Abstract: The distribution of reservoir in lower Tahe 6 block Ordovician carbonate formation is quite complicated which consists of fissure,pore and cave.Correctly identifying the pay zone and its potential interval is the focus of ex- ploration and development in this block.On the basis of log characteristics of major reservoirs,Cross Plot method and Multi-dimensional Diseriminant method are adopted to carry out quantitative identification.The application in Tahe oilfield shows that satisfying results are received from reservoir identification.