Study on Sedimentary Microfacies and Its Oil-Bearing Properties in Chang 6 Member in the Middle Part of Yi-Shan Slope in Ordos Basin

The studied area is located in the middle part of Yi-shan slope in Ordos basin,and Chang 6 is the main target oil-layer.Understanding the sedimentary microfacies and the relationship between sedimentary microfacies and oil-gas distribution is of guiding importance to oil and gas exploration and development.By analyzing the data of drilling cores,logging,image granularities as well as casting thin sections,it can be concluded that delta front subfacies is the main sedimentary subfacies of Chang 6,which includes 6 kinds of microfacies including underwater distributary channel,river mouth bar,interdistributary bay,sheet sandstones,underwater burst fan and natural levee.The distribution of sedimentary microfacies is analysed also.Furthermore,quantitative statistics was used in the analysis of it's oil-bearing properties of sedimentary microfacies in oil-bearing bodies.The study shows that the oil in Chang 6 mainly developed in the underwater distributary channel sand and combined sand from the underwater distributary channel and river mouth bar,and Chang 61 is the main oil-bearing layer,which is the main target of oil and gas exploration.