Gas production from hydrate-bearing sediments:geo-mechanical implications
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Gas hydrate consists of guest gas molecules encaged in water molecules. Methane is the most common guest molecule in natural hydrates. Methane hydrate forms under high fluid pressure and low temperature and is found in marine sediments or in permafrost region. Methane hydrate can be an energy resource (world reserves are estimated in 20,000 trillion m3 of CH4), contribute to global warming, or cause seafloor instability. Research documented in this thesis starts with an investigation of hydrate formation and growth in the pores, and the assessment of formation rate, tensile/adhesive strength and their impact on sediment-scale properties, including volume change during hydrate formation and dissociation. Then, emphasis is placed on identifying the advantages and limitations of different gas production strategies with emphasis on a detailed study of CH4-CO2 exchange as a unique alternative to recover CH4 gas while sequestering CO2. The research methodology combines experimental studies, particle-scale numerical simulations, and macro-scale analyses of coupled processes.