CO2 storage in saline aquifers by dissolution and residual trapping under supercritical conditions: An experimental investigation

The volume of a supercritical CO2 droplet on limestone and sandstone substrates in different solutions (electrolyte solutions and saturated saline water) at 1500 Psi and 40 degrees C was determined as a function of immersion time using a high pressure pendant/sessile drop cell. To differentiate the storage of the supercritical CO2 by residual trapping into the pores from the dissolution in bulk solutions, the measurement was also conducted using a non-porous silica wafer. The limestone, sandstone and silicon wafer were all initially water-wet, with the silicon wafer becoming more CO2-wet over time. Limestone and sandstone were slightly more CO2-wet compared to the SW, which would affect the mobility of CO2. The volume reduction of the CO2 droplet was observed to be much more rapid on porous substrates than on nonporous silica wafer due to the residual trapping (storage) of CO2 into the pores. Residual trapping was found to dominate the kinetics of CO2 storage, especially throughout the initial 10 min of the experiment.