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Shoaling of the gas hydrate stability zone inferred from 3D seismic data of the Cauvery basin.

Gas hydrate formation, identification, and exploration have been well-studied in passive margin basins in India, such as the Krishna Godavari and Mahanadi basins. However, the Cauvery basin, in the southern part of the eastern margin of India, remains largely unexplored in terms of gas hydrate exploration. The gas hydrate formation and dissociation are primarily guided by the temperature and pressure. Due to the rise in global temperatures, the base of the gas hydrate stability zone is shifting to shallower depths in various basins worldwide. To study the impact of rising temperatures on gas hydrate stability the 3D seismic data of the Cuavery basin is analysed. The analysis of the 3D seismic data of the Cauvery offshore basin revealed a continuous and stable BSR at water depths between 945 m and 1000 m. The BSR is observed 90 m below the seafloor (mbsf) from seismic data, and computed stability for the same region shows that the BHSZ is at 90 mbsf at 1000 m bathymetry, which agrees well with the seismic. Our study attempts to study the stability variation by changing the sea bottom temperature, geothermal gradient, and hydrostatic pressure.

a: Seismic section crossline 2936 showing the BSR mimicking the seafloor and shoaling upwards from inline 1400 to 1450.

b: The sweetness attribute of crossline 2936 shows that the BSR is associated with high sweetness.

c: The sweetness attribute of the time slice generated at 1.32 sec near the BSR.

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