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.