Investigation of gas seepages in Thessaloniki mud volcano in the Mediterranean Sea

Gas seepages are commonly observed in marine environment. Especially, gas seepages due to anthropogenic gas hydrate dissociation are big concerns recently. In the Eastern Mediterranean Sea, Thessaloniki mud volcano was detected. Gas hydrate stability conditions in this mud volcano is very fragile. For this reason, in this study, gas seepages were predicted by using HydrateResSim at different seafloor temperature increments varying from 1 to 5 °C and different sediment permeability values varying from 0.1 mD to 5mD in Thessaloniki mud volcano. Both the effect of temperature increment (above 1 °C increment) and the increase in permeability cause faster gas hydrate dissociation. The gas seepages on the seafloor of Thessaloniki mud volcano was investigated in this study by using the bubble rise theory. It was found that the effect of gas bubble diameter is high on the height of gas flare in the study area. The effect of permeability and lithology near seafloor on gas release after gas hydrate dissociation is huge. Generally, in Thessaloniki MV, clays are dominant so it is advantageous for environment because even if gas hydrate dissociates, free gas reaches to the seafloor slowly. Moreover, since the next 100 years, it is expected that temperature will increase by +2 °C on the seafloor of Thessaloniki MV. It was indicated that gas release will be obvious if temperature increment is above 1 °C in this area according to the numerical simulations with HydrateResSim.