Abstract: In the lower sub-member of the third member of Xujiahe Formation in the Zhongtaishan Area of central Sichuan is characterized by obvious differences in stratigraphic composition and rapid lateral changes of fluvial-phase sands, which makes the delineation of sequence stratigraphy difficult, and thus affects the identification and characterization of high-quality reservoirs. For this reason, the sequence characteristics of the lower sub-member of the third member of Xujiahe Formation in the Zhongtaishan Area were analyzed based on the logging, mud logging and seismic data, and the distribution range of different lobes was circled in order to make a preferential selection of favorable zones for reservoirs. The results show that: for the stratigraphic deposition of the lower sub-member of the third member of Xujiahe Formation in the Zhongtaishan Area of Central Sichuan, the stratigraphic features of the upper sub-member of the second member of Xujiahe Formation are inherited, which is a gently sloping paleotectonic background with high terrain in the southeast, low terrain in the northwest and elevated in the middle of the depression, and three phases of sequence boundary and two phases of flooding surfaces have been identified; the mineral components of the dense sandstone reservoir are mainly rock chips and feldspar, and the pore types are dominated by dissolution pores and microfractures; there are three main types of lithologic assemblages: thick sandstone assemblages, thick sand interbedded with thin mudstone assemblages, and thick mud interbedded with thin sandstone assemblages; combined with the fact that the high-yield wells have the characteristics of fracture, crack and reservoir development, and are located in the relatively high tectonic parts, the reservoirs in the study area are divided into 3 types of favorable zones. The research results can provide important reference and theoretical support for the subsequent exploration and development.

Key words: dense sandstone, sequence characteristics, reservoir prediction, lower sub-member of the third member of Xujiahe Formation, Zhongtaishan Area