Recognition and new understanding of braided river delta in second member of the Shahejie formation in Jinzhou 25-1 Nan-oilfield

The second member of Shahejie formation in Jinzhou 25-1 Nan-oilfield was considered to come from the low raised fan delta sedimentary in Liaodongwan waters of Bohai Sea.Aiming at this previous view,in combination with regional sedimentary background,the tectonic evolution and the characteristics of geomorphology,through comprehensive analysis,the results indicate the second member of the Shahejie formation in Jinzhou25-1 Nan-oilfield belongs to double sources sedimentary system.The provenance source in the north mainly comes from northwestern Gudong Shahe and the provenance source in the south mainly comes from southwestern low raised of Liaoxi.Among the oilfield,it only developed the braided river delta front subfacies deposition,and there are six kinds of microfacies,namely underwater distributary channel,between tributary bay,mouth bar,underwater shore,far sand dam and sand sheet.Among them the underwater distributary channel and mouth bar are the best ones for best reservoir performance and the most favorable reservoir facies belt for well deployment in the later period.