Gas hydrates stability zone thickness map of Indian deep offshore areas - A GIS based approach

Abstract

Natural gas hydrates, which have the potential of being an alternate energy resource, are known to occur worldwide in the sediments of the outer continental margins and in the polar regions in association with permafrost. The gas hydrates are stable under limited range of temperature and pressure conditions, which normally exist within few hundred meters of ocean sediments, in water depths greater than about 300 m. For the first time, GIS software has been used to map potential areas for the gas hydrate occurrence in offshore regions and around the Indian sub-continent. This was accomplished by estimating the gas hydrate stability zone (GHSZ) thickness from the saptial analysis of the physical parameters that control the formation and stability of gas hydrates. The required data (bathymetry, seabed temperature and geothermal gradient etc.) were obtained from published literatrue, digital data bases and unpublished source. These data were supplemented with predicted values, in areas having insufficient measured data. The compiled data bases were stored as GIS coverages. The thickness of gas hydrate stability zone was computed by superimposing the GIS maps of individual parameters and solving the gas hydrate phase and pressure-temperature equations for each grid. The GHSZ thickness values in meters as well as in TWT (msec) were calculated over the entire region