陆相碎屑岩中钙质胶结物沉淀机制及油气储集意义——来自济阳坳陷孔店组和川西须家河组的对比研究

摘要

The mechanism of calcareous cementation in clastic rocks in the Kongdian Formation in the Jiyang Depres?sion and the Xujiahe Formation in the western Sichuan Basin were studied by means of cathode luminescence, scanning electron microscopy, inclusion homogenization temperature measurement, isotope content of carbon and oxygen, and chemical ion. The calcareous cements mainly consist of carbonates, hard gypsum and fluorite. Their microscopic characteristics are influenced by cementation time and environment. Calcium sources and precipitation controlling factors affect the mechanism of calcareous cementation. The calcium sources for calcareous cements mainly include meteoric water eluviation, feldspar dissolution, compaction and dissolution, thermochemical action of organic salt rocks, and clay mineral transformation. The precipitation mechanism of calcareous cements is not influenced by a single factor, but by many factors such as temperature and pressure, pH value and the concentration of chemical ions. The time of calcareous cementation is divided into early, middle and late. The physical properties of reservoirs are in?fluenced by the time of calcareous cementation. Calcareous cements during the early diagenetic stage are constructive to the reservoir, while those during the late diagenetic stage are destructive.%通过阴极发光、扫描电镜、包裹体测温、碳氧同位素和化学离子等实验对济阳坳陷孔店组和川西地区须家河组碎屑岩中的钙质胶结机理进行研究.结果表明:钙质胶结类型主要为碳酸盐、硬石膏和萤石胶结,其微观特征受胶结时间和环境等影响;钙质来源和控制沉淀的因素共同影响着钙质胶结机制,大气水淋滤作用、长石的溶蚀、压实—压溶作用、有机盐岩热化学作用和黏土矿物转化是钙质胶结物中钙质的主要来源,钙质胶结物的沉淀并不是受单一因素影响,而是由多种因素共同作用形成,温度压力、pH值和化学离子的浓度等是控制钙质胶结物溶解沉淀的关键因素;钙质胶结通常分为早、中、晚3期,储层的物性受钙质胶结期次的影响,成岩早期钙质胶结物对储层具有建设性,成岩晚期钙质胶结物对储层具有破坏性.