Research on the Reservoir of Shahezi Formation in Xujiaweizi Fault Depression

Abstract This study comprehensively analyzed regional structural features based on the comparison of sequence division and sedimentary facies characteristics, and applied reservoir geology theories and methods to investigate the reservoir characteristics of the Shahezi Formation. Through core analysis and thin section identification, it was found that the main rock types of the Shahezi Formation reservoir in the Xujiaweizi fault depression are conglomerate and sandstone, followed by mudstone, with minor amounts of coal and volcanic rocks. The average porosity of the reservoir is 3.7%, and the average permeability is 0.22 mD, classifying it as a III-IV type reservoir. The porosity and permeability of the reservoir decrease with increasing burial depth, with some local outliers observed. A comprehensive analysis using conventional thin sections and cast thin sections revealed that the reservoir space types in the Shahezi Formation primarily include primary intergranular pores, secondary pores, and fractures, with secondary pores being the dominant type. The main diagenetic processes include compaction, cementation, metasomatism, and dissolution. The characteristics of the reservoir are primarily controlled by diagenesis, sedimentary microfacies, and tectonic processes. This study innovatively applied seismic attribute analysis to predict the planar characteristics of reservoirs in the Shahezi Formation of the Xujiaweizi fault depression, despite the scarcity of drilling wells, and completed the favorable reservoir prediction for the target layer in the area by integrating the distribution of sedimentary facies zones and regional structural features.