Spreading and convective dissolution of carbon dioxide in vertically confined, horizontal aquifers

CW MacMinn, JA Neufeld, MA Hesse, and HE Huppert, Water Resources Research, 48:W11516, 2012. doi:10.1029/2012WR012286

When CO2 is injected into a saline aquifer for carbon sequestration, it will rise and spread due to buoyancy. It will also dissolve into the water via a hydrodynamic instability. Here, we use a theoretical model and laboratory experiments to study the impact of dissolution on buoyant spreading.

These videos show three experiments in a quasi-two-dimensional flow cell packed with glass beads. The flow cell is about 15cm tall with a 1cm gap between the plates. The cell is packed with 1mm diameter beads in the first video and 2mm diameter beads in the second and third videos.

Video 1. An experiment without convective dissolution. The buoyant fluid (water; dark) rises and spreads indefinitely over the denser, ambient fluid (saltwater; light). The dark blue curve is from a gravity-current model.

Video 2. An experiment where convective dissolution is slow relative to spreading. The buoyant fluid (a mixture of methanol and ethylene glycol, or MEG; dark) spreads, slows, and then retreats as it dissolves into the denser, ambient fluid (water; light). The dark blue curve is from a gravity-current model.

Video 3. An experiment where convective dissolution is fast relative to spreading. The buoyant fluid (a mixture of methanol and ethylene glycol, or MEG; dark) spreads, slows, and then retreats as it dissolves into the denser, ambient fluid (water; light). However, the dissolution process itself slows as dissolved MEG accumulates on the bottom, obstructing further dissolution. This dense water with dissovled MEG spreads as a dense gravity current along the bottom of the cell. The dark blue and light blue curves are from a model that accounts for both the buoyant current and the dense one.