Numerical analysis of CO2 hydrate growth in a depleted natural gas hydrate formation with free water

A dynamically coupled mass, momentum, and heat transfer model was developed, which demonstrated the unstable behavior of CO2 movement inside porous sediment during high pressure injection and its transformation into solid hydrates. The presented mathematical model was solved using the implicit finite difference method, and through ordering the set of model equations, a complex integrated methodology could be established to analyze the CO2 hydrate nucleation procedure within P‐T equilibrium conditions. The results showed that the intrinsic permeability factor of the porous sediment had great influence on the pressure distribution. At 10−13 m2 intrinsic permeability, the formation pressure distribution became stable at an early stage of the hydrate growth process and remained stable afterwards. The overall hydrate covered length was 320 m due to the massive hydrate growth rate. When intrinsic permeability was reduced to 10−14 m2, it showed delay in pressure distribution and the overall hydrate covered length shifts to up to 310 m due to the delay in pressure distribution. Whereas at a 10−15 m2 intrinsic permeability factor, there was significant delay in pressure distribution so the injection pressure was not fully distributed even after 30 days of the induction process, which squeezed the hydrate covered length to 130 m. This pressure distribution had direct correlation with other parameter variations during the hydrate growth process, such as temperature distribution, hydrate growth rate, CO2 velocity, CO2 density, CO2 and H2O saturation, CO2 permeability, and interface boundary movement speed. Hence, the pressure distribution inside hydrate‐bearing sediment is the most dominant factor to enhance CO2 storage capacity but it does not give satisfactory results in extended formations. © 2019 The Authors. Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons, Ltd.