柴北缘冷湖—马仙地区古近系—新近系成岩作用特征

运用岩心、铸体薄片、扫描电镜和化验资料等,系统研究了柴达木盆地北缘冷湖—马仙地区古近系—新近系成岩作用特征及其对储层物性的影响。研究表明,柴北缘冷湖—马仙地区古近系—新近系储集砂岩主要为岩屑长石砂岩、长石砂岩和长石岩屑砂岩。主要成岩作用为压实作用、胶结作用和溶蚀作用。压实作用以机械压实为主;胶结作用主要为碳酸盐胶结、硫酸盐胶结、石英次生加大和黏土矿物胶结;溶蚀作用主要为碳酸盐岩和碎屑颗粒的溶蚀。压实作用和胶结作用是原生孔隙减少以及储层物性变差的主要原因。碎屑颗粒和胶结物的溶蚀是次生孔隙形成的主要原因。

Diagenesis of Paleogene-Neogene sandstone reservoirs in Lenghu-Maxian area,northern Qaidam Basin

Based on cores,cast thin sections,scanning electron microscope and testing data,this paper studied the diagenesis of Paleogene-Neogene sandstone reservoirs and its influence on reservoir properties in Lenghu-Maxian area in north Qaidam Basin.The result shows that the sandstone reservoirs in this area are mainly composed of lithic arkose,arkose and feldspar lithic sandstone,and mainly experienced such actions as compaction,cementation and dissolution.Mechanical compaction is the main compaction,cementations are mainly carbonate cementation,sulfate cementation,quartz overgrowth and clay minerals cementation,and dissolution comprises carbonate cementation content and detrital dissolution.Compaction and cementation caused the destruction of primary pores and made the reservoir properties poor.Dissolution of the lithic and cement was the main reason for generating secondary pores.According to the characteristics of vitrinite reflectance and clay minerals,it is ascertained that the evolution have reached the early diagenetic stage A,and the minor part reached the middle diagenetic stage B.