川东地区龙马溪组页岩黏土矿物组成与成因

为了分析页岩气储层中黏土矿物特征及其与有机质的关系，以川东地区下志留统龙马溪组页岩为研究对象，利用X-射线衍射分析和扫描电镜观察，并结合薄片、岩心和测井资料，深入分析了研究区龙马溪组黏土矿物成因、分布特征及其主控因素、对有机质的影响。结果表明:黏土矿物组合为伊利石+伊/蒙混层+绿泥石，具有陆源碎屑、自生和次生成岩3种类型，全区具有高伊利石、伊/蒙混层含量的特点；焦石坝地区龙马溪组下段地层具有封闭性，致使烃源岩生烃过程中产生异常高压，抑制伊利石化作用，在垂向上出现了随深度增加伊/蒙混层含量也增加的非正常转化序列，同时也可以用这种非正常转化序列反推地层中异常高压的存在；碎屑组分也间接影响黏土矿物的含量，尤其是钾长石的含量，在伊/蒙混层向伊利石的转化过程中，是否能提供足够多的K⁺，决定了两者之间是否能等量转化。

Composition and origin of clay minerals in the Lower Silurian Longmaxi Formation in eastern Sichuan Basin

In order to investigate the characteristics of clay minerals in shale gas reservoir and its relationship with organic matter,shale from Lower Silurian Longmaxi Formation in eastern Sichuan Basin was studied.Based on X-diffraction analysis and observation of SEM,combined with data of thin sections,core and logging,distribution characteristics and controlling factors of clay minerals and their influence on organic matter were revealed.Chlorite+illite/smectite+illite is the main assemblage,including neoformed,inherited and transformed types.There is abnormal high pressure in the lower segment of Longmaxi Formation in Jiaoshiba area,which inhibits lithificaiton.It has a non-normal transformation sequence that illite/smectite content increase with increasing depth in vertical direction.This non-normal transformation sequence can indicate the existence of abnormal high pressure.Detrital composition especially potash feldspar affect the content of clay minerals indirectly,whether it can provide enough K⁺ during illitization decides the equivalent transformation between illite mixed layer and illite.