Deep water gravity flow sedimentation of Chang 6_3 in Huaqing area and its petroleum geological significance

Previous studies on the sedimentary characteristics and reservoir heterogeneity of Yanchang formation in Ordos basin have been carried out, but the reservoir heterogeneity still restricts the exploration and development of oil and gas. Based on the information of core observation, grain size analysis, logging facies and seismic facies, the sedimentary microfacies of Chang 6_3 in Huaqing area of Ordos basin are systematically studied by establishing high resolution sequence stratigraphic framework and dividing sedimentary microfacies. The results indicate that the deep-water gravity flow sedimentary system developed in Chang 6_3 of Huaqing area can be divided into four microfacies types: sandy debris flow, muddy debris flow, turbidity flow and slump. Among them, the sand debris flow is one of the most important microfacies, and its formation mechanism includes overall freezing, friction consolidation and suspension settlement. The distribution of sedimentary microfacies controls the plane heterogeneity of reservoir. The high-quality reservoir of Chang 6_3 is mainly located in the main part of sandy clastic flow and turbidite, which leads to the plane heterogeneity of reservoir. The vertical stack thickness of gravity flow sand body in deep water is large, which can form largescale reservoir. The sandy clastic flow sand body of the Chang 6_3 reservoir group is developed in the main part of the river channel, with large thickness and good reservoir physical properties. The interlayer is less developed and well connected, which is the key exploration horizon.