GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 3.1 GNGTS 2023 cold seeps emitting methane at the seafloor. The Chilean margin shows a strong variability in the distribution of gas hydrate and free gas concentration. This variability seems driven by an interaction between regional and local factors, such as local geothermal gradient anomalies related to fluid migration through faults linked to seafloor mud volcanoes. Recently, the gas hydrate stability zone was modeled to identify the zone where exist the conditions for its stability along the Chilean margin. Different future scenarios were considered to better understand the effects of climate change on gas hydrate stability. The modeling pointed out that climate change could strongly affect gas hydrate stability and, in particular, the increase in temperature would determine the gas hydrate dissociation along the upper slope. The changes in the gas hydrate system since the last deglaciation associated with tectonic uplift was investigated, allowing to determine a model to link the gas origin to paleo-BSR, on the basis of the geothermal gradient, the base of free gas layers, and the BSR distributions over time. If paleo-BSR coincides with the base of the free gas, the gas presence can be related to the gas hydrate dissociation due to climate change and geological evolution. Only if the base of free gas reflector is deeper than the paleo-BSR, a deeper gas supply can be invoked. On the basis of the above studies, Chilean margin should be considered a natural laboratory to study the hydrate system evolution. Reference author: Giulia Alessandrini, galessandrini@ogs.it