Sedimentary microfacies of the fourth member of the Lower Cretaceous Quantou Formation in northern Qijia,Songliao Basin,Heilongjiang

The examination of the sedimentary microfacies of the fourth member of the Lower Cretaceous Quantou Formation in northern Qijia is based on the cores,well logs and granulometric analysis.Seven sedimentary microfacies have been distinguished,including the distributary channel,natural levee,interdistributary bay,subaqueous distributary channel,subaqueous interdistributary bay,channel mouth bar and distal bar microfacies grouping into the delta plain and delta front subfacies.The oil and gas distribution is mostly controlled by the sedimentary microfacies cited above.The subaqueous distributary channel microfacies is selected as the most favourable area for hydrocarbon accumulation due to the proximal provenance and good reservoir quality whereas the channel mouth bar and distributary channel microfacies are considered as the favourable area for hydrocarbon accumulation.