四川盆地南缘龙马溪组混合岩相页岩及其沉积环境  

Mixed lithofacies shale and depositional environment of Longmaxi Formation in southern margin of Sichuan Basin

作　　者：徐传正 李鑫 田继军 吝文[2] 蒋立伟 张治恒 XU Chuanzheng;LI Xin;TIAN Jijun;LIN Wen;JIANG Liwei;ZHANG Zhiheng(School of Geology&Mineral Engineering,Xinjiang University,Urumqi 830047,China;Langfang Branch,China Petroleum Exploration and Development Research Institute,Langfang 065007,China;China National Petroleum Corporation Zhejiang Oilfield Company,Hangzhou 310023,China)

机构地区：[1]新疆大学地质与矿业工程学院,新疆乌鲁木齐830047 [2]中国石油勘探开发研究院廊坊分院,河北廊坊065007 [3]中国石油天然气集团浙江油田公司,浙江杭州310023

出　　处：《煤炭科学技术》2021年第5期208-217,共10页Coal Science and Technology

基　　金：国家科技重大专项资助项目(2017ZX05063002—008)。

摘　　要：四川盆地南缘海相页岩发育,尤其是上奥陶统五峰组-下志留统龙马溪组下段是页岩气勘探开发的优质储层。为对其页岩岩相和沉积环境进行研究,以四川盆地南缘Y5井龙马溪组页岩(L1段)为研究对象,基于页岩储层品质和压裂品质2个影响页岩气勘探开发的主要因素,提出了以有机碳含量和页岩矿物组成为基础的页岩岩相划分方案,利用X全岩衍射分析及有机碳含量测试资料,开展了页岩岩相划分,分析了不同岩相的属性;通过主量元素和微量元素分析,研究了不同岩相页岩的沉积环境;通过对不同岩相页岩的FE-SEM图像观察,利用Image J软件提取有机质孔和前人提出的有机质孔隙度计算方法,查明了不同岩相页岩有机质孔发育特征,总结了沉积环境对不同岩相页岩有机质丰度和有机质孔隙发育的控制作用。结果表明:L1段主要发育富有机质黏土质-硅质混合页岩(OR-M-1)和极富有机质钙质-硅质混合页岩(OER-M-3);微量元素w(V)/w(Cr)、w(Ni)/w(Co)和w(U)/w(Th)等指标表明龙马溪下段OR-M-1页岩形成于富氧-缺氧的海水中,而OERM-3页岩形成于厌氧水体,w(Ba)/w(Al)、w(P)/w(Ti)和w(Cu)+w(Zn)+w(Ni)等指标表明此2种岩相沉积环境古海洋生产力差异不大,样品中Al和Ti的百分含量表明OR-M-1页岩沉积期的陆源碎屑输入强度大于OER-M-3页岩;基于海平面变化和上升洋流造成的水体分层的古环境,导致OER-M-3页岩沉积期有机质形成条件好于OR-M-1页岩,OER-M-3页岩有机质孔隙体积占页岩总孔隙体积比更高,更有利于页岩气的吸附。Marine shale is well developed in the southern margin of Sichuan Basin,especially the Upper Ordovician Wufeng Formation and Lower Silurian Longmaxi formation,which is a good reservoir for shale gas exploration and development.In order to study the shale facies and sedimentary environment,taking Longmaxi formation shale(member L1)of well Y5 in the southern margin of Sichuan Basin as the re⁃search object,based on two main factors affecting shale gas exploration and development,shale lithofacies division scheme based on TOC content and shale mineral composition is proposed in this paper.By using X-ray diffraction analysis and TOC content test data,shale faci⁃es division is carried out,and the properties of shale with different lithofacies were analyzed;the sedimentary environments of different lithofacies shale were studied by the analysis of major and trace elements;the development characteristics of organic pores of different litho-facies shale were found out by observing FE-SEM images of different lithofacies shale,extracting organic pores with Image J software and the calculation method of organic porosity proposed by predecessors;finally,the sedimentary environments for different lithofacies shale were summarized the control of the abundance of organic matter and the development of organic pores.The results show that the organic rich clayey siliceous mixed shale(OR-M-1)and organic rich calcareous siliceous mixed shale(OER-M-3)are mainly developed in the L1 member;the trace elements w(V)/w(Cr),w(Ni)/w(Co)and w(U)/w(Th)indicate that the OR-M-1 shale in the lower Longmaxi member is formed in oxygen rich anoxic sea water,while the OER-M-3 shale is formed in anaerobic water,and the w(Ba)/w(Al),w(P)/w(Ti)and w(Cu)+w(Zn)+w(Ni)indicators indicate two lithofacies depositsare little difference in environmental paleomarine productivity.The percentages of Al and Ti in the samples indicate that the input strength of terrigenous clasts of OR-M-1 shale in sedimentary period is greater than that of OER-M-3 shale.Based on t

关 键 词：页岩 四川盆地 龙马溪组 混合岩相页岩 沉积环境 

分 类 号：P618[天文地球—矿床学]