海相高演化页岩裂缝方解石脉成因机制及指示意义  

Genetic mechanism and indicative significance of fracture calcite veins in marine high-evolution shale

作　　者：吴安彬 罗群[2] 代兵 李靖[2] 王士琛 张景坤[1] 安尊鹏 刘冬冬[2] 姜振学[2] WU Anbin;LUO Qun;DAI Bing;LI Jing;WANG Shichen;ZHANG Jingkun;AN Zunpeng;LIU Dongdong;JIANG Zhenxue(School of Earth Sciences and Engineering in Nanjing University, Nanjing 210023, China;Unconventional Petroleum Research Institute in China University of Petroleum, Beijing 102249, China;Sichuan Bureau of Geology and Mineral Resources, Yibin 644002, China;Engineering Institute in Tongren Polytechnic College, Tongren 554300, China)

机构地区：[1]南京大学地球科学与工程学院,江苏南京210023 [2]中国石油大学(北京)非常规油气科学技术研究院,北京102249 [3]四川省地质矿产勘查开发局,四川宜宾644002 [4]铜仁职业技术学院工学院,贵州铜仁554300

出　　处：《中国石油大学学报（自然科学版）》2022年第3期25-35,共11页Journal of China University of Petroleum(Edition of Natural Science)

基　　金：国家科技重大专项(2017ZX05035-002);国家自然科学基金项目(41672118)。

摘　　要：以川南地区龙马溪组为例,采用全岩测试、微区原位元素、同位素、流体包裹体相结合的方法,分析海相高演化页岩中方解石脉成因,结合地质背景,探讨其对烃类活动和油气成藏的影响,通过对方解石脉物质组成及成因机制分析,探讨流体成岩与烃类演化的示踪关系,明确方解石充填物可能对储层物性具有临界效应(以方解石质量分数5%为界)。结果表明研究区方解石脉普遍受深部热液与有机流体影响,高温包裹体和δ^(18)O偏负特征记录了深部热流信息,Mn^(2+)元素富集说明火山物质汇入,^(87)Sr/^(86)Sr高值反映壳源锶影响;研究区主要发育3期方解石脉,存在生物氧化、油源改造和甲烷热化学3种成因机制,对应志留纪时期的地层流体、二叠纪以来的油源、侏罗纪以来的甲烷3类流体活动;一定含量的方解石可能有助于改善页岩空间结构,有利于页岩气的吸附和储集。Taking the Longmaxi Formation in the southern Sichuan Basin as an example,the genesis of calcite veins in marine high evolution shale was analyzed by the combination of whole rock test,micro in-situ elements,isotopes and fluid inclusions.Combined with the geological background,its influence on hydrocarbon activities and oil and gas accumulation was discussed.Through the analysis of material composition and genetic mechanism of calcite veins,the tracer relationship between fluid diagenesis and hydrocarbon evolution was also investigated,and the critical effect of calcite filling on reservoir physical properties(bounded by 5%)was determined.The results show that the calcite veins in the study area are generally affected by deep hydrothermal and organic fluids.The high temperature inclusions and negativeδ^(18)O characteristics record the information of deep hydrothermal.The enrichment of Mn^(2+)indicates the volcanic material resorption,and the high value of ^(87)Sr/^(86)Sr reflects the influence of crust source.It is found that three stages of calcite veins are mainly developed in the study area,and there are three genetic mechanisms biological oxidation,oil source transformation and methane thermochemistry,which correspond to the three types of fluid activities of Silurian period,oil source since Permian and methane since Jurassic.A certain content of calcite can improve the spatial structure of shale and is conducive to the adsorption and storage of shale gas.

关 键 词：海相高演化 成因机制 方解石脉 碳、氧、锶同位素 流体包裹体 四川盆地 

分 类 号：P618.130[天文地球—矿床学]