Abstract: The understanding of the reservoir is not constantly unchanged during the process of oilfield exploration, so the status of reservoir development must be recognized. The most parts of the northeast pilot area No.2 have entered extra high water cut production period after 40 years of development and adjustment, and the oil production gradually declines. In order to increase recoverable reserves, the reservoir development status of the northeast pilot area No.2 is recognized and evaluated by using the data of drill core sample hole and the interpretation data of new wells after infill drilling. The effective thickness, permeability and sandstone distribution of every reservoir group are found out, which will provide a strong guarantee for the oil stable production. Keywords: infill well; reservoir; geological features; understanding