Abstract: B304 block of Zhaoao oilfield,located in the middle slope of Biyang depression,is adjacent to the deep depression where source rocks are abundant.The reservoir is the deposit of fan delta from the south depression with a complex lithology.The minute structure extent and the wide oil-water transitional zone bring about 1/3 oil layers low resistance or the resistance equal to that of water layer,thus generating difficulty to identify oil layer.The reasons are analyzed from the structure,the physical properties of reservoir.By synthetically analyzing the four features as lithology,electric property,physical property and oil-bearing character,the standard to identify the low-resistance oil layer is established, thus highly enhancing the coincidence ratio of lowresistance oil layer by logging interpretation.