Molecular Dynamics Study of the Interactions Between Minerals and Gas Hydrate Species

The need for knowledge on gas hydrate "host" and "guest" interactions with reservoir rocks comes from the two folded exploitation of gas hydrates. On one hand natural gas hydrates represent an immense energy source, on the other hand carbon sequestration in the form of CO2 hydrates represents a long-term storage of carbon dioxide. Whether one's goal is to extract methane from natural gas hydrates or store carbon dioxide in the form of hydrates, it requires an understanding of the complex phenomena involving coupled dynamics of hydrates and hydrate stability in porous media. Hydrates can never attach directly to solid mineral surfaces because of the incompatibility of charges between the mineral surfaces and the hydrates. However, adsorption of water and carbon dioxide on mineral surfaces may favor heterogeneous nucleation of hydrate in the immediate vicinity. Different surfaces have their own specific adsorption preferences and corresponding adsorption thermodynamics. We have selected calcite, a common mineral found in porous media. Using molecular dynamics we have initially focused on the water interface in order to evaluate the "host" interactions towards the surface. We also aimed at evaluating the model before including guest molecules.