Properties and phenomena relevant to CH4-CO2 replacement in hydrate-bearing sediments

The injection of carbon dioxide, CO2, into methane hydrate-bearing sediments causes the release of methane, CH4, and the formation of carbon dioxide hydrate, even if global pressure-temperature conditions remain within the CH4 hydrate stability field. This phenomenon, known as CH4-CO2 exchange or CH4-CO2 replacement, creates a unique opportunity to recover an energy resource, methane, while entrapping a greenhouse gas, carbon dioxide. Multiple coexisting processes are involved during CH4-CO2 replacement, including heat liberation, mass transport, volume change, and gas production among others. Therefore, the comprehensive analysis of CH4-CO2 related phenomena involves physico-chemical parameters such as diffusivities, mutual solubilities, thermal properties, and pressure-and temperature-dependent phase conditions. We combine new experimental results with published studies to generate a data set we use to evaluate reaction rates, to analyze underlying phenomena, to explore the pressure-temperature region for optimal exchange, and to anticipate potential geomechanical implications for CH4-CO2 replacement in hydrate-bearing sediments.