川东北普光3011-5井须家河组黏土矿物及胶结物特征

Characteristics of clay minerals and cements of the Xujiahe formation in Well Puguang 3011-5 in northeast Sichuan

根据常规薄片、扫描电镜及X衍射等资料分析,以普光3011-5井取心资料为基础,对须家河组储层中黏土矿物及胶结物特征进行了研究。结果表明:普光3011-5井须家河组以孔隙式胶结为主,泥质和灰质是主要的胶结物类型,次为硅质胶结,少见黄铁矿、硬石膏及石盐晶体;硅质发育使岩石胶结作用强烈,结构较为致密,是导致储层低孔低渗的一个重要原因;黏土矿物主要以伊利石和绿泥石为主,含少量的绿/蒙混层、伊/蒙混层,黏土总含量随深度增加逐渐减少;伊利石与绿泥石的分布具有分带性,两者常以片状结合体充填于粒间孔隙中,或呈薄膜结构覆盖于碎屑颗粒表面,自生绿泥石一方面提高了岩石的抗压实能力,另一方面抑制了石英的次生加大,从而使砂岩中的孔隙得以保存。通过对黏土矿物及胶结物特征的研究,对须家河组的进一步勘探与开发具有重要的指导意义。

Clay minerals and cements of the Xujiahe formation in Well Puguang 3011-5 are studied based on core data through analysis of thin sections,scanning electron microscopy and X-ray diffraction.The results indicate that the cementation in the Xujiahe formation in Well Puguang 3011-5 is dominated by pore cementation,with argillaceous and limy matters as major cements,then siliceous matters,and rarely seen pyrite,anhydrite or halite crystals;the development of siliceous matters had caused intense cementation and dense structure,and is an important reason for low porosity and low permeability reservoir;clay minerals are mainly composed of illite and chlorite,with a little mixed illite/smectite and chlorite/smectite,and the total content of clay minerals decreases with depth;illite and chlorite present zonation distribution,and are often seen filled in intergranular pores as flaky combination,or covering on clastic particles as thin film structure;authigenic chlorite improved the mechanical strength of rocks and inhibited quartz overgrowth,thereby preserved sandstone porosity.The research on clay minerals and cements is of significant implication on further exploration and development for the Xujiahe formation.