Abstract: Northern slope of Biyang depression is a fault - developed area. Because of later tectonism and complicated underground water system caused by surface water filtration, high resistivity oil layers, low resistivity oil layers and high resistivity water layers coexist in the same formation, which makes it difficult to identify low resistivity oil layers. Based on the rock elastic mechanics theory and the method of difference ratio of equivalent elastic modulus, fluid property of intergranular sandstone can be distinguished. In combination with other methods, low resistivity oil layers are identified and the coincidence rate of logging interpretation is greatly enhanced. All these can be exemplified from the case in northern slope of Biyang depression.