The 4th member of the Quantou Formation in Xinli Oilfield shows sedimentary features of a large shallow delta. The area experienced stable sinking of the basement and gentle slopes, leading to the formation of a delta during lake expansion. The delta evolved in two phases, first as a delta plain with branch channels and levees, then as a delta front with distributary channels and bars. Strong water flow shaped the sedimentary model. The study identifies the direction of remaining oil and provides guidance for development projects.