Abstract: Experimenta1 research of dispersion properties on shaly sands with different fluid properties is the petrophysical basis to evaluate the water cut or low resistivity oil-bearing formation using complex resistivity logging technique．The experimental research has been carried on the complex resistivity dispersion properties of water flooding for water,for oil and oil flooding for water．The results indicate that the influence of oil saturation on dispersion is significant and the influence of the formation water salinities is smal1．Especially，the influence of water salinities on the quadrature resistivity is negligible．Corresponding to water bearing shaly sands，the CRL phase ange1 of oil-bearing shaly sands is large． Meanwhile，it increases with the increasing oil saturation. The dispersion properties of water-bearing formation and oil-bearing formation are different．Therefore，the experimental results of dispersion properties of shaly sands show that the formation oilness can be identified effectively by complex resistivity logging developed based on the dispersion properties of the rocks.