Elimination of Water Blockage in Tight Gas Reservoirs Based on the Combined Use of Supercritical CO₂ and Dry Agents

Water blockage constitutes a ubiquitous challenge in tight gas reservoir development. While conventional CO2-EGR has demonstrated success in carbon sequestration and production enhancement, current implementations exhibit critical limitations in concurrent water blockage. This study develops a novel dual-function drying method that combines supercritical CO2 flooding with alkaline metal compound injection to concurrently alleviate water blockage and carbon sequestration. A comprehensive experimental protocol employing visualized micromodel experiments, nuclear magnetic resonance, and magnetic resonance imaging was implemented to characterize the water removal mechanisms and quantify process efficiency. Key findings reveal: The proposed method reduces residual water saturation in macropores to <15%, effectively re-establishing hydraulic connectivity between wellbore and reservoir; dominant water consumption mechanisms involve interfacial tension reduction, wettability alteration, and synergistic chemical-thermal effects; optimal drying efficiency occurs in reservoirs with homogeneous lamellar throat under high-pressure/high-temperature conditions with low injection rates; film water dominates residual water, and the drying method eliminates >50% of films water, achieving permeability recovery in tight sandstone. This integrated solution advances CO2-EGR implementation while addressing water blockage challenges, demonstrating significant potential for both reduction of emissions and improved gas recovery.