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

Min Hao1,2, Bing Bai1∗, Lu Shi1, Hongwu Lei1, Hengtao Yang1, Duoxing YangMin Hao1,2, Bing Bai1∗, Lu Shi1, Hongwu Lei1, Hengtao Yang1, Duoxing YangMin Hao, Bing Bai, Lu Shi, Hongwu Lei, Hengtao Yang, Duoxing Yang

Abstract:

This study developed a one-dimensional coupled model of two-phase seepage and porepressure diffusion wave-saturation interaction based on the theory of pore pressure diffusionwaves. Analytical solutions for fluid saturation distribution and the leading edge positionwere derived, and the interaction mechanism between pore pressure and saturation fieldswas systematically analyzed. The study revealed the governing law of the coupling effectsbetween pressure diffusion waves and two-phase seepage on fluid migration: in the shortterm, 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, thecritical influences of the diffusion coefficient and pore pressure on the advancement ofthe migration front were clarified, and the model’s applicability to CO2geological storagewas explored. The results indicate that dynamic sealing in heterogeneous reservoirs andhigh permeability zones can enhance storage efficiency through a stepped injection pressurestrategy. Additionally, the proposed leakage grading evaluation method offers a theoreticalfoundation for engineering risk management and control. This study provides a novelconceptual framework and analytical tool to ensure long-term safety and optimize the designof CO2storage projects.