Sedimentary Facies Study on II Sand Group of Jurassic Xisanyao Formation of the East Region of Niujuanhu Oilfield in Santang Basin

In view of the situations of complex microfacies of Niujuanhu Oilfield,approximate predecessor's analysis of sedimentation,the support of fine sedimentary microfacies description was badly needed for oil production in the east region of Niujuanhu Oilfield.Through the analysis of core,logging and log data,seismic data and thin rock slice,a fine description was performed on sedimentary facies in the operation area.It is considered that it contains 2 subfacies braided delta front sub-facies and prodelta subfacies and 5 microfacies,of which the channel mouth bar and distributary channel deposit are the most beneficial areas and the potential areas for next oil production.Through heavy mineral and seismic analyses,it is considered that the sand bodies in the region are controlled by north and south sources,especially the south provenance is dominated,which is not mainly of provenance denoted by predecessors.The south of the study area develops alluvial fan facies-braided river-braided river delta-lacustrine facies sedimentary systems,and the north of the study area develops braided river delta-lacustrine facies sedimentary system.