Golmshtok A.Ya.
The change of thermobaric regime of the hydrate-bearing sediment layer caused by an increase in the near bottom water’s temperature in Lake Baikal during the Holocene is investigated by solving the methane hydrate — free gas + water phase transition problem. It was demonstrated that the gas released during the methane hydrates dissociation does not create an abnormal pore pressure and efficiently migrates out from the decomposition zone provided that the primary permeability value of the porous medium is typical for the upper layers of the sedimentary cover in Lake Baikal. The phase transition problem becomes a purely thermal one. Its numerical solution makes it easy to estimate the phase boundary displacement with increasing water temperature in the lake, and hence the mass of free gas released from the hydrate. The specific mass of the released gas per unit area of the lake ranges from 50 to 110 kg/m2 , as shown by the results of such a numerical solution using data on both the lake’s depth and the hydrate-bearing layer thickness obtained from many points in the Southern and Central Basins of the lake. The minimum values correspond to the maximum water depths at the same time with the maximum thicknesses of the hydrate-bearing layer. On the contrary, the maximum values correspond to minima. Distribution maps of gas mass have been constructed. The total amount of methane released in the Holocene from gas hydrates is estimated at approximately 500 million tons (about 800 billion cubic meters under normal surface conditions). This value is obtained by integrating the calculated masses over the area of two regions in the Southern and Central Basins and subsequent extrapolation of the results to the entire their water area (there are no gas hydrates in the sediments of the Northern Basin).
