Sedimentary microfacies characters of Chang 6 oil-bearing formation in Jiyuan area of Ordos Basin

Utilizing core logging,grain size analysis and thin section analysis,the authors identified front delta as the major sub-facies type of Chang 6 oil-bearing formation,including the microfacies of subaqueous distributary channel,river mouth bar,subaqueous interdistributary bay,subaqueous crevasse splay,and subaqueous natural levee.The planar distribution regulation of each layer and the control action of sedimentary microfacies to reservoirs have been analyzed,which show that the high quality reservoirs of Chang 6 oil-bearing formation were mainly hosted in subaqueous distributary channel sand and combination sand between subaqueous distributary channel and mouth bar.In general,the high quality reservoirs of Chang 621,Chang 612 and Chang 622 were wider distributed with better continuity in plane and superimposition in vertical,which are the target layers for the next work.