Abstract: Lithological-stratigraphic traps, which consist of most lowstand sand bodies, are important type and significant reserve of hydrocarbon traps in Qiongdongnan Basin. Basin floor fan, slope fan and lowstand wage are major lowstand sand bodies in this basin, and they form typical valley-fan sedimentary system with incised-valley. In this paper, their controlling factors are analyzed in detail, which includ paleostructural background, provenance conditions (provenance lithology, shelf lithology, shelf width, transporting distance and ability of paleochannel, etc), sedimentary environment and diagenesis and distribution of abnormal geopressure. Through integrated evaluation, it is suggested that slope fans of Lingshui Formation in fault crossing position in western and eastern basin are favorable exploration targets, and lowstand sand bodies on S₆₀, S₅₀, S₄₀sequence boundary in northern uplift zone and its southern hydrocarbon abundant area are the best exploration targets.

Key words: Qiongdongnan Basin, Tertiary, reservoirs of lowstand system tract, distribution characteristics, controlling factors