Plain Language Summary
Typical methane hydrate reservoir system in nature generally includes hydrate, water and gas layers, and the already explored marine hydrate reservoir (recognized by bottom simulating reflector method) is just corresponding to this geological reservoir distribution. In marine geology, real gas layer existing stably under the hydrate and water layers may be with higher pressure because of the sealing effect of hydrate layer, and the accurate pressure condition of fully developed gas layer is rarely investigated. We confirm this assumption of natural hydrate and gas reservoirs system accumulation and obtain an entire image of the typical system visually by magnetic resonance imaging. We find that the sealing effect is mainly due to the hydrate reformation and liquid water residue. In order to evaluate the mechanical stability of the sealing effect, we increase the gas pressure to 13 MPa and verify the permitted pressure difference between the two sides of the sealing layer higher than 9.0 MPa. Future geological exploration and joint exploitation project of hydrate and gas reservoirs should refer to these results.