Kinetic Simulation of CO2 Flooding of Methane Hydrates

Abstract

Abstract 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, CO2-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).