鄂尔多斯盆地中东部下二叠统太原组灰岩沉积特征与沉积模式OA北大核心CSTPCD

The Taiyuan Formation limestone is extensively distributed in the central and eastern parts of the Ordos Basin,with successful gas flow tests conducted in several wells.It has significant exploration potential and has gained increasingly attention in recent years.However,research on the sedimentary mi-crofacies types and sedimentary modes of Taiyuan Formation limestone in the central and eastern parts of the basin remains undeveloped.Based on a detailed analysis of numerous drilling cores,thin sections,and well logging data from the Taiyuan Formation limestone in the central and eastern parts of the basin,the sedimentary characteristics and sedimentary processes were examined,including rock types,sedimen-tary facies,typical sedimentary sequences and sedimentary modes.The results indicate that the rocks of Taiyuan Formation in the central and eastern parts of the Ordos Basin can be classified into three cate-gories:marine carbonates,peperite and terrigenous clastic rocks,which can be further subdivided into 15 types.The marine carbonate platform facies can be further categorized into seven sedimentary microfacies,including clastic beach,interbeach sea,supratidal zone(mud flat)and intertidal zone(mud flat).Six typical sequences in the transition environment from land to sea were identified based on detailed charac-terization of strata section.Sequences 1,2 and 3 consist of marine carbonate sedimentary sequences,and sequences 4,5 and 6 are composed of continental delta sedimentary sequences.The comprehensive analy-sis indicates that the Lower Permian Taiyuan Formation in the Ordos Basin underwent sedimentary evolu-tion from a continental delta(elastic deposits)to a marine continental transition(mixed deposits)to a marine carbonate platform(carbonate deposits).Influenced by the sedimentary landform,the overall se-dimentary filling pattern is characterized by"sandstone in the north and limestone in the south,overlaid with peat".The research findings not only enhance the understanding of the sedimentary geology of Taiyuan Formation in the central and eastern parts of the Ordos Basin,but also establish an important theoretical doundation for the subsequent exploration of natural gas in the Taiyuan Formation.