GNGTS 2017 - 36° Convegno Nazionale

GNGTS 2017 S essione 3.1 593 Geotermal gradient and gas-phases concentration. By using the sea floor and the BSR depths, and knowing the sea bottom temperature (equal to 2.2°C; Grevemeyer and Villinger 2001), we estimated the geothermal gradient. In the northern sector, a variable geothermal gradient ranging between 35 to 87 °C/km was estimated. By contrast, in the southern sector a constant geothermal gradient was recognised: about to 30°C/km. The results of the gas-phase estimates indicate high variability along the sections. Note that in the northern sector the estimate was evaluated considering a variable geothermal gradient (from 35 to 87°C/km) to obtain a more reliable result. In the northern sector, the highest gas hydrate concentration is located between 0 and 7 km corresponding to the accretionary prism (maximun value equal to 22% of total volume; Fig. 3). A similar trend is recognised in the Fig. 2 - Final velocity models superimposed to the pre-stack depth migrated sections (RC2901-727 and SO161-29). In each section zoom of the selected parts, where the BSR and BGR are clearly detected. Fig. 3 - Gas phase’s concentration models superimposed to the pre- stack depth migrated sections (RC2901-727 and SO161-29). Positive values are referred to the gas hydrate amounts and negative values are referred to free gas amounts.