Two-phase Seepage Pore Pressure Diffusion Wave-saturation Model and Its Application in CO2 Geological Storage

This study developed a one-dimensional coupled model of two-phase seepage and pore pressure diffusion wave-saturation interaction based on the theory of pore pressure diffusion waves. Analytical solutions for fluid saturation distribution and the leading edge position were derived, and the interaction mechanism between pore pressure and saturation fields was systematically analyzed. The study revealed the governing law of the coupling effects between pressure diffusion waves and two-phase seepage on fluid migration: in the short term, the process was dominated by pressure-driven rapid migration, while in the long term, it approached a stable diffusion equilibrium. Through a parameter sensitivity analysis, the critical influences of the diffusion coefficient and pore pressure on the advancement of the migration front were clarified, and the model's applicability to CO2 geological storage was explored. The results indicate that dynamic sealing in heterogeneous reservoirs and high permeability zones can enhance storage efficiency through a stepped injection pressure strategy. Additionally, the proposed leakage grading evaluation method offers a theoretical foundation for engineering risk management and control. This study provides a novel conceptual framework and analytical tool to ensure long-term safety and optimize the design of CO2 storage projects. Article type: Research article Cited as: Hao M, Bai B, Shi L, et al. 2025. Two-phase seepage pore pressure diffusion wave-saturation model and its application in CO2 geological storage. GeoStorage, 1(1):42-55. https://doi.org/10.46690/gs.2025.01.03