The Quad-Neutron logging technology is used to identify the remaining oil in casing production Wells, which requires supplementary logging data. Americium-Beryllium neutron source is used in Quad-Neutron logging to emit fast neutrons to the formation, which react with the elements in the formation in a series of ways. By recording the neutron-neutron and neutron-gamma counting rates obtained in the physical processes of neutron-neutron and neutron-gamma, the mud content, porosity and oil & gas saturation are calculated, and interpretation standards and interpretation charts are established. Evaluation of formation physical property and remaining oil distribution was accomplished. The field applications show that the Quad-Neutron logging can provide a reliable basis for identifying the flooded layer and the remaining oil, and obtain a good effect.