鄂尔多斯盆地姬塬地区上三叠统延长组长8油层组成岩作用研究

Research on diagenesis of Upper Triassic Chang 8 reservoir in Jiyuan area of Ordos Basin

利用铸体薄片、阴极发光和扫描电镜等分析方法,对姬塬地区延长组长8油层组砂岩的岩石学特征、成岩作用、自生矿物、孔隙发育特征进行了分析和研究。结果表明:该区储集砂体为成分成熟度较低的长石岩屑砂岩和岩屑长石砂岩;主要自生矿物为高岭石、绿泥石、伊利石、方解石、石英和钠长石等,其中高岭石的含量反映了次生孔隙的发育程度,绿泥石和硅质表现为对储层原生孔隙具有很好的保存作用;而伊利石对储层的影响是负面的;早期形成的自生方解石对储层物性有利,而晚期形成的大量方解石胶结孔隙,使储层物性降低。

The thin section, cathodoluminescence and scanning electron microscopy are applied to analyze the petrological characteristics, diagenesis, authigenic minerals and pore development of Chang 8 reservoir sandstone in Jiyuan area. The result shows that the reservoir rock consists of feldspathic lithic sandstone and lithic arkose with low compositional maturity. The main authigenic minerals include kaolinite, chlorite, illite, calcite, quartzand soda feldspar. The content of kaolinite reflects the development degree of secondary porosity. Chlorite and silica have protective effect on primary porosity of the reservoir, and illite has negative effect on the porosity and permeability. Authigenic calcite which generated in the early stage is favorable for reservoir properties, and a large number of calcite cement pores generated in the later stage have negative effect on the reservoir properties.