GAS HYDRATES IN THREE INDIAN OCEAN REGIONS, A COMPARATIVE STUDY OF OCCURRENCE AND SUBSURFACE HYDROLOGY

• Main Authors: Miriam Kastner, Arthur J. Spivack, Marta Torres, Evan Solomon, D. V. Borole, Gretchen Robertson, Hamendra C. Das
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Indian; Methane hydrate
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.143.5892; http://www.netl.doe.gov/technologies/oil-gas/publications/2008_ICGH/ICGH_5519_GradFellowship.pdf

To establish the structural and lithological controls on gas hydrate distribution and to assess the potential energy resource and environmental hazards in the Indian Ocean, non-pressurized and pressurized cores were recovered from the Krishna-Godavari (K-G) and Mahanadi Basins offshore east India, and from an Andaman Sea site. The pore fluids were analyzed for: salinity, Cl-, sulfate, sulfide, carbonate alkalinity, Ca 2+, Mg 2+, Sr 2+, K +, Na +, Ba 2+, and Li + concentrations, δ 13 C-DIC, δ 18 O, D/H, and 87 Sr / 86 Sr ratios; together with infra-red imaging they provided important constraints on the presence and distribution of gas hydrates, thus on the subsurface hydrology. Evidence for methane hydrate was obtained at each of the sites. Only in the K-G Basin, between the sulfate-methane transition zone (SMT) depth and ~80 mbsf, higher than seawater chloride concentrations are observed; below this zone to the depth of the base of the gas hydrate zone (BGHSZ), chloride concentrations and salinity are lower than seawater value. In the Andaman Sea and Mahanadi Basin, only lower than seawater chloride concentrations are observed, and the shallowest gas hydrates occur at 100-200 m below the sulfate-methane transition zone (SMT) and extend to the depth of the BGHSZ. In the K-G Basin, the highest methane hydrate concentrations are associated with fracture zones in clay-rich sediments and/or