东濮凹陷桥口地区沙三段碎屑岩成岩作用与储层特征

CLASTIC DIAGENESIS AND RESERVOIR PROPERTIES OF THE THIRD MEMBER OF SHAHEJIE FORMATION,QIAOKOU AREA,DONGQU DEPRESSION

东濮凹陷桥口地区沙三段碎屑岩经历了复杂的成岩历史。砂岩的主要成岩事件有:机械压实、碳酸盐胶结、石英加大、黄铁矿生成、高岭石的形成和转化、绿泥石生成、伊利石沉淀、斜长石的钠长石化、石膏和重晶石的形成,以及沸石矿物的生成和次生孔隙的产生。混层蒙皂石-伊利石化随埋深增加而增强,相邻页岩的成岩演化是砂岩胶结物成分的最重要来源。砂岩的成岩作用主要受沉积相的控制,处于中成岩晚期阶段的沙三段砂岩可划分为四种成岩相:(1)碳酸盐胶结成岩相;(2)石英加大自生成岩相;(3)粘土蚀度成岩相;(4)不稳定碎屑溶蚀成岩相。四种成岩相组成了四种不同的储层类型,储层性质的对比分析对识别致密气层中的油气产层具有重要意义。

Detailed examinitions of petrography ,cathodoluminescence,SME,and X-ray diffraction indicate that the sandstones of the third Member of Shahejie Formation, Qiaokou, Dongpu Depression have undergone a complex diagenetic histroy. Diagenetic events in the sandstones principally involve mechanical compaction, carbonate cementation, quartz overgrouth,pyrite formation,chlorite authigenesis,illite formation,albitization of plagioclase,precipitation of gypsum and harite cements,formation of zeolites and framework grain dissolution(FGD). X-ray diffraction of the shales shows evidence of progressive illitization of the mixed-layer illite-smectite with increasing depth of burial. The diagenetic evolution of adjacent shales might provide the most important source of various cement components. Sedimentary facies is the major diamenetic control. According to diagenetic facies,the reservoirs and be divided into four types: (l)carbonate cementation, (2)silica cementation, (3)clay alteration, and (4)unstable clastic dissolution. Diagenetic facies, con trolled by sedimentary facies,significantly influences the reservoir properties. Correlations of reservoir properties wtih sedimentary and diagenetic facies are of great importance to the exploration and development of tight gas-bearing formations.