As a critical technical approach for shale reservoir development, dynamic imbibition displacement during the fracturing stage has emerged as a focal point in reservoir engineering research over recent years. In light of global energy demands and ongoing exploration of unconventional oil and gas resources, the significance of this technology in enhancing the exploitation of shale oil reservoirs cannot be overstated. However, the specific mechanisms of dynamic imbibition process in shale oil reservoirs influenced by various factors still aren’t unclear, and it’s difficult to accurately quantify their impact on imbibition oil production efficiency. These uncertainties significantly hinder further improvement in the development efficiency of shale oil reservoirs, lead to higher development costs and bring huge challenges to sustainable resource development. 

Aiming at the unclear dynamic imbibition mechanisms and action laws of shale oil reservoir, a core-scale numerical simulation model was established, and the control variable method was adopted to set up 15 simulation schemes. By these methods, the mechanisms of displacement pressure difference, capillary radius, wetting angle and oil-water viscosity of dynamic imbibition displacement effect, and the change laws of fluid seepage were revealed. The effects of displacement pressure difference, capillary radius, wetting angle, and oil-water viscosity on the effectiveness of dynamic imbibition oil recovery, and the laws of fluid seepage changes were clarified in this study. The results show that: During dynamic imbibition, as the capillary radius increase from 0.1 μm to 10 μm, capillary force decrease and fluid seepage rate accelerates, leading to 8.0% increase in imbibition recovery. Along with the displacing pressure difference increases from 0 MPa to 3 MPa, the imbibition upgrades from static to dynamic, and the imbibition recovery degree increases by 7.9%. It is considered that the displacing pressure difference and the recovery degree are in accordance with the power function relationship, and there is an optimal displacing pressure difference. With changes in rock wettability from hydrophilic to neutral or oleophilic, extraction degree decreases from 48.9% for water-wet conditions to 33.9% for oil-wet conditions. As crude oil viscosity decreases from 53.3 mPa·s to 13.99 mPa·s, imbibition recovery rate increases by 9.1%; the higher the viscosity of water phase, the smaller the initial imbibition velocity, but the better the imbibition displacement effect. In oil field operation, by optimizing injection pressure, selecting suitable fracturing fluid and surfactant, the hydrophilic degree and displacement phase viscosity can be improved, and the dynamic imbibition process can be improved to increase the oil displacement efficiency. In the future, the complexity of multiphase flows and the heterogeneity of reservoirs should be further considered to study the influence of various factors on the dynamic imbibition process of shale from different scales.