Due to years of water-injection development，the distribution of oil and water is complex in the Upper Karamay Formation of eastern Block Wu2，Karamay Oilfield. To improve the development efficiency is very urgent. Based on the depositional model and characteristics of fan delta and the rock-electricity features of the sedimentary microfacies in the study area，the reservoir architecture unit of fan-delta plain and front facies belt in the study area were identified and divided into four levels，which includes compound distributary channel，single period distributary channel，single braided channel（underwater）and single sandbody. The results show that in the study area，the single period distributary channel interfaces mainly include argillaceous interlayer，calcareous interlayer and erosion interface. Four types of distinguishing marks of single braided distributary channel（underwater）were established as follows：the overbank（muddy deposition），the difference of the height of the channel sand body，the thickness difference of the channel sand body and the difference of logging response characteristics of the channel sand bodies. And then the distribution characteristics of sedimentary microfacies were determined based on analysis of reservoir architecture in the study area. The results show that the thickness of braided distributary channel is more than 4 m and the width is 300-1 500 m. The width of single nderwater distributary channel is 100-740 m and its thickness is 1-8 m. The channel bar is potato-like or block-like，and it is 3-9 m thick，150-750 m wide and 200-800 m long. Based on comprehensive analysis of the architecture interface and the simulation results of remaining oil saturation，it is concluded that the remaining oil distribution is comprehensively controlled by the architecture unit，interface and structure factors，forming a large amount of remaining oil accumulation areas.