四川盆地川西坳陷须家河组砂岩致密化研究

Densification of Upper Triassic Xujiahe tight sandstones, Western Sichuan, China

李嵘 张娣 朱丽霞

Li Rong Zhang Di Zhu Lixia

成都地质矿产研究所, 成都610081

Chengdu Institute of Geology and Mineral Resources, Chengdu, Sichuan 610081, China

从岩石学特征、成岩作用特征、储集空间类型研究入手,并结合盆地模拟分析结果,对四川盆地川西坳陷须家河组砂岩致密化进程进行系统分析。导致须家河组砂岩致密化的主要成岩事件包括机械和化学压实作用、碳酸盐胶结物及自生石英的沉淀。压实作用是造成砂岩孔隙度降低的最主要因素,较高石英、长石、钙屑含量可以提高岩石抗机械压实能力。碳酸盐胶结作用在须四段钙屑砂岩和须二段细粒砂岩中较为普遍,对储层具有明显的破坏作用。相对开放环境以及古构造高位置不利于碳酸盐胶结物的沉淀,对储层发育有利。自生石英主要来自碎屑石英的压溶,具一定厚度、连续性较好的绿泥石衬边可以抑制压溶作用进行以及石英胶结物的形成,对须家河组砂岩储层孔隙保存具有双倍积极作用。

Densification process of the Upper Triassic Xujiahe sandstones were described based on petrologic,diagenesis and basin modeling analyses.The diagenetic events that affect reservoir quality mainly include mechanical and chemical compactions,precipitation of carbonate cements,and cementation by quartz.Compaction is the dominant process of porosity loss.Sandstones with high content of quartz,feldspar and carbonate rock fragment exhibit higher mechanical stability.Pervasive mesogenetic carbonate cementation occurs in the calcarenaceous sandstones in T3x4 and the fine-grained sandstones in T3x2 and reservoir quality is significantly deteriorated by extensive carbonate cementation.Open and paleo-high environment is favorable for relatively good reservoir quality.Quartz cements are mainly sourced by the pressure dissolution of detrital quartz and are more abundant in sandstones rich in detrital quartz and illite and poor in carbonate cements and chlorite.Thick and continuous chlorite pore-linings help to preserve porosity by inhibiting pressure dissolution and quartz cementation and thus can be doubly beneficial to the Xujiahe sandstones.

国家科技重大专项项目(2008ZX05002-004)资助

https://doi.org/10.11781/sysydz201103274