Effect of foam on miscible displacement in the Hele-Shaw cell with a chemical reaction approach

Abstract

In this paper, we discuss the effects of a foam generated by a chemical reaction on viscous fingering (VF) as observed using a Hele–Shaw cell and a microchannel. Sodium bicarbonate solution both with and without surfactant was used as the displacing fluid, and citric acid solution was used as the displaced fluid. We found that the presence of surfactant can significantly increase the coalescence time and decrease the nucleation time; the displacement time was found to change with the injection flow rate. The nature of the VF pattern was found to depend on the interrelationship between these three characteristic times. When the displacement time was significantly larger than the coalescence time, which was, in turn, much larger than the nucleation time, small bubbles were generated at the start of the experiment, but these merged into large bubbles at the end. However, small bubbles were still created and did not coalesce, and the shape of the VF was more stable. When the displacement time was close to the nucleation time but considerably smaller than the coalescence time, many small bubbles were produced without coalescence, inhibiting the flow of the advancing fluid and widening the fingers. The effects of the surfactant and citric acid concentrations were also examined from the viewpoint of the characteristic times in the Hele–Shaw cell. In the microchannel, we discovered that the foam structure produced early in the experiment inhibits the development of preferential flow channels, impedes the formation of an oil film, and enhances the micro-displacement efficiency.