Abstract: Regarding the CⅢ reservoir in Tazhong-4 oilfield of Tarim basin and on the basis of core and logging data, 3 types of argillaceous, calcareous and argillaceous-calcareous seepage barriers are characterized. Based on the core observation, lithological and physical property analysis, logging response analysis and forming mechanism study of the seepage barriers, a classification standard is established for the different seepage barriers within reservoirs. Taking the parallel seepage barrier model as the basis of geological model and combining with the production performance, fully occluded, partially occluded and non occluded interwell seepage barriers are classified according to the influences of the barriers on reservoir fluid flowing in the study area, and the vertical and horizontal distribution laws of the barriers are verified. Vertically the seepage barriers of different intervals have different impacts on fluid flowing, and horizontally the seepage barriers are very developed in the northwest of the study area. Fully understanding the reservoir seepage barrier characteristics, distribution and impact on fluid flowing will provide an important geological basis for remaining oil potential tapping and oil recovery improvement