Fig. 5 . Micro–images during the gas–seawater flow process in Cases 1–3: (a) MRI images; (b) hydrate saturation
In conclusion, the hydrate–containing sealing layer formed when the gas–water flow rate is 1–0.25 ml/min. The seawater is full contact with the methane gas in lower gas–water flow rate, methane saturation in seawater is high enough to induce the hydrate reformation. The decrease of pore volume leads to the increase of capillary force, thus, sealing layer formal formed, this is the formation mechanism of hydrate–containing sealing layer. Then, the hydrate continued to form in the reservoir which enhanced the sealing layer and makes it more difficult to be destroyed.