海相页岩有机质石墨化特征研究:以渝东南地区牛蹄塘组为例  

Graphitization Characteristics of Organic Matters in Marine-Facies Shales

作　　者：赵文韬[1] 荆铁亚[1] 熊鑫 吴斌 周游 Zhao Wentao;Jing Tieya;Xiong Xin;Wu Bing;Zhou You(Huaneng Clean Energy Research Institute, Beijing 102209, China;Chongqing Mineral Resources Development Company Limited, Chongqing 401123, China)

机构地区：[1]中国华能集团清洁能源技术研究院有限公司,北京102209 [2]重庆矿产资源开发有限公司,重庆401123

出　　处：《地质科技情报》2018年第2期183-191,共9页Geological Science and Technology Information

基　　金：国家科技重大专项(2016ZX05034004);中国华能集团科技项目(HNKJ16-30)

摘　　要：我国南方上扬子地区广泛发育上奥陶统五峰组-下志留统龙马溪组和下寒武统牛蹄塘组2套烃源岩,为近年来的页岩气勘探事业提供了坚实的物质保障。四川盆地及周缘牛蹄塘组具有富有机质页岩厚度大、TOC丰度高、岩石脆性较好等特点,整体具备页岩气发育的有利条件,但其含气性明显不及上部的五峰组-龙马溪组。从渝东南地区YY1井牛蹄塘组的极低电阻率测井响应入手,基于干岩样岩电实验、全岩X射线衍射定量分析等测试成果的分析初步认为:在测井曲线和岩电数据中出现的极低电阻率值是由高演化有机质中的高导矿物——石墨引起;石墨为生烃进入高温生气阶段的标志性产物之一,预示着有机质炭化程度达到区域高值。另外,通过对比牛蹄塘组和五峰组-龙马溪组的电性参数、地球化学数据与测井曲线可知,YY1井牛蹄塘组富有机质泥页岩层已发生石墨化,其生气能力、基质孔隙发育等方面均不及上部五峰组-龙马溪组,属于研究区页岩气勘探相对不利层位;此外,电阻率测井可作为页岩气勘探前期预判的重要指标之一,极低电阻率可指示对应层位有机质演化成熟度过高,含气性和生烃能力欠佳,不利于后期页岩气的勘探开发。Two sets of source rocks, including the Wufeng Formation in the Upper Ordovician-the Long- maxi Formation in the Lower Silurian and the Niutitang Formation in the Lower Cambrian, are widely de- veloped in the Upper Yangtze Platform, which provide material sources for the shale-gas exploration in re- cent years. In the Sichuan Basin and its around areas, although the Niutitang Formation has some advanta- ges of shale-gas development, such as thick organic-rich shales, high TOC and favorable rock brittleness, the gas content of this formation is apparently less than that in the Wufeng Formation-Longmaxi Forma- tion. This paper, based on the super-low resistivity log of Well YY1 in the southern Chongqing area, dis- cusses the litho-electricity experiments and X-ray diffraction quantitative analyses of this well. The study results show that the super-low resistivity in the logs and litho-electricity tests is caused by the high-con- ductivity mineral-graphite. Graphite is one of the signature minerals in the high-temperature gas-generation stage, which indicates the organic carbonization reaches a high degree in this region. By comparing the Niutitang Formation and the Wufeng Formation-Longmaxi Formation within electrical data, geo-chemical results and log curves, the paper concludes that the organic-rich shales of the Niutitang Formation in Well YY1 have been graphitized,whose gas-generation and pore-development ability is worse than that of the Wufeng Formation-Longmaxi Formation, demonstrating that the Niutitang Formation is a relatively unfa- vorable layer in the shale-gas development. In addition, the resistivity log could be used as an important indicator in the early shale-gas exploration; super-low resistivity denotes that the organic matters are of high evolution degrees, low gas contents and low hydrocarbon-generation ability, which is harmful to the further shale-gas exploration career.

关 键 词：四川盆地 渝东南地区 牛蹄塘组 海相页岩 极低电阻率 石墨化 

分 类 号：P618.13[天文地球—矿床学]