四川盆地东缘石柱地区五峰-龙马溪组页岩矿物组分及含气性特征

Mineral composition and gas-bearing characteristics of Wufeng-Longmaxi shale in Shizhu area,eastern Sichuan Basin

四川盆地东缘石柱地区上奥陶-下志留统五峰-龙马溪组自下而上由钙质泥岩、黑色硅质页岩、黑色粉砂岩、黑色粉砂质页岩、黑色页岩、黑色粉砂质页岩、灰黑色泥岩、粉砂质泥岩、泥岩和粉砂质泥岩10个岩性段组成.对采自露头的富有机质页岩通过显微鉴定、扫描电镜分析和X-射线衍射进行了矿物组分定量研究和粒度特征分析.页岩中陆源碎屑矿物主要为石英、钠长石和白云母;自生矿物主要为石英、方解石、白云石、黄铁矿、伊利石和绿泥石等.剖面底部的硅质页岩为主要含气层段,石英是该层段的主要矿物.石英质量分数自底部向上逐步降低,和有机碳质量分数呈正相关关系;黏土质量分数和石英质量分数有相反的变化趋势.页岩中较高的脆性矿物质量分数提供了页岩气的储存空间,生物成因石英质量分数高的页岩有利于有机质富集.

The upper-Ordovician to lower-Silurian Wufeng-Longmaxi shale in Shizhu area of the eastern Sichuan Basin consists of ten lithologic sections, i.e. calcareous mudstone, black siliceous shale, black siltstone, black siltY shale, black shale, black siltY shale, film mudstone, siltY mudstone, mudstone and siltY mudstone. Outcrop samples were collected from the Shizhu area in the eastern Sichuan Basin to study the lithofacies, mineral components in the Wufeng-Longmaxi formation. Optical microscopy, X-ray diffraction and particle size analysis were applied, to find that detrital minerals are mainly quartz, albite and muscovite, the authigenic minerals are mainly authigenic quartz, calcite, dolomite, pyrite, illite and chlorite. The siliceous shale is the main gas-bearing at the bottom of the profile. Quartz is the dominant mineral this section, and decreases gradually upwards while clay content increases. There is a correla- tion between the content of quartz and that of, and there is a opposite tendency between the content of quartz and that of clay. The high quartz content affects the fragility of the shale but is favorable for the fracturing of shale. Siliceous biogenic quartz is very important for the increase of TOC and gas-bearing orot^ertv of the shale.