A Unique Dissolution Behavior of Trapped CO₂ into Flowing Water Inside a Porous Medium Compared with Other Gases

Abstract

Dissolution of gas into flowing water inside a porous medium is important in various hydrogeology processes, such as geological carbon sequestration (GCS). The dissolution rate of CO₂ controls the amount of CO₂ injection and the safety of the GCS process. In this report, we investigated the dissolution behavior of four gas species, i.e., CO₂, O₂, N₂, and Ar, into flowing water inside a porous medium by using micro-tomography. The trapped gas characteristics can be observed, and thus interfacial area and mass transfer coefficient can be calculated. Compared with the other gases, we found that the dissolution behavior of CO₂ gas is unique, and the mass transfer coefficient is one order of magnitude lower than other gases. We believe that the high dissolution ratio of CO₂ gas could have generated a layer of the high solute region around the trapped CO₂ gas, disrupting the mass transfer process.