渤海石臼坨凸起古近系沙河街组砂岩成岩作用特征

Diagenetic Characteristics of the Eogene Shahejie Formation Sandstone of the Shijiutuo Uplift in Bohai Sea

摘要: 渤海石臼坨凸起古近系沙河街组砂岩储层的发育主要受成岩作用的控制。利用普通薄片、铸体薄片、X衍射分析、扫描电镜和物性分析等实验测试资料，分析了渤海石臼坨凸起古近系沙河街组砂岩成岩作用和孔隙演化特征。研究表明，砂岩储层孔隙类型主要为粒间孔、粒内溶孔；不同类型的砂岩压实差异较大，分选较好、粒度较粗的砂岩压实较弱；自生矿物主要为(铁)方解石、(铁)白云石、高岭石，其他胶结物(如自生石英、伊利石等)较少；经历的最晚成岩阶段为中成岩B期，大部分砂岩储层目前处于中成岩A期。根据成岩作用类型及其相互关系、包裹体均一温度等资料，建立了成岩演化序列；通过对压实作用、自生矿物和溶蚀的定量估算，反演了砂岩储层的孔隙演化特征。对砂岩储层发育有利的成岩作用主要是整体压实作用不强、早期油气充注以及长石颗粒的溶蚀，方解石胶结物对储层的破坏较显著。

Abstract: The sandstone reservoirs are mainly controlled by diagenesis in the Eogene Shahejie Formation of the Shijiutuo Uplift in Bohai Sea. Using petrographic thin sections, casting thin sections, X-ray dif-fractometry, scanning electron micrograph observations, physical properties data and other analysis materials, diagenesis and porosity evolution characteristics are analyzed in the the Eogene Shahejie Formation Sandstone in Bohai Sea. The sandstone reservoir pores mainly consist of the intergranular pores and intragranular secondary pores. Compaction levels are incoordinate in different sandstones and the well-sorting and fairly coarse sandstones present relatively weak compaction. Calcite, ferrocalcite, dolomite, ferrodolomite and kaolinite are the major cements and other cements like authigenic quart and illite are rarely observed in microscope. The latest di-agenetic stage of the sandstones is the stage B of mesogenetic diagenesis and the most is evolved to the stage A of mesogenetic diagenesis. The sandstone diagenetic evolution sequence is established based on different diagenesis phenomena and relationship among them and fluid-inclusion homogenization temperatures. The sandstone porosity evolution features are inverted through quantitatively estimating the compaction intensity and the contents of authigenic minerals and dissolution. The relatively weak compaction, early hydrocarbon filling and feldspar dissolution benefit for the sandstone reservoir development, and the carbonate cements obviously damaged the sandstone reservoir.