The Effects of Brine Concentration on the Formation of Residual Water

Geological storage of CO2 in deep saline aquifers is achieved by injecting CO2 into aquifers and displacing the brine. Although most of the groundwater is displaced, some residual groundwater remains in the rock pores. We conducted experiments to investigate the formation process of residual water. Rock samples were saturated with brines of different concentrations. CO2 was injected into the samples at aquifer temperature and pressure, and the drained water was measured. The results show that the groundwater drainage was slower and the irreducible water saturation was higher with higher brine concentration. The process of drainage can be classified into three stages according to the drainage flow rates: piston drainage, portable drainage, and dissolved drainage.