抄録
The ultra-low-permeability sandy conglomerate reservoirs of the Baikouquan Formation in the Junggar Basin are characterized by pronounced heterogeneity and complex pore–throat architectures, highlighting the need to clarify the dominant controls on fluid seepage to improve the accuracy of reservoir flow-capacity evaluation. Given that conventional pore–throat parameters often fail to capture the true migration behavior of reservoir fluids, this study aims to identify the key pore–throat scale governing seepage and to elucidate its underlying physical mechanisms. Using representative core samples, we integrated casting thin sections, conventional mercury intrusion, and constant-rate mercury intrusion to achieve high-resolution characterization of pore–throat structures and to delineate effective flow channels. The results show that the sandy conglomerates of the Baikouquan Formation exhibit poor pore–throat sorting and limited connectivity, and that the correlation between average pore–throat size and seepage capacity is weak; actual fluid flow is predominantly controlled by mainstream throats with favorable connectivity and appropriate radii, whose geometric attributes dictate the dominant pathways for gas–liquid transport. Further analysis reveals that the radius of mainstream throats more accurately captures true seepage behavior than traditional metrics such as mean or peak throat radius, thereby serving as a key indicator for evaluating flow capacity in ultra-low-permeability sandy conglomerate reservoirs. This study deepens the understanding of seepage mechanisms in complex conglomeratic reservoirs and provides quantitative support for horizontal-well placement, volumetric stimulation design, and enhanced oil recovery.
