In the medium term, gas hydrate reservoirs in the subsea sediment are intended as deposits for carbon dioxide (CO 2 ) from fossil fuel consumption. This idea is supported by the thermodynamics of CO 2 and methane (CH 4 ) hydrates and the fact that CO 2 hydrates are more stable than CH 4 hydrates in a certain P-T range. The potential of producing methane by depressurization and/or by injecting CO 2 is numerically studied in the frame of the SUGAR project. Simulations are performed with the commercial code STARS from CMG and the newly developed code HyReS (hydrate reservoir simulator) especially designed for hydrate processing in the subsea sediment. HyReS is a nonisothermal multiphase Darcy flow model combined with thermodynamics and rate kinetics suitable for gas hydrate calculations. Two scenarios are considered: the depressurization of an area 1,000 m in diameter and a one/two-well scenario with CO 2 injection. Realistic rates for injection and production are estimated, and limitations of these processes are discussed.

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