Visual observation of gas-hydrate formation and dissociation in synthetic porous media by means of glass micromodels

Visual observation of gas hydrates at the microscopic scale in synthetic po rous media provides unequivocal visual evidence that clathrates can form in systems without the presence of a free-gas phase. Hydrates were formed fro m a soluble liquid hydrate former (tetrahydrofuran, C4H8O), from free gas ( CH4), and from dissolved gas (CO2). Clathrates were found to form within th e center of pore spaces, rather than on grain surfaces. Cementation of grai ns only occurred in regions of a small grain size, or where a large proport ion of pore space was filled with hydrate. However, even at high clathrate saturations, a thin film of free water persisted on grain surfaces. The res ults have important implications for the potential cementing effect of hydr ates on sediments, and thus for sediment permeability, slope stability, and seismic interpretation of hydrate-bearing sediments.