科研之友
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摘要
The application of air or nitrogen injection to extract natural gas from hydrates has attracted considerable attention because air and nitrogen are abundant; however, few studies have considered the relatively new method. This study employed magnetic resonance imaging to investigate the characteristics of hydrate dissociation via N-2 injection. The results show that methane hydrate dissociation using N-2 injection can be divided into three main stages: free gas and water liberation, hydrate dissociation driven by chemical potential differences, and restriction of hydrate dissociation due to increased resistance to N-2 diffusion and a decreased contact area between N-2 and hydrate. Various factors associated with the N-2 injection method were considered, including injection rate and hydrate saturation. Furthermore, a comparison of recovery injection ratio and methane cumulative production ratio to the results of hydrate dissociation via depressurization suggests that during low-hydrate saturation exploitation, N-2 injection has advantages over the depressurization method.
