Effect of silica sand size on the formation kinetics of CO2 hydrate in porous media in the presence of pure water and seawater relevant for CO2 sequestration

Understanding the kinetics of carbon dioxide (CO2) hydrate formation in pure water, seawater and porous media aids in developing technologies for CO2 gas storage, carbon capture and sequestration (CCS) and potentially for methane production from methane hydrates. The present work is focused on understanding the kinetics of CO2 hydrate formation in pure water and seawater at an initial formation pressure of 6 MPa (providing a driving force of about 4.0 MPa) and a formation temperature of 276.15 K with 75% water saturation in three silica sand particle sizes (0.16 mm, 0.46 mm and 0.92 mm). The seawater (3.3 wt% salinity) used in the present study is obtained from sea coast of Chennai (India). It is observed that the gas consumption of CO2 in hydrate is more for smaller silica sand particle and decreases as the size of the sand increases. The total gas consumed at the end of the seawater experiment is found to be less than the gas consumed at the end of the pure water experiment. This is due to the fact that salts in seawater act as a thermodynamic inhibitor resulting in lower gas consumption of CO2 in hydrate. The average rate of hydrate formation observed is optimum in 0.46 mm particles and is observed to be higher as compared to 0.16 and 0.92 mm particles over 10 h experimental time. This indicates that 0.46 mm silica sand provides an optimum environment for efficient hydrate formation. The study can be useful to understand the suitability of potential sandstone reservoir for CO2 sequestration in the form of hydrate in the presence of saline formation water.