Colloid Mobilization by Displacement Fluid Fronts in Porous Media

Colloids mobilized during imbibition and drainage events may serve as carriers of strongly sorbing contaminants and facilitate their transport through the vadoes zone. Passage of imbibition or drainage fronts through porous media involves considerable energy dissipation at the front due to pinning and release of interfaces and rapid pore emptying or filling. The abrupt interfacial jumps and pressure bursts at the front may entrain colloidal particles that otherwise would not be mobilize by the subsequent steady flows forming ahead or behind a passing front. We conducted pore-scale displacement experiments in sintered glass beads Hele-Shaw cells and observed motion of interfaces and colloids using high speed camera (1200 f/s) under varying flow regime and interfacial properties. Predictions based on the pore-scale observations were compared with macroscopic (e.g., column-scale) breakthrough behavior. Theoretical predictions of forces acting on colloids under steady shear and during inertial contact line sweeping a surface and quantification of front colloid-carrying capacity will also be presented.