鄂尔多斯盆地姬塬地区长8油层组砂岩中长石的溶解作用对储层物性的影响

Affect of Feldspar Dissolution to Properties of Sandstone Reservoir of Chang-8 Oil Layer in Jiyuan Area,Ordos Basin

利用岩石铸体薄片鉴定、阴极发光分析和扫描电镜分析等多种测试手段,对鄂尔多斯盆地姬塬地区长8油层组储层砂岩的岩石学特征、物性特征和成岩作用进行了分析。结果表明,该储集岩以长石岩屑砂岩和岩屑长石砂岩为主,成分成熟度和结构成熟度都较低,Q1/(F1+R1)平均值均小于0.8;储层岩石中的长石在成岩流体和大气淡水的共同作用下发生了较强的溶蚀作用,在被溶蚀的长石边缘和孔隙中存在大量粘土矿物、自生石英和方解石,并且孔隙比较发育。这些长石溶解物质对储层物性有着不同程度的影响,其中自生高岭石和自生石英显示了对孔隙生成和保护方面的积极作用,而自生碳酸盐和自生伊利石主要表现为对孔隙生成和保护方面的消极作用。

Based on casting thin section,cathodoluminescence,scanning electron microscope,we discuss the lithological feature,petrophysical property and diagenesis of sandstone in the Chang 8 oil layer of Jiyuan area of Ordos basin.The research results show that the reservoir rock consists of feldspathic lithic sandstone and lithic feldspathic sandstone,with low compositional maturity and textural maturity,and average value of Q1/（F1＋R1） less than 0.8.The dissolution of feldspar in the reservoir rock was happened under diagenetic fluid and atmospheric water action.There is a lot of clay mineral,authigenic quartz and calcite in the dissolved feldspar brim and developed pores.The feldspar dissolved matters give an influence to reservoir physical property,where the self-kaolinite and authigenic quartz give a positive role to the pore formation and protection of,whereas the carbonate and authigenic illite play a negative action to it.