The characteristics of the system domain and the stratigraphic framework of the Beikang-Zengmu Basin since the Middle Miocene

With the development of sequence stratigraphy, it has been widely used in all stages of oil-gas exploration, using sequence stratigraphy to study relative sea level change, sequence stratigraphic framework and sedimentary facies can provide guidance for favorable reservoir facies belt distribution, sand-body morphology and boundary characterization. In seismic data interpretation, analyzing seismic reflection termination relationships (onlap, downlap, toplap and so on), unconformities and depositional trends, fourteen third-order sequence interfaces have been identified in the Beikang-Zengmu basin since the Middle Miocene, respectively named SB1-SB14 and SB11, SB8 and SB1 corresponds to the Guangzhou Marine Geological Survey of T₁, T₂ and T₃ reflection interface. By delineating the inner structure of sequence stratigraphy and restoring the original profile, and combining with the stratigraphic stacking method, in the sequence stratigraphic framework of Beikang-Zengmu Basin since the Middle Miocene, four genetic units have been divided into transgression, high normal regression, forced regression and low normal regression. By further studying the interior layer structure and facies distribution of the four genetic units, three sequence stratigraphic framework patterns since the Middle Miocene in the Beikang-Zengmu Basin were proposed, namely, sand-rich delta advance wedge at the shelf edge, regressive organic reef, and sand-rich mud-rich retreat wedge at the shelf edge. Among them, the supply of sediment source is sufficient and the accommodating space is reduced when there is less space, and the sand-rich delta wedge is developed, and the sand-bearing deep-water fan is developed in the shelf margin-slope-basin area. However, when the increment of accommodating space was much larger than the sediment supply, there were regressive organic reefs and sand-rich mud-rich sedimentation wedges, and sandy deep-water fans in the slope-basin area were underdeveloped.