Characteristics of stratigraphic sequence and the source-reservoir-cap assemblages in the Nanweixi petroliferous basin

Based on the 2D multi-channel seismic data from the Guangzhou Marine Geological Survey and the drilling data collected from foreign companies, we studied in this paper the regional geological evolutionary process of the Nanweixi basin and its influence on the development of basin strata. By referring to the stratigraphic sequence frameworks of adjacent basins, cross basin seismic lines are used as tools for stratigraphic correlation. the stratigraphic sequence and chronology of the Nanweixi basin are established then, and the characteristics of source-reservoir-cap assemblage and their petroleum geological significance are analyzed. A total of seven unconformities(T₁, T₂, T₃, T₃¹, T₄, T₅, T_g)are identified, which can be traced in the basin and used to divide the strata into seven sequences. Excluding the T₁ unconformity, they correspond to important Cenozoic geological events of Guangya movement, Wan^, an movement, Nansha movement, Nanhai movement, Xiwei movement, Liyue movement in descending order. The basement of the basin is late Cretaceous in age, as same as that of the surrounding basins. And it is speculated that igneous rocks dominated by granite and metamorphic rocks are well developed. As the most significant unconformity in the basin, the T₃ unconformity is aged 10.4 Ma, corresponding to the Wan'an movement. Three types of source-reservoir-cap assemblages have formed since Eocene. In Miocene, carbonate strata are developed in the basin, and may become a high-quality reservoir. There are excellent source-reservoir-cap assemblages in the basin which may suggest a promising oil and gas prospect.