Kinetic simulation of CO₂ flooding of methane hydrates

Finding new sources of energy and curbing global warming are two of the most important current problems. CO₂ can be injected into methane-hydrate reservoirs to produce methane and sequester CO₂ simultaneously. CO₂ replaces methane in the clathrate cages producing methane. The goal of this work is to develop a compositional, thermal, and kinetic simulator to design and interpret lab and field scale CO₂ flooding experiments of methane-hydrate in porous media. Five components (water, methane, CO₂, CH₄-hydrate, CO₂-hydrate) and six phases (aqueous, gas, liquid CO₂-rich phase, CO ₂-hydrate, CH₄-hydrate and ice) are considered. The equations are spatially discretized with a finite volume difference method and are solved with a Newton-Raphson method in a fully implicit manner. Primary variable switch method (PVSM) is used to track the phase transitions. 1-D core scale simulations shows that the energy produced from CO₂-hydrate formation is utilized for methane-hydrate dissociation. The methane-hydrate dissociation front moves at a slow rate of approximately 1/40 cm/hr for the kinetics assumed in the base case. High mole fractions of CO₂ lead to CO₂-hydrate formation and methane-hydrate dissociation. To dissociate methane-hydrate by CO₂ injection, either we need to keep the CO₂ mole fraction very high in the fluid phase or operate at a relatively lower pressure (shallower reservoirs of methane-hydrates).