Syn sedimentary corrosion mode of carbonate reef banks in the middle Ordovician Yijianfang Formation within the western Tabei uplift of Tarim Basin

Abstract: On the basis of the detailed drilling data and the core characteristics at the macro and micro level, by means of analyses about characteristics and distribution rules of sedimentary facies, in combination with reef?banks syn?sedimentary corrosion reservoir characteristics,and according to the ancient sedimentary geomorphic units combined with lithofacies, the authors established the syn?sedimentary corrosion model of reef?banks in the Middle Ordovician Yijianfang Formation in the western Tabei uplift of Tarim Basin. According to the results obtained, first, the open platform facies of Yijianfang Formation contain platform?interbank, interbank sea and platform?inter patch reef, and the plane distribution of facies is stable; second, Yijianfang Formation exhibits obvious characteristics of the syn?sedimentary corrosion and widely reflects the characteristics of the intermittent exposure of bank: boring pores and corrosion pores are filled with ancient mud soil formed by the exposure of reef banks, the intertidal zone fossil fragment accumulation and traces of soft?bodied organisms activities are common, the corrosion cycle from seepage to undercurrent belt can be identified by core observation and Image Logging. According to the model, the banks and patch reefs of Yijianfang Formation are classified into five geomorphic units, i.e., supralittoral long?term exposure bank, intertidal intermittent exposure bank, subtidal high?energy bank, Calathium baffles tone and tideway.