元坝地区千佛崖组储层特征及其成岩作用

Study on diagenesis and reservoir characteristics of Qianfoya Formation in Yuanba area,Northeast Sichuan,China

研究川东北元坝地区中侏罗统千佛崖组储层特征,探讨其成岩作用与成岩演化模式。通过薄片观察、物性分析、扫描电镜及阴极发光等测试手段对钻井岩心和露头剖面的147块岩石样品进行分析,结果表明:元坝地区千佛崖组的储层岩石类型以细粒岩屑长石砂岩和细粒岩屑砂岩为主,其次为细粒长石岩屑砂岩。储集空间类型按成因可分为剩余原生粒间孔、次生孔隙和裂缝,次生孔隙可分为粒间溶孔和铸模孔。野外样品和岩心样品皆表现为孔隙度与渗透率较低,但孔渗关系较好。储层经历了压实作用、胶结作用、交代作用、溶蚀作用和自生矿物的沉淀,根据对储层的影响可分为破坏性成岩作用、建设性成岩作用和保持性成岩作用。破坏性成岩作用包括压实作用和胶结作用,建设性成岩作用为溶蚀作用,保持性成岩作用则为自生矿物的沉淀和破裂作用。成岩作用被划分为早成岩阶段A期、早成岩阶段B期、中成岩阶段A期和中成岩阶段B期2个阶段4个期次。

Study of diagenesis and reservoir characteristics of the Middle Jurassic Qianfoya Formation in Yuanba area of Sichuan Basin shows that the main reservoir rock type is fine-grained arkose sandstone and fine lithic sandstone, followed by fine grained feldspathic lithic sandstone. Reservoir space types in terms of genesis can be classified into residual primary intergranular pore, secondary pore and fracture, and the secondary pores can be further divided into intergranular dissolved pore and moldic pore. The porosity and permeability in the rocks are lower, but the relationship between porosity and permeability is well. During the process of rock formation, the reservoir experiences three kinds of diageneses, the destructive diagenesis, the retentivity diagenesis and the constructive diagenesis respectively. There are two stages and four phases for the diagenesis, including early stage A phase and early stage B phase; mid stage A phase and mid stage B phase.