摘要
烃源岩是中国重要的油气来源,石炭二叠纪太原期是华北克拉通重要的成煤期,同时伴生有大量富有机质岩,成烃潜力巨大。以钻深4 km地热钻井中太原组不可采薄煤层下覆富有机质岩为研究对象,应用显微光学、X射线衍射(X-ray diffraction,XRD)、X射线荧光(X-ray fluorescence,XRF)、电感耦合等离子体质谱仪(inductively coupled plasma mass spectrometry,ICP-MS)等方法分析了岩石地球化学特征,探讨了成岩古环境、古气候和古盐度特征,并提出了该区有机质沉积富集模式。结果表明:富有机质岩系的岩石类型为炭质页岩、泥岩和砂岩,矿物以高岭石、地开石、伊利石、云母、石英为主,含少量白云石、方解石、黄铁矿、菱铁矿。所测样品总有机碳(total organic carbon,TOC)含量为2.66%~52.3%,均值为21.46%。炭质页岩H/C(0.06~0.12)和O/C(0.13~0.93)显示有机质类型为Ⅱ-Ⅲ型;镜质体平均反射率介于1.76%~2.02%,可作为烃源岩。全岩主量元素氧化物以SiO_(2)和Al_(2)O_(3)为主,微量元素Li和Bi为全岩富集。根据化学蚀变指数(chemical index of alteration,CIA)、Sr/Cu、Sr/Ba、Th/U、V/(V+Ni)、氧化还原环境判别参数U_(EF)-Mo_(EF)、Ce异常指数Ce_(anom)、Mo/TOC模式分析,该煤系烃源岩形成于温湿气候、半咸水缺氧环境。在古生产力物质基础充沛和有利地理条件下,富集并保存了有机质,并最终形成烃源岩。研究结果对开发太原组煤系烃源岩、揭示有机质富集机理具有理论和实践意义。
Hydrocarbon source rocks are recognized as significant sources of oil and gas in China.The Carboniferous-Permian Taiyuan period is an important coal-forming stage in the North China Craton.During this period,a substantial amount of organic-rich rock strata was deposited,exhibiting considerable hydrocarbon-generation potential.The organic-rich rocks under the unminable thin coal seams of the Taiyuan Formation,which were taken from the geothermal drilling with a depth of 4 km,were selected as the research object.The methods of microscopic optics,X-ray diffraction(XRD),X-ray fluorescence(XRF),and inductively coupled plasma mass spectrometry(ICP-MS)were applied to analyze the petrological and geochemical characteristics of the samples.Based on these analyses,the paleo-sedimentary,paleo-climatic,and paleo-salinity characteristics during diagenesis were discussed,and the organic matter sedimentation and enrichment model for the research area was proposed.The results indicate that the rock types of the organic-rich rock strata are classified as carbonaceous shale,mudstone,and siltstone.The main mineral composition consists of kaolinite,dickite,illite,mica,and quartz,with a minor amount of dolomite,calcite,pyrite,and siderite.The total organic carbon(TOC)in the rock ranges from 2.66%to 52.3%,averaging 21.46%.The H/C(0.06~0.12)and O/C(0.13~0.93)of the carbonaceous shale suggest that the organic matter is classified asⅡ-Ⅲ.The average vitrinite reflectance is determined to be between 1.76%and 2.02%,indicating that the organic matter is classified as high maturity.The major elements of the whole rock are dominated by SiO_(2)and Al_(2)O_(3),Trace elements Li and Bi are observed to be enriched.Based on the analyses of chemical index of alteration(CIA),Sr/Cu,Sr/Ba,Th/U,V/(V+Ni),U_(EF)-Mo_(EF)(the discriminant parameters of redox environment),Ce_(anom)(Ce anomaly index),and Mo/TOC,it is inferred that these strata are formed in a warm and humid climate,a brackish,anoxic,and reducing environment.Under the combined effects of an adequate paleo-productive material base and favorable organic matter preservation conditions,organic matter is enriched and preserved,ultimately leading to the formation of source rocks.The research results are considered to have theoretical and practical significance for developing the source rocks within coal measures in the Taiyuan Formation and for revealing the mechanism of organic matter enrichment.
作者
张琴琴
刘东娜
谢晋强
冯子军
ZHANG Qin-qin;LIU Dong-na;XIE Jin-qiang;FENG Zi-jun(College of Geological and Surveying Engineering,Taiyuan University of Technology,Taiyuan 030024,China;Shanxi Key Laboratory of Bauxite Resources Exploration and Comprehensive Utilization,Jinzhong 030620,China;College of Mining Engineering,Taiyuan University of Technology,Taiyuan 030024,China)
出处
《科学技术与工程》
北大核心
2025年第36期15405-15418,共14页
Science Technology and Engineering
基金
山西省科技重大专项计划“揭榜挂帅”项目(202101060301024)
山西地学智库开放基金(2023010)
山西省自然科学基金(202203021221077)
国家自然科学基金(41802191,41372164)。
关键词
石炭二叠纪
煤系烃源岩
地球化学特征
沉积环境
Carboniferous-Permian
coal measures hydrocarbon source rocks
geochemical characteristics
sedimentary environment
