An experimental study of two distinct regimes during miscible displacement in fracture

Abstract:

Miscible displacement of two-phase fluids in fracture involves a lot production processes, including enhanced oil recovery, carbon capture and storage and contaminant transport. When the lower viscosity fluid displaces another higher viscosity fluid, the viscous fingering instability occurs. In our work, the miscible displacement experiments of water displacing glycerol were conducted under four viscosity ratios (M=50, 100, 500, 1000) and seven constant flow rates (Q=0.01, 0.05, 0.10, 0.50, 1.0, 5.0, 10.0 mL/min) to investigate the evolution of viscous fingering in a transparent fracture model made by epoxy. The results show that the interface of fluid-fluid evolution can be distinguished into dispersive regime and finger regime. At the early time, the interface is relatively stable, the sweep efficiency continually increasing and the mixing zone grow as t^0.5. However, as time increases, the nonlinear finger gradually formed with mixing zone growing as t^1.5 and sweep efficiency decreasing with time. The experimental results further indicate a transformation mechanism between diffusion and convection during the miscible displacement.