Abstract: The present paper deals,on the basis of cores,cast sections,SEM,grain-size analysis and well logs,with the sedimentary microfaciestypes,sedimentary facies evolution and its bearings on the hydrocarbon distribution in the lower member of the Chang-6 oil measures in the Wangyao-Houshui-Xinghe-Pingqiao zone,Ansai Oil Field.The sedimentary facies in the study area is involved in the stream-dominated delta subfacies in the lacustrine environment,including the subaqueous distributary channel,subaqueous interdistributary bay,frontal sand sheet and natural levee microfacies.The hydrocarbon accumulation is controlled by the subaqueous distributary channel sandstones,which may be regarded as the target for further exploration of oil and gas.