Abstract: The traditional method getting the cut-off pore-throat is based on the experience,there is no enough theory and experiment to support the method.According to the relation between NMR and traditional mercury injection,the NMR map is converted into pore-throat spectrum.Combining with the spectrum and centrifugal method,a new method getting the cut-off pore-throat radius is presented.Meantime,the cut-off pore-throat radius of Daqing Oilfield is calculated.The results show there are a good positive correlation between permeability and the cut-off pore-throat radius.The porosity has little effect on the cut-off pore-throat radius.On the basis of Poisseuille formula of capillary model,the new value of cumulative contribution to the permeability,which is corresponding with the cut-off pore-throat radius,is calculated,and the results presented the value reaches 99.9%.Above study provides new reference for reservoir evaluation.

Key words: pore-throat radius, NMR, capillary curve, permeability, mercury-injection