根据大量的钻井、测井及分析化验资料，运用沉积学方法综合研究该区的沉积相及其演化特征，并认为：长2 油层组早、中期（长23、长22）主要发育曲流河沉积，表现为垂向上河道砂体相互叠加，砂地比值高，平面上河道沉积广泛分布，泛滥平原沉积保存较少；晚期（长21）过渡为网状河沉积，河道砂体厚度变薄，地层砂地比变小，平面上河道呈网状分布，广泛发育河漫沼泽沉积。在沉积单元划分、对比的基础上，分析了4 个单元沉积微相的平面展布规律。

Based on drilling cores and logging data, the sedimentary facies and its evolution characteristics of Chang 2 oil-bearing member in Yanchi-Dingbian area, Ordos Basin are studied. The result shows that fluvial system developed in Chang 2 depositional stage in this region. During the depositional period, there is a systematic change in channel types from meandering stream to anastomosing river. The meandering stream deposition developed at the bottom and middle sections （Chang 23, Chang 22） ofChang 2 member with thicker superposed channel sand body, higher sand-stone/ stratum ration, less floodplain and more channel deposits. While the anastomosing river deposition developed at the top section （Chang 21） of Chang 2 member with thinner channel sandstone-body, lower sandstone/stratum ration, less channel and more floodplain, swamp deposits. On the basis of sedimentary units division and correlation, the microfacies plane distributions of the 4 units are analyzed.