Micro-particle Image Velocimetry Measurements of Pore-Scale Velocity Field during Nanoparticle-Assisted Alkaline Flooding

摘要

We report experimental investigations on the pore-scale flow dynamics during two-phase flow in a micromodel using the microscale particle image velocimetry (mu-PIV) technique. The combined effect of alkali (sodium carbonate) and nanoparticles (silica) on oil recovery is investigated using interfacial tension, rheology, emulsification, contact angle, chemical flooding, and micro-PIV measurements. Dynamic interfacial tension (IFT) measurement shows that silica nanoparticles significantly reduce the interfacial tension between crude oil and nanofluid. Reduction in IFT results in a stable emulsion. Microscopic studies reveal that the silica nanoparticle reduces the average droplet size to 3 mu m in the emulsion by covering oil droplets all over, resulting in the reduced coalescence of droplets. Silica nanoparticles significantly altered the wettability by reducing the contact angle. To understand the microscopic displacement mechanism of silica nanofluid-assisted alkaline flooding, the quantitative measurement of the pore-scale velocity field in a 2D porous micromodel was performed, and flow patterns were visualized. During drainage experiments with an alkaline solution, viscous fingering is observed. On the other hand, during the imbibition experiments, as crude oil interacts with the silica nanofluid, a stable emulsion is formed in the porous medium resulting in a regular piston-like displacement. The results reported in this study show that silica nanoparticles mixed with alkali solution help in IFT reduction, emulsification, wettability alteration, and mobility control by rheology modification, which assists the stable displacement of oil from the porous medium.