鄂尔多斯盆地东南部本溪组致密石英砂岩成岩作用与孔隙演化

Diagenesis and porosity evolution of tight quartz sandstones in Benxi Formation,Southeast Ordos Basin

以岩心观察为基础,结合薄片鉴定、阴极发光、扫描电镜、X衍射、包裹体、镜质组反射率、孢粉等测试分析及本溪组地层埋藏史,对研究区的成岩作用和孔隙演化进行研究。研究后认为,研究区石英砂岩经历了多期复杂的成岩作用,达中成岩B期末。早成岩期的强压实作用使储层丧失约22.6%的原生粒间孔隙;中成岩期,有机酸生成使易溶组分和早期碳酸盐胶结物溶蚀,使储层增加了约2.9%的孔隙;至中成岩后期,铁白云石、石英晚期次生加大及黏土矿物的胶结作用使储层损失了约13.7%的孔隙空间;晚期微裂缝及碳酸盐的微弱溶蚀使储层增加了约0.5%的孔隙空间。其中,酸性成岩流体、硅质胶结、烃类充注、有机酸的溶蚀作用及晚期微裂缝与本溪组石英砂岩有利孔隙的发育关系密切,改善了储层物性。

The quartz sandstone of barrier island sedimentary in Benxi Formation is an important gas reservoir southeastern Ordos Basin. Diagenesis and pore evolution research are of great significance in predicting high quality reservoir. Based on core observation, combining with thin section analysis, cathodeluminescence emission analysis, SEM, X-ray diffraction, inclusion thermometry, vitrinite reflectance, pollen analysis, and burial history of Benxi Formation, it is believed that the quartz sandstone has experienced multiphase complex dia- genesis, and the diagenesis reaches B-period of middle diagenetic stage. About 22. 6% primary porosity were destructed after the strong compaction in early diagenetic stage. The porosity of reservoir is improved about of siliceous, hydrocarbon filling, dissolution of organic acids and microfracture in the late stage diagenesis, all above could promote the development of favorable porosity in quartz sandstone and improve reservoir physical property in Benxi Formation.