西北大学学报(自然科学版)

通过各类薄片显微镜下的定量统计与研究,利用图像孔喉、毛细管压力、扫描电镜、阴极发光、荧光分析等分析测试手段,对鄂尔多斯盆地东部盒8段致密砂岩的类型、岩石学特征、成岩作用、成岩-烃类充注演化历史及孔隙结构特征进行深入研究,分析各砂岩的成岩演化过程及其对砂岩孔隙结构与储集性能的影响。研究表明,盒8段不同砂岩类型的岩石学特征、孔隙发育状况及其成岩演化过程存在一定的差异。石英砂岩与岩屑石英砂岩经历了3期明显的烃类充注过程和多期复杂的成岩作用,应是边充注边致密,二者各类孔隙均较发育,含气性和储集性能均较好。高塑性岩屑砂岩与钙质胶结砂岩的成岩-烃类充注演化过程相对简单,前者经历早成岩阶段压实作用后部分成为致密储层,含气性和储集性能较差;后者在中成岩阶段A期后成为致密储层,各类孔隙均不发育,基本为非储层。该研究成果对深入理解砂岩类型,岩石学组分的成岩-烃类充注演化过程及其对储层储集性能的影响,预测有利储集地带均具有重要意义。

Sandstone types,petrologic characteristics,diagenesis and diagenetic-hydrocarbon filling evolution,and pore structures of the He 8 tight sandstone reservoir from the Eastern Ordos Basin were carried out thoroughly,the impact of the diagenetic evolution process of different sandstone types on pore structures and reser-voir quality was analyzed,based upon the quantitative statistics and research of all kinds of thin sections under microscope,the measurement of porosity and permeability,capillary pressure,pore and pore throat image and scanning electron microscope,cathodoluminescence and fluorescence identification. The result shows that different sandstone types are of differentiation in petrology,pore development and diagenetic evolution process.Quartzarenite and sublitharenite experienced three obvious hydrocarbon filling stages and relatively more complex multi-diagenetic processes,speculating they are filling while densing. With developed pores,quartzarenite and sublitharenite both are good gas reservoir in the area. Diagenetic-hydrocarbon evolution of litharenite with high content of plastic fragments and calcareous cemented sandstones are relatively simple. After compaction of early diagenetic stage,parts of the former have become dense reservoir,with undeveloped pore system and poor reservoir performance. While,after middle diagenetic stage,the latter is overall non-reservoir for natural gas,due to undevelopment pores. The result is important in deep understanding sandstone types,evolution process of diagenetic-hydrocarbon filling of petrological component and its effect on reservoir properties,and may predict favorable reservoir zone in the study area.