黏土矿物对低渗致密砂岩储渗性能的影响

Influences of Clay Minerals on Physical Properties of Low Permeability and Tight Sandstones

黏土矿物是碎屑储集岩中最重要的填隙物,广泛分布于四川盆地上三叠统须家河组低渗致密砂岩中,对砂岩储渗性能起着重大的影响。以典型区块营山构造为研究对象,利用铸体薄片、扫描电镜、X–衍射及电子探针等实验技术手段,对砂岩中黏土矿物的类型、产状、性质及其形成机理开展了较为深入的研究,并系统分析了黏土矿物对储层发育的影响。研究表明:(1)黏土矿物以伊利石为主,次为绿泥石,少见混层伊利石/蒙皂石和书页片状高岭石。(2)自生绿泥石类型属于铁镁过渡型偏富含铁的绿泥石,主要是由新生沉淀形成的,高岭石的成岩转化和下伏雷口坡组蒸发盐的物质来源极少。(3)自生绿泥石主要生长时期可能在早成岩期之前,并在成岩中、晚期普遍继续生长。(4)自生绿泥石和伊利石的形成对储层发育具有双重作用,绿泥石和伊利石包膜作为孔隙衬里对残余原生粒间孔隙的保护作用必须是早成岩的,并具有一定厚度和数量。充填于粒间的伊利石和混层伊利石/蒙皂石主要对储层起堵塞作用。

The clay mineral is the most important interstitial material ofclastic reservoir, and is widely distributed in the Xujiahe Formation, which plays a major impact on sandstone reservoir. Taking the typical blocks of Yingshan structure as the research object, with the casting thin sections, scanning electron microscopy, X-ray diffraction and electron probe experiments, we carried out an in-depth research on the type, the occurrence and nature of its formation mechanism of clay minerals in sandstones, and made systematic analysis of clay minerals on reservoir development. The research show： （1） The clay minerals include mainly illite and then chlorite, with rare mixed-layer illite/smectite and kaolinite flakes pages. （2） Authigenic chlorite is mainly formed by the precipitation of newborn, with four major possible sources of iron. （3） Authigenic chlorite major growth period may be in the early diagenetic stage before in diagenesis, and generally continue to grow in the late stage. （4） Authigenic chlorite and illite formation has a dual role in reservoir development, the protective effect of chlorite and illite on primary intergranular porosity must be formed in the early diagenesis, with certain thickness and quantity. Illite and mixed-layer illite/smectite filling the intergranular play a blocking effect on reservoir.