Study on the Wettability Alteration of Tight Sandstone by Low-Frequency Vibration and Nanofluid.

The efficiency of reservoir imbibition in continental tight sandstone reservoirs is severely hindered due to their intricate wettability characteristics. To address this challenge, we propose a novel synergistic approach that combines low-frequency vibration and nanofluid treatment. This method integrates physical shear and chemical wettability alteration to effectively modify the wettability of neutral oil-wet tight sandstone, thereby enhancing the imbibition process. In this study, we formulated a TX-100 nanofluid system through physical modification. By utilizing the contact angle as a benchmark for evaluation, we investigated the impact of low-frequency fluctuations on the wettability of oil-wet sandstone. Subsequently, we identified the optimal combination of wave parameters. Through isothermal adsorption experiments and mechanical analyses of oil droplets subjected to fluctuations, we systematically elucidated the mechanism by which fluctuations collaborate with nanofluids to alter the wettability of oil-wet sandstone. Furthermore, we evaluated the oil displacement efficiency of cores subjected to the combined action of low-frequency fluctuations and nanofluid treatment. Our findings revealed that the TX-100 nanofluid reduced the static contact angle of oil-wet sandstone by 58%. When assisted by the optimal fluctuation parameters, the nanofluid treatment contributed to a 64% reduction in the contact angle of strongly oil-wet sandstone. This effect further amplified the reversal of wettability in oil-wet sandstone. Through the application of various wave-assisted treatment agents, the efficiency of oil removal was increased by a minimum of 16%. Moreover, the recovery degree of wave-assisted nanofluid imbibition experienced a remarkable enhancement of 30.39%. Nuclear magnetic resonance analysis demonstrated a significant improvement in pore sizes smaller than 1 μm as a result of the composite process.