Sedimentary Facies Characteristics of Triassic Yanchang Formation Chang 8 Oil Layer in Huachi Area,Ordos Basin
The Chang 8 oil-bearing formation of Triassic Yanchang Formation in Huachi area of Ordos Basin has great exploration potential,lack of systematic understanding of sedimentary characteristics,which may affect the later oil and gas exploration and development.Based on core observation,particle size analysis and conventional logging facies analysis,the Chang 8 reservoir group of Triassic Yanchang Formation in Huachi area was systematically studied.The results show that:① The sedimentary facies type is braided river delta,which belongs to the braided river delta front subfacies.There are five sedimentary microfacies:underwater distributary channel,interdistributary bay,estuary dam,distal bar and sheet sand.② Vertically,the development of channel sand bodies in Chang 8 1 is better than that in Chang 8 2.Horizontally,the development of channel sand bodies and lateral connectivity in the southwest-northeast direction are better than those in the northwest-southeast direction.③On the plane,the underwater distributary channel in the southwest-northeast direction is developed.The change of sedimentary microfacies of Chang 8 2-Chang 8 1 reflects the continuous advancement of provenance,the scope of underwater distributary channel continues to widen,and the distribution range becomes wider.④ Based on the comparison of physical properties of different microfacies and the vertical,horizontal and plane study of sedimentary facies,the dominant facies are the underwater distributary channel and the interdistributary bay.
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