Abstract: In Sudeerte oilfield, I-IV oil measures of Nantun formation belong to a volcanoclastic reservoir with lithologies of tuffaceous conglomerate, tuffaceous glutenite, tuffaceous sandstone and tuffaceous mudstone. Compaction, cementation, devitrication, mineral cleavage crack and blast trace are its main diageneses. The reservoir physical properties are poor on the whole, but I-III oil measures are relatively bigger and IV oil measure is much smaller than I-III in porosity and permeability. The particle size has decided effect on the reservoir properties, namely, the bigger the particle size is the better the reservoir properties are. Compaction and cementation are the main factors to make the reservoir properties poorer, while devitrication and mineral cleavage crack and blast trace have some favorable effects on them.

Key words: Sudeerte oilfield, volcanoclastic rock, Nantun formation, reservoir character, diagenesis