Dynamic measurements of methane hydrate formation/dissociation in different gas flow direction

Natural gas hydrate (NGH) is a clean energy with huge potential reserves. Therefore, it is essential to understand the hydrate formation and dissociation characteristics for NGH production. Methane hydrate formation under gas migration condition was studied as pre-exploratory step for hydrate reformation research. Vessel pressure changes, methane hydrate saturation (Sh) and residual aqueous water saturation (Sw) were measured and analyzed in this study. Residual aqueous water distribution is also illustrated by magnetic resonance imaging (MRI). We found that, when Sw0 was higher than 0.4, the capillary force affected the aqueous water migration more than when Sw0 was lower than 0.4. Hence, Sh-max had a positive correlation with Sw0 when Sw0 is lower than 0.4. In addition, an upward methane flow is more likely to cause aqueous water redistribution than a downward methane flow. Moreover, we found that the aqueous water distribution changes could not recover after hydrate dissociation. Furthermore, the shifting of the hydrate dissociation boundaries from the vessel wall towards the core can be observed from the MRI images.