Division of high-resolution stratigraphy in sedimentary sequence theory and prediction of lithological traps: a case study of the Neogene in Enping Sag, Pearl River Mouth Basin

Abundant sand-rich deposits in Neogene sequence were identified by a large area of 3D seismic data in the Enping Sag of Pearl River Mouth Basin, in the northern South China Sea (SCS). The mechanism of formation of the lithological traps in the Neogene reservoirs was studied by examining the variation of facies belts in the ancient Pearl River Delta system. Previous studies have shown that many structural-lithological traps in the Shenzhen Branch of the Enping Sag are closely associated with fluvial deposits. However, few studies provide systematic understanding on the origin, classification, and distribution of the fluvial deposits, which impeded the exploration progress in the studied area. A high-precision sequence stratigraphic framework of the first member of the Zhujiang Formation to the sixth member of the Hanjiang Formation was depicted and established systematically through 3D seismic interpretation and sedimentary and seismological analysis. Results show that large braided channel, small curved channel, and medium curved channel developed in the Enping Sag are closely correlated to lowstand, transgression, and highstand systems, respectively. The model of fluvial system was built in combination of stratigraphic variation and channel morphology. This model demonstrates the potentiality and distribution of various types of fluvial deposits in the Enping Sag. This study could effectively guide the exploration of lithological traps in the Enping Sag and other offshore basins in the future.