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Zusammenfassung:
The Krishna Godavari (KG) basin is a passive margin basin with slumps, mass flows occurred due to rapid sedimentation, gas hydrates etc. To understand the dissociation mechanism of gas hydrates on slumping/sliding, 3D seismic data from a small region in the KG basin is examined in the present study. Seismic Interpretation of the data reveals shoaling of the Bottom simulating reflector (BSR) followed by truncation further downslope, creating slope failure. The role of pressure and temperature in altering the hydrate stability is studied and found that the temperature change is the main parameter that controls the gas hydrate stability. The Base of the hydrate stability zone (BHSZ) during the Glacial time and the present day is computed with varying Geothermal Gradients (GTG) of 45 ± 3° C/ km. The obtained results show that the BHSZ has shifted by 80 m post-glacial at a water depth of ~ 1000 m. Our results also shown that changing the GTG in the range of 43-48° C/ km has caused only a ten-meter change in the shift, but changing the seafloor temperature from 4-6.5°C has caused 80 meters shift in the BHSZ. We find a close correlation with the depth of dissociation inferred from interpretation of seismic data and dissociation temperature computed. Two slumping features were observed in the seismic data of varying size; the smaller one is attributable to the over pressurized zone below the BSR and the larger one (~21km), seems to have formed as a result of gas hydrate dissociation.
