A comprehensive modelling investigation of dynamic capillary effect during non-equilibrium flow in tight porous media

Abstract The dynamic capillary effect in capillary pressure plays a significant role during the non-equilibrium flow in porous media for various chemical, environmental and petroleum processes. A unified model is developed in this work to estimate the dynamic capillary effect in matrix during the non-equilibrium flow in tight porous media. Multiple influential parameters (especially fluid viscosity, surfactant and fracture with inconsistent effects) and the interplays between them are comprehensively considered. Firstly, a databank of the relationship between the dynamic capillary coefficient and the main controlling parameters is established through non-equilibrium flow experiments on the fractured and intact tight core samples. Secondly, the previously unclear correlations between the dynamic capillary coefficient and the influential parameters are determined individually, which are then incorporated into an overall model based on the Buckingham’s π-theorem. The proposed model is further validated and simplified, showing accurate matches with the R2 ≈ 0.95. At last, the sensitivity analysis of five different non-equilibrium flow conditions is conducted, through which effects of the influential parameters on the dynamic capillary effect are investigated. The proposed model can reasonably explain the porous media properties, the easiness and uniformity of the fluid flow, and the effect of viscous force for the non-equilibrium flow in tight porous media. The findings of this study can help for a better understanding of multiphase flow in tight porous media.