The study analyzed the sedimentary facies of the Chang-8 oil group in the Yanchang Formation in the Jiyuan area of the Ordos Basin. By examining rock types, sandstone structure, sedimentary tectonics, fossils, and geochemical features, researchers found meandering river delta sedimentary systems in a semi-arid to semi-humid environment. These systems include delta plains with distributary channels and natural levees, as well as delta fronts with subaqueous channels and sandbars. The boundary between these sub-facies was confirmed using geochemical principles.