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台北凹陷柯柯亚构造八道湾组砂岩是在辫状河三角洲沉积环境下形成的一套富含火山物质的长石质岩屑砂岩和岩屑砂岩。根据常规薄片、铸体薄片和扫描电镜观察及X衍射资料分析,对八道湾组砂岩的岩石学特征、成岩作用阶段划分、成岩作用类型及其对孔隙的影响进行了研究。结果表明:研究区八道湾组砂岩现处于晚成岩A2期,经历的成岩作用有机械压实、绿泥石形成、石英次生加大、方解石析出、胶结作用及长石溶蚀作用。压实作用和胶结作用是主要的破坏性成岩作用,而溶蚀作用则是主要的建设性成岩作用,特别是长石的溶蚀是储层物性变好的重要成岩控制因素。
The Bawauwan Formation sandstone in the Kekeya tectonic depression in Taipei depression is a set of volcanic-shaped feldspathic lithic sandstone and lithic sandstone formed in the sedimentary environment of braided delta. The lithology, division of diagenetic stages, types of diagenesis and their influence on porosity of sandstones in Badaowan Formation are studied based on the observation of conventional thin slices, cast thin slice, scanning electron microscope and X-ray diffraction data. The results show that the sandstones of the Badaowan Formation in the study area are now in late A2 stage of diagenesis. The experienced diagenesis includes mechanical compaction, chlorite formation, quartz secondary growth, calcite precipitation, cementation and feldspar dissolution. Compaction and cementation are the major destructive diagenesis while dissolution is the major constructive diagenesis. In particular, the dissolution of feldspar is an important diagenetic controlling factor that improves reservoir physical properties.