Development and Application of a Simulator for Simulating the Behaviors of a Geological System When Replacing CH4 from Hydrate-Bearing Reservoirs by CO2

Abstract

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 CH4 from the hydrate lattice by CO2, without damaging the mechanical structure of sediment, has been proposed. This approach can achieve both the objectives of long-term CO2 sequestration and the safe production of CH4 from hydrates. By coupling the Chen-Guo model into Tough+Hydrate V1.5, an updated simulator CO2-EGHRSim V.10 (CO2 Enhanced Gas Hydrate Recovery simulator) was developed in this work to describe the replacing processes of CH4 from the hydrate lattice by CO2 and to evaluate the storage potential of CO2 and the recovery efficiency of CH4 from the hydrate-bearing reservoirs. The developed simulator was verified using measured data obtained from laboratory experiments. The verification suggested that CO2-EGHRSim performed well in predicting the replacing processes of CH4 with CO2. The simulator was applied to calculate the CO2 storage potential combined with the CH4 recovery from hydrates at the site of Iġnik Sikumi on the North Slope of Alaska. The simulated results indicated that the CO2–CH4 exchange mostly occurred inside the gas plume, and the CO2 hydrate was only present around the production well. The simulated CO2 storage ratio was 0.58, and the CH4 recovery efficiency was 25.95%.