碎屑岩储层中自生绿泥石衬边能抑制石英次生加大吗?——以四川盆地须家河组砂岩储层为例

Can authigenic pore-lining chlorite restrain quartz overgrowth in clastic reservoir? a case study of sandstone reservoir in Xujiahe Formation,Sichuan Basin

应用X射线衍射、铸体薄片、扫描电镜、能谱、微量元素等分析方法，对四川盆地须家河组395块砂岩储层样品的黏土矿物组分和含量进行了分析。结果表明，在须家河组砂岩储层中，黏土矿物主要为伊利石和绿泥石，绿泥石含量占黏土矿物总量的33％，并与储层孔隙度、渗透率呈一定的正相关关系；自生绿泥石属于铁一镁过渡型，偏富铁，主要分布于砂岩骨架颗粒表面，以颗粒衬边形式出现，呈叶片状和针叶状；自生绿泥石形成于pH值介于7～9的碱性水介质中，而石英次生加大形成于pH值介于5～6的弱酸性水介质中。自生绿泥石与自生石英不同的共生关系是由水介质条件变化引起的，绿泥石衬边的存在并不能明显抑制石英的次生加大，自生绿泥石优先生长于孔隙空间大的砂体中。

The composition and content of clay minerals in 395 rock samples from sandstone reservoir in Xujiahe Formation, Sichuan Basin are examined by a combination of X-ray diffraction, thin section casting, scanning electron microscopy, energy spectrum analy- sis, and trace element assays. Results show that illite and chlorite are the major clay minerals in sandstone reservoir in Xujiahe For marion. Chlorite accounts for 33% of total content of clay minerals and has a positive correlation with porosity and permeability of reservoir. The authigenic chlorite is iron-magnesium transition type, which contains abundant iron and is mainly developed on grain surface of sandstone skeleton in the form of foliated and needle-shaped lining. Authigenic chlorite is formed in alkaline aqueous solu- tion at pH 7-9, whereas quartz overgrowth occurs in weak acidic aqueous solution at pH 5-6. Different symbiotic relationships be- tween authigenic chlorite and quartz are resulted from variations of aqueous medium condition. The presence of authigenic pore-lining chlorite could not restrain quartz overgrowth significantly, and authigenic chlorite preferentially grows in sandbodies with macropore spaces.