川东地区下三叠统嘉陵江组二段成岩作用和成岩相研究

Study of Diagenesis and Diagenetic Facies of 2nd Member of Lower Triassic Jialingjiang Formation in East Sichuan

摘要: 根据岩心、薄片观察、扫描电镜分析等测试资料，对川东地区下三叠统嘉陵江组二段储层成岩作用以及成岩相进行了详细研究。研究认为，川东地区嘉二段储层以白云岩为主，储集空间类型主要为次生溶蚀孔隙，属于低孔低渗储层。嘉二段经历的成岩作用类型主要有压实作用、胶结作用、白云石化作用、溶蚀作用以及构造破裂作用等。综合成岩作用组合类型及特征，认为研究区嘉二段已经进入晚成岩阶段，并识别出了胶结–膏化–云岩相、准同生云化相、压实–多期膏化–溶蚀–云岩相、胶结–压实–云岩相、胶结–膏化–破裂–溶蚀–云化相、沉积期膏化相等6个成岩相带，其中胶结–膏化–破裂–溶蚀–云化相和压实–多期膏化–溶蚀–云岩相为最有利储层发育成岩相带。

Abstract: Based on the observation of core, general thin-section, casting lamella, scanning electron microscope, and combining with an analysis of testing data, diagenesis and diagenetic facies of 2nd member of Lower Triassic Jialingjiang Formation in East Sichuan have been studied in detail. The results show that lithology of 2nd member of Lower Triassic Jialingjiang Formation is mainly composed of dolostone, and the main reservoir space type is secondary pore. During the process of diagenesis, compaction and cementation are destructive digenesis, while dissolution, dolomitization and tectonic disruption are constructive digenesis. According to combination types and characteristics of diagenesis, six types of lithogenous phase have been recognized, they are cemented-gypsinated-dolomitized facies, penecontemporaneous-dolomitized facies, compacted-multi-phase gypsinated-corroded-dolomited facies, cemented-compacted-dolo- mitized facies, cemented-gypsinated-ruptured-corroded-dolomitized facies, and gypsinated facies of sedimentary facies, of which cemented-gypsinated-ruptured-corroded-dolomitized facies and compacted-multi-phase gypsinated-corroded- dolomited facies are most favorable for reservoir development.