Abstract: The Guantao Formation (Neogene) is the most important reservoir in the Kongdian oilfield with fluvial facies developed. The complex distribution characteristics and connectivity of the fluvial sand bodies cause a complex relationship between oil and water in the process of water flooding, and which, in turn, control the formation and distribution of the remaining oil. Through the detailed study of the core and logging data, the sedimentary model of the Guantao Ⅲ Member in the study area was determined,and a detailed characterization of the reservoir architecture was completed. On the analysis of the reservoir architecture characteristics, the distribution types of remaining oil were summarized. The authors believe that the third member of Guantao Formation is a braided river with the elements of braided channel, central bar,and levee developed. The central bar is the most important oil and gas enrichment unit in the braided river sediments, and the distribution form of remaining oil can be influenced by water injection. Three types of the silting layers of muddy, calcium and silty exist in the strata. The central bar can be divided into four parts including bar head, bar main part, bar tail, and bar limbs. The silting layer in bar head is poorly preserved; The silting layer in bar main part is preserved relatively complete in a nearly horizontal shape; The silting layer with a low angle in bar tail is preserved relatively well; The silting layer in bar limb is influenced by slope, preserved well in a steepslope but poor in a gentle slope. The remaining oil in a central bar of anatomy area is mainly concentrated in the middle part of the left bar limb and the bar tail that is blocked by a silting layer.

Key words: Kongdian oilfield, Guantao Formation, fluvial, sedimentary characteristics, reservoir architecture, distribution of remaining oil