辽河拗陷滩海东部沙河街组低渗透砂岩储层成岩作用特征

Diagenesis characteristics of the low-permeability sandstone reservoirs from the Shahejie Formation in the eastern beach area of the Liaohe Depression

基于铸体薄片、扫描电镜、X射线衍射及物性资料综合分析,文中对辽河拗陷滩海东部古近系沙河街组一二段(简称沙一二段)储层的岩石学、物性及成岩作用特征进行了详细研究,建立了砂岩孔隙定量演化模式。结果表明:沙一二段储层岩性以长石岩屑砂岩为主,为中低孔、特低渗储层,以长石、岩屑的粒内溶孔为有利储集空间;目前处于中成岩阶段A期,经历了压实、胶结、溶蚀和交代4种成岩作用,其中压实、胶结作用降低储层孔隙度,破坏储层物性,孔隙度因压实作用减少了15.4百分点,因胶结作用减少了12.0百分点;溶蚀作用改善储层物性,并控制优势储层区域的分布,在其他非建设性成岩作用造成减孔与部分高岭石迁移造成增孔的综合控制下,实际溶蚀作用增加孔隙度7.2百分点。

The petrology,physical property and diagenesis characteristics from the first and second Members of the Eocene Shahejie Formation in the eastern beach area of the Liaohe Depression were studied in detail through casting thin section,scanning electron microscope,X-ray diffraction and physical property data.The quantitative evolution model of pore in sand reservoir is established.The results show that the first and second Members reserviors of the Shahejie Formation are mainly composed of feldspar lithic sandstones,belong to a reservoir with medium-low porosity and extra-low permeability,and take the intragranular dissolved pores in feldspars and lithic debris as the chief accumulation space.It is currently in the middle diagenetic stage A,and has experienced four kinds of diagenesis:compaction,cementation,dissolution,and replacement.Compaction and cementation have a significant impact on reservoir property by reducing porosity,porosity decrease by 15.4%because of compaction and porosity decrease by 12.0%because of cementation.Dissolution plays a significant role in improving the reservoir property and control distribution of favorable reservoir.The porosity increase by 7.2%because of actual dissolution under comprehensive control of other nonconstructive diagenesis decreasing porosity and part migrated kaolinite increasing porosity.