Elemental characteristics of lacustrine oil shale and its controlling factors of palaeo-sedimentary environment on oil yield： a case from Chang 7 oil layer of Triassic Yanchang Formation in southern Ordos Basin  

作　　者：Delu Li Rongxi Li Zengwu Zhu Feng Xu 

机构地区：[1]School of Earth Sciences and Resources, Chang'an University, Xi'an 710054, China [2]Shaanxi Center of Geological Survey, Xi'an 710068, China

出　　处：《Acta Geochimica》2018年第2期228-243,共16页地球化学学报（英文）

基　　金：supported with funding from the National Natural Science Foundation of China (No. 41173055);the Fundamental Research Funds for the Central Universities (No. 310827172101)

摘　　要：As an important unconventional resource, oil shale has received widespread attention. The oil shale of the Chang 7 oil layer from Triassic Yanchang Formation in Ordos Basin represents the typical lacustrine oil shale in China. Based on analyzing trace elements and oil yield from boreholes samples, characteristics and paleo-sedi- mentary environments of oil shale and relationship between paleo-sedimentary environment and oil yield were studied. With favorable quality, oil yield of oil shale varies from 1.4% to 9.1%. Geochemical data indicate that the paleo-redox condition of oil shale＇s reducing condition from analyses of V/Cr, V/（V ＋ Ni）, U/Th, δU, and authi genic uranium. Equivalent Boron, Sp, and Sr/Ba illustrate that paleosalinity of oil shale is dominated by fresh water. The paleoclimate of oil shale is warm and humid by calculating the chemical index of alteration and Sr/Cu. Fe/Ti and （Fe ＋ Mn）/Ti all explain that there were hot water activities during the sedimentary period of oil shale. In terms of Zr/Rb, paleohydrodynamics of oil shale is weak. By means of Co abundance and U/Th, paleo-water-depth of oil shale is from 17.30 to 157.26 m, reflecting sedimentary environment which is mainly in semi deep-deep lake facies. Correlation analyses between oil yield and six paleoenvironmental factors show that the oil yield of oil shale is mainly controlled by paleo-redox conditions, paleoclimate, hot water activities, and depth of water.Paleosalinity and paleohydrodynamics have an inconspicuous influence on oil yield.As an important unconventional resource, oil shale has received widespread attention. The oil shale of the Chang 7 oil layer from Triassic Yanchang Formation in Ordos Basin represents the typical lacustrine oil shale in China. Based on analyzing trace elements and oil yield from boreholes samples, characteristics and paleo-sedimentary environments of oil shale and relationship between paleo-sedimentary environment and oil yield were studied. With favorable quality, oil yield of oil shale varies from 1.4% to 9.1%. Geochemical data indicate that the paleo-redox condition of oil shale's reducing condition from analyses of V/Cr, V/(V + Ni), U/Th, d U, and authigenic uranium. Equivalent Boron, Sp, and Sr/Ba illustrate that paleosalinity of oil shale is dominated by fresh water.The paleoclimate of oil shale is warm and humid by calculating the chemical index of alteration and Sr/Cu. Fe/Ti and(Fe + Mn)/Ti all explain that there were hot water activities during the sedimentary period of oil shale. In terms of Zr/Rb, paleohydrodynamics of oil shale is weak.By means of Co abundance and U/Th, paleo-water-depth of oil shale is from 17.30 to 157.26 m, reflecting sedimentary environment which is mainly in semi deep–deep lake facies. Correlation analyses between oil yield and six paleoenvironmental factors show that the oil yield of oil shale is mainly controlled by paleo-redox conditions,paleoclimate, hot water activities, and depth of water.Paleosalinity and paleohydrodynamics have an inconspicuous influence on oil yield.

关 键 词：Elemental geochemistry Palaeosedimentary Main controlling factors Lacustrine oil shale Triassic Ordos Basin 

分 类 号：P618.13[天文地球—矿床学]