Fig. 3 . Characteristics of
pressure at reactor inlet and
reactor outlet flux
In Case 2, the inlet pressure reached about 10.0 MPa twice at the
gas–water flow rate of 2–0.5 ml/min, and finally the inlet pressure
dropped the same as outlet pressure. The inlet pressure increased before
163 min (turning point 1), and the seawater accumulated in the reservoir
because the slope of outlet flux was decreased gradually. The inlet
pressure increase indicating capillary sealing effect (Liu , 2007)
appeared in the hydrate reservoir, and the reservoir permeability
decreased which was caused by the hydrate saturation increase in the
sediments (Mahabadi et al. , 2019). But the capillary sealing
effect of hydrate reservoir was not stable, the hydrate hydrate
saturation was not high enough, the hydrate–containing sealing layer
was broken through at 163 and 194 min, respectively, and caused inlet
pressure decrease, the whole process is shown in Fig. 4. The break
through (BT) pressure were 6.68 MPa, 6.46 MPa, respectively, and the
reason of this phenomenon are the large pressure difference on both
sides of hydrate reservoir (Liu , 2007) and the incompletely
formation of hydrate–containing sealing layer.