鄂尔多斯盆地西缘奥陶系乌拉力克组页岩沉积环境及有机质富集机制  

Sedimentary environments and organic matter enrichment mechanism of Ordovician Wulalike Formation shale,western Ordos Basin

作　　者：张艳妮[1] 李荣西[1] 席胜利[2] 姚泾利[2] 黄何鑫 赵帮胜 吴小力[1] 杨玲 ZHANG Yanni;LI Rongxi;XI Shengli;YAO Jingli;HUANG Hexin;ZHAO Bangsheng;WU Xiaoli;YANG Ling(School of Earth Science and Resources,Chang'an University,Xi'an 710054,China;Research Institute of Exploration and Development,PetroChina Changqing Oilfield Company,Xi'an 710018,China;Shaanxi Geological Survey Experiment Center,Xi'an 710068,China)

机构地区：[1]长安大学地球科学与资源学院,陕西西安710054 [2]中国石油长庆油田分公司勘探开发研究院,陕西西安710018 [3]陕西省地质调查实验中心,陕西西安710068

出　　处：《中南大学学报（自然科学版）》2022年第9期3401-3417,共17页Journal of Central South University:Science and Technology

基　　金：国家自然科学基金资助项目(41772118)。

摘　　要：在岩相学研究基础上,应用有机地球化学、主量及微量元素地球化学分析方法,对鄂尔多斯盆地西缘两口钻井奥陶系乌拉力克组斜坡相页岩沉积环境进行分析,探讨其对有机质富集的影响。研究结果表明:乌拉力克组页岩以石英(平均质量分数为47.5%)和黏土矿物(平均质量分数为24.9%)为主,发育硅质页岩和混合页岩。页岩总有机碳(TOC)含量较低(TOC质量分数平均为0.85%),有机质类型为Ⅰ型,有机质热演化程度达到高成熟阶段(等效镜质体反射率R_(equ)平均为1.42%)。乌拉力克组沉积期古生产力指标w(生物SiO_(2))和w(Ba)/w(Al)显示具有低的古生产力,气候以温暖湿润为主。氧化还原指标(w(V)/w(Cr),w(V)/w(Sc)和w(Ni)/w(Co))及岩相学显示沉积水体为深水贫氧强受限环境。综合分析认为乌拉力克组页岩有机质富集受控于古生产力和较好的保存条件。乌拉力克组有机质含量低的主要原因是古生产力低,而古生产力低可能是沉积期研究区距离火山活动较远、缺乏海底洋流和陆源物质输入较少引起的表层水体营养物质浓度较低所致。Based on petrography,the organic geochemistry in combination with major and trace elements geochemical methods were used to study the sedimentary environments and their roles in organic matter enrichment mechanism of the Ordovician Wulalike Formation in two wells of slope facies shale in the western margin of Ordos Basin.The results show that quartz and clay(averaging of 47.5%and 24.9%,respectively)are the most abundant minerals,and the lithology is siliceous shale and mixed shale.The shale has low TOC contents(averaging of 0.85%)and type I kerogen,and high maturity stage(mean of 1.42%R_(equ)).Paleoproductivity parameters w(biogenic SiO_(2))and w(Ba)/w(Al)show a low paleoproductivity and the paleoclimate is mainly warm and humid in the Wulalike Formation sedimentary stage.Both redox indexes,such as w(V)/w(Cr),w(V)/w(Sc)and w(Ni)/w(Co)and petrography show a deep-water dysoxic and strongly restricted environment.Comprehensive analysis reveals that the enrichment of organic matter in Wulalike Formation is controlled by paleoproductivity and redox condition.The low TOC in Wulalike Formation is mainly caused by the low paleoproductivity,which may be due to the low concentration of nutrients in surface water caused by the long distance from volcanic activity,the lack of submarine ocean current and less input of terrigenous materials.

关 键 词：页岩 沉积环境 总有机碳 鄂尔多斯盆地 乌拉力克组 

分 类 号：P642.6[天文地球—工程地质学]