Sedimentary facies of the Chang-6 oil reservoirs in the Dingbian-Wuqi region, Ordos Basin

The integration of the petrology, colour, sedimentary structures, organic fossils and granulometric analysis shows that the Chang-6 oil reservoirs in the Dingbian-Wuqi region, Ordos Basin are assigned to the braided delta-lacustrine deposits which may be grouped into the delta plain, delta front and abyssal to bathyal lake subfacies. The sediment sources dominantly come from the northwest and northeast of the Basin. In a plan view, there are two subaqueous distributary channels oriented NE to SW and NW to SE, respectively. From Chang-6₃ to Chang-6₁, the study area displays a depositional pattern of lake regression, including southward migration of the lake strandline, the gradual decrease of the abyssal to bathyal lake area, and the increase of the northern delta plain area.