摘要
通过薄片观察、流体包裹体分析、岩石地球化学测试以及盆地数值模拟等,对四川盆地米仓山前缘旺苍地区下寒武统筇竹寺组脉体发育特征进行了研究,并判别了沉积期的流体活动期次和流体性质。研究结果表明:(1)旺苍地区筇竹寺组发育2期方解石脉体和1期石英脉体,石英脉体的形成晚于方解石脉体,第一期方解石脉体形成于早志留世,成脉流体主要为层内地层水,受少量大气淡水和海水影响,与液态烃类流体一起充注,均一温度为83.1~136.2℃,盐度为0.4%~12.2%;第二期方解石脉体形成于早侏罗世,成脉流体为层内地层水,与液态烃类和高密度气相甲烷混合充注,均一温度为140.2~185.4℃,盐度为5.7%~17.3%;石英脉体形成于早白垩世,成脉流体为筇竹寺组硅质流体,与高密度气相甲烷一起充注,均一温度为162.1℃,盐度为13.8%。(2)研究区筇竹寺组方解石脉体样品的δ^(18)O_(PDB)值为-14.95‰~-9.17‰,绝大部分方解石脉体实测δ^(18)O_(PDB)值均小于早寒武世全球海水的平均值,其负偏移特征受控于成脉流体温度和δ^(18)O丰度。方解石脉体和围岩中稀土元素富集,二者均具有Eu正异常和Ce无异常,流体来源于层内地层水。(3)研究区筇竹寺组受外源流体影响较小,节理和裂缝发育,并不沟通上下地层,有利于山前带筇竹寺组页岩气的聚集与封闭保存。
Through thin section observation,fluid inclusion analysis,rock geochemical testing and basin numerical simulation,the development characteristics of veins of Lower Cambrian Qiongzhusi Formation in Wangcang area at Micang Mountain front,Sichuan Basin,were studied,and the fluid activity stages and fluid properties in the sedimentary period were distinguished.The results show that:(1)There are two stages of calcite veins and one stage of quartz veins developed in Qiongzhusi Formation in Wangcang area,and the quartz veins were formed later than the calcite veins.The first stage of calcite veins was formed in the Early Silurian,and the vein forming fluids were mainly inner formation water,which were affected by a small amount of atmospheric fresh water and seawater,and filled veins together with liquid hydrocarbon fluids.The homogenization temperature ranged from83.1 ℃ to 136.2 ℃,and the salinity was 0.4%-12.2%.The second stage of calcite veins was formed in the Early Jurassic.The vein forming fluids were inner formation water,which filled calcite veins together with liquid hydrocarbon and high density methane in gas phase.The homogenization temperature ranged from 140.2 ℃ to 185.4 ℃,and the salinity was 5.7%-17.3%.The quartz veins were formed in the Early Cretaceous,and the vein forming fluids were siliceous fluids in Qiongzhusi Formation,which filled the quartz veins with methane.The homogenization temperature was 162.1 ℃,and the salinity was 13.8%.(2)The δ^(18)_(OPD)Bvalues of calcite vein samples from Qiongzhusi Formation in the study area range from-14.95‰ to-9.17‰,and the measured average δ^(18)O_(PDB)value of most calcite veins is smaller than that of global seawater of the Early Cambrian.The negative migration characteristics are controlled by temperature and δ^(18)O abundance of the vein forming fluids.Rare earth elements are enriched in calcite veins and wall rocks,both of which have Eu positive anomaly and Ce no anomaly,and the fluids came from inner formation water.(3)Qiongzhusi Formation
作者
魏全超
李小佳
李峰
郝景宇
邓双林
吴娟
邓宾
王道军
WEI Quanchao;LI Xiaojia;LI Feng;HAO Jingyu;DENG Shuanglin;WU Juan;DENG Bin;WANG Daojun(Exploration Company of Sinopec,Chengdu 610059,China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu 610059,China)
出处
《岩性油气藏》
CAS
CSCD
北大核心
2023年第5期62-70,共9页
Lithologic Reservoirs
基金
中国石油化工股份有限公司重点科技项目“四川盆地及周缘油气富集规律与分布预测”(编号:P20059)资助。
