Integrative Characterization of Tight Sandstone: A Comparison Between the Bohai Bay Basin and Ordos Basin

Abstract

Tight sandstone has emerged as a primary focus for global oil-gas resource exploration and for increasing reserves and production. Accurate characterization of the microscopic pore structure of tight sandstone reservoirs is crucial for identifying and classifying high-quality reservoirs. This study examines tight sandstone reservoirs in the Sha-4 member of the Dongying area in the Bohai Bay Basin and the Chang-7 member of the Xin’anbian area in the Ordos Basin, China. Through techniques such as cast thin sections, scanning electron microscopy, and high-pressure mercury injection, this study investigates the intrinsic relationships among rock types, petrophysical properties, and pore structures across these two distinct regions. Findings reveal that the types of reservoir rock in the study area are feldspar sandstone, lithic feldspar sandstone and feldspar lithic sandstone, as their feldspar-dissolved pores gradually decrease. Comparative analysis suggests that the contrasting burial histories in the eastern and western regions of China result in significant differences in the petrophysical properties of the involved reservoirs. The eastern regions experienced a more rapid burial history compared to the western regions, which limited the efficiency of destructive diagenetic processes and have better porosity and permeability. Variations in rock types, mineral compositions, and diagenesis are key factors influencing reservoir space and physical property heterogeneity. These results are of great significance for understanding the differences in reservoir storage space, pore structure, and petrophysical properties across different regions and rock types.