Capillary fracturing in granular media.

Area of Science:

• Geophysics
• Fluid Dynamics
• Material Science

Background:

• Understanding fluid displacement in porous media is crucial for various geological processes.
• Non-cohesive granular materials exhibit complex behaviors when subjected to fluid invasion.

Purpose of the Study:

• To investigate the mechanisms of immiscible fluid displacement in deformable, non-cohesive granular media.
• To identify and characterize different invasion regimes and the parameters controlling them.

Main Methods:

• Experimental injection of air into water-saturated glass bead beds.
• Systematic variation of injection rate, bead size, and confining stress.
• Morphological observation and dimensional analysis.

Main Results:

• Identified three distinct invasion regimes: capillary fingering, viscous fingering, and capillary fracturing.
• Capillary fracturing occurs when capillary forces overcome frictional resistance, creating conduits.
• Derived two dimensionless numbers (modified capillary number and fracturing number) governing regime transitions.

Conclusions:

• Capillary fracturing is predicted in fine-grained media under low confining stress.
• This phenomenon is relevant to natural processes like oil migration, gas venting, and crack formation.