Predictions of gas hydrate phase equilibria and amounts in natural sediment porous media

Hydrates in marine sediments are estimated to contain more methane than conventional reserves. Previous estimates of the amounts of methane hydrate ignore pore size effects and variations in hydrate saturation of the pore space. The model presented here uses sediment type, geothermal gradient, and seafloor depths as inputs, and leads to predictions for the maximum depth of hydrate stability for data collected in the Ocean Drilling Program with an average error of 5%. Reaction-mass transfer partial differential equations are solved to estimate the amount of hydrate filling of the pore space, rather than using previous ad hoc choices for hydrate saturation. Predictions for the amounts of methane hydrate in the Mediterranean Sea, the Black Sea, the Gulf of Mexico, and the Northern Indian Ocean are made. (C) 2003 Elsevier Ltd. All rights reserved.