Q型聚类分析在四川盆地南部上三叠统须二段成岩相研究中的应用

Application of Q Type Cluster Analysis in the Study of Quantitative Diagenetic Facies of Member 2 of Xujiahe Formation in Southern Sichuan

上三叠统须家河组二段是四川盆地南部主要的勘探层位之一。对川南须二段储集砂岩进行的铸体薄片观察、物性资料研究表明,须二段储集岩石类型主要为长石岩屑砂岩、岩屑长石砂岩和岩屑砂岩,先后经历了压实作用、胶结作用、溶蚀作用、破裂作用和交代作用等成岩作用。在计算区内须二段储集岩石压实系数、胶结系数和溶蚀系数等成岩系数的基础上,结合Q型聚类分析方法对储集岩石的各成岩系数进行了变量因子的归类,划分出强压实强胶结相、强压实中胶结相、强压实弱胶结相、中压实弱胶结相及弱压实弱胶结相。成岩相的分布明显受到沉积相展布的影响,储层质量较好的成岩相主要发育于三角洲前缘亚相的水下分流河道等高能环境中,同时成岩相的分布还受到填隙物、塑性岩屑的控制。

Member 2 of the Upper Triassic Xujiahe Formation in southern Sichuan Basin is one of the key layers for gas exploration. By identifying the thin sections, analyzing the drill core physical properties, we find that main types of reservoir sandstones are feldspar lithic sandstone, lithic feldspar sandstone and lith- ic sandstone, and reservoir sandstones has experienced compaction, cementation, dissolution, disruption and metasomatism. By calculating the reservoir rock compaction coefficient, cementation coefficient and coefficient of dissolution, we use the Q type cluster analysis to classify reservoir rock according to the simi- lar variable factors, diagenetic facies of the 2nd Member of Xujiahe Formation. The facies are divided into strong compaction-strong cementation facies, strong compaction-medium cementation facies, strong com- paction-weak cementation facies, medium compaction-weak cementation facies, weak compaction-weak ce- mentation facies in five kinds of diagenetic facies quantitatively. The study result shows that the diagenetic facies distribution is obviously controlled by interstitial material, the plastic debris and the distribution of sedimentary facies, which mainly developed in the underwater distributary channel of the delta front.