Multiscale studies of water invasion dynamics in gas reservoirs: experiments and modeling

Water invasion has always been a key focus in natural gas exploration and development. However, most existing studies have focused either on solid–fluid interactions at the interface scale or on fluid flow behaviors at the pore scale, with limited efforts to establish a technical connection between interfacial mechanisms and field-scale engineering performance. In this study, the advancement velocity of the water invasion front was employed as a comprehensive indicator to characterize fluid flow across both pore and reservoir scales. The experimental results revealed that when water saturation exceeded a threshold of approximately 20–40%, the water phase transitioned from a dispersed phase to a continuous phase within the pore space. Moreover, water-phase flow commenced only when the displacement pressure surpassed a critical threshold ranging from 0.23 to 0.44 MPa. Subsequently, a predictive model was developed based on underground oil and gas seepage theory to simulate water invasion behavior at the gas reservoir scale. The results demonstrated that increased gas production rates significantly accelerate bottom-water invasion. Additionally, higher reservoir permeability and greater initial water saturation further promote water advancement. The model’s predictions were validated as more accurate through comparison with both historical production data and classical black-oil model simulations. This study presents an approach for linking microscale seepage mechanisms with macroscale water invasion dynamics. It provides a theoretical basis for the development of effective water control strategies across multiple scales.