Diagenetic facies study on Chang 6-8 oil formations of Triassic Yanchang Formation in Ordos basin, China

In this paper, the authors study in detail the diagenetic types and characteristics of Chang 6-Chang 8 oil formations in the region on the basis of studying the character of sedimentary facies and paleogeographic evolution of the Chang 6-Chang 8 oil formations. The main diagenetic types include compaction, cementation, erosion, recrystallization and so on. The authors further study the types and characteristics of the diagenetic facies. There are five types which include mudstone compaction facies, compaction-pressolution facies, residual protozoal intergranular-secondary dissolution facies, secondary dissolution facies, and micro-fractures facies. Through further studying on the types of fillings in reservoir sandstone, ten sub-diagenetic facies are clssified. The authors describe the plane distribution of diversity diagenetic facies and distribute important basic information for further studying the influence of diagenetic facies on the formation and development of reservoirs.