Formation Characteristics of CO2 Hydrates in the Presence of Porous Media and NaCl

Hydrate-based CO2 sequestration is an effective method for reducing the greenhouse effect, and the presence of porous media and NaCl can impact the formation characteristics of hydrates. This study uses the constant volume temperature search method to investigate the effects of quartz sand particle size (0.006-0.03 mm), water saturation (30%- 90%), and NaCl concentration (1%-9%) on the phase equilibrium and kinetics of CO2 hydrates within a temperature range of 273-285 K and pressure range of 1.0-3.5 MPa. The results indicate that a decrease in quartz sand particle size or an increase in NaCl concentration shifts the hydrate phase equilibrium curve towards lower temperatures and higher pressures, making hydrate generation conditions more demanding. In different particle size systems, there are no significant changes in the rate of CO2 hydrate formation or conversion rate. The highest hydrate conversion rate of 71.1% is observed in a 0.015 mm particle size system. With increasing water saturation, both the generation rate and conversion rate of CO2 hydrates show a trend of first increasing and then decreasing. Meanwhile, low concentrations of NaCl (1%-3%) are found to enhance the formation and conversion rates of CO2 hydrates. However, as NaCl concentration increases, the rate of CO2 hydrate formation and conversion rate decrease.