Fluid Invasion Dynamics in Porous Media With Complex Wettability and Connectivity

Multiphase flow is important for many natural and engineered processes in subsurface geoscience. Pore-scale multiphase flow dynamics are commonly characterized by an average balance of driving forces. However, significant local variability in this balance may exist inside natural, heterogeneous porous materials, such as rocks and soils. Here, we investigate multiphase flow in heterogeneous rocks with different wetting properties using fast laboratory-based 4D X-ray imaging. The mixed-wet dynamics were characterized by displacement rates that differed over orders of magnitude between directly neighboring pores. While conventional understanding predicted strongly capillary-dominated conditions, our analysis suggests that viscous forces played a key role in these dynamics, facilitated by a complex interplay between the mixed-wettability and the pore structure. These dynamics highlight the need for further studies on the fundamental controls on multiphase flow in geomaterials, which is crucial to design, for example, groundwater remediation and subsurface CO2 storage operations.

Automated summary

The study investigated multiphase flow in heterogeneous rocks with different wetting properties, revealing significant variability in driving force balance between different pores and a key role of viscous forces in the dynamics. The complex interplay between mixed wettability and pore structure exacerbated these differences, emphasizing the need for further research on the fundamental controls on multiphase flow in geomaterials.