Analysis of sedimentary characteristics of Sanya Formation on the northern slope of Lingshui Sag, Qiongdongnan Basin

Lingshui Sag is located in the southwest of Qiongdongnan Basin. Explorations have confirmed that submarine fan sedimentary system are developed in Meishan Formation of the Neogene Miocene in Lingshui Sag, with commercial discoveries made. However, underlying Sanya Formation lacks drilling data, resulting in low exploration maturity, unclear distribution of sedimentary systems, and undefined exploration potential. To accurately characterize the sedimentary system of Sanya Formation, this article established a high-precision sequence stratigraphic framework based on drilling data of Meishan Formation and 3D seismic data, restored paleogeomorphology, and used Meishan Formation as a comparative reference to ultimately determine the distribution and evolution laws of the sedimentary system of Sanya Formation. The results indicate that during the sedimentary period of Sanya Formation, the continental shelf-slope background began to form, with the sedimentary system fed by the continental shelf edge delta formed by Lingshui River provenance on Hainan Island. A series of small channels were developed. The provenance from the northwest entered the exploration area, forming three slope fan-basin floor fan sedimentary systems on the plane, with vertical characteristics of "stable development in the west and migration from west to east". Analysis suggests that the distribution of sedimentary systems is mainly controlled by faults and slope break belt, and the developed slope fans and basin floor fans are high-quality reservoirs. The sand-bodies of the first member of Sanya Formation are large scale, representing a favorable exploration target section. The results provide technical basis for selecting favorable exploration targets on the northern slope of Lingshui Sag.