4. Conclusion
The variation of MH distribution during the water flow process was investigated to contribute to the exploitation of hydrates. The results are summarized as follows:
(1) A visualization study on the distribution of hydrates in hydratebearing sediment during the water flow process was carried out. The influence of temperature and pressure variations on MH dissociation was eliminated completely in the experiments. The influence of water migration on MH dissociation was systematically analyzed.
(2) A new method of water flow erosion for natural gas hydrate (NGH) exploitation is proposed in this study. The investigation of water migration will be beneficial to hydrate exploitation in practical engineering. Combining this method with others will improve the efficiency of hydrate exploitation.
(3) The chemical potential difference between the hydrate phase and the aqueous phase caused MH dissociation during water flow process. The MH dissociation rate increased with decreasing backpressure and increasing water flow rate. When the rate of MH dissociation is lower, it will take longer for the flow channel to appear, vary, and disappear.
(4) According to the trend of the variation of flow channel appearing time and disappearing time, it can be predicted that there will be no MH dissociation when the water flow rate is low enough, and there will be no change in the flow channel appearing and disappearing times when the water flow rate is high enough.
