Study On High-resolution Sequence Stratigraphy And Sedimentary Microfacies Of Guantao Formation Of Du 84 Block In Liaohe Oilfield

Du 84 block is located in the middle part of the slope belt in western Liaohe Depression.This block presents a long-strip shape with monoclinic structure tipping to east.With the exploration and development in this area,a detailed description for the promising reservoir is needed.Though the research on the high-resolution sequence stratigraphy and sedimentary microfacies in Guantao formation in this studied area,we characterized the distribution of stratigraphic sequences and the evolution of sedimentary facies,which would provide significant geological references for the further exploration in DU 84 block.Based on the analysis of core,logging and seismic data,and the application of high-resolution sequence stratigraphy,sedimentary petrology,facies disciplinary of ancient geography and reservoir sedimentology methods,we finally established the high-resolution sequence stratigraphy framework on the basis of the identified sequence boundaries and the sequences correlations,and summarized the depositional model of alluvial system on the basis of the identified signals and distribution features of sedimentary microfacies.The Guantao formation in the study area can be divided into 1 long-term depositional cycle(equivalent to third-order sequence),5 mid-term depositional cycles(equivalent to forth-order sequence)and 10 short-term depositional cycles(equivalent to fifth-order sequence).The strata are thickening along with the depositional sources direction,while it is stable in the direction of perpendicular to depositional sources.The major sedimentary facies in the Guantao formation in the study area are root alluvial fan including debris flow,main river channel and diffuse flood and middle alluvial fan including debris flow,braided river channel,diffuse flood and braided sandbar.From the root fan to midding fan,the terrain becomes flatter,the river channel branches becomes more,the curvature of the river channel becomes larger,and the scale of one single river channel sand body become smaller,the stacking patterns of which evolve from vertical stacking,to crisscross stacking,to horizontal stacking,and to isolated stacking.The debris flow microfacies and braided river channel microfacie are easily recognized and distributed stably.From the bottom to top,the Guantao formation is mainly made up of conglomerate deposited by debris flow,conglomerate deposited by river,middle to coarse-grained sandstone deposited by river,and fine-grained sandstone deposited by river.