(222m) Quantitative Measurements of CH4 Production From CH4 Hydrates With the Injection of CO2

Naturally occurring gas hydrates found in oceanic sediments and under the permafrost, contain mostly methane, and present a potential future energy resource. Carbon dioxide, a global climate change gas, has the potential to be used in enhanced gas recovery techniques, where carbon dioxide is injected into the hydrate reservoir with simultaneous release of methane from within the gas hydrate bearing sediments. However, most previous studies in this area have provided only qualitative information on the methane production rates during the methane-carbon dioxide hydrate exchange process. Consequently, the rate of methane production is not well quantified, and thus important information towards quantifying methane release from various methane hydrate saturations observed in natural settings is required

In this study, quantitative experiments have been performed to investigate the possible methane- carbon dioxide exchange kinetics from injection of carbon dioxide and carbon dioxide -nitrogen gas mixtures through methane hydrate. Methane hydrate was formed from ice particles (75~90 micron in diameter) at 1500 psig and 263 K. In order to reduce unexpected errors, nearly full conversion (> 99%) of ice particles to hydrates was achieved. Liquid carbon dioxideor carbon dioxide-nitrogen gas mixtures were injected (123 ml/hr and 286 ml/hr respectively) into the pressure cell to sweep the residual methane atmosphere, ensuring no free methanewas left in the gas phase. After soaking the hydrate for several hours (e.g., 12, 24 and 48 hours), methanewas produced from the hydrates and was transferred into a sample cylinder by injecting liquid carbon dioxide or a carbon dioxide-nitrogen mixture. The final composition and analysis of the produced methane was measured using an in-line gas chromatograph. The methane moles after hydrate dissociation were also measured to confirm the closure of the total mass balance of the experiment. The exchange between carbon dioxide and methane during the experiments was demonstrated through the pressure trace in terms of two possible systems, an exchange and no exchange system, and the penetration depth of hydrate particles was calculated to estimate specific kinetic trends. These experiments are essential in the quantification of the production of methane from methane hydrates with the injection of carbon dioxide or a carbon dioxide /nitrogen mixture.