西湖凹陷某构造花港组致密砂岩储层成岩作用与孔隙演化

通过对东海盆地西湖凹陷某构造中3口钻井岩心的观察研究,并对岩石薄片进行鉴定、电镜扫描及储层物性测试,认识和恢复储层成岩作用及孔隙演化过程。研究结果表明:渐新统花港组致密砂岩主要经历了机械压实作用、胶结作用、溶蚀作用等多种成岩作用,目前已达到中成岩期B亚期至晚成岩期;储层孔隙类型以粒间溶孔和长石溶孔为主;机械压实作用、碳酸盐与高岭石胶结作用是导致储层致密化的主要因素,孔隙率损失达30%～35%;环边绿泥石和硅质胶结占据孔隙的同时也对孔隙有一定的保护作用,大气淡水、煤系地层酸性水与有机酸对长石颗粒及碳酸盐胶结物的溶蚀则是形成次生孔隙的主要因素,孔隙率增加约5%,明显提高了致密砂岩的储集性能。

Diagenesis and pore evolution of Huagang Formation tight sandstone reservoirs in a structure of Xihu depression in East China Sea Basin

Through observing the cores of 3 wells in a structure of the Xihu depression in East China Sea Basin and identifying rock slices,scanning electron microscopy and testing reservoir physical property,people can recognize and restore the reservoir diagenesis and the pore evolution process.The results of the study show that the Oligocene Huagang Formation compacted sandstone has mainly undergone the compaction,cementation,dissolution and many kinds of diagenesis.At present,it comes to from B period of the middle diagenesis stage to the late diagenesis stage.The reservoir pores mainly include two types,that is,intergranular pore and feldspar solution pore.Compaction and the carbonate and kaolinite cementation are the main factors that lead to reservoir densification,and the porosity loss reaches 30%~35%.Chlorite with a ring edge and silicon cementation occupy the pore porosity,at the same time they have a certain protective effect for the pores.Atmospheric fresh water,acid water in coal formation and organic acid that cause the erosion of feldspar particles and carbonate cements are the main factors to which from the secondary pores.The porosity increases about 5%,obviously improving the tight sandstone reservoir property.