SEDIMENTARY FACIES OF THE UPPER CRETACEOUS YAOJIA FORMATION IN THE TAIKANG AREA,SONGLIAO BASIN

The types of sedimentary facies and sedimentary characteristics in the Upper Cretaceous Yaojia Formation in the Taikang area are systematically analyzed, and the spatial distribution and temporal evolution of sedimentary facies of the Yaojia Formation are studied in detail. Our data show that the Yaojia Formation is characterized mainly by deltaic facies. In this area, from the bottom to the top, and from the north to the south, the sedimentary subfacies gradually change from deltaic plain subfacies or subaqueous deltaic plain subfacies to subaqueous deltaic plain subfacies or deltaic front subfacies. The evolution of the sedinentary facies of the Yaojia Formation can be divided into three stages. The sedimentary characteristics are rather different among these stages. Overall, the sedimentary period of the Yaojia Formation shows a transition from aggradation to slowly transgression, with the source area located to the north of the Songliao Basin. There are mainly three types of sandstone reservoirs in the Yaojia Formation. They are branch river sandstone-body, subaqueous branch river sandstone-body and mouth bar sandstone-body. Analysis of the hydrocarbon significance of the different sandstone types shows that subaqueous branch river and mouth bar microfacies are the hydrocarbon accumulation facies. Thus, they should be the targets of future oil exploration.