成岩作用对河流-三角洲相砂岩储层物性演化的影响--以延长油区上三叠统延长组长2砂岩为例

延长油区上三叠统长 2地层河流相-三角洲相砂岩储层的物性明显受埋藏-成岩作用事件的影响。埋藏压实作用是导致砂岩孔隙丧失的主要原因,造成的平均孔隙度丧失为 17.8%。其中黑云母的早期成岩蚀变是造成原生孔隙丧失的一个重要原因。胶结作用造成的平均孔隙度丧失为 7.1%。其中碳酸盐胶结物和次生石英加大是造成砂岩物性降低的主要胶结物。碎屑颗粒周围绿泥石薄膜的存在阻止了一部分石英次生加大及碳酸盐胶结物的沉淀,使一部分原生粒间孔隙得以保存。晚期成岩阶段有机质分解形成的酸性流体及表生成岩作用阶段的大气降水是形成次生孔隙的主要原因,从而使长 2砂岩的物性得到改善

The Diagenetic Impact on Reservoir-quality Evolution of Fluvial-deltaic Sand ston es --Taking an example from the Upper Triassic sandstones of

The reservoir quality of the Upper Triassic Chang 2 fluvial deltaic sandstones of the Yanchang Oil Field in Ordos basin is strongly influenced by the burial history and facies related diagenetic events. The mechanical compaction in the early diagenetic phase, which resulted in 17.8% porosity loss, is the main factor causing the loss of porosity for the sandstones. The diagenetic alteration of biotite during early diagenetic phase accounts for a part of primary porosity loss in the sandstones. The porosity loss caused by cementation is 7.1%. In the cements, carbonate and quartz overgrowths are the main cements that reduced the reservoir quality of the sandstones. Thin chlorite film around detrital quartz grains prevented part of quartz overgrowth and carbonate cement precipitation, which resulted in a part of primary pore preservation and hence caused a better reservoir quality. The acidic liquid related to decomposition of organic mater during hydrocarbon enrichment in the late diagenesis, and meteoric waters during epidiagenesis, have resulted in dissolution of detrital feldspars and carbonate cements, and in the formation of kaolinite, contributing a better retention of reservoir quality for the sandstones.