The Effects of Brine Species on the Formation of Residual Water in a $$\hbox {CO}_{2}$$ CO 2 –Brine System

Geological storage of $$\hbox {CO}_{2}$$ in deep saline aquifers is achieved by injecting $$\hbox {CO}_{2}$$ into the aquifers and displacing the brine. Although most of the brine is displaced, some residual groundwater remains in the rock pores. We conducted experiments to investigate factors that influence how much of this residual water remains after $$\hbox {CO}_{2}$$ is injected. A rock sample was saturated with brines of two different salts. Supercritical $$\hbox {CO}_{2}$$ was injected into the samples at aquifer temperature and pressure, and the displaced water and water–gas mixtures were collected and measured. The results show that deionized water drains more completely than either of the two brines, and NaCl brine drains more completely than $$\hbox {CaCl}_{2}$$ brine. The ranking of the irreducible water saturation at the end of the experiment is deionized $$\hbox {water}