To investigate the influence of shale oil with different oil saturation on imbibition recovery rate

shale samples from the Jiangling sag in the Jianghan Basin were taken as the research object. Imbibition experiments were conducted to examine the variation of core imbibition curves at oil saturation of 20%

30%

40%

and 50% under conditions of similar and increasing permeability. Nuclear magnetic resonance (NMR) technology was used to analyze the changes in oil-phase signals within the core pores before and after imbibition. Additionally

the imbibition volume and oil displacement volume during the imbibition process were compared. The results showed that under similar permeability conditions

cores with higher oil saturation exhibited higher imbibition recovery rates. In contrast

cores with higher oil saturation had slower imbibition rates at the initial stage of imbibition and required a longer time to reach imbibition equilibrium. When permeability gradually increased

cores with higher oil saturation achieved higher imbibition recovery rates. In this case

cores with higher oil saturation also exhibited faster imbibition rates in the early stages compared to those with lower oil saturation. The hydration and expansion of shale resulted in the imbibition volume exceeding the oil displacement volume during the imbibition process. Moreover

the difference between these two volumes increased with higher oil saturation. The findings of this study provide a theoretical basis for improving shale oil recovery.