Study on Petrophysical Property Cutoff of the Southern W Chang 6 Extra-low Permeability Reservoir in the S Oilfield

With the main porosity range of 10% to 12% and the main permeability range of(0.1～0.5)×10-3 μm2,the Southern W chang 6 reservoirs in the S oilfield of the Ordos Basin are typical low porosity and extra-low permeability reservoirs.According to the static and dynamic data and petrophysical experiments,the effective porosity and permeability cutoffs of these reservoirs were determined by physical property test,oil test data constraints,oil-water relative permeability,mercury-parameter and mercury analysis.The results show that the lower limit of porosity is 10% and the lower limit of permeability is 0.15×10-3 μm2,which can provide a basis for determining effective reservoir and estimate reserves.