鄂尔多斯盆地合水地区长7致密油储层伊利石成因  

Genesis of illite in Chang 7 tight oil reservoir in Heshui area,Ordos Basin

作　　者：田建锋[1] 高永利[2] 张蓬勃[1] 王秀娟[3] 杨友运[1] 

机构地区：[1]西安石油大学地球科学与工程学院,陕西西安710065 [2]西安石油大学石油工程学院,陕西西安710065 [3]中国石油长庆油田勘探开发研究院,陕西西安710021

出　　处：《石油与天然气地质》2013年第5期700-707,共8页Oil & Gas Geology

基　　金：国家自然科学基金项目(41202105);国家科技重大专项(2011ZX05044-02)

摘　　要：鄂尔多斯盆地合水地区长7油层组为典型的致密油储层,伊利石平均含量高达9.1%是其重要特征,也是控制储层性能的关键因素。扫描电镜、铸体薄片、能谱分析、X-衍射等分析表明,合水地区长7油层组发育浊流沉积的极细砂岩,孔隙类型以长石溶蚀孔为主,且发生溶蚀的长石均为钾长石;伊利石化学成分复杂,以分散杂乱片状为主,仅分布于残余粒间孔隙内,且岩石粒度越细伊利石含量越高;与相邻泥岩相比,粘土矿物相对含量相似,但砂岩中钾长石/斜长石比值小于泥岩。合水地区长7沉积时期火山活动强烈,具有早期蒙脱石形成的地质条件,同时伊利石产状具有蒙脱石化的特征,且镜下可见大量的杂基伊利石化,表明研究区伊利石主要由大量蒙脱石等杂基转化而来;而研究区最高古地温一般不超120℃,也无外来富钾热流体的加入,不具备其他成因伊利石大量生成的地质条件。Chang 7 reservoir in Heshui area ,Ordos Basin is a typical tight oil reservoir with high content of illite up to 9.1%,which is the key factor controlling the quality of reservoir .Analyses of the composition ,distribution and occurrence of illite through SEM ,EDS,cast thin section and X-diffraction show that the Chang 7 reservoir is very fine turbidity sand-stones .The pervasive dissolution of K-feldspar yield lots of secondary pore which is the main pore type .The illites are com-plex in chemical composition and are mainly in scattered ,chaotic sheet-like shape .They only occur in residue intergranular pores .And their content increases with the decreasing of grain size .In comparison with the adjacent shales ,the relative con-tent of clay mineral is similar ,but the K-feldspar/plagioclase ratio is smaller .Volcanic activities were very intense during the deposition of Chang 7,which provides the favorable condition for semctite development at the early diagenetic stage . The semctites were transformed to illites subsequently .This process may be the main genesis of illite in Chang 7 ,as illiti-zation of smectite is very common .In addition,the palaeo-geotemperature in the study area is generally lower than 120℃and there are no external potassium-rich hot fluid input ,making it impossible for the formation of illite of other genesis .

关 键 词：致密油 伊利石 储层特征 长7油层组 合水地区 鄂尔多斯盆地 

分 类 号：TE122.2[石油与天然气工程—油气勘探]