Potential map of gas hydrate formation in Caspian Sea based on physicochemical stability evaluation of methane hydrate.

Using physicochemical equations for methane hydrate stability at different pressures, temperatures and salinities, and salinity data taken from the 2005 World Ocean Database for 641 locations in the Caspian Sea basin, the potential of gas hydrate formation at various depths beneath the seafloor was calculated and predicted. The upper and lower limits of the methane hydrate stability zone were calculated for each location for low (11 degrees C/km) and high (17 degrees C/km) geothermal gradient conditions, and zoning maps are presented. The thickness of the hydrate zone for low and high geothermal gradient conditions was estimated at over 3 500 and ca. 1 500 m, respectively. A comparison of the results of the physicochemical evaluation with gas hydrate zones obtained from geophysical surveys of Absheron, Azerbaijan and Turkmenistan offshore indicated that, in the Caspian Sea, the actual gas hydrate zones developed close to the estimated lower limit of methane hydrate in high geothermal gradient conditions.
Using physicochemical equations for methane hydrate stability at different pressures, temperatures and salinities, and salinity data taken from the 2005 World Ocean Database for 641 locations in the Caspian Sea basin, the potential of gas hydrate formation at various depths beneath the seafloor was calculated and predicted. The upper and lower limits of the methane hydrate stability zone were calculated for each location for low (11 degrees C/km) and high (17 degrees C/km) geothermal gradient conditions, and zoning maps are presented. The thickness of the hydrate zone for low and high geothermal gradient conditions was estimated at over 3 500 and ca. 1 500 m, respectively. A comparison of the results of the physicochemical evaluation with gas hydrate zones obtained from geophysical surveys of Absheron, Azerbaijan and Turkmenistan offshore indicated that, in the Caspian Sea, the actual gas hydrate zones developed close to the estimated lower limit of methane hydrate in high geothermal gradient conditions.