Influence of Viscous and Capillary Forces on Immiscible Fluid Displacement: Pore-Scale Experimental Study in a Water-Wet Micromodel Demonstrating Viscous and Capillary Fingering

Abstract

Unstable immiscible fluid displacement in porous media affects geological carbon sequestration, enhanced oil recovery, and groundwater contamination by non-aqueous phase liquids. Characterization of immiscible displacement processes at the pore scale is important to better understand macroscopic processes at the continuum scale. A series of displacement experiments was conducted to investigate the impacts of viscous and capillary forces on displacement stability and fluid saturation distributions in a homogeneous water-wet pore network micromodel with precisely microfabricated pore structures. Displacements were studied using seven wetting–non-wetting fluid pairs with viscosity ratios M (viscosity of the advancing non-wetting fluid divided by the viscosity of the displaced wetting fluid) ranging 4 orders of magnitude from log M = −1.95 to 1.88. The micromodel was initially saturated with either polyethylene glycol 200 (PEG200) or water as the wetting fluid, which was then displaced by a non-wetting alkane...