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川西地区雷口坡组成岩流体期次及其来源
陈智远,孟宪武,宋晓波,郝晓波,隆轲
0
(1.中国石化西南油气分公司博士后科研工作站,四川成都610041;2.中国石化西南油气分公司勘探开发研究院,四川成都610041;3.中国石油西部钻探工程有限公司试油公司,新疆克拉玛依834000)
摘要:
为了明确川西地区雷口坡组成岩流体的期次和来源,在镜下岩石薄片和阴极发光精细观察的基础上,利用成岩矿物流体包裹体与碳、氧和锶同位素等地化资料,综合分析川西地区雷口坡组四段成岩矿物的充填序列,确定成岩流体的期次和来源。研究结果表明,川西地区雷口坡组四段不同粒级充填矿物分为3期,充填序列分别为:第Ⅰ期微-粉晶白云石和方解石、第Ⅱ期细晶白云石和方解石及第Ⅲ期中晶白云石、方解石和嵌晶白云石,3期流体大致分别对应于晚三叠世早—晚期(距今232~214 Ma)、晚三叠世末期—晚侏罗世末期(距今212~145 Ma)、早白垩世—晚白垩世末期(距今142~70 Ma)。雷口坡组四段基质白云石与孔缝充填物的碳、氧和锶同位素组成显示,成岩流体具有正常海相碳酸盐岩的地化特征,并揭示了雷口坡组四段87Sr/86Sr高值是由于蒸发潮坪环境下同生-准同生期毛细管浓缩作用、渗透回流作用以及埋藏期封存海水释放作用的流体侵入造成的。
关键词:  矿物期次  包裹体特征  碳、氧和锶同位素  流体来源  雷口坡组  川西地区
DOI:10.13673/j.cnki.cn37-1359/te.2021.01.004
基金项目:中国石化股份“十条龙”项目“龙门山前雷口坡组气藏勘探开发关键技术研究”(P16093)。
Analysis of sequences and sources of diagenetic fluid in Leikoupo Formation,Western Sichuan Basin
CHEN Zhiyuan,MENG Xianwu,SONG Xiaobo,HAO Xiaobo,LONG Ke
(1.Post-doctoral Research Station,Southwest Oil & Gas Company,SINOPEC,Chengdu City,Sichuan Province,610041,China;2.Research Institute of Petroleum Exploration and Production,Southwest Oil & Gas Company,SINOPEC,Chengdu City,Sichuan Province,610041,China;3.Well Testing Company,CNPC Xibu Drilling Engineering Company Limited,Karamay,Xinjiang,834000,China)
Abstract:
Based on the thin section and cathodoluminescence,a comprehensive study of the filling sequence of diagenetic minerals in T2l4 is carried out by using the geochemical data of diagenetic minerals fluid inclusions and Sr,C,O isotopes,etc.,to clarify the sequences and sources of diagenetic fluid in Leikoupo Formation,Western Sichuan Basin. The results show that the filling minerals of different grain sizes in T2l4 in Western Sichuan Basin can be divided into three stages with filling sequences as follows:micro-powder dolomite and calcite(the first stage)→fine-grained dolomite and calcite(the second stage)→meso-crystalline dolomite,calcite and intercalated dolomite(the third stage). The three stages by which fluid accumulating are roughly corresponding to the early to late of Late Triassic(232-214 Ma),the end of Late Triassic to the end of Late Jurassic(212-145 Ma),and early Cretaceous to the end of late Cretaceous(142-70 Ma),respectively. The C,O,Sr isotopes of matrix dolomite and pore fillings in T2l4 show that the diagenetic fluid has the geochemical characteristics of normal marine carbonate rocks,and it is revealed that the high value of 87Sr/86Sr diagenetic fluid in T2l4 is from the fluid intrusion of capillary concentration,infiltration and backflow in the syngenetic-quasi syngenetic period under the environment of evaporating tidal flat,and the release of sealed seawater during the burial period.
Key words:  mineral sequestration  inclusion characteristics  C,O,Sr isotopes  fluid source  Leikoupo Formation  Western Sichuan Basin

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