As the development of complex fault-block small sandbody reservoirs continues to deepen, the obvious high-resistance thick oil layers have basically been ejected. The remaining reserves are mainly concentrated in thin oil layers, oil and water layers or suspicious layers, with uncertain oil content. Therefore, there is an urgent need to carry out research on oil and water layer identification methods with strong qualitative and quantitative operability, using the same layer series comparison method in the well, the logging plate method, the calcium-corrected C/O logging method and the comprehensive geological analysis method, to identify and evaluate oil and water layers in unknown reservoirs in the study area. The research results show that: ① The oil and water layers can be identified and evaluated qualitatively, reliably, conveniently and quickly by using the same layer series comparison method and comprehensive geological analysis method in this well; ② Thin and poor reserves can be quantitatively identified using Vsh and Rwa(Rt)/Rwa(SP) chart method and calcium-corrected C/O logging method; and the reliability of the identification results can be verified through on-site implementation.