Enhanced gas recovery and CO2 storage: investigating the effect of connate water salinity on recovery
摘要
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 CO2 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 CO2 breakthrough, the measured methane recovery and CO2 solubility storage for brine salinities of 1.04 wt%, 1.72 wt%, 2.47 wt%, and 6.33 wt% were 80.44 cm3/94.02%, 60.65 cm3/91.62%, 59.33 cm3/90.01%, and 42.39 cm3/43.50%, respectively. Numerical simulations conducted using CMG software reproduced similar recovery trends, confirming that both CO2 solubility and gas recovery decline with increasing salinity. These findings demonstrate that high-salinity formation water negatively affects CO2 dissolution, gas recovery efficiency, and breakthrough behaviour. Reservoirs with lower salinity therefore offer more favourable conditions for implementing EGR–CS operations.