Experimental evidence of the effect of solute concentration on the collective evolution of bubbles in a regular pore-network

Abstract

The dissolution of bubbles confined in porous media is relevant to applications such as carbon sequestration and soil remediation. Recent numerical work indicates that a rich variety of collective dissolution behaviors can be obtained depending on the initial solute concentration, the size distribution of bubbles and the structure of the porous network. However, there is only sparse experimental evidence that supports these findings. Here, we present an experimental study that uses optical microscopy to track the dissolution of CO2 bubbles in a two-dimensional porous network etched on a microfluidic chip filled with CO2–saturated water. We consider two distinct level of initial liquid supersaturation for situations involving a single isolated bubble and small bubble clusters, and observe dissolution, growth or a combination of these processes. A pore-network model is used to complement the experimental observations with information on local concentration development. The model captures qualitatively the evolution of the bubble size in each case tested experimentally and enables shedding light on the interplay between the inter- and intra-pore diffusive fluxes in driving the dissolution process.