摘要
研究了川东北普光气田下三叠统飞仙关组白云岩储层的岩石结构Sr的含量和Sr同位素组成,讨论了它的成因,飞仙关组优质储层为成岩期埋藏交代白云化作用的产物,来自岩石结构和Sr同位素和Sr含量的证据包括如下几个方面:(1)与准同生白云岩比较,埋藏白云岩的岩石结构和Sr同位素和Sr含量地球化学特征与前者有显著差别;(2)飞仙关组所有各类碳酸盐岩(或矿物)具有早三叠世海水Sr同位素组成特征,^(87)Sr/^(86)Sr比值变化范围为0.706588～0.708187,覆盖了全球早三叠世海水Sr同位素的变化范围(0.7076～0.7078),平均值0.707656与全球早三叠世平均值(0.707743)基本一致;(3)埋藏白云岩^(87)Sr/^(86)Sr比值变化范围为0.707122～0.707419,平均值0.707421,都略低于全球早三叠世海水Sr同位素变化范围和平均值,但与已报道的川东北早三叠世飞仙关期海水Sr同位素变化范围(0.707330～0.707383)和平均值(0.707350) 都非常接近,说明白云石化流体具有强烈的川东北地区早三叠世飞仙关期海水Sr同位素组成特征;(4)综合岩石结构、Sr同位素和Sr含量地球化学特征,证明飞仙关组白云岩储层为成岩期埋藏交代作用产物,白云石化流体来自地层中高Sr和高盐度的海源地层水。
On the basis of analysis of rock structure and strontium isotopes composition and content, in this study the genesis of dolostone reservoir in the Feixianguan Formation, Lower Triassic of the NE Sichuan Basin is discussed. Results indicate that the dolostone reservoir is the product of replaced dolomitization during the deep burial diagenesis period. This conclusion comes from following evidences: (1) rock structure and characteristics of strontium isotope and strontium content of the deep burial dolostone are quite different from that of penecontemporaneous dolostone. (2) carbonate rocks and minerals of the Feixianguan Formation have the composition characteristics of Triassic seawater strontium isotope, and their ^(87)Sr/^(86)Sr ratios range from 0.706588 to 0.708187 ,covering the range (0.7076～0.7078) of strontium isotope in early Triassic and the average value 0.707656 being consistent with the average value of 0.707743 for global early Triassic. (3) ^(87)Sr/^(86)Sr ratios of burial dolostone range from 0.707122 to 707419, being slightly under the changing range of strontium isotope of the global early Triassic seawater, but within the range of 0.707330～0.707383 for early Triassic seawater of northeast Sichuan Basin suggested in earlier studies,and the average value 0.707421 is closer to the earlier reported value 0.707350 than global early Triassic seawater, which shows that dolostone diagenetic fluids were very similar to the Triassic seawater. (4) Based on comprehensive study of rock structure, geochemistry characteristics of strontium isotope and strontium content,it can be well proved that the dolostone diagenetic fluids come from sea source water rich in strontium and salinity sealed up and kept in the stratum.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2009年第10期2459-2468,共10页
Acta Petrologica Sinica
基金
中国石油天然气总公司科技信息部重点实验室2002年项目'川东北三叠系飞仙关组鲕滩白云岩储层形成机理与分布特征研究' 部分研究成果
