Abstract: By means of the analysis for various facies markers, this article discussed the sedimentary facies type, microfacies buildups and their characteristics of Upper Karamay formation reservoir in the District No.8 of Karamay oil-field, based on core analysis, logging and production dynamic data. It is considered that the Upper Karamay formation in this area belongs to fan-delta sediments, which was formed by alluvial fan or braided stream directly entering lacustrine. The lower segment (S1 sandstone layer) is fan-deltaic deposits. A series of microfacies types have been differentiated, such as subaqueous distributary channel,inter-channel bottom land, channel-mouth bar, sheet sand and braided distributary channel, etc. On the basis of substrata division and vertical evolutionary conditions of the 10 substrata, 19 single sand-layers from S5-S1 have been analyzed.

Key words: Karamay oilfield, Middle Triassic, sedimentary facies, depositional feature, sedimentary type