石油实验地质2018，Vol.40Issue(1)：78-89,12.DOI:10.11781/sysydz201801078
四川盆地焦石坝地区五峰—龙马溪组页岩元素地球化学特征及对页岩气开发的意义
Element geochemical characteristics of the Wufeng-Longmaxi shale in Jiaoshiba area, Sichuan Basin and their significance to shale gas development
摘要
Abstract
A total of 85 shale core samples from wells JYA and JYD in Jiaoshiba area of Sichuan Basin were selected to test their organic carbon contents, major and trace elements. The redox conditions and paleoproductivity of the gas-bearing shale in the Wufeng-Longmaxi formations in the Jiaoshiba area were studied by analyzing the vertical variation characteristics of the major and trace elements in the profile. Meanwhile, the controls for organic matter enrichment in the Wufeng-Longmaxi formations were explored. Moreover, the impact of geochemical elements on shale compressibi-lity and gas-bearing property were studied. The organic carbon content in the high gas-bearing interval from the Wufeng Formation to the lower part of Longmaxi Formation is high with an average value of 3.07％. Compared with the common gas-bearing shale, SiO2 and CaO contents are higher in the high gas-bearing shale, and redox-sensitive elements such as Mo, Cr, V, Ni, Th and U are enriched. The redox condition indicators such as V/Cr, V/Sc, U/Th and Ni/Co indicated that the Wufeng Formation was mostly deposited in suboxic to anoxic conditions, whereas the anoxic environment dominated during the early sedimentary stage of Longmaxi shale and evolved into aerobic condi-tions later on. The contents of biological productivity-related element Ba(xs) reflected a high paleoproductivity, whereas TOC content has an obvious positive correlation with redox proxies (Mo/Al, U/Th, Ni/Co and V/Sc) in the high gas-bearing interval, suggesting that the enrichment of organic matter was predominantly controlled by redox environ-ment . In addition, the biogenic siliceous content of high-quality gas-bearing shale is high, and the organic carbon con-tent is positively correlated with the SiO2 content, which is conducive to the formation of natural fractures and the later artificial fracturing. The ratio of geochemical elements in the high gas-bearing interval is significantly higher than that of common interval, indicating that there is a certain correlation between chemical element ratios and shale gas.关键词
主、微量元素/有机质富集/可压性/含气性/页岩/五峰组—龙马溪组/焦石坝地区Key words
major and trace elements/organic matter enrichment/compressibility/gas-bearing/shale/Wufeng-Longmaxi formations/Jiaoshiba area分类
能源科技引用本文复制引用
甘玉青,王超,方栋梁,杨兰芳,周新科,张萍..四川盆地焦石坝地区五峰—龙马溪组页岩元素地球化学特征及对页岩气开发的意义[J].石油实验地质,2018,40(1):78-89,12.基金项目
国家科技重大专项(2016ZX05060)和中国石化科技项目(P17014-3)资助. （2016ZX05060）
