通过岩心描述、岩石薄片鉴定、古生物、物源区及测井曲线等资料的综合分析，对鄂尔多斯盆地陇东地区三叠系延长组长 9 油层组沉积相和层序地层学特征进行了详细研究，确定长 9 油层组属于浅水三角洲沉积体系，可划分为 1 个长期、2 个中期和 4 个短期旋回层序。 以古盐度的定量计算和盐度分区为依据，进一步确定了陇东地区长 9 油层组沉积期的古湖岸线位置。 在此基础上，以物源区、沉积相和层序分析等资料为基础，选取中期旋回层序的上升和下降相域作为等时地层单元编制陇东地区长 9 油层组各时期层序-岩相古地理图。 结果表明，各时期古地理面貌和砂体展布格局主要受湖平面升降和物源区方向控制，最有利储层发育的水上和水下分流河道主要出现在各中期旋回的湖侵相域，砂体的延伸方向与西南部的主物源方向相平行。 该研究成果对陇东地区长 9 油藏的后续勘探具有一定的指导意义。

Based on comprehensive analyses of core description, thin section observation, paleontology, source area and well logs, this paper studied the characteristics of sedimentary facies and sequence stratigraphy of Chang 9 oil reservoir set in Longdong area, Ordos Basin. It is determined that Chang 9 oil reservoir set belongs to shallow-water fluvial dominated delta system and it can be divided into one long-term, two middle-term and four short-term sequences. On the basis of the quantitative calculation of paleosalinity and its subarea, the position of palaeo-lakeshore during Chang 9 depositional stage was determined. According to the source area, sedimentary facies and sequence, the rising and falling base level phases of middle-term sequence cycles were selected as the isochronic stratigraphic unit to draw up the sequence-based lithofacies and paleogeography map of Chang 9 oil reservoir set in Longdong area. It is concluded that paleogeography features and sand body distribution are controlled by lake level fluctuation and source direction. Distributary channels and underwater distributary channels during the transgressive phases are favorable for reservoir development, and the sand body direction is parallel to the major source direction. The results can guide the following exploration for the Chang 9 reservoirs in Longdong area.