Experimental study on the mechanism of oil displacement by imbibition of fracturing fluids in tight sandstone reservoirs

作者：Zhifeng Luo, Dingfeng Xia, Tianshu He, Jia Yuan Yu, Yiming V. Wang, Hongyuan Zhang, Minmao Cheng · 发表于：Geosystem Engineering · 年份：2025 · DOI：10.1080/12269328.2025.2589204 · 研究领域：Hydraulic Fracturing and Reservoir Analysis、Enhanced Oil Recovery Techniques、Hydrocarbon exploration and reservoir analysis

The imbibition of fracturing fluids plays a crucial role in enhancing the oil recovery efficiency of tight sandstone reservoirs. To elucidate the differential imbibition behaviors and oil-displacement mechanisms among distinct reservoir types, two representative cores from the S tight sandstone reservoir in China were selected for investigation. Microstructural characterization was conducted to analyze variations in mineral composition and pore structure, while spontaneous and pressure-driven imbibition experiments were performed to investigate imbibition behavior. The nuclear magnetic resonance (NMR) technique was further employed to examine pore-scale crude oil mobilization characteristics. Results indicate that capillary force is the dominant driving mechanism during spontaneous imbibition. After 600 hours, the imbibition efficiencies of S-1 and S-2 were 8.56% and 5.95%, respectively, indicating that smaller pores contribute more significantly to imbibition-driven oil displacement in denser reservoirs. The synergistic action between external pressure and capillary force during pressure-driven imbibition markedly enhances fluid penetration and oil-displacement efficiency, increasing imbibition efficiencies to 47.36% and 15.88%, respectively. NMR results reveal that, in ultra-low-permeability reservoirs, medium and large pores dominate crude oil mobilization during the early stage, whereas small pores exhibit delayed mobilization in the middle and late stages, and medium por...