鄂尔多斯盆地华庆地区长9储层成岩作用与有利成岩相

Diagenesis and favorable diagenetic facies of Chang 9 reservoir in Huaqing Area of Ordos Basin

对岩心薄片鉴定、扫描电镜、X衍射、物性等分析化验资料进行综合研究,以查明鄂尔多斯盆地华庆地区延长组长9油层组的主要成岩类型、成岩阶段、成岩序列及有利成岩相的分布规律。研究后认为,研究区长9储层经历了压实压溶作用、胶结作用、溶蚀作用等主要成岩作用。其中,对储层起破坏性成岩作用的有压溶压实作用和包括碳酸盐胶结、长英质胶结、自生黏土矿物胶结等的胶结作用,起建设性成岩作用的主要有绿泥石薄膜胶结作用、浊沸石和长石溶蚀作用。综合研究成岩作用的组合类型和演化序列,认为长9砂岩的成岩演化主体已进入中成岩阶段A期,成岩相可划分为5种:Ⅰ绿泥石膜-粒间孔+浊沸石溶蚀相;Ⅱ绿泥石膜-粒间孔+长石溶蚀+浊沸石胶结相;Ⅲ铁方解石胶结+绿泥石膜-粒间孔+长石溶蚀相;Ⅳ硅质胶结+铁方解石胶结+绿泥石膜-粒间孔+长石溶蚀相;Ⅴ铁方解石胶结+水云母胶结+硅质胶结相。Ⅰ类成岩相物性好,Ⅱ和Ⅲ两类次之,它们成为储层发育的有利成岩相;Ⅳ和Ⅴ类物性较差,为不利成岩相。

To identify the main diagenetic types, diagenetic stage, diagenetic sequence and the distribution of favorable diagenetic facies of Chang 9 reservoir of Yanchang formation in the Ordos Basin Huaqing Area. Comprehensive study of chemical analysis data was done, such as core slice identification, scanning electron microscopy, X-diffraction, physical property,etc. The Chang 9 reservoir experienced the main diagenesis, such as compaction pressure dissolution, cementation, dissolution and so on. Among them, destructive diagenesis are compaction by carbonate cementation, felsic cementation and clay mineral cementation. Constructive dia- genesis are chlorite cementation, laumontite and feldspar dissolution. According to the types and evolutionary sequences of diagenesis, it is regarded that the diagenetic evolution of Chang 9 sandstone has already been in stage A of the middle diagenetic stage. It is divided into five kinds of diagenetic facies, as follows ： I chlorite membrane-intergranular pore ＋ laumonite dissolution phase Ⅱ. chlorite membrane-intergranular pore ＋ feldspar dissolution ＋ laumonite cementation phase Ⅱ ferrocalcite cement ＋ chlorite membrane-intergranular pore ＋ feldspar dissolution phase IV. siliceous cement ＋ ferrocalcite cement ＋ chlorite membrane-intergranular pore ＋ feldspar dissolution phase V. ferrocalcite cement ＋ hydromica cement ＋ siliceous cement phase. The type I diagenetic facies have good physical properties, the tpyes Ⅱand m are secondary to the former phase, and they are favorable diagenetic facies of reservoir. While, the tpyes Ⅳand V phase have bad physical properties, they are adverse diagenetic facies of reservoir.