Depositional pattern and source-to-sink process of submarine fans in Lingshui and Sanya formations, Baodao Sag, Qiongdongnan Basin, China

Abstract

The deepwater area is one of the frontiers of oil and gas exploration, with the understanding of distribution and genesis of deepwater reservoirs being crucial for reservoir formation research. Despite Baodao Sag in the Qiongdongnan Basin being proven to be rich in hydrocarbon generation, significant oil and gas fields have yet to be discovered in the ultra-deepwater areas, and the distribution patterns of reservoirs in deep water remain unclear. Taking the southern slope area of the Baodao Sag as an example, the distribution characteristics of submarine fans are studied by employing seismic prediction methods, including seismic reflection structure analysis, seismic facies geometry, seismic attribute analysis, and the source-to-sink theory. The results show distinct characteristics: the fan delta exhibits parallel oblique progradational reflection, the slumping submarine fan displays lenticular reflection, and the submarine fan of the Sanya Formation demonstrates subparallel sheet reflection. The provenance of sediment is traced back to the denudation area of the Songnan low uplift and the Southern Uplift area in the southwest. The sediments were primarily transported through two main incised channel systems in the north and south, ultimately flowing into the southern slope area of the Baodao Sag. The application of seismic sedimentological prediction methods and source-sink theory has laid a solid geological foundation for oil and gas exploration and the analysis of reservoir forming conditions in the deepwater area of the Baodao Sag.