This study explores oil-water imbibition dynamics in rock samples of tight sandstone with similar physical properties using a novel NMR signal calibration method. This method can translate the total NMR signal output into oil volume via a regression model

offering enhanced convenience and accuracy compared to traditional approaches. The imbibition process is characterized by two distinct phases: a rapid imbibition stage and a stable imbibition stage. Optimal imbibition times were identified as approximately 68 hours for oil from coal samples and 188 hours for tight oil samples. When imbibition times are sufficient

the recovery ratios for oil from coal and tight oil are comparable. However

with insufficient imbibition time

the recovery ratio for oil from coal is lower than that for tight oil. Within the same stratigraphic layer

samples with identical viscosity exhibit similar imbibition dynamics

with tight oil samples reaching the stable stage more quickly than oil from coal samples. The pivotal radius distinguishing large and small pores is established at 0.5 μm. In low-viscosity crude oil samples

small pores significantly dominate the imbibition process

contributing 83.93% to the recovery

while large pores contribute only 16.07%. The overall mobilization of crude oil is low at 8.50%

frequently resulting in the formation of water locks. In contrast

tight oil samples show a more balanced contribution across all pore sizes during the soaking period. The average utilization ratios of crude oil are 14.82% in small pores and 29.82% in large pores.