Objective After fracturing and putting into production of the low-permeability tight oil in reservoir Zhuangxi, the single-well productivity declined rapidly, and the effect of re-fracturing technology was poor. In order to improve the development effect of low-permeability tight reservoirs in Zhuangxi, the fracturing with imbibition technology was proposed and studied.

Methods Through laboratory experiments, the imbibition effect of imbibition fluid on oil-bearing tight cores and its effect on core displacement efficiency were evaluated, the oil-water interfacial tension and wetting angle of different concentrations of imbibition fluid were measured.

Results The imbibition fluid reduces the oil-water interfacial tension to 2.6×10^-2 mN/m, and transforms a weakly oleophilic reservoir with a water-to-rock wetting angle of 118.3° to a weakly hydrophilic reservoir with a water-to-rock wetting angle of 63°.

Conclusions The addition of imbibition fluid can significantly improve imbibition repellency efficiency, imbibition rate and recovery, which is the main mechanism of increasing daily oil production and slowing production decline with permeate-assisted repetitive fracturing. The upgrading effect becomes slower after the imbibition fluid concentration rises to 0.5%. In 2021, the imbibition-assisted re-fracturing technology was implemented in 5 wells, and the cumulative annual oil increase was 5 451 t compared with 5 conventional re-fracturing wells in the same block. This study is a guideline for fracture modification of low permeability tight reservoirs.