摘要
通过野外露头剖面实测和岩心观察,结合薄片鉴定、氩离子抛光、X射线衍射、扫描电镜、能谱分析和激光剥蚀元素面扫描等方法,对四川盆地东部地区中二叠统茅口组一段(简称茅一段)含海泡石层系泥质灰岩中自生黏土矿物类型、产状及其组成进行了分析,明确黏土矿物的成岩演化序列,建立黏土矿物沉积-成岩演化模式。研究表明,川东地区茅一段在富Si^(4+)、Mg^(2+)的凉水文石海中沉淀自生海泡石矿物,形成含海泡石层系;在埋藏成岩过程中,自生黏土矿物会经历两条可能的演化序列:①早成岩A期到中成岩A_(1)期,在普遍缺乏Al^(3+)的浅埋藏环境中,海泡石维持稳定状态;中成岩A_(2)期,自生海泡石开始演化为斯蒂文石;中成岩B_(1)期演化为无序滑石;中成岩B_(2)期至晚成岩期,最终演化为滑石,形成了茅一段主要的自生黏土矿物成岩演化序列“海泡石—斯蒂文石—无序滑石—滑石”。②早成岩A期,风暴和上升洋流携带的Al^(3+)参与成岩过程,微量海泡石向蒙脱石演化,部分蒙脱石继续演化为绿泥石;早成岩B期至中成岩A_(1)期,部分蒙脱石演化为伊/蒙混层;中成岩A_(2)期至中成岩B_(2)期,伊/蒙混层向伊利石发生演化,至晚成岩期全部转化为伊利石,由此形成茅一段次级自生黏土矿物成岩演化序列“海泡石—蒙脱石—绿泥石/伊利石”。含海泡石层系泥质灰岩中自生黏土矿物的类型与演化具有两方面的油气地质意义:①海泡石吸附和聚集大量有机质,有效提升茅一段烃源岩的品质和生烃潜力。②海泡石向滑石演化过程中形成大量有机质孔和黏土收缩孔(缝),同时释放富Mg^(2+)成岩转化流体,使凹陷内或凹陷边缘区的灰岩发生白云石化,在中二叠统形成自生自储和(旁)下生(侧)上储型的源储配置新模式,提高了油气成藏效率。
The types,occurrence and composition of authigenic clay minerals in argillaceous limestone of sepiolite-bearing strata of the first member of the Middle Permian Maokou Formation(Mao-1 Member)in eastern Sichuan Basin were investigated through outcrop section measurement,core observation,thin section identification,argon ion polishing,X-ray diffraction,scanning electron microscope,energy spectrum analysis and laser ablation-inductively coupled plasma-mass spectrometry.The diagenetic evolution sequence of clay minerals was clarified,and the sedimentary-diagenetic evolution model of clay minerals was established.The results show that authigenic sepiolite minerals were precipitated in the Si^(4+)and Mg^(2+)-rich cool aragonite sea and sepiolite-bearing strata were formed in the Mao-1 Member.During burial diagenesis,authigenic clay minerals undergo two possible evolution sequences.First,from the early diagenetic stage A to the middle diagenetic stage A_(1),the sepiolite kept stable in the shallow-buried environment lack of Al^(3+).It began to transform into stevensite in the middle diagenetic stage A_(2),and then evolved into disordered talc in the middle diagenetic stage B_(1) and finally into talc in the period from the middle diagenetic stage B_(2) to the late diagenetic stage.Thus,the primary diagenetic evolution sequence of authigenic clay minerals,i.e.sepiolite-stevensite-disordered talc-talc,was formed in the Mao-1 Member.Second,in the early diagenetic stage A,as Al^(3+)carried by the storm and upwelling currents was involved in the diagenetic process,trace of sepiolite started to evolve into smectite,and a part of smectite turned into chlorite.From the early diagenetic stage B to the middle diagenesis stage A_(1),a part of smectite evolved to illite/smectite mixed layer(I/S).The I/S evolved initially into illite from the middle diagenesis stage A_(2) to the middle diagenesis stage B_(2),and then totally into illite in the late diagenesis stage.Thus,the secondary diagenetic evolution sequence of authigenic clay minerals,i.e.sepiolite-smectite-chlorite/illite,was formed in the Mao-1 Member.The types and evolution of authigenic clay minerals in argillaceous limestone of sepiolite-bearing strata are significant for petroleum geology in two aspects.First,sepiolite can adsorb and accumulate a large amount of organic matters,thereby effectively improving the quality and hydrocarbon generation potential of the source rocks of the Mao-1 Member.Second,the evolution from sepiolite to talc is accompanied by the formation of numerous organic matter pores and clay shrinkage pores/fractures,as well as the releasing of the Mg^(2+)-rich diagenetic fluid,which allows for the dolomitization of limestone within or around the sag.As a result,the new assemblages of self-generation and self-accumulation,and lower/side source and upper/lateral reservoir,are created in the Middle Permian,enhancing the hydrocarbon accumulation efficiency.
作者
宋金民
王佳蕊
刘树根
李智武
罗平
江青春
金鑫
杨迪
黄士鹏
范建平
叶玥豪
王俊轲
邓豪爽
王斌
郭嘉欣
SONG Jinmin;WANG Jiarui;LIU Shugen;LI Zhiwu;LUO Ping;JIANG Qingchun;JIN Xin;YANG Di;HUANG Shipeng;FAN Jianping;YE Yuehao;WANG Junke;DENG Haoshuang;WANG Bin;GUO Jiaxin(State Key Laboratory of Oil&Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu 610059,China;Xihua University,Chengdu 610039,China;PetroChina Research Institute of Petroleum Exploration&Development,Beijing 100083,China)
出处
《石油勘探与开发》
EI
CAS
CSCD
北大核心
2024年第2期311-322,共12页
Petroleum Exploration and Development
基金
国家自然科学基金企业创新发展联合基金(U19B6003)
国家自然科学基金面上项目(41872150)。
关键词
含海泡石层系
自生黏土矿物
成岩演化
中二叠统茅口组
四川盆地
sepiolite-bearing strata
authigenic clay minerals
diagenetic evolution
Mao First Member of Middle Permian
Sichuan Basin
