Gas Hydrates at Minimum Stability Water Depths in the Gulf of Mexico: Significance to Geohazard Assessment

Abstract Gas hydrate stability is a function of water depth, bottom water temperature, pressure, and thermal gradient in sediments, pore water salinity, gas availability, and composition. The modeled minimum water depths at which gas hydrates crystallize at present in the Gulf of Mexico is 330-615 m, depending on the source gas composition. The minimum water depth at which gas hydrates have been found by shallow coring is about 440 m. Bottom water temperature is variable because of seasonal variations, and the propagation of warm core Loop Current eddies. The influence of heat flow associated with these two factors on gas hydrate stability is presented in the paper. Seasonal variations in bottom water temperature may affect gas hydrate stability only in the upper 1-2 m of sediments, depending on water depth. Warm core eddies also only affect the upper 1-2 m of sediments depending on the duration of their propagation. Our data imply a thin but extensive gas hydrate geohazard zone in the Gulf of Mexico at water depth ranging from ~440 m to ~720 m. Repetitive gas hydrate formation and decomposition could cause sediment deformation, slumps, and gas blowout craters, and increase the rate of oil venting to the water column. Such events may impact sub-sea petroleum exploitation within the Gulf of Mexico.