Abstract: After years of development of fractured-vuggy carbonate reservoirs in Tahe Oilfield, the bottom water coning occurs and oil/water contact rises, and the remaining oil accumulates mainly by way of attic oil. Field practice shows that oil recovery by injecting nitrogen is viable in fracture-vuggy carbonate reservoirs, which can effectively produce the attic-type remaining oil. It is a highly-efficient technique to increase crude recovery rate. In field practices, the experiences in well selection for producing oil by injecting nitrogen were summarized, and the model for efficient gas injection well classification was built, providing the basis for the development of fractured-vuggy carbonate oil reservoirs. Oil production by nitrogen injection is a technique to efficiently improve oil recovery rate.