Modeling of CO 2 storage as hydrate in vacated natural gas hydrate formation

Abstract

Holding CO2 at massive scale in enclathrated solid matter called hydrate can be perceived as one of the most reliable method for CO2 storage in subsurface geological environment. In this study, a dynamically coupled mass, momentum, and heat transfer mathematical model is developed, which elaborates uneven behavior of CO2 flowing into porous medium in space and time domain and converting itself into hydrates. The combined numerical model solution methodology by explicit finite difference iteration method is provided and through coupling the mass, momentum, and heat conservation relations, an integrated model can be presented to investigate the CO2 hydrate growth within P-T equilibrium conditions. The article results illustrate that pressure distribution in hydrate formation becomes stable at initial phase of hydrate nucleation process, but formation temperature is unable to maintain its stability and varies during CO2 injection and hydrate nucleation process. The hydrate growth rate increases by increasing injection pressure from 15 MPa to 16 and 17 MPa in 500-m-long formation, and it also expands overall hydrate-covered length from 200 m to 280 m and 320 m, respectively, in 1 month of hydrate growth period. Injection pressure conditions and hydrate growth rate affect other parameters like CO2 velocity, CO2 permeability, CO2 density, and CO2 and H2O saturation. In order to enhance hydrate growth rate and expand hydrate-covered length, injection temperature is reduced from 282 K to 280 K, but it did not give satisfactory outcomes. In addition, hydrate growth termination and restoration effect is also witnessed due to temperature variations.