Study on fluidizing the highly converted methane hydrate for gas storage and transportation

Fluidizing highly converted hydrate particles is a potential way for continuously producing gas hydrate in gas storage application. However, the fundamental problem is to prevent hydrate agglomeration while keeping a high formation rate. In this study, water–oil systems were used to investigate the feasibility of fluidizing the methane hydrate with fast formation rate. The formation kinetics and the slurry morphology of methane hydrate were systematically studied in the presence of single or commingled additives. Among the single additives, Span 20 provided the highest volumetric gas uptake of 177.7 V/V w (standard volume of gas per volume of water) at water cut of 20 vol%; with an increase in water cut, the volumetric gas uptake decreased and more hydrate agglomerated. All the single additives could not prevent hydrate agglomeration perfectly, even for Span 20, the best-performing single additive, prevented hydrate agglomeration well only at low water cut of 5 vol% and 10 vol%. The commingled additives comprised 1.0 wt% (to water) Span 20 and 2.0 ~ 3.0 wt% co-additives. When these co-additives were used in coordination with Span 20, most of them inhibited hydrate formation. By decreasing the concentration of TBAB from 5.5 wt% to 0.025 wt%, the inhibiting effect of TBAB faded away, while the anti-agglomerating effect remained. Similar phenomena were also found with some other co-additives. The results showed that low water cut, high Span 20 concentration, particularly the commingled additives could be solutions for fluidizing highly converted hydrate particles.