic-time parallel seismic events, seismic resolution analysis, petrophysical analysis, selection of seismic attributes, stratal slicing, seismic depositional faces analysis, and applications to exploration and development.