Seismic geomorphology applied to sediment dispersal patterns and an analysis of the stages of channel-lobe systems in the Yinggehai Basin, northern South China Sea

Abstract

The lithostratigraphic plays in the Dongfang area of the Yinggehai Basin at the northern margin of the South China Sea consist of a Neogene multistage, thinly bedded, channel-lobe system. Integrating high-resolution 3D seismic, lithological and well log data shows that the channel-lobe system developed primarily in the lowstand system tract of the Huangliu Formation. We investigated the developmental stages of lobes based on the stacking relationships of seismic events, the degrees of channel downcutting in lobes, and the occurrences of sandstone facies observed in the stratal slices. The lobes finally identified 9 small-scale stages, which reveal a complete sedimentary cycle controlled by high-frequency sea-level fluctuations. Facies architectures such as main channels, channels and overbank deposits were identified by using seismic sedimentology and geomorphology. Seismic stratal slices display the different characteristics of the sediment dispersal patterns in the northern part (block DF-a) and the southern region (block DF-b). The northern part contains isolated lobes. The southern region mostly contains deeply incised channels and meander belts that are wider than those in the northern part. Three main sediment dispersal patterns have been recognized, namely, channel-lobe, channelized lobe and non-channelized lobe. Sea level fluctuation and topographic variations exert strong influences on spatial-temporal evolution of the sediment diffusion and are the key controlling factors for the patterns. The methodology used in this study characterizes the submarine fan development in an area with limited well control; this methodology is more accurate for reservoir-scale exploration and development compared to other uses.