Study On The Law Of Oil Enrichment Of Chang 2 Member In Zhangjiagou Area Of ??Ordos Basin

There are a great number of oil and gas resources in the Mesozoic of the Ordos Basin,.The Zhangjiagou area is located in the Jingbian oilfield in the middle part of the Yishan slope of the basin.The current exploration results show that the Chang 2 reservoirs in the study area are widely distributed,but the law of petroleum enrichment has not yet been clarified.This undoubtedly constrains the exploration and development in the region.Therefore,the study on the law of petroleum enrichment in the Chang 2 reservoir group in the Zhangjiagou area has been conducted.the data of drilling geology,well logging,and logging are used to define the structure and reservoir characteristics,identify the types of sedimentary facies by using the rules of geology of petroleum,and comprehensively analyze the affecting factors of petroleum enrichment.Based on the principles of sedimentary cycle,formation thickness,and the application of the logging interpretation,the Chang 2 reservoir components are divided into four layers of Chang 21,Chang221,Chang222,and Chang 223.The distribution of the layers in the study area is stable,and the variation in thickness is small.In the study area,three sets of nose-like low-amplitude uplift structures were developed near the northeast-southwest direction.The structures of the layers were qualitatively arranged,and the inheritance of the structural development was good.The Chang 2 reservoir group belongs to delta plain subfacy,which mainly has three types of microfacies,including distributary channels,natural embankments,and swamps.The plane distribution of sand bodies is controlled by sedimentary facies and vertically stacked into pieces.Among them,the Chang 223 sand bodies are the most developed,from deep to shallow,and the continuity of the sand bodies is deteriorating.The part of the Chang 21 layer sand bodies are dispersed in the lens body.The lithology of Chang 2 reservoir is mainly mesogranite,and diagenesis includes compaction,cementation and dissolution.The types of reservoir space include intergranular pores,feldspar dissolved pores and intergranular dissolved pores.The porosity is in the range of 17%?20%,and the permeability is between 0.07 and 60mD,with an average of 10.8mD.By the Comprehensive assessment of Chang 2 reservoirs,it belongs to type ?b and ?a reservoirs.The Chang 2 reservoir is a lithologic-structural reservoir with developed bottom water,and the formation water is CaCl2 type.The average depth of the reservoir is 915m,reservoir pressure is 8.8MPa,and reservoir temperature is 34?36?.The distribution of petroleum is controlled by multiple factors such as sedimentary microfacies,structure,and reservoir properties.The Chang 2 reservoirs are distributed in strips on the plane,and the petroleum enrichment zone and the nose uplift region are in good agreement,indicating that the enrichment of oil is obviously controlled by the low-amplitude structure.The porosity and permeability and other physical parameters of reservoir sand bodies controlled by distributary channels are better and the oil saturation of the sand body is higher,indicating that the main part of the distributary channel is a favorable place for petroleum enrichment.Micro-phase sand bodies such as marshes and natural embankments have poor physical properties and are not conducive to petroleum enrichment.