Abstract:

Due to complex geological conditions and technical limitations, the migration of metal cations, changes of energy and other processes during the diagenesis of zeolite cement in deep reservoirs are difficult to quantify. Previous studies have compared the genesis of natural and synthetic zeolites, but most have focused on a single type; therefore, systematic comparisons on the genetic conditions among different zeolite types remain lacking. This study examines the Permian volcaniclastic-rich sandy conglomerate reservoirs in the Shawan sag of the Junggar Basin. Using microscopic methods such as thin section observation, scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS), natural and synthetic zeolites of the same type were compared for their compositional and structural characteristics. The formation processes of natural and synthetic zeolites were compared based on the genetic conditions of synthetic zeolites. The paper preliminarily revealed the diagenetic conditions of natural zeolite and identified the genetic mechanisms and abnormal growth processes of zeolite cements, as well as the controlling factors for different zeolite phases. The results show that natural and synthetic zeolites are similar in formation temperature, pH value, and Si/Al ratio, and are also highly similar in chemical composition, crystal morphology, and structure. Furthermore, the dissolution of volcanic glass increases the concentration of OH^- ions, which in turn raises the salinity and alkalinity of pore water, promoting the formation and abnormal growth of zeolite cement and controlling the formation of different zeolite phases. Zeolite transformation is mainly influenced by the compositional differences of volcanic materials and the dissolution of volcanic glass.

Key words: Junggar Basin, Shawan sag, Permian, synthetic zeolite, natural zeolite, formation environment, genetic analysis