Abstract: This paper presents four methods of empirical statistical analysis, throat radius cut off, relative permeability curve and gas test for effective determination of reservoir porosity and permeability cutoff values for the purpose of oil-gas reservoir identification and reserves estimation. These methods are applied to determination of cutoffs of porosity and permeability of the He-8 member, Shihezi formation in Wellblock-8 in a gas field in Ordos basin, showing that the porosity cutoff value is 6.25%, the permeability cutoff value is 0.1×10^-3 μm².

Key words: reservoir rock, porosity, permeability, cut off