上扬子区奥陶系五峰组—志留系龙马溪组沉积期火山活动对页岩有机质富集程度的影响  

Effects of volcanic activities in Ordovician Wufeng–Silurian Longmaxi period on organic-rich shale in the Upper Yangtze area, South China

作　　者：吴蓝宇 陆永潮[1] 蒋恕 刘晓峰[1] 何贵松 WU Lanyu;LU Yongchao;JIANG Shu;LIU Xiaofeng;HE Guisong(Faculty of Earth Sciences,China University of Geosciences,Wuhan 430074,China;Energy&Geosciences Institute,The University of Utah,Salt Lake City,Utah 84108,USA;East China Branch of SINOPEC,Nanjing 210011,China)

机构地区：[1]中国地质大学(武汉)资源学院,武汉430074 [2]Energy & Geosciences Institute,The University of Utah [3]中国石化股份有限公司华东分公司,南京210011

出　　处：《石油勘探与开发》2018年第5期806-816,共11页Petroleum Exploration and Development

基　　金：国家重点基础研究发展计划(973)项目(2017CB239102);国家科技重大专项(2016ZX05060004;2016ZX05034002003;2016ZX05061)

摘　　要：利用等时地层格架内建立的火山活动事件与海洋古生产力及氧化还原环境的对应关系,对上扬子区奥陶系五峰组—志留系龙马溪组沉积期火山活动及其对页岩有机质富集程度的影响进行研究。结果表明,研究区斑脱岩主要发育在五峰组沉积期海侵体系域(TST1)与龙马溪组沉积期海侵体系域(TST2)中,这两个体系域均对应高硅高炭的优质页岩相。根据斑脱岩发育的分段性特征,将TST1划为斑脱岩密集段,TST2划为斑脱岩稀疏段,前者斑脱岩发育频次大于1.5层/Ma且斑脱岩累计厚度比(斑脱岩厚度/页岩厚度)大于1%,后者斑脱岩发育频次小于1.5层/Ma且累计厚度比小于1%。TST1(密集段)较TST2(稀疏段)火山活动强度大且频次高,造成TST1有机质含量普遍较TST2高。剧烈且频繁的火山活动对页岩有机质富集具有双重促进作用,一方面火山灰提供营养物质促进海洋生物生产力,另一方面火山作用产生极度缺氧的环境提高有机质的埋藏量和保存率。Based on the corresponding relationship between the paleoproductivity,redox conditions and volcanism within a isochronous stratigraphic framework,the effects of volcanic events in the Wufeng–Longmaxi period on organic abundance of shale were examined.Bentonite layers were mostly developed in the transgressive systems tract 1(TST1,Wufeng Formation)and transgressive systems tract 2(TST2,Longmaxi Formation),and the two systems tracts corresponded to favorite shale lithofacies with high silica and total organic carbon(TOC)contents.According to the stratigraphic characteristics of bentonite rich interval,TST1 is classified as the interval with dense bentonite layers with the frequency of bentonite layer(bentonite layers/time)of more than 1.5 layers/Ma and the cumulative thickness ratio of bentonite layers(thickness of bentonite layers/thickness of shale)of more than 1%;TST2 is classified as the interval with sparse bentonite layers(frequency<1.5 layers/Ma;cumulative thickness ratio<1%).TST1(dense interval)witnessed more intense and high-frequency volcanic activities than TST2(sparse interval),so the TST1 has higher TOC than TST2 in general.The intense and frequent volcanic activities had dual effects on organic-rich shale:on one hand,volcanic ash provided a sufficient supply of nutrients,which triggered high marine productivity;on the other hand,the extremely anoxic environment caused by volcanic activity enhanced the burial amount and preservation rate of organic matter.

关 键 词：页岩 有机质富集程度 火山活动 层序地层 奥陶系五峰组 志留系龙马溪组 上扬子区 斑脱岩 

分 类 号：TE122.2[石油与天然气工程—油气勘探]