Sedimentary facies evolution in the lower submember of the third member of the Shahejie Formation in the Wei-2 block, Weicheng Oil Field, Dongpu depression

The delta front subfacies in the delta depositional system predominates in the lower submember of the third member of the Shahejie Formation in the Wei-2 block, Weicheng Oil Field, and may be subdivided into five sedimentary microfacies, including the subaqueous distributary channel, channel-mouth bar, interdistributary bay, overbank and sand sheet microfacies. During the deposition of the lower submember of the third member of the Shahejie Formation in the Wei-2 block, Weicheng Oil Field, frequent lake-level changes occurred in the Dongpu depression. Vertically, the sandstones display the incomplete delta sequences and the couplets of shallow-water sandstones and deep-water mudstones, and in a planar view, the alternation of progradation and retrogradation of the delta deposits. The results of research in this study may assist in the future development of the Weicheng Oil Field.