川中太和气区震旦系灯影组二段储层成岩流体演化及油气成藏史——来自岩石学、原位地球化学、流体包裹体及年代学的证据  

Diagenetic fluid evolution and hydrocarbon accumulation history of second Member of the Sinian Dengying Formation in the Taihe gas area,central Sichuan basin:Evidence from petrology,in situ geochemistry,fluid inclusions and chronology

作　　者：杨鹏 袁海锋[1] 马奎 肖钦仁 叶子旭 李跃杰 谌辰 谭谦 匡明志 徐婷 YANG Peng;YUAN Haifeng;MA Kui;XIAO Qinren;YE Zixu;LI Yuejie;SHEN Chen;TAN Qian;KUANG Mingzhi;XU Ting(State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu,Sichuan 610059,China;Exploration and Development Research Institute of Southwest Oil&Gas Field Branch Company Ltd.PetroChina,Chengdu,Sichuan 610041,China)

机构地区：[1]成都理工大学,油气藏地质及开发工程国家重点实验室,四川成都610059 [2]中石油西南油气田公司勘探开发研究院,四川成都610041

出　　处：《地质学报》2023年第7期2332-2353,共22页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41572133、41872130)资助的成果。

摘　　要：川中地区震旦系灯影组四段已获得巨大勘探突破,太和含气区灯二段目前也已展示出较大勘探潜力。但灯二段储层时代老、埋深大、成岩演化历史长,经历了多期次构造运动,储层中矿物胶结充填期次复杂,成岩演化与油气充注关系不清,一定程度上制约了灯二段油气勘探。本文基于岩石组构分析,利用阴极发光、原位微区分析、流体包裹体及白云石U-Pb年代学等方法厘定了川中太和气区灯二段储层成岩序列,明确了不同期次白云石胶结充填物的成岩环境、成岩流体特征、形成时间及代表的油气充注事件,明确了其油气地质意义及灯二段油气成藏历史。研究表明区内灯二段储层孔洞中沥青及胶结充填物的成岩序列为:第一世代海底环境纤维状白云石→第二世代表生成岩环境大气淡水白云石→第三世代浅埋藏环境粉—细晶粒状白云石→第Ⅰ期氧化降解沥青→第四世代中埋藏环境中晶白云石→第五世代深埋藏环境粗晶白云石→第Ⅱ期热裂解沥青→第六世代深埋藏环境巨晶-鞍状白云石→第七世代抬升埋藏环境石英、萤石等矿物。主要反映了四种不同类型的成岩流体特点:(1)具有高Na、K含量,低Fe、Mn含量,负Ce异常,Y正异常特征的高盐度海源流体;(2)具有较低Fe、Mn含量,平缓REE模式,无Eu异常特征的淡水与残余海水的混合流体;(3)具有高Fe、Mn含量,Eu明显正异常特征的高温热液流体与早期海水的混合流体;(4)具有高Mn含量,Fe/Mn<1,HREE较富集,Eu正异常特征且自生石英、萤石矿物沉淀的深部与高温热液相关的酸性、还原性流体。不同世代矿物的充填关系、流体包裹体相态、均一温度以及白云石U-Pb年代学分析表明,开始发育含烃包裹体的第三世代粉—细晶白云石与形成于加里东运动导致的构造隆升期的第Ⅰ期沥青分别记录了加里东期古油藏的形成及破坏;第四世代中晶白�Great exploration breakthrough has been achieved in the fourth Member of the Sinian Dengying Formation in central Sichuan.The 2nd Member of the Sinian Dengying Formation in Taihe gas-bearing area has also shown great exploration potential.However,the reservoir of the 2nd Member of the Dengying Formation has the characteristics of old age,large burialdepth,long diagenetic evolution history,and has experienced multiple tectonic movements;the mineral cementation filling periods in the reservoir are complicated,and the characteristics of diagenetic fluids are unclear.All of these limit oil and gas exploration in the 2nd Member of the Dengying Formation reservoir to a certain extent.Based on the rock texture analysis,this paper uses cathode-luminescence,in situ microzone analysis,fluid inclusion and dolomite U-Pb chronology to determine the diagenetic sequence of the 2nd Member of the Dengying Formation in Taihe gas area,its diagenetic environment and diagenetic fluid characteristics.The formation time and representative oil-gas charging events of dolomite cemented backfill at different times,as well as its geological significance and hydrocarbon accumulation history are clarified.The results show that the diagenetic sequence of bitumen and fillings in the reservoir pores of the 2nd Member of the Dengying Formation in the study area are as follows:fibrous dolomite of the first generation in the submarine environment→atmospheric freshwater dolomite of the second generation in the epidiagenetic environment→silty-fine grained dolomite of the third generation in the shallow-burial environment→oxidized degradation bitumen of the first stage→medium crystal dolomite of the fourth generation in the moderate burial environment→coarse crystal dolomite of the fifth generation in the deep-burial environment→thermally cracked bitumen of the second stage→giant-saddle crystal dolomite of the sixth generation in the deep-burial environment→quartz and fluorite of the seventh generation in the uplifting burial environme

关 键 词：太和气区 灯影组二段 油气成藏 成岩流体 成岩序列 四川盆地 

分 类 号：P618.13[天文地球—矿床学]