Development and Application of a Simulator for Simulating the Behaviors of a Geological System When Replacing CH 4 from Hydrate-Bearing Reservoirs by CO 2

Conventional techniques for hydrate production may cause the deconstruction of hydrate, changing the geomechanical stresses of the reservoir, which could trigger the subsidence of the seafloor. A new method for replacing CH 4 from the hydrate lattice by CO 2 , without damaging the mechanical structure of sediment, has been proposed. This approach can achieve both the objectives of long-term CO 2 sequestration and the safe production of CH 4 from hydrates. By coupling the Chen-Guo model into Tough+Hydrate V1.5, an updated simulator CO 2 -EGHRSim V.10 (CO 2 Enhanced Gas Hydrate Recovery simulator) was developed in this work to describe the replacing processes of CH 4 from the hydrate lattice by CO 2 and to evaluate the storage potential of CO 2 and the recovery efficiency of CH 4 from the hydrate-bearing reservoirs. The developed simulator was verified using measured data obtained from laboratory experiments. The verification suggested that CO 2 -EGHRSim performed well in predicting the replacing processes of CH 4 with CO 2 . The simulator was applied to calculate the CO 2 storage potential combined with the CH 4 recovery from hydrates at the site of Iġnik Sikumi on the North Slope of Alaska. The simulated results indicated that the CO 2 –CH 4 exchange mostly occurred inside the gas plume, and the CO 2 hydrate was only present around the production well. The simulated CO 2 storage ratio was 0.58, and the CH 4 recovery efficiency was 25.95%.