Enhanced gas recovery and CO2 storage: investigating the effect of connate water salinity on recovery

Abstract To assess the suitability of gas reservoirs for enhanced gas recovery and carbon sequestration (EGR–CS), it is essential to understand the influence of connate water salinity on natural gas recovery. Although the reduction of CO 2 solubility with increasing salinity is well established, its direct effect on gas recovery remains poorly explored. In this study, four formation brines with different salinities were analysed experimentally using sandstone core samples at reservoir-representative conditions of 41 °C and 1440 psi. Multiple injection rates were tested, and 0.45 ml/min produced the lowest dispersivity value (0.00039 m). At CO 2 breakthrough, the measured methane recovery and CO 2 solubility storage for brine salinities of 1.04 wt%, 1.72 wt%, 2.47 wt%, and 6.33 wt% were 80.44 cm 3 /94.02%, 60.65 cm 3 /91.62%, 59.33 cm 3 /90.01%, and 42.39 cm 3 /43.50%, respectively. Numerical simulations conducted using CMG software reproduced similar recovery trends, confirming that both CO 2 solubility and gas recovery decline with increasing salinity. These findings demonstrate that high-salinity formation water negatively affects CO 2 dissolution, gas recovery efficiency, and breakthrough behaviour. Reservoirs with lower salinity therefore offer more favourable conditions for implementing EGR–CS operations.