Relationship between Diagenesis and Hydrocarbon Accumulation in Deep Reservoir of YQ Structure, Xihu Sag

Based on the effect of Longjing Movement on the diagenesis evolution in the reservoirs of Huagang Formation in YQ structure, the authors discussed dissolution, cementation and transformation of clay minerals under different diagenetic environment of acid and alkaline, analyzed the cause of the current situation that the cementation is stronger than the dissolution from the point of fluid potential, and indicated that the compaction dominated the physical properties of deep reservoirs based on the analysis of particle contact relationship. It is concluded that Longjing Movement played an important role in the diagenesis evolution. Before Longjing Movement, there were scarce secondary pores developed because of insuffcient acid dissolution and the less quartz secondary enlargement also lead to the weak ability to resist the compaction. After Longjing Movement, the physical properties of reservoirs were deteriorated by the strong cementation under alkaline environment.