Based on observations of a large number of cores and thin sections

and the experimental analysis of vitrinite reflectance(Ro)

Xray diffraction of clay minerals

scanning election microscope(SEM)

this paper discusses in detail diagenetic phenomenon

sequence and evolution of the Silurian Xiaoheba Formation in the Shizhu Synclinoyium

western Hubei easternChongqing Area

It is defined that the Xiaoheba Formation currently is in the epigenetictelogenetic stage. We establish the diagenetic evolution sequence in the area and discuss the influence of diagenesis on reservoir porosity and the densification process of reservoirs. According to this study

sandstone reservoirs in the Xiaoheba Formation experienced a densification process during sedimentation

synsedimentation and eogenetic stage and a positive alteration process during the mesogenetic and telogenetic stages. When eogenetic phase ended

reservoirs in the study area had become very tight

which badly affected the development of secondary pores. Therefore

secondary pores failed to be formed in the best period of their development.