Possible Influx of Seawater during Gas Production from Unsealed Gas Hydrate Reservoirs has Economic and Environmental Implications

Reservoir depressurization currently appears to be the most effective method for extracting gas from natural gas hydrates. In this paper, we modeled the possible effects of gas hydrate production on fluid flow at the seafloor for various overburden permeabilities, i.e., sealed and unsealed overburdens. Our models predict a significant influx of water from the ocean downward through the seafloor during production from a high-permeability gas hydrate reservoir that is overlain by a silt-dominated overburden with moderate permeability. Such a reversal of fluid flow at the seafloor may have profound implications for production efficiency and chemosynthetic-based seafloor communities. A low-permeability seal, such as clay, needs to be present in the overburden to prevent such a water influx.