Sedimentary microfacies and hydrocarbon potential of the Chang3 oil measures in the Yanchang Formation,Huachi Oil Field,Ordos Basin

The Chang3 oil measures in the Yanchang Formation of the Huachi Oil Field in the Ordos Basin were formed during the lacustrine basin collapse and basinward progradation of the delta deposits.The sedimentary microfacies mainly consist of delta plain distributary channel,flood plain,delta-front subaqueous distributary channel,channel-mouth bar,composite bar,distal bar and interdistributary bay microfacies.Sedimentary environments have gone through the evolution from the delta front to the delta plain.The reservoir sandstones are dominantly composed of delta-front subaqueous distributary channel sandstones,channel-mouth bar sandstones and composite bar sandstones.The controls of the above-mentioned sedimentary microfacies on the hydrocarbon potential of the Chang3 oil measures in the Yanchang Formation in the Chenghua region include:(1) the controls on source-reservoir-seal associations;(2) the controls on the distribution of reservoir sandstones,and(3) the controls on the reservoir quality.