中上扬子区下寒武统页岩有机岩石学特征及成熟度综合评价  

Organic petrological characteristics and comprehensive evaluation of maturity of the Lower Cambrian shale in Middle-Upper Yangtze region

作　　者：赵延铭 高平 肖贤明 周秦 ZHAO Yanming;GAO Ping;XIAO Xianming;ZHOU Qin(School of Energy Resources,China University of Geosciences(Beijing),Beijing 100083,China;State Key Laboratory of Organic Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Guangdong,China)

机构地区：[1]中国地质大学(北京)能源学院,北京100083 [2]中国科学院广州地球化学研究所,有机地球化学国家重点实验室,广东广州510640

出　　处：《地球化学》2024年第3期386-398,共13页Geochimica

基　　金：国家自然科学基金项目(42030804)资助。

摘　　要：我国南方下寒武统是页岩气勘探的重点层位,资源潜力巨大。由于下古生界缺乏镜质体,固体沥青成因复杂且常具有光学各向异性,固体沥青反射率(BRo)与等效镜质体反射率(EqVR_(o))之间的转换公式繁多,使得下古生界页岩成熟度评价面临巨大挑战。本研究识别了中上扬子区下寒武统页岩中的显微组分,测试不同显微组分的光学反射率特征和激光拉曼光谱,综合评价了研究区下寒武统页岩的成熟度水平。结果表明:(1)固体沥青和类镜质体是研究区下寒武统页岩中最主要的两类显微组分;(2)通过光学方法和激光拉曼光谱法揭示了中上扬子区下寒武统页岩处于高–过成熟演化阶段;(3)中上扬子区下寒武统页岩普遍进入有机质石墨化阶段,但宜昌地区典型页岩气井(宜页1井)的页岩有机质尚未发生石墨化作用,成熟度较低;(4)EqVR_(o)>3.50%时,有机质呈现石墨化趋势,拉曼光谱参数(D峰和G峰峰位值)的演化规律发生倒转。对于高–过成熟页岩,激光拉曼光谱法可为有机质成熟度评价提供依据,联合光学反射率法可以获得更加可靠的评价结果。在进一步完善方法和参数的标准化后,激光拉曼光谱法可以在前寒武系–下古生界页岩有机质成熟度评价领域具有更加广泛的应用。The Lower Cambrian in southern China is a key horizon for shale gas exploration with great resource potential.The lack of vitrinite in the Lower Paleozoic,the complex origin of solid bitumen that is often optically anisotropic,and the diverse conversion formulas between solid bitumen and vitrinite reflectance make the evaluation of the maturity of the Lower Paleozoic shale especially difficult.In this study,the organic macerals in the Lower Cambrian shale in the Middle-Upper Yangtze area were identified,the optical reflectance characteristics and Raman spectra of different macerals were tested,and the maturity level of the Lower Cambrian shale in the study area was comprehensively evaluated.The results show that:(1)Solid bitumen and vitrinite-like maceral are the two most important organic macerals in the Lower Cambrian shale in the study area.(2)Optical method and laser Raman spectrometry revealed that the Lower Cambrian shale in the Middle-Upper Yangtze area is in a high-over mature evolution stage.(3)The Lower Cambrian shale in the Middle-Upper Yangtze area has generally entered the stage of graphitization of organic matter,but the organic matter of the typical shale gas well(Well YY1)in the Yichang area has not yet graphitized,and the maturity is relatively low.(4)When EqVR_(o)>3.50%,the organic matter showed graphitization trend,and the evolution law of Raman spectrum parameters(D peak and G peak)was reversed.For high-over mature shale,Raman spectrometry can provide a basis for the evaluation of organic matter maturity,and the combined optical reflectance method can yield more reliable evaluation results.After further improving the standardization of the methods and parameters,Raman spectrometry can be widely used in the evaluation of organic matter maturity in shales from Lower Paleozoic to Precambrian.

关 键 词：固体沥青反射率 拉曼光谱 显微组分 高–过成熟度 页岩气 

分 类 号：P618.12[天文地球—矿床学]