Submarine slope failures due to gas hydrate dissociation and degassing along the edge of gas hydrate stability zone in the Krishna Godavari basin

Gas hydrate dissociation typically occurs due to the changes in the gas hydrate stability conditions and can act as a trigger for marine slides. The 3D seismic data from the Krishna Godavari basin is examined to understand the role of the dissociation mechanism of gas hydrates on slumping/sliding. Interpretation of the seismic data in the study area reveals the shoaling of the bottom simulating reflector (BSR) followed by truncation, creating slope failure/slumps. The role of pressure and temperature in altering the hydrate stability and triggering slides is studied, and it is observed that the temperature is the main parameter that controls the gas hydrate stability. The hydrate stability zone during the glacial time (sea-bottom temperature 4 °C) and the present day (sea-bottom temperature 6.5 °C) is computed with varying geothermal gradients (GTG) of 45 ± 3 °C/km. The results show that the base of the hydrate stability zone (BHSZ) has shifted by 80 m post-glacial at a water depth of ~ 1000 m. The computed depth of hydrate dissociation and the dissociation temperature was also studied for all the BSR instances in the study area, and we find a close correlation with the depth of dissociation inferred from the interpretation of seismic data. Two slumping features were observed in the seismic data of varying sizes: The smaller one is attributable to the over-pressurized zone below the BSR and the larger one (~ 21 km2) seems to have formed as a result of gas hydrate dissociation in the region where the BSR intercepts the seafloor.