Kinetic insight on CO2 hydrate formation and dissociation in quartz sand in presence of brine

Abstract

CO2 storage as hydrates in porous media is a promising method to sequester carbon dioxide (CO2) that need to be comprehended to guide its potential site selection prospects. In this study, CO2 hydrate formation and dissociation were studied in three quartz sand particles with varying petrophysical properties such as surface area, pore size, and porosities. The studied quartz sand particle sizes are QS-1 (<0.6 mm), QS-2 (0.6–0.8 mm), and QS-3 (0.8–2.0 mm). The hydrate formation experiments were conducted in a high-pressure hydrate reactor with and without brine (3.3 wt.% NaCl) at 4 MPa and temperatures of 274.15 K and 277.15 K in 100% sample saturation. The hydrate dissociation kinetics were studied at two different temperatures of 277.15 K and 279.15 K. The results show that hydrates form faster in deionized water (DI) than brine solution. The presence of brine reduced the CO2 storage capacity by 30% compared with deionized water. In addition, the presence of brine reduces the stability of CO2 hydrates. CO2 hydrate formation and dissociation behavior in porous media is highly controlled by the quartz sand porosity, pore size, and surface area. The quartz sand particles with low porosity were found to efficiently store more CO2 with a fast onset hydrate formation time of 6 hr and high gas to hydrate conversion of 55%. However, the CO2 hydrates in the sand particles with low porosity were less stable and averagely prolonged the time take to release 90% of CO2 of the systems with high porosity by 39%.