Suppressing viscous fingering in structured porous media

Area of Science:

• Fluid dynamics
• Porous media physics
• Interfacial phenomena

Background:

• Viscous fingering occurs during fluid displacement in porous media when low-viscosity fluids replace high-viscosity fluids.
• This hydrodynamic instability leads to finger-like protrusions at the fluid-fluid interface, which is often detrimental in natural and engineered processes.
• Controlling interfacial instabilities is crucial for optimizing processes like oil recovery and groundwater remediation.

Purpose of the Study:

• To investigate the effect of pore size variation on viscous fingering during immiscible fluid displacement.
• To explore a novel phenomenon where gradual pore size changes suppress interfacial instabilities.
• To provide a theoretical and experimental basis for controlling fluid displacement in porous media.

Main Methods:

• Pore-scale numerical simulations to model fluid flow and interface dynamics.
• Experimental investigations using controlled porous media with varying pore structures.
• Development of an analytical model to correlate displacement front morphology with pore size gradients.

Main Results:

• A gradual, monotonic variation in pore size along the displacement front path was found to suppress viscous fingering.
• This suppression effect contradicts the conventional understanding that pore size variability enhances instability.
• The observed phenomenon aligns with predictions from gradient percolation theory for specific flow conditions.

Conclusions:

• Gradual pore size reduction effectively restrains viscous fingering, offering a method to control interfacial instabilities.
• The findings provide design principles for engineered porous materials, such as membranes and filters.
• This research contributes to a better understanding of fluid displacement in complex media and its applications.