Evolutionary and controlling factors of sedimentary system in the First Member of the Zhujiang Formation in the Zhu Ⅲ Depression

Abstract

Objective The First Member of the Zhujiang Formation in the Zhu Ⅲ Depression underwent significant changes in its sedimentary system. It transitioned from a large-scale delta system to a shallow sea shelf system. Understanding the evolutionary process and controlling factors of this basin is important for studying the sedimentary system during transgression and predicting favorable sedimentary facies zones on shallow sea shelves. Methods In this study, we used core, well logging, and high-resolution 3D seismic data to establish a stratigraphic framework for the First Member of the Zhujiang Formation. By combining geology and geophysics, we determined the temporal and spatial evolution characteristics of the sedimentary system and discussed the main controlling factors. Results Our findings show that the First Member of the Zhujiang Formation can be divided into four sequences: PS1, PS2, PS3, and PS4. PS3 and PS4 were dominated by delta deposits, including underwater distributary channels, estuarine dams, and distal dams. PS1 and PS2 were characterized by the development of large-scale shallow-sea shelf systems, with tidal sand ridges in the west and offshore sand dams in the east. The evolution of the sedimentary system in the Zhu Ⅲ Depression is influenced by sea level changes, source supply intensity, structural subsidence, and paleogeomorphology. Conclusion Microfacies sandstones, such as underwater distributary channels, tidal sand ridges, and coastal sand dams, have high percentages and good physical properties, making them favorable sedimentary facies zones for oil and gas reservoirs.

Keywords

• sedimentary system
• controlling factor
• first member of the zhujiang formation
• zhu ⅲ depression
• pearl river mouth basin
• shallow sea shelves
• stratigraphic framework