Assessment of gas hydrate stability zone and geothermal modeling of BSR in the Andaman Sea

• Gas hydrate reported from the Andaman Sea, India after coring and drilling.
• Geothermal modeling of base of gas hydrate stability zone.
• Gas hydrate stability thickness map of Andaman Sea.
• Gas hydrate saturation using rock physics modeling.
• Seismic attributes (i.e. reflection strength and instantaneous frequency etc.).

Wide-spread bottom simulating reflectors (BSRs) are observed along available multichannel seismic profiles covering an area of about 290 km2 in the Andaman Sea. The seismic data shows that the BSR occurs at places where water depth exceeds 1000 m, and is identified by cross-cutting relationships with the dipping reflectors. The BSR that represents the base of gas hydrate stability field can be used to infer the gas hydrate stability thickness, which ranges between ∼518 m to ∼861 m depending on water depths. In situ measurement at site 17 during the Indian National Gas Hydrate Program (NGHP) Expedition-01 shows very low geothermal gradient 19 ± 2 °C/km. A conductive model was used to determine geothermal gradients from BSRs, which is calculated and varying between 10 °C/km to 40 °C/km. The low geothermal gradient is responsible for the deepest BSR or gas hydrate stability zone (GHSZ) in the Andaman region and in the world. The geothermal modeling shows a close match of the predicted base of the gas hydrate stability zone with the observed BSR depths.