The traditional cognition of "oil south and gas north" in the Ordos Basin has been broken through,and there are abundant natural gas reserves in the Benxi Fm of Upper Carboniferous in SE Ordos Basin.To provide a guide for the prediction of favorable reservoirs of Benxi Fm,two main sedimentary facies (i.e.,tidal flat and barrier-lagoon) were identified in the deposit of Benxi Fm barrier coast according to their grain sizes,textures,sedimentary structures and lithofacies assemblages.Then,multiple sedimentary subfacies were identified further,including tidal channels,subtidal zones,intertidal zones,supratidal zones,barriers,lagoons,washover fans and tidal deltas,and they were compared and summarized to establish the vertical sequence.Afterwards,the areal distribution laws of Benxi Fm sedimentary facies were analyzed in the framework of sedimentary patterns based on sandstone thickness data.And finally,the factors controlling overall sedimentary distribution patterns and sedimentary evolution laws were analyzed.It is indicated that the sedimentary facies in this area follows the change law of tidal flat-barrier-lagoon-neritic shelf.And the facies zone of the first Member of Benxi Fm shift wholly to the west of the second Member;and that this barrier coast is derived from the fan delta in northern Ordos Basin due to the reworking of waves and tides under the control of paleo-uplifts.And its evolution is mainly affected by the slow decline of basin base and the overall rise of sea level.%鄂尔多斯盆地已突破“南油北气”的传统认识,其东南部上石炭统本溪组天然气储量丰富.为了给本溪组有利储层的预测提供指导,首先根据颗粒粒度、结构、沉积构造和岩相组合等特征在本溪组障壁海岸沉积之中划分出潮坪和障壁—澙湖2种主要沉积相,进一步识别出潮汐水道、潮下带、潮间带、潮上带、障壁、澙湖、冲溢扇和潮汐三角洲等多种沉积亚相,并对上述沉积亚相进行了总结和对比,建立了垂向序列.进而在沉积模式的指导下,依据砂岩厚度资料剖析了本溪组沉积相的平面展布规律,最后研究了该区整体沉积展布格局和沉积演化规律的控制因素.结论认为:①该区自西向东呈现潮坪—障壁澙湖—浅海陆棚的变化规律,本1段沉积相带较本2段整体向西迁移;②障壁海岸沉积是在古隆起控制下由盆地北部扇三角洲经波浪和潮汐改造而形成的,其演化主要受到盆地基底缓慢下降和海平面整体上升的影响.
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