Susan Hovorka demonstrates how CO2 gets trapped in the brine and sandstone pores of the Frio formation: "If you were an ant down where the CO2 is being injected, this is what you would see." She uses a jar of glass beads, water and oil (red) to show how residual saturation works. She turns the jar upside down and as the oil rises, some gets trapped between the beads. Photo by Marc Airhart.