Diagenesis and Diagenetic Facies Analysis on the Second Member of the Upper Triassic Xujiahe Formation Reservoir in the South of Western Sichuan Basin

Diagenesis and diagenetic facies have great significance in controlling tight sandstone reservoir development and distribution.Petrologic features,diagenesis and diagenetic facies of the Second Member of the Upper Triassic Xujiahe Formation reservoir in the south of western Sichuan Basin are studied by application of common thin sections,cast thin sections,physical properties analysis and other analytical testing information.Analysised the diagenetic evolution,and six types of diagenetic facies have been classification based on petrologic and diagenesis features:little siliceous-chlorite cementation diagenetic facies,siliceous cementation-dissolution diagenetic facies,Calcite cementation diagenetic facies,compaction diagenetic facies,Miscellaneous filling-compaction diagenetic.The results show that the reservoir has experienced complex diagenetic evolution,and is currently in the middle diagenetic A-B stage;Compaction and cementation is the most important factor of reservoir densification,and secondary pores resulted from dissolution improved the property of reservoir to some extent.The siliceous cementation—dissolution diagenetic facies is the best.