Sedimentary System Evolution and Petroleum Geological Significance of the Quaternary Ledong Formation in Qiongdongnan Basin

Abstract

Quaternary Ledong formation in Qiongdongnan Basin is rich in hydrate, it is import to clarify the evolution and distribution rule of the sedimentary system of Ledong formation in this area. Based on 3D seismic data and drilling data, combined with the characteristics of regional sea level change, and guided by the principle of sequence stratigraphy, this paper established a high-precision sequence stratigraphic framework of Ledong Formation, identified five third-order sequences, and pointed out that the S14 interface was the conversion surface of progradational continental slope to accretive continental slope. The Ledong Formation was divided into the upper member of Ledong Formation and the lower member of Ledong Formation, which controls the development of submarine fans. The results show that the lower member of Ledong Formation has developed a large channelized submarine fan of the western provenance central canyon system, and the upper member of Ledong Formation has developed a small scale submarine fan, mass flow and sheet sand complex sedimentary body outside the northern provenance canyon system. The sedimentary type and temporal and spatial evolution characteristics are defined, which provides geological basis for the prediction of favorable reservoir distribution of hydrate and shallow gas in this area.