Effect of multiphase flow on natural gas hydrate production in marine sediment

Natural gas hydrates (NGHs), regarded as an alternative future energy source. Currently, tests for hydrate exploitation from marine sediment have been performed in the Nankai Trough of Japan and the Shenhu area of the South China Sea. Hydrate exploitation is influenced by water-gas flow in the sediment, and considering the huge seawater reserves in hydrate accumulation areas, an experiment of seawater-gas flow was performed to dissociate hydrate. The effects of seawater-gas flow rates and initial hydrate saturation on methane hydrate (MH) production were analyzed. The results showed that seawater-gas flow efficiently promotes hydrate dissociation and inhibits hydrate reformation. Moreover, there was a faster heat and mass transfer with increasing seawater flow rates and decreasing gas flow rates, which enhanced the average MH dissociation rate. In addition, the variation time of the flow channel increased with higher initial hydrate saturation. Additionally, seawater-gas flow promotes MH dissociation stronger than deionized water-gas flow.