| The Ordos Basin has a large amount of petroleum resources in the Mesozoic.There are good source rocks in Upper Triassic Yanchang Formation of Binchang area.The reservoir and cap rock combined well.Therefore,it is clear that the sedimentary characteristics and reservoir distributional rules of Chang 7 member are significant for future oil and gas exploration.In this paper,through field exploration,core observations,indoor analysis,and the sedimentary microfacies characteristics,diagenetic facies characteristics,reservoir quality of each layer are studied in Chang 7 member.The understanding and conclusions are as follows:(1)A deep-water gravity flow depositional system is developed in Chang 7 member,which is dominated by sandy debris flow and supplemented by turbidity current.The thick sandstone is the main sand body of Chang 7 member,which is often caused by multiple phases and superimposed.(2)Microscopic heterogeneity of sandstone is strong in Chang 7 member.Different types of reservoirs have similar physical properties in the conventional analysis,but their microcosmic characteristics are quite different.(3)The diagenetic types and reservoir diagenesis sequences of the Chang 7 member have been defined.Five typical diagenetic facies(strong dissolution diagenetic facies,weak dissolution diagenetic facies,strong compaction diagenetic facies,strong calcium cementation diagenetic facies and micro crack diagenetic facies)and the characteristics of the logging are summed up.On this basis,the distribution of diagenetic facies of each small layer has completed.(4)Lithologic facies,diagenetic facies and fracture are the main controlling factors for the development of reservoirs.Based on the analysis,the favorable area of the study area is mainly in the area of development and thickness of sand body,which is mainly distributed in the area of dissolution.While local crack development zone is also the dessert area which has rich oil and gas. |
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